After what has seemed like an endless dry season, the Bay Area and the rest of Northern California will see the onset of actual rain and wintry conditions this week.
The National Weather Service says that after a day of gusty winds and declining humidity Monday that will increase fire danger across the region, we'll see a dramatic pivot to a cold winter storm that will sweep into the North Bay counties early- to midafternoon Tuesday and spread across the rest of the region by early Tuesday evening.
That will be the start of two days of on-and-off rain that will bring a half-inch to an inch of rain to most Bay Area locations by late Thursday and up to 1.5 inches to the typically wettest higher elevation sites in the North Bay and Santa Cruz Mountains. The Santa Lucias, the coastal range that runs down the Big Sur coast, could see even higher totals.
But there's more: Cold and the possibility of snow on our highest peaks.
Temperatures will fall as the storm's cold front passes late Tuesday and early Wednesday. Overnight temperatures are expected to fall into the 30s Wednesday through Friday mornings, with readings in the 20s possible in some of the region's inland valleys; daytime temperatures are forecast to range from the high 40s through the mid-50s. Snow is possible on peaks and ridges above 3,000 feet.
Bottom line: Not a gully washer or frog choker by any means, but welcome relief to a region where many locations have gone nearly 200 days since they've seen any meaningful rainfall.
The sudden onset of winter will be more dramatic for the entire length of the Sierra Nevada, where the highest elevations could get 4 feet of snow by the end of the week. The storm's cold temperatures mean that significant snowfall is forecast throughout the Sierra foothills above 2,000 feet.
In a winter storm warning issued early Monday, the NWS Sacramento office offers this advisory for those who might be getting ready to head into the mountains for the holiday:
"Travel is highly discouraged Tuesday night through Thanksgiving. ... Be prepared for significant reductions in visibility at times. Major travel delays likely and road closures possible. ... Travel is not recommended while the warning is in effect. If you must travel, keep an extra flashlight, food and water in your vehicle in case of an emergency....
Weather models are suggesting we could be in for a somewhat warmer, wetter storm starting Saturday that could bring significant rainfall and snowfall across Northern California.
"Things get tricky with the forecast going into the weekend the next storm drops south in the eastern Pacific and is off the West Coast by Saturday. This looks to be a large area of low pressure that could spin off the coast for several days. It could also pull in quite a bit of moisture. The question is how close to the coast will it sit and will it push that moisture into California Saturday night into Sunday.
"The forecast models have been back and forth on that with some keeping it off the coast and keeping us dry through the weekend. While others, like the latest European and GFS (Global Forecast System) model runs push in more snow by Saturday night into Sunday."
How much precipitation might we get if a storm pushes into California?
Monday morning's GFS precipitation forecast for the coming week — the model runs four times a day, so this is subject to change — shows totals ranging from more than 2 inches in the central Bay Area to more than a foot of liquid precipitation equivalent in the southern Sierra.