Although temperatures averaged above normal for most of the month, below normal temperatures at the beginning and end of the month brought the November averages down to near normal. No daily records were tied or broken.
Precipitation was sparse, totaling only .07 inch. It was the driest November ever at the airport, where records go back to 1940. Going back to 1868, the start of continuous precipitation records in the Boise area, there have been only two drier Novembers.
Following a period of cool northwest flow aloft at the beginning of the month, an upper level high pressure ridge which resided near the west coast kept our weather mainly dry with above normal temperatures on all but two days from the 4th through the 24th.
On the 16th a low pressure system weakened as it moved through the ridge. It produced only a trace of rain at the airport.
On the 19th and 20th a more robust system split as it moved inland, with the strongest portion heading south toward southern California and Arizona. Before going south, it managed to squeeze out a hundredth of an inch of rain at the Boise Airport. Following the system, the ridge rapidly rebuilt over the Northwest U.S.
By the 24th a pattern change was underway as the ridge shifted west over the Pacific, allowing an upper level cold low pressure trough to deepen over the Intermountain region. Weather systems from the Gulf of Alaska strengthened as they moved into the trough. On the 25th the first system dropped a trace of snow on Boise before heading for the four corners area.
The next system was more dramatic in terms of wind. As the trough intensified over northwest coast on the 26th, it generated a steep west-to-east pressure gradient across southeast Oregon and southwest Idaho. This resulted in strong southeast surface winds. At the airport the wind peaked at 47 mph on the 26th and 46 mph on the 27th.
— NWS Boise (@NWSBoise) November 26, 2019
Nearly half an inch of snow fell at the airport on the 27th. Only traces of snow fell on the 28th, 29th, and early on the 30th before the trough jumped the Rockies and headed across the Midwest.
On the 30th skies cleared under a transitory high pressure ridge. Abundant sunshine melted the light snow which fell the previous night and temperatures warmed into the upper 30s.