2021

Fall 2021 Season in Review

Overall, fall was warmer and wetter than normal. Temperatures were generally above normal in September and October, and above or much above normal in November. September precipitation ranged from above to below normal. In October the entire area was wetter or much wetter than normal. The trend reversed in November, with below normal precipitation nearly everywhere.

September

September 2021 precipitation

September 2021 temperature

Temperatures were above normal over more than half of the area. Precipitation presented a patchwork pattern, reflecting the predominantly convective nature of the heavier precipitation events.

A weak upper level low pressure trough hanging over the northwest U.S. kept temperatures 5-10 degrees below normal through the 3rd.

A warming trend commenced on the 4th as an upper level high pressure ridge built over the Intermountain Region. Temperatures topped out at 10-15 degrees above normal on the 9th. Wildfire smoke limited heating to some extent, but temperatures still managed to reach the 93 at Baker City, Burns, and Twin Falls, 94 at Ontario, 95 at Jerome, and 98 at Boise. Except for Ontario, these were all records for the date.

The high the following day was 20 degrees cooler as a Pacific cold front and upper level trough crossed our area. Many locations experienced wind gusts in the 40-50 mph range as the front passed.

Following the trough, temperatures remained cool on the 11th. Slightly warmer westerly flow aloft from the 12th through the 15th provided highs in the lower 80s at lower elevations…near normal for mid September.

Another Pacific cold front passed on the evening of the 15th, lowering highs on the 16th by around 10 degrees.

Southwest flow aloft ahead of a much stronger Pacific cold front added 10-15 degrees to highs on the 17th and 18th. As the front passed, gusts of 40 to 55 mph were measured at many locations. Precipitation with the front was generally light, but a bit more fell on the 19th under the upper level trough which followed the cold front. Highs on the 19th and 20th were mostly in the 50s and 60s, the coolest of the season so far.

A high pressure ridge brought a warming trend on the 21st and 22nd. Warming was briefly interrupted on the 23rd as a weak trough crossed our area. The ridge strengthened behind the trough, and highs rose into the 80s at lower elevations from the 25th through the 27th.

During the afternoon of the 27th, desert winds from the south brought dry air with humidity dropping into the single digits at several locations.

On the 27th gusts of 45-50 mph were reported at many locations following a strong cold front. On the 28th the winterlike trough following  the front lowered snow levels to around 5000 feet. At Bogus Basin, nearly 3 inches had accumulated at the snow stake just before 11 am MDT.

Temperatures in the north Pacific air that afternoon were as much as 30 degrees cooler than the previous day`s highs.

By sunrise on the 29th, cool air and clear skies allowed the temperature to drop into the mid and upper 30s in the Treasure and Magic Valleys. Since winds were light, that was cold enough for patchy frost. McCall froze with 29 degrees, but the coldest readings were in eastern Oregon, with 23 at Baker City and 20 at Burns.

The month ended under a high pressure ridge which brought sunny skies and near normal temperatures.

October

October 2021 prepitation October 2021 temperature

October was noteworthy for heavy rainfall events. Precipitation was over 150 percent of normal across wide areas of southeast Oregon and southwest Idaho. Significant areas had over 300 percent of normal.

During the first five days of the month, temperatures rose to summerlike values under a high pressure ridge. On the 4th, southwest flow aloft ahead of a low pressure trough raised the temperatures into the 80s at many valley locations.

After reaching the coast, the trough deepened far enough south on the 6th and 7th to pick up tropical moisture. As the system moved inland on the 8th, precipitation was hit and miss. Ontario reported no rain, only .04 inch was measured at Baker City, and Burns got only a trace. But Boise picked up .46 inch, Jerome .65 inch, McCall .63 inch, and Twin Falls received a total of .71 inch on the  7th and 8th.

Cool showery weather persisted through the 10th.

A colder trough moved inland on the 11th. Temperatures averaged 10-15 degrees below normal through the 14th. There was only light of precipitation.

