Two rain events this week will bring widespread rain, mountain snow and the possibility of thunderstorms

November 10, 2024 – A fast-moving system will bring mountain snow, rain and the possibility of thunderstorms to inland NorCal on Monday. A second system arrives later in the week, bringing more rain and mountain snow chances later in the week and into the weekend.

discussion

Some high clouds will move over northernmost parts of California very early today as a weak system moves through overnight. Despite the cloud cover, no heavy precipitation is expected from this system today.

A more impactful, faster-moving system will move through California on Monday, bringing widespread chances of precipitation, mountain snow, gusty onshore winds and a slight chance of isolated thunderstorms over the north-central Sacramento Valley and northeastern foothills. The rapid progression of this system will limit precipitation totals somewhat, although the NBM still has a 45 to 90% chance of 0.5 inches or more of rain across most of the valley (increasing from the northern San Joaquin Valley north), with a 60 to 90% chance of an inch or more in the northern Sacramento Valley, foothills and mountains.

The majority of the snowfall appears to remain above 6,000 feet, with the NBM indicating a 45 to 90% chance of 4 inches or more at those elevations. In areas at the top of the pass, elevation differences of up to 20 cm can occur, which can cause significant travel difficulties, especially considering that Monday is the end of a holiday weekend. With this in mind, a Winter Weather Advisory remains in effect for the Sierra at elevations above 6,000 feet from 10 a.m. Monday through 12 p.m. (midnight) Tuesday morning. By Tuesday morning, snowfall is expected to decrease to just a few lingering showers.

This system will also bring gusty south to southwest winds across the Delta, Sacramento Valley and over the Sierra on Monday. The Delta and Valley may experience winds of up to 30 miles per hour, while over the Sierra, winds of up to 45 miles per hour may occur. Gusty winds can make driving in the Sierra even more difficult.

Finally, there is a 10 to 15% chance of isolated thunderstorms across the north-central Sacramento Valley and northeastern foothills Monday afternoon and early evening. Most will develop with the cold front, although cloud cover could limit instability.

Tuesday will see mostly dry and calm conditions with slightly cooler than normal temperatures as we prepare for a new, longer lasting system beginning as early as Wednesday afternoon. Impacts on Wednesday will be minimal, but there is still a 35 to 60 percent chance of an inch of new snow at elevations above 6,000 feet Wednesday afternoon and evening and a 50 to 85 percent chance of a half inch or more Rainfall the northern Sacramento Valley, its foothills and mountains.

Extended discussion (Thursday to Sunday)

The storm system beginning Wednesday will continue well into the weekend, with the majority of rainfall and impacts expected Thursday through Saturday. The NBM shows a 20 to 50% chance of an inch or more of rain in the valley (increasing from south to north) and a 40 to 65% chance at higher elevations.

Snow levels will start at around 6,000 to 6,500 feet and fall to around 4,500 to 5,000 feet on Friday. Snow chances 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 6,000 feet. We will also see gusty winds again with this system; Periodic gusts of around 15 to 25 mph are expected in the valley, with gusts of up to 35 to 40 mph expected over the Sierra. There is still some uncertainty about the exact timing of the heaviest rainfall. Be sure to keep an eye on the weather forecast.