30-Day Weather Outlook for January 8 to January 31, 2025

Jan 08, 2025

BASIC PATTERN:

Large Scale Pattern

Precipitation Dates for Jan 8 - 31: rains Jan,10,17,21-24.
Support for troughing continues in the central N Pacific from about 130-145W (mainly NE to N of Hawaii), and at 160W to near the Dateline is N to NNW of Hawaii. A third (weaker) area of troughing extends from about Hawaii to near Central California.
The pattern in Jan 12 ñ-19 appears to return to overall warmer than average with warm upper high pressure developing at times, and Santa Ana type winds following cold frontal passages. Dry and windy periods occur 11-13th, and again later in the month about 29-30. A period of rains occurs during 22-23, and possibly again 25-28.
For forestry. After a wet start in early Jan, we expect drier than average winter fire season conditions in NORCAL and Central California. Moisture in dry brush has increased, but will decrease again due to Santa Ana type winds developing in the central to north Sierra west slope areas. The bottom line is: Continued drier than average, overall, but briefly interrupted with the rain or showers, mostly with higher snow levels. Trends in snow level have been irregular in the medium range model guidance, but are trending to higher levels again at this time. It should be remembered that a drier climate scenario does not necessarily mean smaller rains, but more infrequent though heavy rains, and a shorter wet season. This is something to remember in preparation for fire season readiness.

Forecast for Northern California

NORCAL Precipitation: Jan 8- 31: rains Jan 10,16-17,22-25.
NORCAL Mild/Dry Periods: 4-6 Jan.
NORCAL Cold Periods & Frost: Warmer with below normal frost occurrence.
North Sierra Precipitation: Jan 8-9, 16-17, 22-25, 25-27.
Central Sierra Precipitation: Jan 8-9,16-17, 22-24, 25-27.

Forecast for Central California
CENTRAL CALIFORNIA Precipitation: Jan 8,10,17, 22-24,26-27.
CENTRAL CALIFORNIA MILD DRY PERIODS: Jan 18-21, 29-31.
Central California Cold Periods, Frost: Jan 8-9, 18-20, 29-31.

Forecast for Southern California
SOCAL PRECIPITATION: Jan 8,10,17,23 or 24.
SOCAL MILD PERIODS: Jan 12-16,18-21,29-31.
SOCAL COLD/FROST PERIODS: Jan 8,10,17,25-28 2025.
Note that we can receive both mild daytime conditions, and frosty early mornings during the same dates. Note that the dates for these rains are to be considered very approximate.

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The listings of dates normally included for hot and cold spells, and precipitation are approximate. They are based on GFS and our CFSDaily and CFSDailyAI products; and present expected trends in precipitation and temperature (FoxCFSDailyAI) to 5km. Our AI system gives some consideration to terrain and coastal influence. Although we consider the CFSv2 one of the better ways to represent basic weather in the sub-monthly time scale, performance of the CFSDaily. CFSv2 daily products during storm seasons has been especially inconsistent and difficult to apply to the useful criterion needed by cropland agriculture, and viticulture beyond the 15thday GFS.

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Southern California Deserts Outlook.
SOCAL deserts: Colder than average during rainy periods. Rainfall amounts about average. Rain dates in SOCAL Deserts: Jan 8-9, 17,25, 27-28.

(Terms and Definitions Used In This Weather Outlook)