textproduct: San Joaquin Valley
This forecast discussion was created in the public domain by the National Weather Service. It can be found in its original form here.
KEY MESSAGES
1. Seasonally average weather returns this weekend. Next warm- up expected later next week.
2. Another monsoon push early next week increases probability of Sierra Nevada thunderstorms.
DISCUSSION
A neutral atmospheric pattern is establishing over California as the closed low off the Pacific Northwest coast and high pressure ridge over the western US shift away northward and eastward respectively. Thus, the next couple days will be indicative of typical summer conditions. The Heat Advisory currently in effect is set to expire at 11 PM PDT tonight, as afternoon highs and overnight lows return to typical summer averages with the eastward shift of high pressure.
Outside of the Sierra Nevada crest, any chances for precipitation and thunderstorms do not enter the forecast until late this weekend. Both the ECMWF and GFS deterministic models are picking up on a favorable pattern setting up to bring back another monsoon moisture push. Latest probabilistic guidance is picking up on an increased probability for crest thunderstorms from 5-10% to 15-20% late on Sunday, extending further down the Sierra Nevada. This will ultimately depend on how well situated Tropical Storm Elida ends up, as this will provide the necessary low pressure off the coast to steer monsoonal air northwestward into California. Longer range ensemble analysis has the heat dome centered closer to the Mid-West as the associated flow pattern pushes the monsoon moisture back toward Central California late in the weekend. Climate Prediction Center (CPC) is indicating that the extended time frame of the 6 to 10 day period will remain on the warm side. Current CPC analysis has a 40-50 percent chance that temperatures will lean toward above normal conditions.
AVIATION
VFR conditions expected for the next 24 hours.
AIR QUALITY ISSUES
None.
CERTAINTY
The level of certainty for days 1 and 2 is high. The level of certainty for days 3 through 7 is medium.
Certainty levels include low...medium...and high. Please visit www.weather.gov/hnx/certainty.html for additional information and/or to provide feedback.
HNX WATCHES/WARNINGS/ADVISORIES
Heat Advisory until 11 PM PDT this evening for CAZ305>307- 309>316-319-321.
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