2021 Spring in Review

Temperatures did not depart significantly from normal. Precipitation was below normal region-wide, with a large portion of our area receiving less than 50 percent of normal spring precipitation.

March

Typical of early spring, March was a month of changeable weather and wide temperature variations.  Temperatures averaged near normal. It was a dry month, with much of the region receiving fifty percent or less of average March precipitation.  On the 5th, southeast winds ahead of a slow-moving cold front raised temperatures to record highs at some locations. The high of 69 at Ontario broke the old record of 66 set in 2012.  The front weakened as it moved inland, bringing only light precipitation.  A second cold front crossed the area on the evening of the 7th ahead of a cold low pressure trough from the Gulf of Alaska. Again only light precipitation fell as the cooling trend continued.  Skies cleared as the cold air moved inland on the 10th, resulting in some of the coldest lows of the month:

Baker City 20
Boise 25
Burns 22
McCall 5
Mt. Home 19
Ontario 22
Rome 16
Twin Falls 19 (11th)

An upper-level high pressure ridge building over the Pacific Northwest brought a warming trend from the 11th through the 14th.

A weak cold front crossed the area on the 15th. After brief cooling on the 16th, high pressure provided gradual warming, resulting in the warmest high temperatures for the season so far.  On the 19th, moderate amounts of rain accompanied a cold front. A record daily rainfall of 0.27 inch was set at Twin Falls.  An upper-level low pressure trough with much cooler air followed the front, but an even colder system was on the way.  On the 22nd, a strong cold front and upper-level trough from the Gulf of Alaska brought more precipitation.  A record daily rainfall of 0.46 inch was set at Boise, including half an inch of snow during the evening. Most of the precipitation was in the form of thunderstorm rain which preceded the snow.  Many locations experienced some the coldest highs of the month on the 22nd and 23rd:

Baker City 49 (23rd )
Boise 46
Burns 49
Jerome 46
McCall 35
Mt. Home 49
Ontario 54
Rome 49 (23rd )
Twin Falls 44 (23rd )

Another cold upper-level trough from the Gulf of Alaska continued the cold wet weather on the 24th and 25th.  An upper-level ridge brought much warmer weather. On the 28th, a record high of 70 was set at Twin Falls, and a record high of 75 was tied at Baker City. But very windy and much colder weather would soon arrive from the Gulf of Alaska.  During the evening of the 28th, a very strong cold front crossed the area.  Northwest winds increased rapidly behind the front, driven by a steep surface pressure gradient and enhanced by a powerful jet stream on the southern periphery of the upper-level trough which followed the front.

A gust of 61 mph was measured at the Boise airport shortly after midnight on the 29th.  No major damage was reported, but a number of shallow-rooted trees were toppled, and there were numerous broken branches. Downed lines left around 23,000 Boise customers without power, and a semi trailer was blown over on I-84 near Gowen Road, blocking most of the west-bound lane for several hours.  Afternoon highs on the 20th were 10-15 degrees below normal, and breezy northwest winds made it feel even colder.  A warming trend commenced during the afternoon of the 31st as a high pressure ridge moved in from the west.

precipitation percent of normal Marchtemperature departure from normal March

 

 April

April 2021 is memorable for dry windy weather and temperature extremes, although the average temperature for the month was close to normal.  It was an unusually dry April, with about half of the area receiving less than fifty percent of normal precipitation.  A high pressure ridge kept temperatures warm from the 1st through the 4th.  Record highs were set at Twin Falls on the 1st, 2nd , and 3rd with 73, 72, and 75.  On the 3rd Ontario tied a record high of 80, originally set in 1990.  Temperatures were below normal on the 5th and 6th following a cold front on the 4th. Another cold front from the Gulf of Alaska initiated a cool spell which persisted through the 14th. A record low of 17 was set at Baker City on the 7th.  Record lows were set on the 9th at Burns, Ontario, and Baker City, with 14, 22, and 12.  A record low of 15 was set at Burns on the 11th. Record lows were set at Twin Falls and Baker City on the 12th, with 23 and 16.  Early on the morning of the 19th, a dry cold front from western canada crossed the area. After the front passed, northwest winds increased through the day, and gusts around 50 kts were observed at a few locations.  A high pressure ridge near the coast maintained dry weather from the 20th through the 23rd.  The ridge moved inland and weakened on the 24th, allowing moist and unstable air to spread inland ahead of a low pressure trough.

Locally moderate amounts of rain fell with showers and a few thunderstorms on the 24th and 25th:

Baker City .19 .25
Boise .53
Burns .07 .27
McCall .25 .37

Then on the 26th, a disturbance from the Gulf of Alaska moved down the coast and into the trough, generating more rain.

On the 27th, a strong high pressure ridge building inland from the northwest coast kicked the trough south to the Mexican border.  The ridge brought a warming trend which culminated on the 30th.  A record high of 83 was set at Burns on the 29th.  A record high of 86 was set at Twin Falls on the 30th.

precipitation percent of normal April temperature departure from normal April

 

 

May

May continued the dry pattern of April. Precipitation was below normal across most of the area, but some locations in Malheur, Canyon, and northwest Owyhee Counties reported near or above normal precipitation.  This was probably the result of isolated convective showers.  Much of the area had no measurable rain from the 2nd through the 20th.  Cool spells alternated with warm spells, resulting in an average temperature for the month that was very close to normal for most of the area.  There were no record highs or lows.  Early on the morning of the 1st, a Pacific cold front crossed southeast Oregon and southwest Idaho. That afternoon the moist and unstable air which followed the front spawned thunderstorms with gusty outflow winds. Gusts around 60 mph were observed in Ada and Elmore Counties. Damage was minimal, but 5500 customers in north Meridian were without power for awhile.  At Boise, a gust of 62 mph at 3:15 pm MDT, was the strongest gust for May on record going back to 1980.

A high pressure ridge brought a warming trend which started on the 2nd and culminated on the 6th with highs of 89 at Mountain Home, 90 at Boise, and 91 at Ontario.  Highs on the 7th were around 20 degrees lower following a strong Pacific cold front. Highs on the 8th were 10 additional degrees cooler under the cold low pressure trough which followed the front.  Temperatures slowly recovered starting on the 9th, maxing out on the 17th under a high pressure ridge.  Another Pacific cold front crossed the area on the 18th ahead of a cold wet low pressure trough from the Aleutians. By the 20th the trough had settled over the Intermountain Region.  The system produced the first significant rain of the month at Boise and Burns, where nearly half an inch fell on the 22nd. Mountain Home got a third of an inch, but only two tenths of an inch was measured at Ontario. A record rainfall of .32 inch was set at Twin Falls on the 21st, breaking the old record of .23 inch set in 2016.

