textproduct: San Joaquin Valley

KEY MESSAGES

1. Extreme Heat Warning issued for the Mojave Desert and Indian Wells Valley Thursday 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 this Friday, 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 for most of the week.

DISCUSSION

Ridging continues to be the dominate pattern over much of Central California, especially for the Mojave Desert where daytime highs are expected to be in the 108 to 112 degree range from tomorrow through early next week. As a result, an Extreme Heat Warning has been issued for that region from 8 AM tomorrow through 9 PM Monday. While the desert will be seeing these hot temperatures, the San Joaquin Valley is likely to see temperatures around or a couple degrees above normal through mid next week as the ridge holds its position over the Four Corners.

Thunderstorm chances also continue to appear in the forecast, though not as strongly as seen at the beginning of this week. Current chances for tomorrow afternoon are 5-15%, while tomorrow sees similar chances to today's forecast, although that amounted to little actual activity this afternoon. But, as the ridge migrates further west over the coming days into next week, monsoonal moisture is likely to be cut off and thunderstorm chances dive below 5% by Sunday. This may also hold true as the current 500mb forecast shows the ridge centered squarely over Arizona and flow into the Valley coming from the southwest.

This flow pattern would also lead to a warming trend for the Valley, similar to what the Mojave Desert is going to see through Monday. The Climate Prediction Center continues to highlight the Valley for hazardous temperatures, including a high risk (>60%) for extreme heat on July 30th and 31st, and the first few days in August are under the moderate and slight risk through the 1st and 5th respectively, which is a marked increase in confidence since the last forecast they issued for the CONUS.

AVIATION

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 from 8 AM Thursday to 9 PM PDT Monday for CAZ337-339.