textproduct: San Joaquin Valley

KEY MESSAGES

1. Less than a 10 percent chance of lingering thunderstorms will exist across the Sierra Nevada Crest today.

2. Warming trend Wednesday into the weekend with high confidence of at least Moderate Heat Risk in the Valley Sunday through Tuesday.

3. Moderate chance for High Heat Risk in the San Joaquin Valley areas.

DISCUSSION

Clear conditions are developing across central California today that will continue into the weekend and early next week as a high pressure ridge gradually builds in over the area. Slight amounts of moisture tracking over the Sierra Crests have potential to develop thunderstorms during the afternoons through Friday, however daily chances are generally less than 10 percent. A warming trend will begin today, with afternoon temperatures near season averages in the San Joaquin Valley before warming to ten degrees above average by the weekend. The peak in heat is expected to occur Monday and Tuesday of next week across the valley areas. On Monday, there is a 50 to 60 percent probability for maximum temperatures to exceed 100 degrees, with greater probabilities of 70 to 80 percent in the western valley areas. However, these greater probabilities extend to the entire San Joaquin Valley on Tuesday. These temperatures bring a 90 percent probability for a Moderate Risk (level 3 of 5) of heat-related illnesses on Tuesday, though there is upwards of a 60 percent probability in Fresno for High Risk (level 4 of 5).

AVIATION

VFR conditions will prevail for the next 24 hours over Central California.

FIRE WEATHER

Warming temperatures rising above 100 degrees early next week will result in lowering relative humidities across the region. For Monday and Tuesday, minRHs in the Mojave Desert are expected to fall to 5 to 10 percent, with valley and mountain RHs between 15 and 20 percent. A drop in 100- and 1000-hr fuel moisture will follow, though will remain above critical fire weather territory. Additionally, subsidence from the high pressure ridge will keep winds relatively light across the region.

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.