The trough finally exited into Canada on the 24th, but close on its heels was another trough which brought more rain along with scattered thunderstorms on the 25th and 26th. Around a quarter inch of rain fell at Boise, Burns, and Ontario. Baker City got over a third of an inch, and nearly three-quarters of an inch fell at McCall.  A weak high pressure ridge brought brief warming on the 27th.  During the early morning hours on the 28th, the cold front preceding the last trough of the series crossed our area. No measurable rain accompanied the trough at lower elevations east of the Cascades, but temperatures were 10-15 degrees cooler.  On the 29th a high pressure ridge started a warming trend as it began to build over the region. Temperatures were above normal for the last three days of the month.

precipitation percent of normal May temperature departure from normal May

Winter 2020-2021 in Review

December

Temperatures were above normal in the mountains and below normal at lower elevations due to temperature inversions.  The entire region was drier or much drier than normal. The driest areas were the central Snake River Valley, the Camas Prairie, and the Boise Mountains.   An upper-level high pressure ridge dominated through the 10th, keeping our region dry. Burns was an exception, where a weak upper level low pressure trough brought light snow on the 6th.  From the 11th through the 16th, a temperature inversion resulted in areas of night and morning fog. A trough from the Gulf of Alaska brought light snow on the 13th and 14th. It was too weak to mix out the inversion, as most of its energy crossed the Intermountain Region well south of our area. 

The inversion finally broke as a stronger trough crossed the area on the 17th, bringing 5-10 inches of snow to the mountains, but only light precipitation in the valleys. An exception was the .55 inch rainfall at Jerome, which established a new record for the date.  Mild westerly flow aloft brought a warming trend from the 18th through the 22nd.  High temperature records were tied or broken at several locations on the 21st and 22nd

City New Record Old Record Year
Baker City 56 55 1972
Burns 53 51 1972
Jerome 58 58 1969
McCall 43 43 2019
Twin Falls (21st) 59 53 2014
Twin Falls (22nd) 50 50 2005

A strong Pacific cold front crossed the area on the 22nd, followed by a 10-20 degree temperature drop. Strong northwest winds gusting to 40-50 mph followed the front. A gust of 57 mph was measured north of Andrews in Harney County.  The trough which followed the front produced light precipitation at lower elevations. Moderate amounts of snow fell in the mountains, including 5 inches at Brundage.  

https://twitter.com/NWSBoise/status/1341508962311688197/

Following this system, a strong ridge kept skies mostly clear through Christmas eve.

A weak trough brought mainly light precipitation on the 25th and 26th. Boise was an exception, where a third of an inch of precipitation fell on the 26th, which included half an inch of snow. A few inches of snow fell in the mountains. 

Another temperature inversion formed on the 26th, and locally dense fog returned to the valleys.  With cold air trapped in the valleys, temperatures failed to reach the freezing mark at many of the usually warmer locations in the 28th and 29th

https://twitter.com/NWSBoise/status/1343759866368675842?s=20

The final trough of the month weakened as it moved inland on the 31st, but it was able to drop several inches of snow on the mountains, including 8 inches at McCall and 6 inches at Tamarack.

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January

Temperatures were above normal across the region, and much above normal in the Snake River Valley and parts of southeast Oregon.  Most of southern Idaho and parts of Baker and Harney Counties in Oregon were drier than normal, while the Treasure Valley and west central Idaho received above normal precipitation.  

https://twitter.com/NWSBoise/status/1345922598413062145

Strong westerly flow across the Pacific was charged with abundant moisture as it swept inland with a warm front on the 3rd, resulting in heavy precipitation. Totals from a half inch to an inch of water were common, falling as rain at lower elevations and snow in the mountains. Bogus Basin accumulated 7 inches.  Strong west winds, mostly in the 40 to 50 mph range, followed a cold front on the 4th.  A gust of 63 mph was measured at Wagontire in Harney County.  On the 5th another warm front brought heavy snow to the mountains. Banner Summit got 14 inches. Bogus Basin and Tamarack received 10 inches. Atlanta also got 10 inches. Bogus Basin got 7 additional inches on the 7th as a trough crossed the area. Little if any precipitation fell at lower elevations from the 5th through the 7thOn the 12th a weak but moist trough embedded in the westerly flow brought more snow to the mountains, while relatively light precipitation fell at lower elevations. At Council 7 inches was measured, and 6 inches fell at Brundage and McCall.  A cold front crossed the area on the 13th, followed by wind gusts of 30-45 mph.

High pressure kept the area mostly dry from the 14th through the 20th.  From the 21st through the 26th, weak troughs moving down the coast from the Gulf of Alaska brought only light precipitation to our valleys and a few inches of snow to the higher elevations.  A record low temperature of 10 degrees was set at Twin Falls on the 25th, breaking the old record of 12 set in 2008.  On the 27th a stronger trough centered over southeast Alaska deepened southward just offshore. Southerly flow aloft on the east flank of the trough was felt at the surface as gusty south to southeast winds, generally in the 40 to 50 mph range. A gust of 68 mph was measured at Trail Gulch, 14 miles east-southeast of Hollister.   Also on the 27th, moderate amounts of snow fell in eastern Oregon and west-central Idaho, due mainly to lifting of the air by the mountains. At McCall 9 inches was measured, and 7 inches fell at Midvale. At Huntington in Baker County 5 inches was reported. 

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January

February

February was a month of very active weather. Temperatures were near or above normal at most locations. February is normally warmer than January, but this year it was actually colder than January at Boise, McCall, Mountain Home, and Ontario. It’s not the first time this has happened, but at Boise it was the fourth year in a row.