During the next couple of days, a ridge brought a warming trend. As it shifted east, southwest flow ahead of the next Pacific cold front raised the temperature from the upper 60s to the mid 75s on the 17th.  Cool air behind the front lowered highs on the 18th by 10-15 degrees.

By the 19th a weak ridge had again built over the Intermountain Region.

Southwest flow aloft intensified as the next trough approached the coast. Like the system earlier in the month, it had entrained tropical moisture. As it moved inland over the northwest states on the 22nd, rainfall totals ranged from a quarter inch to over half an inch in the valleys. McCall got .88 inch.

Another even deeper trough from the Aleutians intensified as it approached the coast on the 24th, resulting in even stronger southwest flow from the tropics to the Pacific Northwest and Northern Rockies by way of California.

This cool-season phenomenon is known as an “atmospheric river” or AR. It is a narrow region of poleward transport of moisture, where strong flow taps very moist air from the tropics and carries it to higher latitudes. An intense low pressure system developing on the west side of the AR, plus the associated cold front and warm front, lend lift to the extremely moist and potentially unstable air. So the northern Sierra Nevada, Cascade, and Owyhee ranges, which usually create “rain shadows”, have limited effect on the amount of rain falling downwind.

Heavy precipitation was widespread on the 24th and 25th. By far the heaviest amounts fell in the Boise mountains, where totals exceeding 2 inches were common. The winning totals were 3.05 inches 4 miles southwest of Featherville, and 4.83 inches 1 mile south-southeast of Featherville.

The 24th was not only wet, but very windy. Gusts over 40 mph were common. Several locations experienced gusts over 50 mph. A gust of 65 mph was measured at a location 6 miles north of Wagontire in Harney County, Oregon. In Washington County, Idaho, a gust of 64 mph was measured 15 miles west-northwest of Cambridge.

The ridge warmed temperatures to 10-15 degrees above normal on the 28th and 29th. Then another Pacific cold front dropped temperatures to near normal on the the 30th.

November

November 2021 precipitation November 2021 temperature

November was unseasonably warm and dry.  The month began with above normal temperatures under an upper level high pressure ridge. Disturbances moving into the ridge brought only light precipitation.

Southwest flow aloft brought more light showers on the 5th and 6th, and temperatures cooled to near normal on the 7th following another weak Pacific cold front.

On the 9th moderate amounts of precipitation accompanied a Pacific cold front and upper level low pressure trough. Totals from a quarter to a half inch were common, the largest one day precipitation totals of the month at many locations.

On the 11th a high pressure ridge initiated a warming trend, and temperatures averaged 10-15 degrees above normal through the 15th. Disturbances moving around the northern periphery of the ridge brought light showers from the 11th through the 14th.

During the night of the 16th, a strong but dry cold front from the Gulf of Alaska was followed by the coldest air so far this season, with lows below freezing at nearly all locations. Both Burns and McCall registered lows of 15 degrees.

On  the 19th a Pacific cold front triggered scattered thunderstorms. In the Boise area, small hail was reported at a few locations, and there were a couple of reports of wind gusts over 50 mph.

A high pressure ridge built in from the southwest on the 20th and kept our area dry through the 22nd.

On the 23rd another pacific cold front brought showers and cooler temperatures.

A high pressure ridge centered off the California coast expanded north on the 24th. It kept the area dry through the end of the month, but it created a temperature inversion, resulting in air stagnation in the lower valleys. Despite the inversion, afternoon heating under mostly sunny skies pushed temperatures above normal during the final week of the month.

https://twitter.com/NWSBoise/status/1465115860431867906

Season in Review – Summer 2021

Summer was, in a word, hot…the hottest on record at several locations. Many monthly and daily temperature records were broken or tied. It was also drier than normal overall, with the notable exception of the Treasure Valley.

