Snow showers are possible over the mountains today, with accumulating snow over the Shasta County mountains. Sunday into Monday expect more widespread mountain snow with periods of moderate to major travel impacts expected. Strong gusty winds are expected, especially for the northern Sacramento Valley and northeast foothills.
Discussion
Drier weather has returned to much of the area overnight with weak ridging developing over the area, with just a some lingering light mountain snow showers evident this morning. A disturbance to the north will bring moisture and renewed intensity to showers to far northern California later today and tonight, with accumulating snow over the mountains. A Winter Storm Warning has been issued for elevations above 4000 feet for Shasta County from 11 AM this morning through 11 PM Sunday, with 6 to 12 inches of snow accumulation and up to 2 feet over peaks. Some light rain showers may extend into the northern and central Sacramento Valley today, with generally dry conditions farther south. High temperatures this afternoon will remain about 6 to 12 degrees below normal.
Our next widespread winter storm system arrives Sunday and continues through early Tuesday bringing more rain, mountain snow, and strong southerly winds. Strong winds aloft are forecast to mix down to the surface, with ensembles showing the potential for 65 mph gusts (60-80% probability) over the northeastern foothills, with gusts up to 50 to 60 mph (50-70% probability) over the northern Sacramento Valley.
A High Wind Warning continues for the area from 11 PM Sunday until 11 PM Monday. A Wind Advisory continues for the Central Sacramento Valley, portions of the southern Sacramento Valley, and adjacent foothills for gusts 40 to 50 mph, also from 11 PM Sunday until 11 PM Monday.
Ensemble guidance continues to show high probability of heavy snow in the southern Cascades and northern Sierra. A Winter Storm Warning has been issued for above 5000 feet for the southern Cascades from 11 AM Sunday to 11 PM Monday, and from 5 PM Sunday to 11 PM Monday for the northern Sierra. Snowfall amounts of 1 to 2 feet are expected, with up to 3 feet over higher peaks. This could bring moderate to major mountain travel impacts. Afternoon thunderstorms are possible in clearing behind a cold frontal passage, with best potential over the eastern Valley and into the foothills.
Latest probabilities moving into next week are as follows:
Probability of Rain > 1″ Late Sunday-Tuesday AM: 20-40% Valley/foothills
Probability of Snow > 12″ Late Sunday-Tuesday AM: 70-95% above 4500′
Probability of Thunderstorms Monday: 15-20%
It continues to look like most precipitation is expected to be coming to an end by very early Tuesday morning. Dry weather is expected for the rest of the day, with cold morning temperatures. The NBM projects near freezing for the northern Sacramento Valley, mid to upper 30s for the rest of the Valley, with areas of morning frost possible.
Extended Discussion (Wednesday through Saturday)
Mesoscale ridging brings just a brief lull in the active pattern, with a shortwave from the Gulf of Alaska bringing a return to wet weather by Wednesday afternoon. Ensemble guidance is trending toward continued active weather moving into late next week, but impacts look limited at this point. Be sure to monitor the latest forecast at weather.gov/sto and plan ahead for periods of unsettled weather.