On average, February is the driest winter month, but this year it was the wettest in the Treasure Valley and eastern Oregon. However, the Boise Mountains, Camas Prairie, and Magic Valley were drier than normal.  The month began with above-normal temperatures under southwest flow aloft ahead of an offshore trough. As the trough moved inland, a cold front crossed our area during the afternoon and evening of the 2nd.  This marked the beginning of a pattern change which would lead to long overdue winter weather for the valleys. Northwest flow aloft developed on the 4th and strengthened during the following days.  On the 5th, a fast-moving trough from the Gulf of Alaska brought a few inches of snow to the mountains, but its main impact was strong west to northwest wind. Gusts of 45-55 mph were common, but by far the strongest wind measured was 92 mph at Soldier Mountain.  Meanwhile on the 3rd, arctic air had plunged south across the Canadian border east of the Rockies. The mountains, and strong northwest winds aloft, kept it out of Idaho. A second invasion of even colder arctic air entered Montana on the 5th. By the 6th, its western margin had stalled along the Montana border.  Meanwhile, the “milder” western portion of the same arctic airmass was drifting south through the mountains of British Columbia. It entered Washington on the 8th and northeast Oregon on the 9th.  The front marking its leading edge reached eastern Oregon and southern Idaho on the 11th.  Moist air streaming inland ahead of an approaching trough was lifted over the cold air north of the front, resulting in snow which became heavier as the trough drew closer on the 12th and crossed our area on the 13th.  Snowfalls of 3 to 6 inches were common in the valleys on the 12th.  Up to 6 more inches fell on the 13th, with heavier accumulations in the mountains. By the time the snow ended, 7 to 10 inches had accumulated in the Treasure Valley. McCall, which nearly always gets way more snow than Boise, also reported a storm total of 10 inches. Totals of 13 inches were measured at both Bogus Basin and Magic Mountain ski areas, while Twin Falls reported only 2 inches.  The 4.4 inches which fell at the Boise airport on the 12th broke the old record for the date of 1.3 inches set in 1966, and the 5.5 inches on the 13th broke the old record of 4.3 inches set in 1995.  

On the 15th another trough from the Pacific brought more snow, with 1 to 4 inches in the valleys and 5 to 10 inches in the mountains. Wind gusts of 40 to 55 mph were observed in Harney County and the Magic Valley.  From the 16th through the 22nd, Pacific systems brought more snow to the mountains but generally light precipitation in the valleys. With afternoon temperatures above freezing, there was little if any snow accumulation in the lower valleys.  On the 23rd, a cold front was followed by a wind event which mainly affected southeast Oregon and areas east of Boise. There were many reports of gusts in the 45 to 55 mph range, but a gust of 67 mph was measured at Twin Falls.  On the 26th, another strong cold front swept across the region. One of the stronger gusts was 59 mph from the west-northwest at the Boise airport. A brief snow squall followed the front, but less than half an inch fell at the airport.  

On the 27th a trough from the Gulf of Alaska brought heavy snow to the mountains. Some of the heavier totals were 12 inches at Mores Creek Summit, 15 inches at Banner Summit, 20 inches at Tamarack, and 22 inches at Brundage.

2021 Idaho Spring Flood and Water Resources Outlook

Spring Flood Potential

Screen Shot 2021-03-23 at 10.28.21 AMThe risk for spring flooding due to snowmelt is near average across most of Idaho. The exceptions are the Big Lost Basin and Little Wood Basin, and the Medicine Lodge, Beaver, and Camas Basin in central and east-central Idaho where the risk is slightly below average due to well below normal snowpack and low soil moisture. Above normal
temperatures in December and January helped limit the snowpack in the low elevations which significantly reduces the snowmelt flood risk during late winter and early spring.

The primary factors in the development of spring flooding are the occurrence of persistent above normal temperatures, and rain on snow precipitation events. Even if mainstem rivers do not reach flood stage, smaller creeks and streams can still overflow their banks. Under the right scenario, spring flooding is possible even for areas that have low snowpack. Additionally, wildfire burn scars can have a significant impact on local flood potential during spring snowmelt.Screen Shot 2021-03-23 at 10.28.15 AM

Water Supply

National Weather Service water supply volume forecasts for the spring and summer of 2021 are near normal for northern Idaho watersheds. Meanwhile, forecasts vary considerably across central and southern Idaho with subpar snowpack and longer term hydrologic drought leading to well below normal forecasts in some areas. Forecasts for the Snake River headwaters region along the Wyoming border and the West Central Mountains are generally 75 to 85 percent of normal. Volume forecasts for the rest of the Central Mountains and southern Idaho watersheds are well below normal ranging from 25 percent to 70 percent of normal. The lowest forecasts are for the Big Wood and Little Wood Basins, and the Big Lost River Basin. Low snowpack and poor streamflows in these areas could lead to water supply concerns, especially for those relying on natural flows. These forecasts may change considerably over the next couple of months since seasonal snow accumulation and rainfall typically occur during March and April.

Temperature and Precipitation

The 2021 Water Year started out well across northern Idaho with above normal precipitation in October, while rather dry conditions prevailed across southern Idaho. Most of the state received near normal or above normal precipitation in November with the exception being near the Canadian border and portions of central Idaho where only 50 to 70 percent of normal occurred. December was a very dry month for the state as a whole. Precipitation in January was improved for some areas but dry conditions continued for the majority of Idaho. A favorable storm track in February brought normal or well above normal precipitation to the majority of the state except for the Northern Panhandle and the Central Mountains east of the Sawtooths which received less than normal precipitation. Temperatures were around normal in October and November with warmer than normal conditions prevailing in December and January. February temperatures were near normal across far southern Idaho and below normal across the remainder of the state.

Screen Shot 2021-03-23 at 10.28.08 AM

Snowpack

As of March 3, mountain snowpack was near normal for most of Idaho. The Clearwater Basin led the way with 113 percent of normal while the Little Wood and Big Lost River Basins were lagging at 66 and 69 percent of normal. Idaho snowpack as a whole typically builds through March and peaks in early April.Screen Shot 2021-03-23 at 10.28.00 AM

Reservoirs

Reservoir storage across Idaho was in good shape as of early March with major reservoir systems holding near average water with the exception of the Wood and Lost River Basins. Across southern Idaho, basin-wide total storage in the Bear River Basin was near 136 percent of average while Southside Snake Basins were near 81 percent of average. Storage in West Central Basins was near 103 percent of average while the Wood and Lost Basins were only 59 percent of average. The Upper Snake River Basin was at 120 percent of average, the Clearwater Basin at 103 percent of average and Panhandle Region was 106 percent of average. Weather patterns, irrigation demand, and flood control needs will drive reservoir operations over the next several months. Wet spring weather or extended periods of above normal temperatures resulting in rapid snowmelt and large reservoir inflows could result in significant fluctuations in reservoir discharge and downstream river levels.

Drought

Drought conditions continue to plague portions of southern Idaho. The Wood River Basins and Big Lost River Basin of south central Idaho are the focus for drought due to subpar snowpack and precipitation dating back to the winter of 2019-2020. Meanwhile, long-term dryness along the Utah and Nevada border is resulting in drought conditions as well. Weather and precipitation for the remainder of winter and this spring will determine whether or not drought conditions improve or deteriorate.

Screen Shot 2021-03-23 at 10.27.52 AM

Long Range Outlook

The outlook for March through May favors below normal temperatures across the Idaho Panhandle and above normal temperatures along the Utah and Nevada border. Elsewhere across the state, the chances for either below, above, or normal temperatures are equal. The precipitation outlook slightly favors above normal precipitation across the Panhandle Region. Elsewhere the precipitation outlook is equal chances for either below, above, or normal precipitation.

