textproduct: San Joaquin Valley

KEY MESSAGES

1. Extreme Heat Warning in effect for the Mojave Desert and Indian Wells Valley through Monday. Major HeatRisk expected with afternoon highs 108 to 112 each day.

2. A small increase in monsoonal moisture will bring a slight chance for thunderstorms across the Sierra Nevada crest again today, but the rest of the week into next will see chances less than 10%.

3. High pressure over the region will maintain temperatures near season averages for the remainder of Central California before hotter conditions appear late next week.

DISCUSSION

A ridge of high pressure continues to dominate over the Western U.S., however, ensembles have a trough sliding over the top of the ridge this weekend. The current setup has some moisture still being advected in brining a 15 to 30 percent chance of thunderstorms over portions of the Sierra Nevada today. However, as that trough slides over the ridge, temperatures slightly decrease but will be at or just slightly above average through the weekend with a 30 to 50 percent chance of triple digits south of Merced through Tuesday. The heat will continue to remain over the Kern County Desert through Monday as the Extreme Heat Warning continues with a 85 to 95 percent chance of highs of at least 105 degrees.

The ridge slides west Monday into the work week and will strengthen leading to a warming trend. Latest probabilities show a 30 to 50 percent chance of a Major Heat RIsk for most valley locations by next Friday. This bodes well with a 15 to 40 percent chance of a high of 105 degrees south of Merced on Thursday and a 25 to 65 percent chance of 105 or higher on Friday for the entire Valley. CPC has most of the Valley in the 70 to 80 percent chance of above average temperatures in the 6-10 and 8-14 day outlook.

AVIATION

A 10-25% chance of afternoon thunderstorms along the Sierra Nevada Crest through 03Z Saturday. Otherwise, VFR conditions will prevail in the San Joaquin Valley 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

Extreme Heat Warning until 9 PM PDT Monday for CAZ337-339.