Periodic chances for moderate precipitation and breezy to gusty southerly winds are expected to continue through the weekend as a series of weather systems impacts the region. Isolated thunderstorms possible on Tuesday.
Discussion
Current radar imagery shows a few lingering light showers early this morning, mainly over the Sierra and east side of the Valley. Otherwise, generally drier conditions are anticipated today ahead of the next storm. Patchy Valley fog is possible this morning across portions of the Valley and Delta.
A stronger, colder system is still on track to impact interior NorCal Monday night into Tuesday. Current probabilities of exceeding 1 inch of liquid precipitation are around 70-100% across the northern Sacramento Valley, foothills and mountains.
Forecast precipitation totals sit around 0.5-1″ across the Valley, with 1-2.5 inches possible along the Sierra/southern Cascades and foothills.
Snow levels will start above pass levels, but rapidly lower to around 5000-6500 feet by Tuesday morning. NBM advertises a 60-90% probability of exceeding 6 inches of snowfall through Tuesday evening. Moderate mountain snow is expected, with snowfall rates up to 1-2.5″ per hour possible Tuesday morning.
A Winter Weather Advisory remains in effect for the southern Cascades and northern Sierra for elevations above 6000 feet from 7 AM to 7 PM Tuesday. Total snow accumulations of 5 to 10 inches are forecast above 6000 feet; locally higher amounts over peaks.
Additionally, NBM depicts a 10-20% probability of thunderstorm development on Tuesday.
Isolated thunderstorms will be possible along the main frontal band, and also behind the front with some possible clearing.
Gusty southerly winds are also anticipated late Monday night through Tuesday morning as the system moves through, with gusts up to 25-35 mph over the northern Sacramento Valley and northeast foothills; stronger gusts over the Sierra.
Precipitation chances are expected to taper off Tuesday night, with overall dry conditions anticipated for much of Wednesday (Christmas Day) as short-lived ridging moves overhead. With a drier period expected to follow, additional chances for fog development will likely be possible (10-20% probability of visibilities less than 1 mile).
Ensembles indicate an active pattern continuing through the weekend. The next wave is expected to arrive late Wednesday night or early Thursday, bringing another round of widespread Valley/foothill rain and mountain travel impacts. Snow levels will start around 4500 to 5500 feet early Thursday, then increase to around 5500-6000 feet by Thursday afternoon. Moderate snow is possible, with probabilities of snowfall exceeding 6 inches above 6000 feet ranging from 40% to 70% through Thursday night. Breezy southerly winds will accompany the system.
Please continue to check weather.gov/sto for the latest updates and check quickmap.dot.ca.gov before you go this holiday season!
Extended Discussion (Friday through Monday)
While uncertainty remains, ensembles suggest an active pattern persisting late week into the weekend as additional waves move across the area. Probabilities of liquid precipitation exceeding 0.5 inches range from 40% to 60% across the Delta and southern Sacramento through Sunday night, while probabilities of exceeding 1 inch around 60% to 95% favor the northern Sacramento Valley, foothills and mountains.
Probabilities of snowfall exceeding 6 inches above 6000 feet through Friday evening sit around 20% to 50% at this time, with minor to moderate mountain travel impacts. Snow levels start around 6000 feet Friday morning, then rise above pass levels by Saturday. Drier conditions may return by early next week.
Please continue to check weather.gov/sto for the latest updates and check quickmap.dot.ca.gov before you go this holiday season!