Weather Outlook — March 17 - April 17, 2025

LARGE SCALE SUMMARY

1. NORCAL rain dates include February 16-17 (light rain or showers). For Central California, rain dates in coastal valleys are: February 16, 17, 19, 27, 28 and March 1.  Dates of main precipitation centers from CFSv2 are: February 28 - March 1, showery; March 2-3 few sprinkles; March 4-5 light showers; March 7-10 light showers; March 14-18 mostly light rain or showers.  Periods of moderate to heavy rain are possible March 21-26.
2. Support for troughing continues in the central N Pacific from about 130-145W (mainly NE to N of Hawaii), and at 160W to near the Dateline is NW of Hawaii. A third (weaker) area of troughing extends from about Hawaii to near Central California, paralleling a weak IVTinit zone, and the zone of higher values of IVTinit located farther south.
3. For forestry, we have a wet spell for the following dates — rains and snows February 16-17 N and Central California including Sierra Nevada, coastal ranges, and Siskiyouís. Where these numbers disagree with the CFSv2 guidance given above, nearer term guidance was from GFS and MtnRT/WRF.

MEDIUM TERM OUTLOOK — MARCH 17 - APRIL 17

• North half of California:  Near average precipitation with slightly colder than average. Frosts: greater number of frost/freezes than average.
• South half of California:  Below average precipitation with a near average temperature. Near to little above average number of frosts/freezes in valleys of SOCAL, especially north part, i.e. valleys of San Luis Obispo, Santa Barbara, Ventura Counties. The Riverside Valley, Ramona(San Diego Co) areas will also dip briefly into the 30s.

LONGER TERM OUTLOOK — April 17 – May 17 

• North half of California: Near to a little above average precipitation, highest precipitation anomaly will be at the North Coast Mendocino Co north in first half of April.  Temperatures well above average Sacramento Valley, and well above average in central to southern Sierras  (warm nights on slopes with inversion conditions). Frosts: greater number of frost/ freezes than average in mid Apr, recovering to near or a little above average number of frosts/freeze only slightly above average number of frosts/freezes by May 1.
• South half of California:  Below average precipitation with above average temperature. We will still see some frosts in valleys of Southcentral California, including San Luis Obispo and Santa Barbara Coís. Turning warmer than average in SOCAL mountain areas overnights (peaks and slopes due to inversion conditions as high pressure 
  tends to build more frequently in late Apr to first week of May, even though valleys are still seasonably cool.

FUTURE OUTLOOK — May 17 – June 30

• Northern California:  Temperatures recurrently above average for the early summer period, precipitation remaining below average.
• Southern California:  For the valleys of Southern California:  Warmer and drier than average during the late spring and the first month of early summer (June).
• Northern California:  For valleys and mountains of Northern California, warmer and drier than average during late spring and first month of summer (June).                                                      

Figures: Alan Fox, Text: Alan Fox, Fox Weather, LLC.

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