30-Day Weather Outlook for December 13, 2024, to January 13, 2025

  • Dec 16, 2024

BASIC PATTERN:

Large Scale Pattern

  1. Moderate to heavy rains and mountain snows December 12-14,16th-early 17th. Heavy rains occur December 23rd, light showers December 26-30 and showers December 28-30. The next rains. January 2025 is looking pretty dry until the next significant rain on January 11. January is also drier than average in late month, per CFSDaily model. 
  2. Support for troughing continues in the eastern N Pacific from the Oregon/Washington coast at 125W to about 145W, and Central Pacific from 155W to the Dateline. Still some troughing in California is possible due to downstream forcing from the persistent troughing near the Dateline to 160W. However, there is small support for significant rains in late Dec or Jan 2025, other than the dates already mentioned.
  3. The pattern in mid to late Dec is looking seasonably cold, with low snow levels, but not particularly wet. Watch for seasonably wet and cold upper low with rain lower elevations and snow in foothills/mountains around Christmas holiday. However, movement of upper lows can be erratic.
  4. Seasonably cool and drier than average conditions occur in mid January 2025. After a January mild and dry break after midmonth, late January and February appear to return to near then above average precipitation. 
  5. In February and March 2025, watch for a possibly robust return of cold and snowy conditions focusing in NW California and the ORWA coast (Oregon and Washington).
  6. For forestry. we expect drier than average winter fire season conditions in NORCAL and Central California. Moisture will slowly increase at vegetation levels near the surface. The bottom line is: Continued very near term breezy periods with rapid shifts to cold and showery (rainy in NORCAL), with low snow levels in foothills and mountains.
  7. For season 2024-25 in California we could actually see some additional wetter than average months: periods of heavy rains focusing in most likely 4th week of January, February 2025, and early Mar 2025.

Forecast for Northern California

NORCAL Precipitation: Dec 13-14, 16-17, 21-24, cold rain/snow showers 25-26,and 28-30 Dec. Storm with rain/snow Jan 11.
NORCAL Mild/Dry Periods: Dec 17-20.
NORCAL Cold or Frost Periods: Dec 14-18 and 19th, 25-30.

North Sierra Precipitation: Dec 13-14, 16-17, 21-24, minimal showers 25-26. Significant rain/snow Jan 11.
Central Sierra Precipitation: Dec 13-14, 16-17, 25-26, 28-30.Cold with rain and snow showers foothills/mountains of Sierras 25-26 and 28-30.

Forecast for Central California

CENTRAL CALIFORNIA Precipitation: Dec 14-15,16, 21-23, possible heavy showers 23rd. Showers and low snow levels 24-26th and 29-30. Storm with rain and mountain/foothill snows Jan 11.
CENTRAL CALIFORNIA MILD DRY PERIODS: Dec 17-21, 27. First part of Janueary Central California Cold Periods. Frost: Dec 17-20, 27-28 and first week of new year.

Forecast for Southern California

SOCAL PRECIPITATION:  Dec 13-14, 22-26 cutoff low.
SOCAL MILD PERIODS:  Dec 12, 18-21, First week of new year. 
SOCAL COLD/FROST PERIODS: Dec 12, 18-20, 25-28, Jan 1-6 2025.
Note that we can receive both mild daytime conditions, and frosty nights during  the same dates. Note that the dates for these rains are to be considered very approximate.

---------

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 15ñday GFS.

---------

Southern California Deserts Outlook

SOCAL deserts: near average temperatures, and about average rainfall for the period. However, it appears that there are some cold and showery/rainy events in S California deserts Dec 14, 16-17, 22-24, shower  25th cutoff low. 

Looking Farther Ahead — January 1-31, 2025
January starts out dry in the deserts, after a cutoff low with showers and hail during the last week or so of Dec 2024. Freezes continue possible in SOCAL valleys Riverside-San Diego Coís at times in Jan and Feb following cold fronts, mainly when dry airmasses occasionally pass through.

Share This Post: