Precipitation chances return this weekend, unsettled next week

March 4, 2021 – Dry and mild weather through Friday. Rain and mountain snow chances return over the weekend and early next week with possible mountain travel delays.

Discussion

GEFS shows upper low moving east over the southern Rockies today with ridge building briefly over northern California with dry weather and Valley high temperatures ranging from the low to upper 60’s. GEFS then shows upper level trough approaching the West Coast Friday with some light showers possibly reaching the Coast Range and Shasta during the afternoon.

Rain and mountain snow will spread east over NorCal Friday night. The heaviest snow over the Sierra will fall after midnight into Saturday morning. Snow levels will be around 5000 feet with 4 to 8 inches likely at pass level. Sref ensembles show 5 inches at Blue Canyon(5280ft). This will likely cause a brief period of mountain travel delays and chain controls. Valley rainfall amounts will range from 0.25 to 0.75 inches, heaviest over the Northern Sacramento Valley and lighter progressing southward. A brief period of gusty winds possible Friday night with a few gusts to 30 mph, especially over the Central Sacramento Valley.

Trough will weaken, as it moves east into Nevada Saturday with precipitation diminishing during the afternoon. Broad southwest flow over the area with dry weather Sunday before a series of systems impact the area next week. Valley temperatures will be a bit cooler with highs from the upper 50’s to low 60’s.

Extended discussion (Monday through Thursday)

Ensembles are in good agreement for a cooler, wetter pattern to set up next week. A series of short wave troughs will bring periods of rain and mountain snow. The first short wave arrives Monday.

A second reinforcing short wave is expected on Tuesday and will bring more widespread rain and snow to the area. There is the potential for significant mountain snow with travel impacts, especially Tuesday into early Wednesday.

Shower chances continue into Thursday as we remain on the western edge of the long wave trough. Overall confidence is good through mid week, with more uncertainty late in the week.