30-Day Weather Outlook for November 12, 2021, to December 12, 2021

Nov 12, 2021

BASIC PATTERN:

Large Scale Pattern –

A moderate to strong sea surface temperature anomaly gradient, coinciding with the dashed curve off the N California and Pacific Northwest coast will be the main player for storm developments into N California in Nov and Dec. Along this recurrent frontal zone, smaller troughs and lows will tend to develop.
It rains occasionally, but there is insufficient moisture, even in N California. Soils and vegetation have moistened in N California and Sierras (North and Central) from storms in 1 to 8 Nov. It appears that we have difficulty reaching a level of regular winter moisture recharge.
Latest updated CFSv2 forecast model results show a tendency for a return of near or a little above normal rain amounts for N and Central California coast and mountain areas for Nov. SOCAL will remain drier than normal, although some rains of interest are possible in Nov, and in Dec.
Wetter periods appeared in a couple of early storms for Oct and Nov in early, and mid Nov. Given the focus of moisture mainly to the north of California, it is not reasonable to expect dependable rains. Bottom line…appreciate the rain and snow events when they occur!
Dry conditions return for midwinter months of Jan – Feb in northcentral through S California, as the La Nina pattern re-establishes and remains dominant through the rest of the season into March.

FORECASTS FOR CALIFORNIA

We had some good rains on 1st, 4th, and 8th Nov. Troughs and lows bring the possibility of rains and showers into N California, and a few showers into central California during Nov. However, with the sea surface temperature anomaly (SSTA)– based support favoring the continued focus of troughing into the central Pacific, Dec has a chance for being meager for rain amounts. Jan and Feb continue the drier than normal pattern. A stronger La Nina pattern is expected to shift the pattern to dry in most of California in late Dec 2021. Continued dry in Jan-Feb 2022.
Precipitation Trend Nov 13-Dec 22: Dates of rain are: Nov 16-17 showers, 19-20, 25, 29-30. Dec 1-3, Dec 12-15.
N and Central California- Nov 13-Dec 13: Troughs with strong west flow occur at times across northern California through November with near normal to slightly above normal precipitation in some areas. Lighter rain through Central California but near normal conditions are likely in Nov. Average precipitation early in Dec across N California.

NORCAL Rains: Nov 16-17, 19-20, 25, 29-30. Dec 1-3, 12-15.

CENTRAL CALIF Rains: Nov 16, 25, 29-30, Dec 2, 12-14.

WARM SPELLS: Nov 18-19, 25-27, Dec 1, 4-7, 12-16, 19-21.

COLD SPELLS: Nov 15-16, 21-22, 28, Dec 3, 7, 9-10, 16-17.

FROST AND FREEZE: Nov 21, 23, 30, Dec 3-4, 7-8, 11-12, 17-18.

Forecast for S California – Nov 13 – Dec 13:

SOCAL Rains: Nov 21, 29, Dec 3, 12, 17.

SOCAL WARM SPELLS: Nov 13-15, 25-28, Dec 6-8, 14-15, 19-21.

SOCAL COOL OR COLD SPELLS: Nov 21-23, 29-30, Dec 3-4, 10-12, 17-18.

FRONTS WITH RAINS: Nov 21, 29, Dec 3, 10, 17.

Frosts may follow on: Nov 23-24, Dec 4-5, 19-20.

Sierra Nevada: Nov 13-Dec 13:

Dates of mountain rains and snows: Nov 16, 21-22, 28-29, Dec 2-3, 9, 17-18.

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The listing of dates normally included for hot and cold spells, and precipitation are based on our CFSDaily and CFSDailyAI forecast products, and present generally expected trends in precipitation (both products) and temperature (CFSDailyAI) to 4km. Our system gives some consideration of terrain and coastal influence. We consider the CFSv2 as one of the better ways to represent basic weather down in the sub-monthly time scale beyond the 15 day GFS or monthly maps from CFSv2 or NMME.

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Southern California Deserts Outlook for Nov 13-Dec 13:

Highlights: Not much precipitation is expected into the desert region though if any will fall it will be in Nov with little or none expected in Dec. Possible light rain dates into the southern California deserts will be Nov 22, 29, Dec 10. Above normal temperatures are expected through the rest of Nov with even warmer than normal temperatures through the start of Dec.

Forecast: High pressure will continue to dominate the weather pattern with the storm track staying to the north of SOCAL deserts. Occasional weakening systems will bring some light showers on the precipitation dates listed above. With high pressure comes warmer and drier than normal conditions.

Looking Ahead – Long Range Outlook

Dec 13 – Jan 31 2022... N and Central California. Latest versions of CFSv2 monthly guidance suggest a few fronts with near normal precipitation across northern California in Dec, but drying out at the holidays. Drier across northern California in January as La Nina develops. For central California: Some rain reaches central California in early Dec with drier conditions late in the month and very dry through all of Jan.

For SOCAL Dec 13 - Jan 31 2022:

In Dec: Dec dries out almost completely across southern California though a couple of deeper troughs will bring a little light rain into mainly north areas (Ventura County to the N) Dec 3, 10, 17. A few sprinkles but no rain of consequence is expected through most of southern California with these weak systems.

In Jan: January will be very dry with near or a little colder than normal. Some Santa Ana wind episodes will continue at times in Jan. Watch for dry freeze events and wetbulb freezes in Jan for SOCAL valley areas. General Frost Risk….Dec 1 – Jan 31 2022…: Dec 1-2, 5, 13-14, 19-20, 27-30. Frosts in Jan will usually follow dry fronts with lighter offshore winds. Stronger offshore flows will bring stronger winds which blow out the valley inversions (cold air) with warmer valleys lows expected.

(Terms and Definitions Used In This Weather Outlook)