Large Scale Summary
- For near term conditions, the longwave pattern supports maximum of warm upper high pressure through 5 Apr, and again in mid or 3rd week of Apr.. ëRainí dates in the near term are: 8,9,10,11,13 Apr. For SOCAL, heaviest rains are 11th. Other rains occur 13,15,17,19, 21. Heaviest rains for SOCAL are on late 10-11th, then there appears to be another aggressive rain on the 15th.
- During 15-18 April, there is less tendency for dry conditions in California and a return to more of the usual cool upper troughs and cold fronts with some more showers coming through on about 15-16. The main set of storms with rain and cold weather will be occurring 18-21 Apr in California. the more intense circulations will occur
18-21 April, focusing in central and southern California and northern Baja. We look for greatest variation in speed of the westerlies at 30N and 40N. Most of this variation is due to interruptions in the westerlies at 32 to 43N. - Those functions that introduce increased variation in the westerlies occur at 32-43N for the most part as mentioned above. The increased variation is tending to occasionally interrupt westerlies which move along the usual development path in subtropics and midlatitude.
- While April precipitation continues above average, these trends will occasionally interrupt and cause a decrease in the precipitation occurring in April, and the first part of May as well. Fronts will be robust through the 20th of Apr, but we should also see more weakening, as the fronts move to the coast.
- In summary, the westerlies try to start up toward the end of the mid spring season. However, the favored location of troughs continues to be mid Pacific around 130-150W with a westward bias to maintain support of troughing into California and effect more consistent rains into the near coastal areas of California for rest of Apr and early May.
- Looking ahead to early summer: June (shown below) and July see a maximum of rainfall in SW Mexico and Baja, as well as up the Sierra Madre western mainland mountains, and in the Sierra Nevada in Central to South-central California. Some of rain in W and SW Mexico may be due to monsoonal moisture coming north towards the SW U.S. and SOCAL-Sierras in California. In July we also the monsoonal influence could become robust, bringing a chance for more rains into California and the SW U.S.
NORTHERN CALIFORNIA
- PRECIPITATION DATES: APR,15-16, and Apr 19-21, and 1-7 MAY.
- MILD to WARM/DRY PERIODS:25-29 APR.
- MOUNTAIN showers,rain/snow COLD: 15-16 and 19-21 APR, as well as 1-7 MAY.
CENTRAL
- PRECIPITATION_DATES: 15-16 APR, 18-21 APR, AND 1-7 MAY.
- MILD AND DRY: 25-29 APR.
- CENTRAL SIERRA: PRECIP: 15-16 APR, AND 18-21 APR. 1-7 MAY
SOUTHERN CALIFORNIA
- PRECIPITATION DATES: APR 15 ñ MAY 16, 19-21, 22-23 APR.
- COLD/FROSTS DRY WINDS:FROSTS VALLEYS 16-17APR
- MOUNTAIN SNOW: 15-16 APR, HVY SNOW 18-20 APR.
SOUTHERN CALIFORNIA DESERTS
- PRECIPITATION DATES. 15-16 APR, 19-21 APR.
- MOUNTAIN SNOW: NOT CALCULATED.
MEDIUM TERM OUTLOOK - May 2026
NORCAL
- PRECIP Dates: APR 29-30, MAY 1-2, Mountains AND EARLY (1-2 MAY), possibly COLD/SNOWY AGAIN IN EARLY MAY. MOSTLY NEAR AVERAGE IN THE EAST .BELOW IN WEST. ABOVE AVERAGE NORTH COAST.
- MOUNTAIN SNOWS: BELOW AVERAGE, HIGH SNOW LEVELS.
CENTRAL CALIFORNIA
- PRECIPITATION: MOSTLY COLD AND NEAR AVERAGE RAIN AND SNOW IN SIERRAS, including Late May.
SOUTHERN CALIFORNIA
- PRECIPITATION: NEAR AVERAGE. BEST CHANCES SHOWERS: MAY 8-15 and 28-31. POSSIBLE EARLY BURST OF THE MONSOONAL RAINS IN MID JUNE, AND ANOTHER BURST IN EARLY JULY.
SOUTHERN CALIFORNIA DESERTS
- PRECIPITATION: NEAR AVERAGE. BEST CHANCES SHOWERS: MAY 8-15 and 28-31. POSSIBLE EARLY BURST OF THE MONSOONAL RAINS IN MID JUNE, AND ANOTHER BURST IN EARLY JULY.
Figures and Text: Alan Fox, Fox Weather, LLC
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