High pressure will weaken today as broad troughing takes hold across the area through Monday. Shortwaves will drop southeast in the flow, but best moisture and dynamics remain across the Pac NW, so local area will remain dry. Troughing will serve to bring high cloudiness and cool temperatures slightly today and Monday, though highs will remain above normal. As pressure gradient strengthens, breezy north winds are likely during the day Monday with gusts of 20-30 mph possible across the Sac Valley. Ridging builds back over the area for Tuesday into Wednesday with lighter winds. Temperatures will warm a few degrees from Monday’s highs. Wetter, more active pattern takes hold in the extended period.
Extended discussion (Thursday through Sunday)
By late next week, there is an increasing probability of an anomalously strong Pacific moisture surge impacting interior NorCal. Thus, confidence is increasing that widespread precipitation will occur late next week into next weekend; though models still show some uncertainties regarding timing and precipitation amounts. At this point, precipitation is anticipated to remain generally in the mountains north of I-80 on Thursday. More widespread precipitation is forecast on Friday with a second and stronger impulse on Saturday. Early QPF amounts suggest 0.50-1.5 inches of precipitation for the valley and 1-2 inches for the foothills and mountains, locally higher possible, through Saturday morning.
Given the warm nature of this system, snow levels are anticipated to be well above pass levels during most of the event. Snow levels could drop below pass levels Saturday afternoon as colder air begins to filter in. Overall, only a few inches of accumulating snow are expected at this time mainly over the highest peaks. Stay tuned as guidance comes into better agreement.