A colder weather system arrives today bringing widespread rain and major mountain snow and travel impacts with gusty southerly winds. Drier weather with cold morning temperatures return this weekend and into early next week.
Discussion
Scattered high level clouds are currently being observed via GOES-West imagery as our next weather system begins to bring light rain and mountain snow to Shasta County. Mountain snow will be the main impact of this colder, fast-moving system with overall lower rain amounts compared to those previous.
Periods of light to moderate rainfall are expected later this morning with the bulk of rainfall accumulations staying in the Sacramento Valley. The Sacramento Valley has a 60 to 90% chance of seeing 0.50″ or more of rain while the northern San Joaquin Valley has a 40 to 60% chance.
In the northern Sacramento Valley and in the foothills, there is a 60 to 90% chance of 1.00 or more. Showers will become more scattered further south in the Valley after the initial push of rain this morning.
Southerly winds are expected to be gusty through the Valley this afternoon with gusts up to 40 mph in the northern San Joaquin Valley and portions of the southern Sacramento Valley. As a result a Wind Advisory will be in effect from 4 PM today until 1 AM Friday. Lastly, we’ll also see a 10 to 20% chance of isolated afternoon/evening thunderstorms.
Periods of moderate to heavy snowfall will accompany this system with snowfall rates of 1 to 2 inches per hour at times. A Winter Storm Warning is in effect for the Shasta County mountains and the Coastal Range above 3000 feet until 4am Friday, and for the Sierra above 5000 feet from 10am this morning until noon on Friday.
Over Shasta County/Coastal Range, snow levels start out between 2000 to 3000 feet through this afternoon before rising to 4000 feet by this evening. Snow levels then drop to around 3000 feet again early Friday morning. Probabilities for 8 inches or more of snow are between 50-90% with a 30 to 60% chance of 18 inches or more at the highest peaks. Overall we’re forecasting between 6 to 14 inches of snow above 3000 feet over the Shasta County mountains/Coastal Range with up to 2 feet possible at the highest peaks.
Over the Sierra, snow levels start between 5000-6000 feet, rising to 6000-7000 feet this evening, before lowering down to 4000-5000 feet Friday morning. Total snow amounts are forecast between 8 and 18 inches with up to 3 feet possible at the highest peaks. Currently, there is 60 to 90% chance of 10 inches or more of snow with 40 to 70% chance of 20 inches or more along the highest peaks. Southerly gusts are forecast up to 65 mph with a 40 to 60% chance of gusts greater than 75 mph.
Slippery and snow-covered roads, chain controls, and significant travel delays are all expected so please exercise caution if planning any mountainous travel.
Rain and snow will taper off Friday afternoon and evening, leaving us with drier weather and cold mornings over the weekend. Morning temperatures look to hover in the low 30s in the Valley and foothills, with the mountains seeing single digits to teens. Take time now to prepare for expected colder temperatures and be sure to protect pets, plants, and people, especially those more susceptible cold weather impacts.
Extended Discussion (Monday through Thursday)
Dry weather continues Monday thru Tuesday with cold morning lows. Active weather has the potential to return as early as Wednesday, but there is still uncertainty on the timing and intensity of this next system. Some solutions point towards more precipitation on Wednesday, while others show a dry but windy pattern with precipitation beginning on Thursday. The majority of ensembles highlight a return to active weather sometime around the mid to late week period, but confidence is low on the details. Stay tuned for updates to the forecast as we get closer to the weekend.