Quick-moving weather system moves south today with remaining showers over the Sierra ending by afternoon. Breezy north winds will pick up today and continue into Wednesday and may lead to local elevated fire weather concerns. Milder temperatures return for the second half of the week.
Discussion
Quick moving strong vort center clearly evident on satellite and radar imagery dropping south across the northern Sierra. Precipitation amounts so far have mostly been under a tenth of an inch with a few spots approaching a quarter inch. Snow was sticking on I-80 near Donner Pass earlier when a heavier shower moved through, but traffic cameras indicate the road surface is currently wet as the milder ground temperatures quickly melted the snow. Donner Pass may see a little more snow in the next couple hours before the low moves further south and showers end.
The cold front has swept south already and current temperatures are colder over most of the region compared to 24 hours ago. Much of the Central Valley is running around 5-10 degrees cooler, while readings in the northern Sierra are 15-25 degrees cooler compared to early Monday.
Area of strong forcing shifts south of the area by this afternoon as the low moves into central California. A few showers may linger in the Sierra south of Tahoe, but the remainder of the forecast area will see dry weather as north to east flow develops. The MFR to SAC gradient has already increased to a little over 7 mbs and northerly gusts of 15-30 mph have spread across the northern half of the Sacramento Valley and surrounding terrain.
Northerly breezes will spread south, and gusts will increase this morning once better mixing develops with gusts of 35-40 mph over the western half of the Central Valley. Breezes will continue tonight and Wednesday, but likely won`t be as strong as today. Today will likely see the coolest temperatures for most of the area. Dry and milder weather will return for the second half of the week with highs returning to the upper 60s to mid 70s over the valley.
Extended Discussion (Saturday through Tuesday)
We will be on the eastern edge of the Pacific high for the start of the extended period. This will bring the return of mild high temperatures. The Pacific ridge will flatten some and push back west later Friday into Saturday as a weak short wave pushes over NorCal. This will bring some cloud cover but with no moisture to work with the forecast will remain dry.
Things them become more uncertain for Sunday into early next week. Ensemble solutions diverge as a trough digs out of the Gulf of Alaska. The main uncertainly will be if it takes another inside slider track (~45% of the members) or dig along the coast (~40% of the members) or slow and stay much further west (~20% members).
Right now stuck with the NBM with some light PoPs over the higher elevations Sunday into Monday. This will depend on the track but increased north and east winds look possible Monday and Tuesday.