textproduct: San Joaquin Valley

KEY MESSAGES

1. Another round of monsoonal moisture will bring chances for thunderstorms across the Sierra Nevada crest through the middle of the week.

2. High pressure over the region will maintain temperatures near season averages for most of this week.

DISCUSSION

The ridge over much of the Great Basin and the southwestern CONUS is showing no signs of moving through the next 7 days, meaning highs are expected to be steadily in the lower triple digits for much of the Valley through this week and into next week. Its position over the Four Corners will allow for monsoonal moisture to be pulled into the region and may lead to thunderstorms developing along the Sierra Nevada crest, particularly on Monday and Tuesday when the most moisture is expected to come into the region. Current chances for thunderstorms on those days are 20-30% on Monday and 20-40% on Tuesday. Probabilities for a wetting rain (0.1 inches) on Tuesday are 50-70% above 8000 feet and 30-50% above 6000 feet around Mount Whitney. The Weather Prediction Center has also issued a Marginal Risk (at least 5%) for excessive rainfall in the high Sierra Nevada on both Monday and Tuesday due to these increased thunderstorm and rainfall probabilities.

Thunderstorm chances will continue into Wednesday, with chances in the 15-30% range due to lingering moisture, but the following afternoons will see a drop-off in probabilities as the flow becomes more westerly and loses the direct southerly component that would pull monsoonal moisture north into California. Looking into the long term forecast, the ridge still remains in place and may even gain strength by the last week of July into the first few days of August, as the Climate Prediction Center has the Valley in a slight risk (20-40%) for hazardous temperatures form July 27th through August 2nd, as well as likely above average temperatures from day 6 through day 14.

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

None.