30-Day Weather Outlook for March 15, 2024 to April 15, 2024

Mar 19, 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. The IVTinit pattern extends south to 35N to the west of southcentral California.
Our IVTinitô analysis shows the calculated estimate of one day (Day0 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 areas of troughing and support for rains upstream from California and the West Coast.
The IVTinitô analysis shows support for rains at 130-145W off the California coast. It also continues to show another area of troughing that extends from N Baja ñSE California to Arizona. This does not appear to show up on the CFSv2 maps but should be considered anyway.
As we approach the end of the rainy season, the westerlies weaken. As the westerlies weaken, there is increasing risk of dry troughs developing in the southern Great Basin, and south into central Baja California. We saw this last fall in Nov-Dec 2023. Watch for the dry conditions to occur again this spring at end of winter as the westerlies weaken.
Rain Dates: Mar 12-14 Sierras, 15, showers 21-22, 27,29-31, and mid Apr.
In March, CFSv2 shows it turning dry later this month in coastal central and N California.
Note that temperature during March is forecasted below normal for Central and S California. This supports a higher probability of frost and freeze events in March for those sensitive agricultural areas in the west San Joaquin Valley, Delta, Central Coast to Santa Maria-Santa Ynez Valley, and Santa Barbara County.
During April, CFSv2 suggests a return to warmer than normal conditions in N and Central California. Above normal precipitation focuses in the Sierras, mostly showers. And thunderstorms (TSTMS). These should continue into May.otherwise precipitation is near normal during April in SOCAL. Precipitation is well below normal in NW California to Bay Area/Monterey Co per the CFSv2 maps.
For forestry and upcoming Fire Season 2024 in NORCAL and Sierras. If the early return to dry conditions coastal mountains continues in late Mar-Apr-May, this could set up conditions for another aggressive fire season. This could begin in at least May and June Napa/Sonoma Coís, Bay Area Counties, as well as Santa Barbara/LA/Ventura Coís in May-June.
As the season turns hot with early start of dry warm N-NNE winds along the N, Central and Santa Barbara south coast areas (sundowner, diablo, or Gaviota winds depending on region) this fire season could become robust. Especially at risk would be the N Sierras, and Trinity/Siskiyou regions. In the coastal mountains/foothills, rapid dryoff of abundant fuels after a wet season on the North Coast as transition occurs from the sundowner season to the midsummer heat season. The TSTM season does not look aggressive at this time, with below normal summertime TSTM-related precipitation. However, the ìhot-dry-windyî factor in mid to late June will need to be monitored more than usual. Outlook maps for June are showing below normal precipitation for the monsoonal areas of Mexico.

FORECASTS FOR CALIFORNIA

Forecast for Northern California:
NORCAL Precipitation: Mar 15-16 (Sierra snow) 21-22,24-25,27-28,29-31, Apr 10-11,14-16.
NORCAL MILD OR WARMER SPELLS: Mar 17-19 and Apr 2-8
NORCAL COOL/COLD/FROSTS: Mar 21-Apr 1, 10-12 and 14-16

Forecast for Central California:
Central Calif Precipitation: Mar 15(Sierra snow), 21, 24, 26 and Apr 10-11.
Central Calif WARM SPELLS: Mar 17-20, Apr 1-8 and 13-14
Central Calif COOL/COLD/FROSTS: Mar 21-28 and Apr 10-12

Forecast for S California:
SOCAL RAINS: Mar 15-16 (mtn shwrs),26 and Apr 10
SOCAL WARM SPELLS: Mar 18-25, 30-Apr 1-9, 12-15
SOCAL COLD OR FROST: Mar 15-16, 19, 26, 28-29, and Apr 10-11.

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 system gives some consideration to terrain and coastal influence. We consider the CFSv2 one of the better ways to represent basic weather down in the sub-monthly time scale beyond the 15ñday GFS or monthly maps from CFSv2 or NMME.

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Southern California Deserts Outlook:

Troughing Dates: Mar 15,27-31
Some of the earliest dates may contain a shower as well as gusty winds.

Looking Ahead — Longer Range Outlook April 3 - April 30, 2024

N and Central California and Sierras: We pretty much echo what we have already said in j) above.

S California:
Dry. Warmer than normal May and June.

(Terms and Definitions Used In This Weather Outlook)