Screen Shot 2021-03-23 at 10.27.43 AM

On-line Resources

Water Supply Volume Forecasts…
National Weather Service-Northwest River Forecast Center www.nwrfc.noaa.gov/ws/

National Weather Service-Colorado Basin River Forecast Center
www.cbrfc.noaa.gov/

USDA-Natural Resources Conservation Service
www.nrcs.usda.gov/wps/portal/nrcs/main/id/snow/

Snowpack Information…
National Weather Service-Northwest River Forecast Center
www.nwrfc.noaa.gov/snow/

National Weather Service-National Operational Hydrologic Remote Sensing Center
www.nohrsc.noaa.gov/

USDA-Natural Resources Conservation Service
www.nrcs.usda.gov/wps/portal/nrcs/main/id/snow/

Reservoir Storage…
Bureau of Reclamation Reservoir Storage
www.usbr.gov/pn/hydromet/select.html

USDA-Natural Resources Conservation Service
www.wcc.nrcs.usda.gov/basin.html

Drought Information…
U.S. Drought Portal
www.drought.gov

Peak Flow Forecasts…
Northwest River Forecast Center
www.nwrfc.noaa.gov/peak/

Colorado Basin River Forecast Center
www.cbrfc.noaa.gov/rmap/peak/peaklist.php

Temperature and Precipitation Outlook…
Climate Prediction Center
www.cpc.ncep.noaa.gov/

Idaho 2020 Spring Flood and Water Resources Outlook

Spring Flood Potential

swe2020The risk for spring flooding due to snowmelt is near normal across most of Idaho. The exception is the Big Lost Basin and Wood River Basins where the risk is below normal due to well below normal snowpack and low soil moisture.  Relatively warm winter temperatures and a rather dry February have limited the snowpack in the low elevations which significantly reduces the snowmelt flood risk during late winter and early spring.

The primary factors in the development of spring flooding are the occurrence of persistent above normal temperatures, and rain on snow precipitation events. Even if mainstem rivers do not reach flood stage, smaller creeks and streams can still overflow their banks. Under the right scenario, spring flooding is possible even for areas that have low snowpack. Additionally, wildfire burn scars can have a significant impact on local flood potential during spring snowmelt.

Water Supply

The water supply runoff volume forecasts for the spring and summer of 2020 are near average for northern Idaho watersheds. Meanwhile, forecasts vary considerably across central and southern Idaho.  Forecasts for the Snake River headwaters region and along the Utah and Nevada border generally indicate near normal runoff volumes. Forecasts for the Middle Snake River and Central Mountain watersheds indicate below or well below normal runoff volumes. The lowest runoff volume forecasts are for the Big Wood and Little Wood basins, ranging from 33 to 55 percent of normal. Low streamflows across portions of the Central Mountains could lead to water supply concerns for those relying on natural flows. These forecasts may change considerably since seasonal snow accumulation and rainfall typically occur during March and April.ws2020

Temperature and Precipitation

A wet September closed out the 2019 Water Year, but very dry conditions dominated through the first quarter of the 2020 Water Year. Precipitation for October through December was only 40 to 70 percent of average for most of the state with the driest conditions across the Central Mountains and southern Idaho. The January storm track brought above normal precipitation to most of Idaho with the exception of the Wood River Basins and Big Lost Basin where precipitation was below normal. In February, the Clearwater and Lemhi Basins, the Salmon River Basin, and areas along the Wyoming border had near normal or above normal precipitation while the rest of the state was below normal. Water Year to date precipitation in general is normal to below normal for northern Idaho and areas along the Wyoming, Utah, and Nevada borders. For the Snake Plain and Central Mountains, Water Year precipitation is below or well below normal. After a cold October where mean temperatures were 5 to 10 degrees below normal for most of the state, above normal temperatures have dominated for the 2020 Water Year.

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Snowpack

As of March 5, mountain snowpack was near normal for most of Idaho.  The Boise River Basin was lagging at 84 percent of normal. The Big Wood and Little Wood River Basins and Big Lost River Basin had the lowest snowpack percentages ranging from 56 to 68 percent of normal.  Idaho snowpack as a whole typically builds through March and peaks in early April.

swe2020per

Reservoirs

Reservoir storage across Idaho was in good shape as of early March with major reservoir systems holding near average or well above average water. Across southern Idaho, reservoir storage in the Bear River Basin and Southside Snake River Basins was 144 to 153 percent of average. Storage in West Central Basins, Wood and Lost Basins, and the Upper Snake River Basin ranged from 110 to 168 percent of average. Meanwhile, reservoir storage in the Clearwater and Panhandle Regions was 96 to 104 percent of average. Weather patterns, irrigation demand, and flood control needs will drive reservoir operations over the next several months. Wet spring weather or extended periods of above normal temperatures resulting in rapid snowmelt could result in significant increases in reservoir outflows and river levels.

Drought

After a drought free start to the 2020 Water Year, dry fall conditions followed by low snowpack led to the development of drought conditions across portions of the Central Idaho Mountains. Weather and precipitation for the remainder of winter and this spring will determine whether or not drought conditions improve or deteriorate.

drought

Long Range Outlook

The outlook for March through May favors above normal temperatures across the south half of Idaho while chances for either below, above, or normal temperatures are equal across the north. The precipitation outlook slightly favors above normal precipitation along the Wyoming border, otherwise the probabilities are not shifted one way or another for the rest of the state.

MAM2020

MAM2020pOn-line Resources

Water Supply Volume Forecasts…
National Weather Service-Northwest River Forecast Center
www.nwrfc.noaa.gov/ws/

National Weather Service-Colorado Basin River Forecast Center
www.cbrfc.noaa.gov/

USDA-Natural Resources Conservation Service
www.nrcs.usda.gov/wps/portal/nrcs/main/id/snow/

Snowpack Information…
National Weather Service-Northwest River Forecast Center
www.nwrfc.noaa.gov/snow/

National Weather Service-National Operational Hydrologic Remote Sensing Center
www.nohrsc.noaa.gov/

USDA-Natural Resources Conservation Service
www.nrcs.usda.gov/wps/portal/nrcs/main/id/snow/

Reservoir Storage…
Bureau of Reclamation Reservoir Storage
www.usbr.gov/pn/hydromet/select.html

USDA-Natural Resources Conservation Service
www.wcc.nrcs.usda.gov/basin.html

Drought Information…
U.S. Drought Portal
www.drought.gov

Peak Flow Forecasts…
Northwest River Forecast Center
www.nwrfc.noaa.gov/peak/

Colorado Basin River Forecast Center
www.cbrfc.noaa.gov/rmap/peak/peaklist.php

Temperature and Precipitation Outlook…
Climate Prediction Center
www.cpc.ncep.noaa.gov/

2019 Idaho Water Year Summary

Overview:

The 2019 Water Year can be characterized as a year with a lot of variability, which is quite normal when talking about weather in Idaho.  Overall, it was a good year with respect to moisture as the majority of the state received normal or above normal precipitation. The exceptions were east-central Idaho and the panhandle region where water year precipitation was below normal. With respect to temperature, mean temperatures across the state were close to normal.

