Another cold night/morning with frost and some areas dropping to freezing. Dry weather with a slight warming trend through the week of Thanksgiving. Pattern change possible late weekend into next week.

Discussion

Another chilly morning so far across the region, with some rural areas in the Valley and in the Delta area dipping to near freezing. The weak shortwave overhead will continue to shift southeast, with a more potent shortwave on it’s heels, which is more visible on satellite moving into the PacNW.

In response to these two systems, weak northwest flow will be overhead much of Tuesday, producing similar afternoon temperatures to Monday. As the shortwave moving into western WA digs into the northeastern Great Basin (aka inside slider), gradients will increase Wednesday into Thursday across NorCal. This will allow some breezy north to east winds to develop, with gusts to 20-25 mph in the Valley and gusts to 25-35 mph in the Sierra.

While the inside slider digs into UT, a broad ridge off the western CONUS will continue to build and slowly shift eastward, increasing heights initially across western CA Wednesday. The combination of increased heights plus breezy winds will allow temperatures to be about 5-10 degrees warmer than Tuesday’s.

As the ridge axis continues to shift eastward through late week, the axis will be overhead by Thursday afternoon, allowing winds to decrease some with little change in temperatures for the Holiday.

By Friday, a weak shortwave will begin to influence NorCal, mainly providing increased cloud cover, which will temper afternoon temperatures.

Extended Discussion (Saturday through next Tuesday)

The next weather system will impact NorCal Sunday night into early next week, bringing periods of light rain and mountain snow, gusty winds, and colder temperatures. The details of this system are still murky, especially regarding the evolution of the low and the amount of moisture associated with it.

Considering the uncertainty in amount of moisture associated with this system, confidence is low, but considering the lack of significant moisture (lack of AR), the impacts with this system should be fairly minor for much of the region.

This will be a fairly cold system, allowing snow levels to dip to around 4500-3000 feet. The main impacts expected will be mountain snow and gusty winds, creating periods of hazardous driving conditions in the Sierra.