Clear skies across interior NorCal early this morning as strong high pressure along with offshore surface flow continue. Current temperatures are a little cooler compared to 24 hours ago and generally range from the 20s and 30s in the mountain valleys to the mid 40s to mid 50s elsewhere.
Another unseasonably mild day is ahead with highs today expected to be around 10-15 degrees above average for mid-March. Highs in the Central Valley will be in the mid 70s to lower 80s, but shy of daily records.
Ridge weakens and shifts east Tuesday into Wednesday as upstream trough over the Gulf of Alaska approaches the West Coast, and the main impact will be to bring a return of cooler temperatures. Not much in the way of much precipitation is expected across the region as the system quickly weakens as it moves onshore. Some light QPF may make it about as far south as I-80 later Wednesday into early Thursday, but snow levels will remain too high for any impacts to travel.
Weak ridging is then forecast to return dry and milder weather for Thursday.
Extended discussion (Friday through Monday)
Dry conditions should persist Friday before the next system moves through Saturday. Forecast models show some instability on Saturday with showers remaining generally north of I-80. Daytime highs are expected to remain above average at least through Saturday before gradual cooling takes place on Sunday, and more so on Monday. Southwest flow aloft under subtle cyclonic flow will continue the weakening threat for showers Sunday and early Monday. Then decent model agreement moves a dynamic upper trough near the NorCal coast Monday into Tuesday within an increasing threat of widespread showery activity. Pattern recognition suggests that thunderstorm activity may be a concern early next week. However, we did not mention thunderstorms in official forecast just yet, as timing and trough strength can change dramatically in this Spring transition period.