30-Day Weather Outlook for April 5, 2024 to May 5, 2024

Apr 01, 2024

BASIC PATTERN

Large Scale Pattern

The focus of lingering upper lows continues west of the Pacific Northwest, and also at 132-140W to the west of N and 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 off the West Coast, out to the Dateline (180W). This is calculated by Fox Weather LLCís CyclogenIVT AI application each day. It shows for us the potential areas of troughing and rains upstream from California and the West Coast.
As we approach the end of the rainy season, the westerlies weaken. As the westerlies weaken, there is increasing risk of troughs with scattered showers developing in the Great Basin, and south into Arizona and central Baja California.
Rain Dates for most of California including Central, most of Southern, and Northcentral: Apr 4,5,6,7, 13-14 (cold front). Better chances for rain also occur 19,20,23 24,28, and May 2-3.
Note that temperature during mid to possibly late April is forecasted below normal for Central and S California as well as Nevada and Arizona. This supports a higher probability of frost events in April for those sensitive agricultural areas in the west San Joaquin Valley, Delta, Central Coast to Santa Maria-Santa Ynez Valley, and Santa Barbara County.
For forestry and upcoming Fire Season 2024 in NORCAL and Sierras We continue to see support for above normal rainfall (precipitation) in NORCAL and rain with higher elevation snow in the Sierras during April. Showers and rains occur at normal frequency and amount in the Sierras during May. However, these are mostly cold showers, and do not appear connected with monsoonal conditions or moisture. Monsoonal TSTMS and rainfall are currently expected below normal for W and NW Mexico. Therefore, the moisture source for monsoonal conditions in California and Arizona appears to drier than normal.

FORECASTS FOR CALIFORNIA

Forecast for Northern California:

NORCAL Precipitation: Apr 4-6, 13-15, 19-20, 23-24, 28, May 2-3.
NORCAL MILD OR WARMER SPELLS: Apr 8-12,17-18, 22, 26-27, Apr 30-May 1
NORCAL COOL/COLD/FROSTS: Apr 4-7, 13-15, 19-20, 23-25, 28-29, May 2-4

Forecast for Central California:
Central Calif Precipitation: Apr 4-5, 23-24, May 4
Central Calif WARM SPELLS: Apr 6-7, 9-14, 17-21, 25-May 2
Central Calif COOL/COLD/FROSTS: Apr 4-5, 14-15, 20, 23-25, 28-29, May 3

Forecast for S California:
SOCAL RAINS: Apr 4-5, 23-24, May 4
SOCAL WARM SPELLS: Apr 6-7, 9-14, 17-21, 25-May 2
SOCAL COLD OR POSSIBLE FROST: Apr 4-5, 23-25, May 4

Central Sierra Nevada Precipitation
Main dates of rains or showers and mountain snow - Mar 15-16, 27, 29-31

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The listings of dates normally included for hot and cold spells, and precipitation are approximate. They are based on 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 April 3 - April 30, 2024

N and Central California and Sierras: We basically echo what we have already said in paragraphs 5) and 6) above. Frequency of frost will be less, but the overall tendency for cool conditions with near normal rains has fairly high confidence at this time.

S California: Apr 24-June 2024: Near normal temperature and precipitation for May and June.

S California Deserts: Mar 30 - Apr 30 roughing Dates: Apr 4-5, 13-14, 19-20, 23-24, 28, May 4. Some dates may contain a shower as well as gusty winds.

(Terms and Definitions Used In This Weather Outlook)