April 1 snowpack percentages were above normal for central and southern Idaho and a little below normal across northern Idaho. Northern Idaho and areas near the Nevada border received the better snow through the first half of the accumulation season while most of central and southeast Idaho lagged considerably.  In February, a series of cold and moisture storm systems brought abundant snow to the state which more than made up for the drier conditions earlier in the water year.

Springtime was rather typical with periods of warm and dry weather followed by cool and wet conditions.  Except for portions of east-central Idaho and the panhandle, spring precipitation was normal or above normal across the state. Above normal temperatures prevailed across northern Idaho during the spring while temperatures across central and southern Idaho were generally near normal or below normal. A healthy snowpack and favorable spring weather produced good spring runoff with most reservoirs topping off and adequate water supply for the state.

Summertime temperatures and precipitation were close to normal across Idaho. With the exception of the panhandle region, normal to above normal streamflows were sustained through the spring and summer months. Major irrigation projects serving Idaho ended the 2019 Water Year on a good note with normal or above normal carryover.

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Precipitation:

Well below normal precipitation occurred across most of the central mountains and far southwest Idaho during the 1st quarter (Oct.-Dec. 2018) of the 2019 Water Year. Meanwhile, the rest of the state varied from a little below to a little above normal. January and March were quite dry across the state as a whole, but sandwiched in between was an exceptionally wet February with precipitation 150 to 300 percent of normal for the majority of the state. April was another wet month, highlighted by widespread river and small stream flooding across much of west-central Idaho April 7-13 when 2 to 5 inches of rain fell on top of snowmelt. Above normal precipitation fell across southern Idaho in May while most of central and northern Idaho saw below normal precipitation. June was a rather dry month for the state followed by near normal precipitation for most of the state through the summer. The water ended on a high note with above normal precipitation in September, helping recharge soils after the moisture sapping summer months.

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Temperature:

Mean temperatures for the 2019 Water Year were near normal for most Idaho. During the 1st quarter (Oct.-Dec. 2018) of the water year mean temperatures were generally above normal for northern and central Idaho, while most of southern Idaho experienced normal to below normal temperatures. Typical monthly variability occurred during the January through June period. Cold temperatures in February and March were vital in building and maintaining a good snowpack while cool temperatures across southern Idaho in May and June resulted in a slower snowmelt and good streamflows heading into the warm and dry season.  Summertime temperatures as a whole were close to normal.Capture

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Snowpack:

Overall it was a good snow year for Idaho.  The storm track favored northern and far southwest Idaho the early part of the accumulation season with January 1 snowpack percentages ranging from 88 to 117 percent of normal. Elsewhere, snowpack lagged considerably by January 1, especially across the central mountains where percentages ranged from 44 to 73 percent of normal. Subpar snowpack was the rule through the month of January but a favorable storm track in February brought a series of cold and wet storm systems to the region. From February 1 to March 1, snowpack increased by 25 to 60 percentage points across most of central and southern Idaho while gains of 10 to 15 percent occurred across northern Idaho. By early April, when Idaho’s overall snowpack typically peaks, snowpack percentages from the Salmon River Basin south to the Nevada and Utah border ranged from 106 to 145 percent of normal while northern Idaho basins ranged from 85 to 95 percent of normal. This set the stage for an adequate water supply through the growing season.

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Streamflow:

A warm and very dry summer in 2018 left streamflows in Idaho below to much below normal in many river basins to start the 2019 Water Year, particularly across the panhandle, west-central mountains, and southern Idaho.  Streamflow percentiles varied considerably from basin through the core winter months. The snowmelt season and good spring precipitation brought robust streamflows to the state in April. Heavy rain combined with snowmelt caused main stem river flooding, flash flooding, and small stream flooding across much of central Idaho April 7-13 with record or near record crests observed on a number of waterways. Favorable spring weather resulted in a nearly ideal melt of the mountain snowpack and extended healthy streamflows through the summer for southern and central Idaho. Across the panhandle region, lower snowpack and drier spring weather resulted in below normal streamflows in many basins from late spring through summer.

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Reservoirs:

Reservoir storage carryover to start the 2019 Water Year was near normal. A healthy snowpack by early April and good spring runoff allowed major reservoir systems to either fill or come close to filling.  Flood control releases were necessary on some reservoir systems during spring runoff resulting in high flows on some rivers. As the irrigation season hit full stride reservoir systems began drawing down in mid to late June. By the end of the growing season reservoir storage was normal to above normal for almost all reservoirs across the state with good carryover for the 2020 Water Year.

CaptureCaptureDrought:

Moderate to severe drought plagued much of the panhandle region along with west central and southern Idaho through the 1st quarter (Oct.-Dec. 2018) of the 2019 Water Year. However, abundant snowfall and good spring precipitation erased drought conditions by early April. Moderate to severe drought returned to the panhandle region over the summer while central and southern Idaho remained drought free. Minimal drought across the state contributed to a rather quiet wildfire season.

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2019 Idaho Spring Flood and Water Resources Outlook

Spring Flood Potentialswe38

The potential for spring flooding due to snowmelt is slightly elevated for much of the central Idaho Mountains, particularly in the Big Lost and Wood River Basins, as well as the Upper Boise, Payette, and Weiser Basins. For the remainder of the state the spring flood potential due to snowmelt is average.

The primary factors in the development of spring flooding are the occurrence of persistent above normal temperatures, and rain on snow precipitation events. Even for areas that may have low snowpack, spring flooding is possible under the right scenario. Additionally, wildfire burn scars can have a significant impact on local flood potential during spring snowmelt.

Water Supplywatersupply

The water supply forecast for the spring and summer of 2019 is near average for the majority of watersheds across Idaho. Exceptions are some above average forecasts in the central mountains and Upper Snake Region, and some below average forecasts along the southern border and in the Idaho Panhandle.

