December 7, 2020 – Gusty north to east winds will continue through early Tuesday over much of Northern California. Dry weather expected through the work week with above normal high temperatures.
Discussion
Cut-off inside slider low pressure system is dropping southwest over the Sierra from Nevada early this morning. This is a favorable track for strong downslope east to northeast winds over the Sierra and foothill locations. The strongest winds will be on the top side quadrant of the low or a few hundred miles north of the low center. At the present the strongest winds are north of Highway 50, but the winds will pick up over areas south of Highway 50 and Coast Range, Southern Sac Valley and Delta areas over the next few hours. A wind advisory is in effect trough 4 pm for many areas with speeds from 30 to 40 mph, gusts to 55 mph expected. There will be locally much stronger winds through canyons and gaps, such as Jarbo gap there have been gusts to 65 mph.
These dry, gusty winds in combination with relatively dry fuels will create elevated fire weather concerns. As a result, a Red Flag Warning is in effect for the central to southwestern portions of the Sacramento Valley through 5 pm.
Upper low will drop to off the SoCal coast this evening with the gradient relaxing, which will allow the winds to diminish. Upper ridge will set up behind the system with northwest flow into the end of the week.
A weak system will drop southeast in this flow Wednesday, but only an increase in cloud cover is expected. Temperatures will be from 5 to 15 degrees above normal through the week.
Extended discussion (Friday through Monday)
EPAC upper ridging off the West Coast Friday shifts inland Saturday. Dry weather expected, however models suggest potential for some overrunning precipitation extending into Shasta county.
Models differ with progression of next frontal system. GFS spreads precipitation into interior NorCal Sunday while EC holds off until Sunday night. Forecast blends timing with NBM keeping precip mainly over the northern third of the CWA Sunday PM into Monday. High temperatures remain slightly above average through the extended forecast period.