April 4, 2017 – Dry and warm weather continues through Wednesday. Stormy weather returns Thursday with heavier precipitation Friday and into the weekend, potentially bringing heavy mountain snow, valley thunderstorms, and strong winds.
Discussion
Mid and high clouds are beginning to increase across interior NorCal. Current temperatures are in the mid to upper 20s in the colder mountain valleys with mainly 40s to mid 50s elsewhere.
Upper ridge transits the area today then shifts east into the interior West on Wednesday. Dry and mild weather will continue across the region despite periods of cloudiness.
Upper trough presently over the Gulf of Alaska will continue to gradually approach NorCal through the remainder of the week. Shower chances are expected to hold off until Thursday when the initial short-wave lifts out across NorCal ahead of the main trough.
Models continue to pinpoint Thursday night into Friday as a particularly active period of weather for the region as a stronger wave moves into NorCal tapping deeper moisture and bringing increasing rain, mountain snow and strong gusty southerly winds.
Extended discussion (Saturday through Tuesday)
After the brunt of the storm on Friday, NorCal will continue to have showery, unsettled weather into early next week. On Saturday, our region will have light valley rain and light to moderate Sierra snow as snow levels lower between 3500-4500 feet. Since the main cold front will have tracked eastward, clearing behind the front plus lingering instability could trigger a slight chance of afternoon thunderstorms. Moving into Sunday, valley rain is still possible and snow levels could lower to around 3000 feet, however, any additional rain/snow accumulations will be light.
Models suggest that another storm is set to move across NorCal late Sunday into Monday. The ECMWF looks much stronger and wetter with this system compared to the GFS run. Have chances for precipitation across our region on Monday diminishing early Tuesday, but details on this storm are still vague.