30-Day Weather Outlook for November 15, 2024, to December 15, 2024

Nov 19, 2024

BASIC PATTERN:

Large Scale Pattern

Rain Dates from GFS and CFSv2 models during Nov 15-Dec 15: Nov 14-15, 21-28, 12/7-15. Snow in Sierras 14-15,17, 19-22 for N and Central California, NE Plateau and N Sierras/Siskiyouís 11,13-14. 15,19-22 Dec 7-15.
Support for troughing continues in the eastern N Pacific 137-146W, and in the Central Pacific from 160W to the Dateline.
In Nov-early Dec: warm conditions are frequently interrupted by cold NNW-N wind events and some rains. If warmer than average temperatures occur, they will be related to subtropical moisture coming up from the SW in some of those heavier rain events.
Seasonably cool and wet conditions occur in mid to late Dec and in Jan 2025. Feb appears to have near to below average precipitation, with usual mountain snows.
For forestry. we expect a reduction in the fire season conditions as moisture continues to increase at vegetation levels near the surface. Bottom line is: Still some very near term warm and breezy periods with rapid shifts to cold and showery (rainy in NORCAL), with snow in mountains.
For season 2024-25 we could actually see two wet months: a week in mid November, and the other periods of heavy rains in Dec and Jan.
The monthly outlook maps from the CFSv2 model are posted at the end of this report (pdf version). Other than some showers for Central and S California in mid to late Nov, predicted rain amounts appear to continue near or below average through most of Dec.

Forecast for Northern California

NORCAL Precipitation: Nov 14-15, 16, 21-28, Dec 7-9 and 11-15.
NORCAL Mild/Dry Periods: Nov 20-21, Nov 30 ñ Dec 5.
NORCAL Cold or Frost Periods: Nov 15-19, 26-29 and Dec 9-10, 13-15.

North Sierra Precipitation: Nov 14-15, 17, 18-20, 21-29, Dec 7-9 & 12-15.
Central Sierra Precipitation: Nov 15, 17, 19-20, 22-29, Dec 8-10 & 13-15.

Forecast for Central California

CENTRAL CALIFORNIA Precipitation: Nov 14-15, 18, 23-28, Dec 8-10 and 12-15.
CENTRAL CALIFORNIA MILD DRY PERIODS: Nov 19-23, Dec 1-6 and 16-17.
Central California Cold Periods: Nov 15-18, 26-30 and Dec 11-15.

Forecast for Southern California

SOCAL PRECIPITATION: Nov Dec 15, 18, 24-29, Dec 9-10 and 13-15.
SOCAL MILD PERIODS: Nov 19-22, Dec 1-7,and 16-18.
SOCAL COOL PERIODS: Nov 15-17, 18, 25-30 and Dec 8-12, 14-17.

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 15ñday GFS.

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Southern California Deserts Outlook

SOCAL deserts: above 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 on Nov 14-15, 18 and 22-28.

Looking Further Ahead — December 15 – January 15 2025
Precipitation appears to turn above average for mid to late Dec. Mid Dec turns above average for precipitation in NORCAL and north-central Sierras for about 14-25 Dec. January 2025 has above normal rainfall with mountain snows. Heavy rains at ORWA coast and coastal mountains with possibly some higher than average snow levels occur ORWA region (Oregon, Washington). In midwinter, heaviest rains occur mainly coast/Cascades, due to Atmospheric Rivers in Jan-Feb. Some of these, though smaller amounts of these rains from ORWA reach into NORCAL and N Sierras. Bottom line: while ORWA receives heavy rains in Dec, NORCAL and Central California mostly receive near average amounts. We note that CFSv2 monthly guidance shows drier than normal for most of Dec, which we do not believe. Wetter than average with plenty of mountain snows in the Sierras during most of the latter part of Dec, and in Jan. Dry and warmer weather returns to Sierras and Central-S California finally in Feb. 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.

(Terms and Definitions Used In This Weather Outlook)