Widespread precipitation returns to interior NorCal Tuesday through Wednesday

March 23, 2020 – Chance of showers today with a few thunderstorms possible during the afternoon. Widespread precipitation will return Tuesday and Wednesday with showers lingering into Thursday. Dry and warmer late this week.

Discussion

Closed low that’s been off the coast of central California is opening up and shifting inland. Radar shows much of the heavier precipitation associated with this system is occurring to the south of the forecast area, though a few light showers are creeping northward into the southern Motherlode and portions of the valley to the south of Modesto. Otherwise, skies are clear across the Sacramento Valley as clouds with the approaching cold front are moving into northwest California. Current temperatures range from the 20s and 30s in the mountains, to the mid 40s to mid 50s across the Central Valley.

Generally light precipitation is expected across mainly the mountains today, the southeast corner of the forecast area this morning from the departing low, and over the northern mountains and northern Sierra Nevada this afternoon as the upstream cold front nears. A few late day thunderstorms will be possible, particularly across Shasta County and Motherlode.

Main precip event expected Tuesday into Wednesday as the cold front drops into NorCal. QPF will be considerably lighter than the storm a week ago, but a foot or more of new snow will be possible across the higher elevations of the northern Sierra with the heaviest snowfall expected Tuesday afternoon and night. Snow levels lower into the foothill elevations by early Wednesday as precipitation will be tapering off.

In the valley, QPF is expected to be generally less than a third of an inch. A few thunderstorms will be possible again on Tuesday afternoon, especially across the northern Sacramento Valley.

Generally drier and milder weather is expected on Thursday with some lingering showers over the northern Sierra.

Extended Discussion (Friday through Monday)

Weak upper ridging moves through early Friday then upper low to the NW approaches, filling as it move across northern portions of the CWA Saturday. This will bring a slight chance of showers, mainly over the northern mountains from Friday afternoon through Saturday evening. Large differences in models then exists by Sunday leading to lowered confidence forecast. NBM solution more similar to ECMWF which keeps a slight chance of showers over the northern mountains Sunday and Monday.