Dry and mild weather today, then cooler and more unsettled weather returns beginning Monday.
Discussion
High clouds ahead of the approaching trough have moved south and now cover the northern half of the forecast area. Winds are generally light as surface gradients have slackened. Current temps are running milder over most of the area and readings are in the 40s across the Central Valley.
Models remain pretty consistent with the trough dropping south into NorCal early this week bringing a return of cooler temps and unsettled weather. The cooling trend will begin today with highs expected to be down about 5-10 degrees compared to Saturday’s.
Shower chances will develop across the northern Sierra tonight into early Monday as an initial vort moves south. QPF will be light with a dusting of snow expected across the higher elevations.
More widespread showers are expected Monday night and Tuesday as the trough digs south into NorCal. QPF has trended slightly higher as the trough has shifted a bit west and a little deeper.
Precipitation will become more convective as lapse rates steepen, and more impactful snowfall will be possible across the northern Sierra where up to a foot of accumulation may occur across the passes with an inch or two down to around 2000 ft elevation.
Behind the trough, cold air settles into the region for the second half of the week with freezing temperatures likely in the valley each night, especially along the eastern edge where northerly breezes will be lighter.
Extended Discussion (Thursday throgh Sunday)
Models differ with westward extent of upper trough riding down leading edge of EPAC ridge Friday, with EC farther west over NorCal. Moisture is limited even with this solution, so dry weather expected. Heights trend up into Saturday as upper ridge shifts inland.
Widespread frost possible Thursday and Friday morning in the Central Valley as the mercury drops into the upper 20s to lower 30s. Models continue to differ with progression and track of next upstream Pacific frontal system. NBM showing some POPs over northern portions of the forecast area Sunday. However, cluster analysis is holding on to upper ridging over the CWA into Sunday.