30-Day Weather Outlook for May 24, 2024 to June 24, 2024

May 31, 2024

BASIC PATTERN

Large Scale Pattern

The focus of lingering upper lows continues west of the Pacific Northwest, and also at 138-145W to the west of Northern and North-Central California.
Our IVTinitô analysis shows the calculated estimate of one day (Day0 Total Integrated Vapor Transport (TIVT24), based on the sea surface temperature anomaly pattern from the coast out to 180W. This is calculated by Fox Weather LLCís CyclogenIVT AI application each day. It shows for us the potential areas for development of troughs and rains upstream from California and the West Coast.
As we approach the end of the rainy season, the upper westerlies continue to gradually decrease speed. The surface onshore flow strengthens as the deserts heat up while the coast remains cool.
Rain Dates from our CFSDailyAI system: rain in north coast area May 29-30, and June 5-8. Rain in central coast, and into the Sierras 6-9. It appears that none of these rains reach into SOCAL. After 10th, a long dry trend appears to develop from 10th onward through about 25 June.
There continues an increase in support for dry troughs with, and followed by gusty downslope winds in central California, and dry/occasionally windy conditions in the SOCAL desert areas.
For forestry and upcoming Fire Season 2024 in NORCAL and Sierras support will be decreasing for showers in NORCAL and in the Sierras after the final rainy fling at end of May and in June 5-9.
Monsoonal TSTMS and rainfall are currently expected below normal for W and NW Mexico. Therefore, the moisture source for tropical monsoon conditions in California and Arizona appears to be drier than normal during the transition to early summer.

FORECASTS FOR CALIFORNIA

Forecast for Northern California

NORCAL Precipitation: May 29-30 and Jun 5-8 (N areas).
NORCAL Warm-Dry Periods: May 26-28, 31-Jun 2, 10-16 and 21-25.
NORCAL Cool and Breezy Periods: May May 29-30, Jun 4-8 and 18-19.
North Sierra Precipitation: May 30 and Jun 6-9.
Central Sierra Precipitation: Jun 7-9.

Forecast for Central California

Central Calif Precipitation: May 30 and Jun 6-7.
Central Calif Warm Dry Periods: May 25-29, Jun 1-4, 9-16 and 20-25.
Central Calif Cool Periods: May 30-31 and Jun 6-8.

Forecast for Southern California

SOCAL RAINS: Dry with rain unlikely.
SOCAL Warm Dry Periods: May 24-29, Jun 1-5, 8-17 and 20-25.
SOCAL Cool Periods: May 31 and Jun 6-7.

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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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Looking Ahead — Longer Range Outlook for June

Southern California Deserts Outlook
Troughing Dates: May 30-31, June 6-7.

N and Central California and Sierras
Overall tendency for cool conditions with near to above normal rains has greatest confidence in the northern mountains (Siskiyouís) and Lake Tahoe to Yosemite NP in the Sierras. The cool showery conditions may linger into mid June.Some hot weather spikes may occur after 10 June in NORCAL and the N Sierra foothills (west slope), similar to the hot spell on 8-9 May. For S California June 2024: Late May is cooler than normal for the most part. Early to mid June also appears cooler than normal due to deep coastal marine layer and residual troughing through 10 June. Troughing through mid June would favor breezy and dry conditions for the S and E Deserts of Southern California.

Outlook for July - Monsoonal Conditions
W Mexico is shown by CFSv2 monthly outlook maps to have below normal precipitation and above xcnormal temperature. The same basic pattern continues for August 2024. Bottom line for California monsoonal rain conditions and thunderstorms below normal rainfall and below normal lightning, for late June ñ September period, but recurrently or persistently dry and hot conditions.

(Terms and Definitions Used In This Weather Outlook)