June-August 2021 3-Month Averages vs  Previous Warmest              
               Summer 2021         Previous warmest
Boise              78.0                   76.6/2015
Baker City         67.2                   69.0/1961  
Burns              69.6                   69.2/1961
Jerome             74.2                   74.2/1961
McCall             65.6                   65.3/1961
Ontario            79.4                   78.5/1961
Rome               71.0                   72.4/2007
Twin Falls         73.9                   75.1/2013
June-August 2021 Monthly Averages vs Previous Warmest
             June               July               August
Boise        75.9  70.5/2007    83.8  83.1/2007    74.4  78.7/2001
Baker City   65.4  66.0/1961    71.3  72.3/1985    64.9  71.3/1961
Burns        66.9  66.9/2015    74.5  73.2/1960    67.3  72.3/1967
Jerome       73.5  71.8/1974    79.0  77.9/1985    70.1  77.3/1967
McCall       62.9  63.3/2015    71.1  68.7/2017    62.8  67.9/1961
Ontario      75.9  80.0/1971    85.1  82.3/2007    75.9  80.0/1971
Rome         68.9  72.4/2015    75.2  78.1/2007    68.8  74.2/1967
Twin Falls   72.2  73.5/2015    78.8  79.6/2007    70.6  77.1/2013
2021 Monthly Highs vs Previous Monthly Highs
             June               July              August
Boise        105  110/2015      107  111/1960     105  110/2018
Baker City   103  102/1961      101  105/2020      98  109/2018
Burns        103  102/2015      102  107/2002     101  103/2018
Jerome       100  110/1940      100  108/1973      99  107/1940
McCall        96   97/2015       95  102/1928      93  104/1928
Ontario      107  109/2015      107  113/1967     106  113/1961
Rome         101  107/2015      105  110/2002     103  107/2018
Twin Falls   100  103/2013      100  107/2003      96  102/2013

June

June temp anomalyJune precip anomaly

A persistent and very warm upper level high pressure ridge resulted in a number of record highs. It was the warmest June on record at Boise, Burns (tied), and Jerome.  The high of 103 at Boise on the 3rd was not only a new record for the date, it was also the highest for so early in the season.

A dry pacific cold front crossed the Boise area on the 4th, and temperatures were back to near normal from the 6th through the 9th.

A cold upper level low pressure trough from the Aleutians arrived at the northwest coast on the 7th. After deepening southward, it moved inland over the Pacific Northwest and northern California on the 9th and crossed the Intermountain Region on the 10th. The 0.71 inch of rain at Boise that day was only 0.04 inch short of Boise’s normal precipitation for the entire month of June.

Temperatures rose from the 11th through the 13th under southwest flow aloft ahead of an offshore trough.

As the trough moved inland on the 14th and 15th, the coolest air was diverted north of our area by an expanding upper level high pressure ridge over the four corners. So the trough brought only slight cooling, lowering temperatures to near normal on the 16th.

As the ridge amplified, temperatures rose again.

A low pressure trough formed off the California coast on the 20th. A disturbance generated by the trough lifted north, heading for southeast Oregon and southwest Idaho. It spawned strong, but mostly dry, thunderstorms in southeast Oregon on the 22nd. Cloud cover and cool air in the trough kept temperatures in the 60s and lower 70s in Harney County, while Boise`s high soared to 98 degrees. The increased pressure gradient caused by the temperature difference enhanced outflow from the storms as they drifted north, resulting in strong west winds in the Treasure Valley. A gust of 59 mph was measured at the Boise Airport, but there were reports of even stronger gusts elsewhere in the valley.

On the 23rd, an upper level ridge began to build off the coast. By the 26th it had moved inland over B.C. and the northwest U.S., unusually far north for such a strong and very warm ridge. Temperatures responded with a number of record highs from the 28th through the 30th.

During the hottest part of the day, humidities were low, falling into the teens and single digits.