Temperature and Precipitation

Wet weather at the beginning of the Water Year (Oct. 2018) was beneficial in recharging the soil moisture after a very dry and warm summer. However, fall precipitation as a whole was below normal across the state and subpar precipitation continued through most of January. February precipitation was exceptional across west-central and southern Idaho with much of the area receiving 200 to 300 percent of normal. February temperatures were well below normal across the state, especially in northern Idaho. Precipitation for the 2019 Water Year through February has been normal or above normal for most of central and southern Idaho, and a little below normal for most of the Panhandle Region. Mean temperatures for the 2019 Water Year have been near normal.

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Snowpack

As of March 8, snowpack from the Salmon River Basin to the southern border was above normal. The highest percentages were in the Big Lost Basin, Wood River Basins, Payette Basin, and Weiser Basin, ranging from 133 to 152 percent of median. Northern Idaho snowpack varied from 89 to 100 percent of median for the Northern Panhandle, Spokane, and Clearwater Basins. Idaho snowpack as a whole typically builds through March and peaks in early April.

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Reservoirs

Reservoir storage across Idaho is in good shape as of early March with major reservoir systems holding near average or above average water. Across southern Idaho, reservoir storage in the Bear River Basin was near 140 percent of average and Southside Snake River Basin storage was near 95 percent of average. The Upper Snake Basin and Wood River and Lost River Basins was near 125 percent of average. Storage in West Central Basins was near 98 percent of average, and the Clearwater and Panhandle Regions were near 97 and 104 percent of average. Weather patterns, irrigation demand, and flood control needs will drive reservoir operations over the next several months. Wet spring weather or extended periods of above normal temperatures resulting in rapid snowmelt could result in significant increases in reservoir outflows and river levels.

Drought

Moderate to severe drought plagued portions of Idaho through the fall and early winter, especially across southern Idaho and near the Utah and Nevada border. Drought conditions were eased by well above normal precipitation and a large increase in mountains snowpack during February. The latest U.S. Drought Monitor shows lingering drought across far southwest Idaho and along the Utah border. Weather and precipitation for the remainder of winter and this spring will determine whether or not drought conditions continue to improve or deteriorate.

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Long Range Outlook

The outlook for March through May favors above normal temperatures across Idaho. The precipitation outlook slightly favors wetter than normal conditions over far southeast Idaho, but does not shift the probabilities one way or another for the rest of the state.

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On-line Resources

Water Supply Volume Forecasts…
National Weather Service-Northwest River Forecast Center www.nwrfc.noaa.gov/ws/
National Weather Service-Colorado Basin River Forecast Center www.cbrfc.noaa.gov/
USDA-Natural Resources Conservation Service www.nrcs.usda.gov/wps/portal/nrcs/main/id/snow/

For a comprehensive report on each river basin in Idaho, see the Natural Resources Conservation Service report:   Idaho Water Supply Outlook Report March 1, 2019

Snowpack Information…

National Weather Service-Northwest River Forecast Center www.nwrfc.noaa.gov/snow/
National Weather Service-National Operational Hydrologic Remote Sensing Center www.nohrsc.noaa.gov/
USDA-Natural Resources Conservation Service www.nrcs.usda.gov/wps/portal/nrcs/main/id/snow/

Reservoir Storage…

Bureau of Reclamation Reservoir Storage  www.usbr.gov/pn/hydromet/select.html
USDA-Natural Resources Conservation Service https://www.wcc.nrcs.usda.gov/basin.html

Drought Information…

U.S. Drought Portal www.drought.gov

Peak Flow Forecasts…

Northwest River Forecast Center www.nwrfc.noaa.gov/peak/
Colorado Basin River Forecast Center www.cbrfc.noaa.gov/rmap/peak/peaklist.php

Temperature and Precipitation Outlook…

Climate Prediction Center  www.cpc.ncep.noaa.gov/

2018 Idaho Water Year Summary

Overview:

The 2018 Water Year was pretty good for Idaho overall. The hydrologic system was still benefiting from the extreme moisture received the previous year which provided excellent reservoir carryover and above normal streamflow through the fall and winter.  

Precipitation patterns favored northern Idaho and portions of the Upper Snake Basin in eastern Idaho, resulting in normal or above normal precipitation for these regions. By winter’s end, basin snowpack percentages for these areas were around 120 percent of median. Large snowpacks in adjacent areas of British Columbia and western Montana helped set the stage for spring flooding across the Panhandle region.  In contrast, precipitation was subpar for much of southern Idaho with some locations receiving only 50 to 70 percent of normal. The Owyhee Basin in far southwest Idaho had the lowest snowpack percentage in the state at 45 percent of median.

Dry and very warm conditions through the summer brought a return of drought conditions to the Panhandle region while drought conditions expanded near the Nevada and Utah border.  Streamflows fell below normal in a number of basins from late spring through summer as very dry weather persisted.

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Temperature:

Mean temperatures for the 2018 Water Year were above normal for almost the entire state. The southern half of Idaho, particularly the higher elevations, experienced the greatest anomalies with much of the area in the top 10 percentile.

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Fall and winter temperatures were normal or slightly below normal for the northern half of Idaho. Meanwhile, fall temperatures across the southern half of Idaho had a warm tendency. Springtime brought above normal temperatures to the entire state which spurred a strong snowmelt runoff for northern Idaho and portions of eastern Idaho. Summertime temperatures were generally around normal across the northern half of the state while southern Idaho experienced above normal temperatures.

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The storm track favored northern and central Idaho during the first quarter of the 2018 Water year resulting in normal to above normal fall precipitation across the northern half of the state.  Most of southern Idaho wasn’t as fortunate and started the water year off rather dry. Precipitation patterns continued to favor northern and central Idaho along with much of eastern Idaho during the winter and early spring. This served to build a healthy snowpack in these areas and set the stage for a good runoff season.  Across southwest Idaho winter precipitation lagged considerably which raised concerns for drought and agricultural water supply. By the end of June, hot and dry weather typical of summer settled in across the state and very little precipitation was received through the remainder of the water year.

Precipitation:prec1

 

Although a small percentage of annual precipitation occurs during the summer, it was an exceptionally dry period across the state. Almost all of Idaho was in the bottom 10 percentile for July through September precipitation and many areas experienced near-record dryness. For example, Lewiston experienced its 6th driest July through September on record.

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Snowpack:

By late winter a robust snowpack accumulated across northern Idaho, portions of the Upper Snake Basin in eastern Idaho, and adjacent areas of western Montana and British Columbia.  In contrast, much of south-central and southwest Idaho missed out on a lot of the winter storms resulting in a subpar snowpack, especially near the Utah and Nevada border. By early April, when Idaho’s overall snowpack typically peaks, basin percentages were around 120 percent of median from the Panhandle region south across the Clearwater Basin, and across portions of the Upper Snake Basin. In south-central and southwest Idaho, snowpack percentages dropped off to around 70 percent of median or less. The Owyhee Basin had the lowest early April percentage at 47 percent of median.

