Breezy north to east winds are forecast across interior NorCal on Thanksgiving

November 25, 2020 – Light showers possible over mainly the mountains today, otherwise dry weather expected into next week. Mild days and cool nights will continue with breezy north to east winds on Thanksgiving.

Discussion

Radar shows a few light showers over Shasta and northern Tehama Counties along a cold front that is moving to the southeast. Rainfall amounts have been very light with rain gages reporting only a few hundredths of an inch across the mountains of northern and western Shasta County. Elsewhere, skies are clear to partly cloudy ahead of the approaching front and current temperatures are rather mild, ranging mostly from the 30s in the mountains to the mid 40s to lower 50s across the Central Valley.

Front will drop southeast today with just a dusting of light snow expected across the northern Sierra as the system has rather limited moisture to work with (TPW less than 1/2 inch) and will be moving rather quickly. Travel impacts are expected to be rather minor across the higher northern Sierra passes.

Northerly breezes will begin to increase across the Central Valley this afternoon behind the front. Highs today will be noticeably cooler compared to Tuesday across the northern half of the Sacramento Valley (around 10 degrees cooler) and over the mountains (10-15 degrees cooler).

North and east surface pressure gradients will really begin to tighten late tonight into early Thanksgiving as the MFR-SAC gradient is forecast to be around 10 mbs, and the RNO-SAC gradient climbs to around 6-7 mbs. Gusts of 25-35 mph will be possible along the western edge of the Central Valley on Thanksgiving, with local gusts over 45 mph possible across the more wind-prone locales in the foothills and mountains.

Winds drop off across most areas on Thursday night, however, lingering east gradient will continue some locally gusty winds overnight for the west slopes of the northern Sierra Nevada and foothills.

Ridging returns for the end of the week resulting in lighter winds, milder daytime temperatures, and cool nights with areas of morning frost in the Central Valley.

Extended discussion (Sunday through Wednesday)

Quiet pattern is expected this weekend under upper level ridging. By early next week, deterministic models indicate a disturbance dropping into the region that may bring precipitation chances Monday afternoon into early Tuesday.

Have kept interior NorCal dry per latest ensemble guidance. At the very least, this system could bring increased cloud cover and slightly cooler temperatures on Monday. Some enhanced north to east winds may be possible behind the system. Upper ridging redevelops behind this system, with continued dry weather and above normal highs.