November 10, 2024 – A quick moving system on Monday will bring mountain snow, rain, and chances for thunderstorms to interior NorCal. A second system arrives later in the week, bringing further chances for rain and mountain snow at the end of the week and into the weekend.
Discussion
Some high clouds are moving over the northernmost portions of California this very early morning, as a weak system pushes through overnight. Despite the cloud coverage, no ground-reaching precipitation is expected from this system today.
Monday, a more impactful, quick moving system progresses through California, bringing widespread chances for precipitation, mountain snow, gusty onshore winds, and a slight chance for isolated thunderstorms over the northern and central Sacramento Valley and northeast foothills. The fast progression of this system will somewhat limit precipitation totals, though the NBM still has a 45 to 90% probability of 0.5 inches or more of rain in the majority of the Valley (increasing moving northward from the northern San Joaquin Valley), with a 60 to 90% probability of an inch or more in the northern Sacramento Valley, foothills, and mountains.
For majority of snowfall looks to remain above 6000 ft, with the NBM showing a 45 to 90% probability of 4 inches or more at those elevations. Areas at pass level may see up to 8 inches, which may cause significant travel difficulties, especially considering Monday is the end of a holiday weekend. Considering all of this, a Winter Weather Advisory remains in effect for the Sierra at elevations above 6000 ft from 10am Monday to 12am (midnight) Tuesday morning. By Tuesday morning, snow is expected taper off to just a few lingering showers.
This system will also bring gusty south to southwest winds in the Delta, Sacramento Valley, and over the Sierra on Monday. Winds in the Delta and Valley could gust up to 30 mph, while winds over the Sierra may gust up to 45 mph. Gusty winds may cause additional complications for driving in the Sierra.
Finally, there is a 10 to 15% probability of isolated thunderstorms in the northern and central Sacramento Valley and northeast foothills on Monday in the afternoon and early evening. Most will develop with the cold front, though cloud cover could limit instability.
Tuesday sees mostly dry and calm conditions, with slightly cooler than normal temperatures, as we gear up for a new, longer lived system starting as early as Wednesday afternoon. Impacts on Wednesday will be minimal, but there’s still a 35 to 60% chance for an inch of new snow at elevations above 6000 ft on Wednesday afternoon and evening, as well as a 50 to 85% probability of half an inch or more rainfall in the northern Sacramento Valley, foothills, and mountains.
Extended Discussion (Thursday through Sunday)
The storm system starting Wednesday will continue well into weekend, with the bulk of precipitation and impacts expected on Thursday through Saturday. The NBM shows a 20 to 50% probability of an inch or more of rain in the Valley (increasing from south to north) and a 40 to 65% probability at higher elevations.
Snow levels will start around 6000 to 6500 ft, lowering to around 4500 to 5000 ft on Friday. Snow probabilities are generally 55 to 80% for totals of 8 inches or more in the Sierra and southern Cascades, with the majority of snow still expected above 6000 ft. We’ll also see gusty winds again with this system; periodic gusts around 15 to 25 mph are expected in the Valley, with gusts up to 35 to 40 mph over the Sierra. There is still some uncertainty with exact timing of the heaviest precipitation, so be sure to keep an eye on the forecast.