Weather Watch 18-Day Analysis for East Central and South San Joaquin Valley

By WeatherAg Chief Meteorologist Scott Borgioli

Wednesday, May 8, 2024, through May 26, 2024

Lows (through May 26)

  • Through Thursday night: +/- 0 to 5° of seasonal average through Thursday night
  • Friday through Saturday, May 18: +5 to +10° above seasonal average
  • May 19-May 26: +3 to +8° of seasonal average

HIGHS (through May 26)

  • Today: 0-3° of seasonal averages
  • Thursday (May 8) to Thursday May 16: + 10 to +15° above seasonal average –May 17-May 20: odds favor +8 to 10° of seasonal averages
  • May 21-May 26: odds favor 0 to +5° of seasonal averages (esp May 23-26)

 GENERAL SUMMARY THROUGH MAY 26 (based on data at this time)

Through Thursday of next week, May 16:

  • Multiple areas of moderate to strong high pressure will build into the Pacific NW / North Pacific and will remain moderate/strong around the middle of next week (May 15-16) before weakening. No rain is expected.  Winds here in the valley are expected to be light overall, with gusts of 10-15 mph at times and perhaps a few spots of 20 mph at times.

Friday, May 17-May 26:

  • In parts of the North Pacific, Pacific NW, high pressure is expected to weaken starting around Friday, May 17, through Monday, May 20. This may allow weak low-pressure systems to pass through parts or all of the Pacific NW, resulting in cooler temps here, especially highs, along with some passing high clouds at times and potentially some breezy periods.
  • However, uncertainties currently exist as to the exact location of high pressure and which area(s) may/will weaken. Therefore, although slightly cooler temps are expected, the amount of cooling and breezy periods are conditional on high-pressure location/weakening and storm systems passing through the Pacific NW. Right now, it looks like we’ll see more of a pattern change around May 22/23-ish.

Valley Rainfall:

  • At this time, I don’t think we’ll see any valley precipitation during this period. However, some mountain areas north of Shaver Lake may get scattered light precipitation if high pressure weakens as expected and storm systems pass through WA/OR/NorCal.

PRECIPITATION PROBABILITIES (preliminary, based on current signals)

  • May: 50-70% of average
  • June: 70-100% of average through mid-June, then 50-70% of average (N/A for July/Aug)
  • Sept-Nov: 40-60% of average due to expected “moderate” strength La Nina

TEMPERATURE ANOMALY PROBABILITIES (preliminary, based on current signals)

  • Odds favor +/- 5° of average mean temperatures (as a whole) for June 1-20
  • Odds favor +5 to +10° of average mean temperatures (as a whole) for June 20-30 / July / August


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