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Streamflow:

2017 set the stage for the 2018 runoff season. With the exception of a couple basins, streamflows for the 2018 Water Year started strong and were normal to much above normal through the fall, winter, and spring. Abundant water in the hydrologic system kept water flowing in some streams that are typically dry during the fall and winter, such as lower reaches of the Big Lost River in eastern Idaho.  Rapid melting of the large snowpack and full reservoir systems pushed spring snowmelt flows to much above normal for portions of the Panhandle, Central Mountains, and upper Snake River regions. As a result, spring flooding occurred across portions of the state, especially the Panhandle region. Despite the strong spring runoff for much of Idaho, streamflows fell below normal in many basins from late spring through summer.

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Reservoirs:

Reservoir storage got a head start due to excellent carryover from the previous water year and most major reservoir systems were able to fill.  Large snowpack in British Columbia, western Montana, and northern Idaho resulted in near-record or record high runoff prompting large flood control releases on some river systems. Even in parts of southwest Idaho where lower snowpack resided, large reservoir releases were necessary to accommodate high snowmelt inflows. As the irrigation season hit full stride reservoir systems were drawn down near a normal pace and ended the water year with near average carryover for the next water year.

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Drought:

Abundant fall precipitation erased drought conditions during early stages of the 2018 Water Year. However, above normal temperatures, subpar snowpack, and limited spring rains across the south allowed drought to creep back into the picture by late spring over southwest Idaho.  As has been the trend in recent years, above normal temperatures and below normal precipitation dominated through the summer. This allowed drought to expand across southern Idaho into the West Central Mountains as well as the Panhandle Region.

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2018 Idaho Spring Flood and Water Resources Outlook

M1The potential for spring flooding due to snowmelt is elevated for portions of eastern Idaho and northern Idaho. The spring flood risk for the rest of the state is average or below average. There remains an elevated risk of spring flooding across portions of the Upper Snake Basin due to above average mountain snowpack. This includes the mainstem Snake River above American Falls Reservoir and the Henrys Fork near Rexburg. An elevated flood risk also exists across the Panhandle Region where some of the highest snowpack percentages in the state reside. Elsewhere across Idaho, early May snowpack conditions suggest a low probability of spring flooding due to snowmelt. The primary factors in the development of spring flooding are the occurrence of persistent above normal temperatures, and rain on snow precipitation events. Even for areas where drought conditions exist, or that have low snowpack, spring flooding is possible under the right conditions. Additionally, burn scars can have a significant impact on local flood potential during spring snowmelt and rain events.M2

Water Supply

National Weather Service April through September water supply volume forecasts for northern and eastern Idaho, and the mainstem Snake River across southern Idaho range from 115 to 150 percent of average. Elsewhere, water supply forecasts are 85 to 110 percent of average for most of the Central Mountains and only 30 to 70 percent of average for south central and southwest Idaho. The lowest forecast percentages are in far southwest Idaho in the Bruneau and Owyhee River Basins at less than 40 percent of average.M3

Temperature and Precipitation

As of May 1, temperatures for the 2018 Water Year have been average or slightly below average across the northern half of the state while most of southern Idaho has experienced a little above average temperatures. Water Year precipitation was above average for the Panhandle, Spokane, and Clearwater Basins. The Clearwater Basin had the greatest anomalies in the state at 130 to 150 percent of average. The Salmon Basin and Upper Snake Basin near the Wyoming border were generally 100 to 130 percent of average. Elsewhere in southern and southwest Idaho the Water Year precipitation was mostly in the 70 to 90 percent of average range with pockets of around 60 percent.

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Snowpack

As of May 2, the highest snowpack percentages in the state ranged from 138 to 145 percent of median in the Clearwater, Spokane and Northern Panhandle Region. Not far behind were basins in eastern Idaho such as the Little Lost and Birch Basins, Henrys Fork, Teton, and Snake Basin above Palisades at 120 to 130 percent. The Payette, Boise, Salmon, Wood and Lost Basins ranged from 74 to 109 percent of median. Southside Snake River Basins along the Nevada border were a mixed bag ranging from a low of 17 percent of median in the Owyhee Basin to a high of 86 percent of median in the Raft River Basin. Northern Idaho basins and those near the continental divide reached their peak snowpack in mid to late April. The low elevation snow is gone and melting of the high elevations will increase over the next few weeks as temperatures warm.

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Reservoirs

Reservoir storage across Idaho is in good shape. As of May 1, storage in major reservoir systems throughout Idaho was 100 percent of average or greater, except where systems were heavily drafted to make space for anticipated snowmelt runoff. Weather patterns and irrigation demand will continue to drive operations through late spring as reservoirs are topped off. Wet spring weather or extended periods of warmth resulting in rapid snowmelt and large reservoir inflows could result in significant fluctuations in reservoir discharge and downstream river levels.

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Drought

Idaho is currently free from any official drought classification according to the U.S. Drought Monitor. However, below average precipitation for the Water Year and poor snowpack has put much of southern Idaho in the abnormally dry category. Weather and precipitation for the remainder of spring will determine whether or not conditions improve or deteriorate for areas experiencing the dryness. Good reservoir storage will ease drought concerns for those served by major storage projects.

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Long Range and Seasonal Outlooks

The outlook for May favors above normal temperatures across the state. The May precipitation outlook favors above normal precipitation for southeast Idaho and below normal precipitation for the northwest half of the state. The seasonal outlook for June through August favors above normal temperatures and below normal precipitation.

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On-line Resources

Water Supply Volume Forecasts…
National Weather Service-Northwest River Forecast Center www.nwrfc.noaa.gov/ws/
National Weather Service-Colorado Basin River Forecast Center www.cbrfc.noaa.gov/
USDA-Natural Resources Conservation Service www.nrcs.usda.gov/wps/portal/nrcs/main/id/snow/

Snowpack Information…
National Weather Service-Northwest River Forecast Center www.nwrfc.noaa.gov/snow/
National Weather Service-National Operational Hydrologic Remote Sensing Center www.nohrsc.noaa.gov/
USDA-Natural Resources Conservation Service www.nrcs.usda.gov/wps/portal/nrcs/main/id/snow/

Reservoir Storage…
Bureau of Reclamation Reservoir Storage www.usbr.gov/pn/hydromet/select.html
USDA-Natural Resources Conservation Service www.wcc.nrcs.usda.gov/basin.html

Drought Information…
U.S. Drought Portal www.drought.gov
U.S. Drought Monitor www.droughtmonitor.unl.edu/
National Drought Mitigation Center www.drought.unl.edu/

Peak Flow Forecasts…
Northwest River Forecast Center www.nwrfc.noaa.gov/peak/
Colorado Basin River Forecast Center www.cbrfc.noaa.gov/rmap/peak/peaklist.php

Temperature and Precipitation Outlook…
Climate Prediction Center www.cpc.ncep.noaa.gov/

 

Spring Snowpack and Flood Outlook – April Update

The potential for spring flooding due to snowmelt in 2018 is well above average across most of northern and eastern Idaho and Montana. Meanwhile, the spring flood potential is slightly below average for southwest Idaho and southeast Oregon.

