textproduct: San Joaquin Valley

KEY MESSAGES

1. Cooler Juneteenth and Saturday temperatures until warming temperatures start again on Sunday. Triple-digit heat expected by next Tuesday.

2. Hot and dry conditions next week will create increased fire risk across the region.

3. 20-25% probability for thunderstorms in the Sierra Nevada, including isolated risk for dry lightning.

4. Practice safety around lakes, rivers, and streams, as water is still running cold.

DISCUSSION

While warm and dry weather is likely to continue for a while, a small cooling trend is expected to start tomorrow and last through Saturday. High temperatures will hover around 90 degrees across the high desert, San Joaquin and Kern River valleys by Saturday as the ridge currently aloft breaks down and gives way to a weak trough. Minimum relative humidity across the San Joaquin Valley is expected to slightly improve to 25-35% as the troughing moves through the region.

Unfortunately, minimum RH will remain at 10-15% across the Mojave Desert before even dryer air settles into all of Central California as temperatures increase next week. Latest models indicate triple-digit heat returns to the Mojave Desert by next Monday and the San Joaquin Valley next Tuesday. Combined with minimum RH falling to as low as 15-20% and 5-10% respectively, both widespread moderate heat risk and elevated fire risk are expected to return (once again) by the start of the next work week.

Troughing crossing over our area will also encourage afternoon thunderstorm development along the Sierra Nevada crest today and on Juneteenth. Latest probabilistic forecasting indicates a 20-25% probability for thunderstorms, including a 10% chance for isolated dry lightning around Yosemite and Sequoia National Parks. This carries with it an increased fire risk for the Sierra Nevada mountains.

Above normal temperatures are likely to continue; the Climate Prediction Center has the 6 to 10 day and 8 to 14 day outlooks in the likely above normal temperature category.

AVIATION

VFR conditions expected across the area for the next 24 hours. 20-25% probability for afternoon thunderstorms across the Sierra Crest today and on Juneteenth.

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

Lake Wind Advisory until 5 AM PDT Friday for CAZ300.