December 4, 2017 – Dry weather this week with cool nights and mild days. Breezy north winds in the Central Valley today with strong east winds across the northern Sierra Nevada tonight. Wind Advisory from 6 PM this evening to 8 AM Tuesday and Freeze Warning from 2 AM to 8 AM Tuesday.
Clear skies across interior NorCal as a short-wave drops south across the region ahead of the building ridge over the eastern Pacific. North and east surface pressure gradients have been increasing overnight (MFR-SAC up to 11 mbs and RNO-SAC nearly 6 mbs), and wind have become increasingly gusty through the Sacramento Valley and locally in the Sierra as subsidence increases.
The wind has kept current temperatures mainly in the lower to mid 40s through the valley while readings in the mountains are chilly with mainly teens and 20s.
Cold advection and strong subsidence will continue breezy to windy conditions across the region into Tuesday. The strongest north winds in the Central Valley are expected today with gusts around 40 mph while easterly gusts are expected to top out tonight and early Tuesday across the northern Sierra with local gusts of 60 mph or greater possible along the crest and exposed ridges.
The north winds are expected to decrease, but not completely disappear, through the Sacramento Valley by this evening. Enough breeze is expected to linger overnight to keep much of the valley above freezing. However, winds will likely decrease enough over the northern San Joaquin Valley and along the eastern edge of the southern Sacramento Valley for freezing temperatures to occur there early Tuesday.
Enough modification of the valley airmass is expected by Tuesday night/Wednesday morning, with dew points returning to the lower to mid 30s, to preclude much risk of widespread freezing temperatures.
Dry weather, with lighter winds returning by mid-week, and mild daytime temperatures and cool nights through the week.
Extended discussion (Friday through Monday)
Little weather of consequence in the extended period as high pressure remains in control. This will continue dry and mild conditions with above normal temperatures during the day. Cool nights expected due to clear skies and light winds.