Moisture circulating around the ridge resulted in numerous showers and thunderstorms around the region on the 30th, but many locations reported only sparse precipitation.

jun2021recs

July

July temp anomalyJuly precip anomaly

July 2021 was the warmest on record at several locations, including Boise, Burns, Jerome, McCall, and Ontario.  It could have been even warmer. Persistent smoke from wildfires restricted sunlight from reaching the surface, so highs were slightly lower than they would have been under clear skies.

At Boise, several other temperature records were broken, tied, or approached.

Consecutive days
     highs >= 90...44(6/17 - 7/31) ranks 2nd (50 in 1875 ranks 1st)
           >= 100...9(6/28 - 7/6) ties 2015, 2006, and 2003 
     lows  >= 60...43(6/19 - 7/31) ranks 1st (37 in 2007 ranks 2nd)
           >= 70...11(6/27 - 7/7) ranks 1st (5 in 2015 ranks 2nd)
Number of days
     highs >= 90...31...ties July 2017 (30-year average is 22)
           >= 100...12...ranks 4th (15 in 2003 ranks 1st)
     lows  >= 60...31...ties July 2007 (30-year average is 20)
           >= 70...16...ranks 1st (9 in 2007 ranks 2nd)
                                 (30-year average is 3)

It was a dry month overall, but a storm on the 31st brought significant rain to many Idaho locations.

An upper level warm high pressure ridge was responsible for the heat. Weak cold fronts associated with Pacific weather systems crossing western Canada occasionally pushed far enough south to lower temperatures by a few degrees. But other than breezy northwest winds, they had little noticeable effect.

By the 20th the ridge had shifted east and was centered over Colorado. Southwest flow between the ridge and an upper level trough centered over the B.C. coast transported monsoon moisture north of the Nevada border. The resulting thunderstorms brought generally light precipitation, along with gusty winds.

On the morning of the 22nd, a cold front passed our area as the upper level flow began to shift into the west, carrying the monsoon moisture east. Cooler drier air following the front resulted in the below normal average daily temperatures from the 22nd through the 24th.

On the 28th a brief influx of monsoon moisture generated early morning showers and thunderstorms, but precipitation was sparse. Skies cleared, and it was another hot afternoon and evening. Drier southerly flow brought even higher temperatures on the 29th and 30th.

By the 26th the center of the upper level ridge had migrated to the central Great Plains. Easterly flow south of the ridge picked up very moist air from the Gulf of Mexico and carried it west to New Mexico and Arizona. Southerly flow on the west side of the ridge then transported it north to the northern Intermountain Region.

On the 31st a low pressure system formed over Nevada. As it moved north, it interacted with the Gulf moisture, setting off numerous showers and thunderstorms with locally heavy rain. The Boise and Ontario areas, the Magic Valley, southern Twin Falls County, and the central Idaho mountains got the brunt of the rain.

 

jul2021recs

August

August temp anomalyAugust precip anomaly

 

In contrast to June and July, August was a relatively wet month with near normal temperatures, although it certainly had its share of record daily high temperatures. But smoky skies prevented highs from reaching their full potential. Temperatures were mostly above normal for the first half of the month and mostly below normal for the last half.

An upper level high pressure ridge kept temperatures hot from the 2nd through the 5th.

On the 6th a cold front and weak upper level trough crossed our area. Temperatures warmed briefly on the 7th ahead of a stronger trough from the Gulf of Alaska. That trough, and the northwest flow that followed, cleared the smoke and kept temperatures below normal through the 10th.

The heat returned on the 11th as an upper level ridge centered off the coast built inland. The heat persisted through the 16th. By the 14th the smoke had overspread our area again.

A major pattern change on the 17th ended the heat. An upper level trough deepened south from Canada over the Pacific Northwest and the Intermountain Region as an upper level ridge between Alaska and Hawaii strengthened and expanded north. The resulting northwest flow aloft put us in the path of more troughs coming out of Alaska. One of these systems brought light but measurable rain on the 20th and 21st, plus another brief respite from the smoke.

 

aug2021recs

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.

DecemberDecemberp

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 7th. On 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. 

Januaryp

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/