textproduct: San Joaquin Valley

KEY MESSAGES

1. Low pressure trough moves through California today, bringing cooler temperatures and a possibility for precipitation along the Sierra Nevada crest.

2. Low but notable chances (10-20%) for thunderstorms across the Sierra Nevada Monday.

3. Lake Wind Advisory for Lake Isabella will continue through this evening.

4. A ridge will build over our area by the middle of next week, leading to temperatures well above average for an extended period of time.

DISCUSSION

A deep trough that has the potential for a closed low to be associated with it has moved into our region. Due to this strong trough temperatures will be much cooler today compared to the weekend. There is an 80-90% chance of highs in the Valley today not exceeding 85 degrees. Gusty winds are possible today due to the influence of the trough, but they will mostly be confined to areas typically prone to high wind gusts, such as along the highest elevations of the Sierra Nevada, and Mojave Desert slopes. Wind gusts increase in the Valley and mountains over the afternoon with a 5 to 15 percent chance of gusts of 25 mph in the Valley. Gusty winds exceeding 45 mph are possible in wind prone areas along the highest elevations of the Sierra Nevada mountains and Mojave Desert slopes (40-55%, with some localized areas along the Sierra Nevadas with a higher probability). A Lake Wind Advisory remains in effect through this evening for Lake Isabella, while the Lake Wind Advisory for the San Luis Reservoir has been allowed to expire.

Increases in moisture and rising motion from the trough will help bring a 10 to 20 percent chance of thunderstorms over the Sierra Nevada. In addition, there is a 10 to 40 percent chance of an inch of snow on Monday above 10,000 feet. The Valley, however, has a 5 percent chance or less of any precipitation. The foothills have less than a 30% chance of any rain on Monday with sharp gradients in the probability of rain as elevation increases. Meanwhile, the higher elevations see a 25 to 50 percent chance of a tenth of an inch of rain. While low, there is a potential for dry lightning today along the Sierra Nevada crest given the limited amount amount of moisture associated with potential thunderstorms.

However, temperatures begin to climb again on Tuesday as the trough slides away. A ridge of high pressure will slide in on Wednesday, bringing in a 60 to 80 chance of highs of 95 degrees and greater in the Valley from Thursday into next Monday. It is likely that a moderate heat risk will be in place throughout much of the Valley during that same time period, posing a risk to populations particularly vulnerable to hot temperatures and people who are not properly hydrated. Dry conditions will begin to dominate the entire region after today. In addition, the chances of widespread gusty winds along the Sierra Nevadas and Mojave Desert slopes will quickly decrease by the middle of this week. This expected warmth aligns with the CPC's temperature outlook that has a 70 to 90 percent chance of above average temperatures in the next 6-10 and 8-14 days.

AVIATION

VFR conditions will prevail for the next 24 hours. There is the potential for brief periods of light wind gusts today likely at or below 20 mph, especially at KBKL and KMCE with winds out of the NW throughout most of the day today.

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 7 PM PDT this evening for CAZ332.