BASIC PATTERN:
Large Scale Pattern –
- December: Troughs and cold fronts are supported near the coast of North-Central and Northern California. This will maintain the cold, showery weather, and blustery cold frontal passages. Periods of moderate rains, and locally moderate to seasonable nowfall in Sierra Nevada.
- January: Colder than normal with near normal rains and snowfall to start Jan. Turning drier than normal along the California coast later in Jan, and struggling to maintain normal snow amounts in the mountains after a good start to the snows and rains in late Dec and early Jan.
- February: Very dry in all of California, including SOCAL, but possibly a chance for near normal rainfall in far N California and the Siskiyou Mountains, and north coast Humboldt Co north. Freezes in SOCAL early in the month, then warmer days after a period of blustery cold fronts 9 Feb to mid-month.
- March: Continued somewhat dry in most of California, but with above normal precipitation in N California Humboldt Co north, and in the mountains (northern Sierras, and Siskiyou’s).
- After subnormal rains last year, and some more subnormal rains this winter, despite the nice snows in Dec and early Jan, the water budget deficit continues problematic due to subnormal rainfall in the main rain months of winter.
- Recurrent NW flow from an area of colder than normal sea surface will tend to shift California into a colder than normal pattern. This suggests more frequent frost/freeze events than usual for Jan and Feb, including SOCAL citrus and avocado regions.
FORECASTS FOR CALIFORNIA
- We shift to a predominantly cold and seasonably wet period for most the remainder of Dec.
- Precipitation Trend: : The main dates of precipitation are: Dec 18, 20, Dec 24-28, 31-Jan 1. Heaviest are 25-28, Jan 1. Other rains occur Jan 17-22.
N and Central California- Dec 19 2021-Jan 19 2022:
NORCAL Rains: Dec 24-28, 31-Jan 1 (heavy on 31st ), Jan 17-22. Jan 8-9, 10-11 currently appear scattered and light.
CENTRAL CALIF Rains: Dec 24-28, 31-Jan 1 (heavy in north on Jan 1st). Other rains Jan 9, and 18-21.
WARM SPELLS: Jan 13-16.
COLD SPELLS: Dec 26-27, Jan 2-7, 10-14.
FRONTS WITH RAINS: Dec 24,25, 26-28, 31, Jan 1, 9 weak, and 18-21.
FROST AND FREEZE: Dec 29-30, Jan 3-8, 10-15, and 23-25.
Forecast for S California – Dec 19 2021-Jan 19 2022:
SOCAL RAINS: Dec 24-25 (wet), 28-29, Jan 1, 4-5 and 18-20.
SOCAL WARM SPELLS: Jan 10-11, 15-16.
SOCAL COOL OR COLD SPELLS: Dec 24-Jan 1, 4-6, and 21-23.
FRONTS WITH RAINS: Dec 22, 24-25, 28th -Jan 1 and 18.
Frosts may follow on: Dec 21-22, 27, Jan 2-3, 6, and 21-23.
Sierra Nevada: Dec 19-Jan 19 2022:
Dates of mountain rains and snows are: Dec 23-29, 31-Jan 1 (heavy snow 1st). More snow occurs Jan 5, 8-9, 10-11, and 18-21.
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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 Dec 19 2021-Jan 19 2022:
Highlights: Predominantly cold, and occasionally wet for the deserts is suggested for the holidays in Dec and early Jan. It appears to turn warmer during the last third of Jan following a midmonth showery period, and some freezes on 21-23 Jan. Best chances for freezes are in the dry cool airmasses behind cold fronts, after dry N-NE winds diminish to calm overnights.
Looking Ahead – Long Range Outlook
Jan 20 – Mar 15, 2022... N and Central California:
Summary: Colder than normal is expected across northern and central California Jan 20-25, then warmer than normal days, and not so cold at night about 25th onward through about 8 Feb. We return to a period of windy frontal passages with sparse or small rains during 9-16 Feb. This is followed by a dry and warmer regime during 18-25 Feb, then frontal passages with rains during late Feb through the first week to 12 days of Mar. A shift to near or above normal rainfall and Sierra snow again is possible during this wet period during the first half of Mar. We suggest that from this scenario, risk of frost in the Delta is seasonable up to mid-March.
For SOCAL Jan 20 – Mar 15. 2022:
Jan 9 onward will have near or below normal temperatures for S California, and continued cool in Feb. Watch for an increase in frost/freeze frequency in Jan and Feb from dry cold fronts. The best chances for frost/freeze Jan 20-25th, then possibly some moderation in nighttime temperatures due to Santa Ana winds at end of Jan. There is a chance for more frosts and freezes into SOCAL, especially the southcentral coast (San Luis Obispo Co to Santa Barbara Co in the last week of Jan. Last few days of Jan and start of Feb may see an increase in valley fogs in the southern San Joaquin Valley, but with some morning frosts/freezes in the San Luis Obispo-Santa Maria areas, and possibly into SOCAL coastal and inland valleys as well Should be prepared for multiple occasions of wetbulb freeze in the valleys under calm wind conditions, and occasionally some hard freezes on occasion, in the coldest locations, including Riverside Co valleys, Ramona (San Diego Co), and so forth.
CFSv2 monthly guidance suggests some troughs coming south into SOCAL and Arizona at times during Jan and Feb. There is not much rain in such a pattern, but plenty of wind and opportunity for frost and freeze in the prime winter food-crop areas of the southern deserts and SW Arizona. Again, the best chance of frost/freeze will be following dry cold frontal passages and after offshore winds subside. Cold inversions develop when winds are light and the air mass is dry. Many times these come with light offshore flow or weak onshore flow that have little inland penetration of moisture from ocean or beach.
Looking Ahead – March 2022:
The overall trend for late February (26-28), and month of March… recurrently colder than normal, with trend towards near normal precipitation but with more active frost and freeze periods occurring in the early spring part of the budding period in central and northern California.
(Terms and Definitions Used In This Weather Outlook)
Alan Fox & Zane Stephens...Fox Weather, LLC
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