Warm and dry weather through most of this week. Widespread rain and high-elevation snow along with cooler weather returns by the end of the week. 10-20% chance of thunderstorm development in Valley and Foothills on Saturday.
Discussion
Other than a few high clouds, skies remain clear across the region. Winds are generally light except for local easterly wind gusts of 20-30 mph over ridges in the northern Sierra. Current temperatures are several degrees milder compared to 24 hours ago and range from mainly the 30s and 40s in the mountains, to the upper 40s to mid 50s across the Central Valley.
Dry and unseasonably mild weather will continue early this week as the strong blocking ridge over the PacNW and NorCal gradually weakens. In addition to bringing warm weather, the high will likely suppress deep convection over NorCal. Highs today will be around 10-20 degrees above average, and around 5-15 degrees above average on Tuesday. The north valley may see highs climb into the mid 80s again today under subsidence and light northerly surface flow.
The ridge is forecast to weaken beginning mid-week allowing a return of temperatures closer to average the second half of the week.
A few late-day showers may be possible over the northern mountains Wednesday and Thursday, but more widespread precipitation chances will likely hold off until the end of the week.
EXTENDED DISCUSSION (Friday THROUGH Monday)
Pacific frontal system modeled to spread widespread light to moderate precip over interior NorCal Friday into early Saturday. Associated upper trough and embedded vort maxes progged through over the weekend keeping showers and mountain snow showers.
NBM keeps POPs over the CWA Monday, however this may be overdone as potential for upper ridging exists with some model solutions. WPC QPF for Friday through 12z Monday showing around a third of an inch in the N San Joaquin Valley to over an inch in the N Sacramento Valley. 1-3.5 inches of liquid precip predicted in the foothills and mountains through the same time period.
Snow levels begin around 6000 feet early Friday, lowering to 3500 to 4500 feet in post frontal airmass over the weekend. Snow accumulations of 5-10 inches possible above 6000 feet with local amounts up to a foot or more.