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Gusty southwest winds will result in critical fire weather conditions today over portions of the northern Sierra and southern Cascades. Cooler temperatures expected through Thursday, with a warming trend returning Friday into the weekend.

Discussion

Skies are clear across interior NorCal early this morning. Surface pressure gradients are trending a bit more onshore which has brought cooler temperatures and higher humidity through much of the Central Valley as the marine layer has deepened to around 2k ft. Above the valley, conditions remain very dry with humidity presently in the teens to around 30 percent.

Dry and cooler weather will continue across the region today and Thursday as the trough remains over NorCal. Temperatures will be around 5-10 degrees below average over most of the area. Humidity will remain very low outside of the portions of the Central Valley influenced by the Delta Breeze. It will be breezy again this afternoon across the higher elevations of the northern Sierra where gusts to around 30 mph will be possible in windier spots. Combined with the very dry conditions, critical fire weather conditions will persist into this evening when winds will decrease.

As for smoke, it looks to linger in portions of the valley today, and near wildfires. Winds become a bit lighter and more terrain driven Thursday and Friday which may lead to a return of smoke or haze over the lower elevations, especially in the mornings.

The trough lifts out by the weekend bringing another warming trend to the region.

Extended Discussion (Sunday through Wednesday)

Desert SW upper ridge axis extends over interior NorCal Sunday, shifting over the Great Basin Monday as closed upper low off the CA Coast approaches. Models and ensembles exhibiting typical differences with progression rate of closed low. Increasing onshore flow and synoptic cooling expected as low moves inland.

EC solution points towards potential for deep moist convection over the Coastal Range and Shasta mountains Tuesday. Will leave forecast dry for now but continue to monitor.