The storm track over much of the winter brought above normal precipitation values to much of the region. However, it was a tale of two cities on the northern end (cooler) and the southern end of the storm track. Cooler conditions on the northern portion of the storm track led to above normal snow values across Washington, northern Idaho, and western Montana, while the southern end of the storm track brought warmer conditions to Oregon, southwest Idaho, Nevada and Utah, leading to a below normal snow pack. The following graphic illustrates the amount of snow pack compared to normal for mid April.

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Idaho Spring Flood and Water Resources Outlook

The potential for spring flooding due to snowmelt is slightly elevated for portions of eastern and north central Idaho. The spring flood risk for the rest of the state is average to below average. SWE-2-12

Good soil moisture recharge from autumn rains and well above average reservoir storage has resulted in a slightly elevated threat of spring flooding along the mainstem Snake River in eastern Idaho, and along smaller tributaries above Idaho Falls. Spring flood risk is also slightly elevated in the Clearwater Basin which is currently holding one of the greatest snowpack percentages in the state. Elsewhere, the absence of low elevation snow and areas of below average mid elevation snow suggest an average or below average spring flood threat.

The primary factors in the development of spring flooding are the occurrence of persistent above normal temperatures, and rain on snow precipitation events. Even for areas that have low snowpack, spring flooding is possible under the right scenario. Additionally, wildfire burn scars can have a significant impact on local flood potential during spring snowmelt.

Precipitation and Temperature

As of early February, Water Year precipitation was near normal or above normal for the Panhandle, Spokane, Clearwater, and Salmon Basins, as well as the Upper Snake Basin near the Wyoming border. The Clearwater Basin had the greatest anomalies at 130 to 150 percent of  average. Aside from the Snake River headwaters region, Water Year  precipitation across southern Idaho stood at 60 to 80 percent of  average with south side Snake River Basins having the lowest  percentages.  Average temperatures for the Water Year have been above average for almost the entire state, especially across southern Idaho. 1

 

Snowpack

As of February 12, the highest snowpack percentages in the state were 114 and 116 percent of median in the Clearwater Basin and the Upper Snake above Palisades. Percentages were 91 to 107 percent of median for basins along the Montana border in eastern Idaho, and the Salmon, Spokane, and Panhandle Basins. Elsewhere in south central and southeast Idaho the snowpack was 57 to 81 percent of median, decreasing to 33 to 49 percent of median in the Owyhee and Bruneau Basins in southwest Idaho. Daily snowpack readings indicate record low levels for a handful of SNOTEL locations in southern Idaho.  Mountain snowpack in Idaho typically builds through March. Early April snow conditions will be pivotal to water supply conditions through the summer.  23

Reservoirs

Reservoir storage across Idaho is in good shape. Major reservoir systems across the northern half of the state were holding near average or above average storage as of February 1. Across the southern half of the state, with the exception of Brownlee at 85 percent and Mann Creek at 45 percent of average, most major projects had well above average storage which is great news considering the below average snowpack in many basins. Weather patterns, irrigation demand, and flood control needs will drive reservoir operations over the next several months. Wet spring weather or extended periods of above normal temperatures resulting in rapid snowmelt could result in significant increases in reservoir outflows and river levels.

Drought

After record setting precipitation and snowpack last year, abnormally dry conditions have returned to portions of west central and southern Idaho. Weather and precipitation for the remainder of winter and this spring will determine whether or not conditions improve or deteriorate for areas experiencing short term dryness. Good reservoir carryover will help ease drought concerns for those served by major storage projects.

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Long Range Outlook

The outlook through the end of February favors below normal temperatures and normal or below normal precipitation for the state. The outlook for March, April, and May favors below normal temperatures for the Panhandle, and above normal temperatures across far southern Idaho. The precipitation outlook for March, April, and May slightly favors wetter than normal conditions for the Panhandle, but does not shift the probabilities one way or another for the rest of the state.

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Water Supply Forecast

National Weather Service April through September water supply volume forecasts vary from 90 to 135 percent of average for most of the central Idaho mountains and north across the Clearwater and Panhandle regions. In southern Idaho, forecasts for the Big Lost Basin, the mainstem Snake River and tributaries above American Falls range from 80 to 125 percent of average, with the exception of Willow Creek near Ririe with a forecast of 38 percent of average. Forecasts for the rest of southern Idaho range from 39 to 73 percent of average with the lowest percentages in southwest Idaho. These forecasts may change considerably over the next couple of months since seasonal snow accumulation and rainfall typically occur during February, March, and April.

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Online Resources

Water Supply Volume Forecasts…
National Weather Service-Northwest River Forecast Center www.nwrfc.noaa.gov/ws/

National Weather Service-Colorado Basin River Forecast Center
www.cbrfc.noaa.gov/

USDA-Natural Resources Conservation Service
www.nrcs.usda.gov/wps/portal/nrcs/main/id/snow/

Snowpack Information…

National Weather Service-Northwest River Forecast Center
www.nwrfc.noaa.gov/snow/

National Weather Service-National Operational Hydrologic Remote Sensing Center
www.nohrsc.noaa.gov/

USDA-Natural Resources Conservation Service
www.nrcs.usda.gov/wps/portal/nrcs/main/id/snow/

Reservoir Storage…
Bureau of Reclamation Reservoir Storage
www.usbr.gov/pn/hydromet/select.html

USDA-Natural Resources Conservation Service
www.wcc.nrcs.usda.gov/basin.html

Drought Information…
U.S. Drought Portal
www.drought.gov

U.S. Drought Monitor
www.droughtmonitor.unl.edu/

National Drought Mitigation Center
www.drought.unl.edu/

Peak Flow Forecasts…
Northwest River Forecast Center
www.nwrfc.noaa.gov/peak/

Colorado Basin River Forecast Center
www.cbrfc.noaa.gov/rmap/peak/peaklist.php

Temperature and Precipitation Outlook…
Climate Prediction Center
www.cpc.ncep.noaa.gov/