February 12, 2021 – Multiple opportunities of wet weather are forecast to impact Northern California into next week, each of which may bring travel impacts to the mountains.
Radar continues to show rain and snow impacting portions of interior northern California this early Friday morning as an upper level low pushes southeast across the region. Overall, this system has dropped beneficial precipitation to the region over the past 12-24 hours. A sampling of rain totals across the Valley include 0.67 inches at Redding, 0.50 inches at Sacramento Executive, and 0.45 inches at Modesto. Climbing in elevation to the Sierra foothills, rain totals ranged from about 0.50 inches up to 1.50 inches. CalTrans webcams and snow level profilers put snow levels around the 5000 to 6000 ft range. Precipitation will wrap up over the next several hours as we approach sunrise. The Winter Weather Advisory for the Sierra above 6000 ft goes through 4 AM PST.
Aside some isolated early morning showers from I-80 southward, Friday should overall be a tranquil weather day for most communities in the Sacramento and northern San Joaquin Valleys. Highs this afternoon will warm to the upper 50s to low 60s, or within a few degrees of where we should land for early/middle February climatology.
After sunset today, renewed precipitation chances will return as a shortwave trough approaches from the northwest. Impacts with this quick-moving system will remain low, especially in the Valley where some locations south of Sacramento may see little/no rain. Up in the mountains, could see a quick 3-6 inches of snow impacting some routes such as I-80, mainly overnight Friday and into late morning Saturday. Taking into consideration of the weekend timing of this system, will opt to issue a Winter Weather Advisory at/above 5500 ft for the Western Slopes of the Sierra. As always, travelers are urged to check with CalTrans for the latest road conditions.
Mostly dry conditions will prevail on Sunday with only minor day- to-day changes in high temperatures through the weekend. Can’t rule out some light rain/mountain snow in far northern California (e.g., Shasta County) late in the day as yet another quick-moving system drops south into northern California overnight Sunday/Monday. Ensemble guidance suggests that this storm will provide generally light precipitation amounts for most across northern California.
Extended discussion (Tuesday through Friday)
Dry weather with above normal temperatures expected Tuesday into Wednesday under EPAC upper level ridge. Pacific frontal system spreads widespread light to moderate precipitation over interior NorCal Thursday with lingering showers, mainly over the mountains, Friday.
Snow levels start out around 3500 to 4500 feet Thursday morning, rising to around 4500 to 6000 feet Friday.