Updated 11/27/20

(CBS13/NWS) Less wind today with chilly mornings followed by mild afternoons through the holiday weekend. Slightly cooler with a very slight chance of light rain showers over the Shasta County mountains on Monday while dry conditions continue elsewhere. Dry and mild weather follows Tuesday through next Friday.

DISCUSSION
Upper-level low pressure passes south of the 4-Corners area today allowing the upper-level ridge off the west coast to move inland today. This will relax the Nly and Ely pressure gradients resulting in less wind over Norcal than yesterday. The lingering north wind and mixing effects kept some isolated temps elevated into the evening (e.g. RDD +12, OVE +13, SUU +6 from 24 hrs ago) but as the wind diminished past midnight, strong traditional cooling from the clear skies and dry air mass (dewpoints in the teens and 20s) sent temps plummeting into the 30s and 40s very quickly. For example, in just one hour, RDD went from 54 degrees at 09z to 38 degrees at 10z. Not much frost is expected this morning due to the dry air mass (except perhaps in the Nrn SJV) but that will change in the next couple of mornings as dewpoints gradually recover above freezing.

Looks as if the strongest band of 925 mbs winds has moved through
Norcal with the Jarbo Gap wind for example, not as strong as expected. With the 925 mbs winds about one-third less than forecast, the gusts have also been about one-third less than forecast from yesterday, more in the 40 mph range instead of 60 mph. After 12z, the 925 mbs winds rapidly decrease over our CWA, hence less wind today.

A progressive weather pattern across NOAM will tend to flatten the ridging over the W coast this weekend. One short wave moves across Wrn Canada on Sat, followed by a 2nd which is forecast to move across the Pac NW on Mon. This second system tracks a little farther south than the first and may brush our far Shasta Co zone with at least a chance of light showers. However, this system is trending farther N and looks drier for our CWA than it did yesterday. However, it should spread more cloud cover across our
CWA than the first.

Only minor changes in temperatures through the weekend with highs near to several degrees above normal, and lows near to several degrees below normal. Perhaps a little cooler on Mon with the weather system passing to our N and an increase in cloud cover.

EXTENDED DISCUSSION (Tuesday THROUGH Friday)
Tightening surface gradient may lead to increased north to east wind Tuesday into Wednesday as a weak trough digs east of the forecast area. These offshore winds may bring a period of increased fire weather concerns to areas that have not received much precipitation. Otherwise, guidance maintains a dry forecast across interior NorCal as an upper-level ridge dominates the pattern. Forecast highs will be 5 to 10 degrees above seasonal normals, with Valley highs in the 60s.

FRIDAY: Sunny with a high of 60 and a low of 35.

SATURDAY: Sunny, patchy frost, with a high of 62, and a low of 32.

SUNDAY: Partly cloudy with a high of 62, and a low of 32.

MONDAY: Partly cloudy with a high of 62, and a low of 36.

TUESDAY: Partly cloudy with a high of 63, and a low of 33.

WEDNESDAY: Partly cloudy with a high of 63, and a low of 35.

THURSDAY: Sunny, with a high of 63, and a low of 35.

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