textproduct: San Joaquin Valley

KEY MESSAGES

1. Minor Heat Risk across the lower elevations of central California Tuesday with a warming trend and increasing risk starting Wednesday.

2. Widespread Moderate Heat Risk, including triple-digit heat, in the lower elevations Thursday until next weekend. Pockets of Major and Extreme Heat Risk as well.

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

DISCUSSION

The second of a pair of troughs over the Pacific Northwest is beginning to clear the area today, and with that will come a significant warming trend. There is a 20-50% chance of high temperatures exceeding the 90-degree mark in Valley areas south of Fresno today. On Wednesday, there is a 60-80% chance of exceeding 95 degrees for the entire Valley, and there is a 40-80% chance of exceeding 100 degrees on Thursday for the entire Valley. The worst of the heat is expected to continue into the weekend. This will create a prolonged period of widespread moderate heat risk, with some areas experiencing major and even extreme heat risk. It is extremely important to plan ahead now by reducing outdoor activity, having cooling and hydration available, and having a plan for vulnerable people and animals. Heat products will likely be issued this week.

While relative humidity values will be above normal today, they will return to normal ranges tomorrow and the rest of the week, with minimum RH values in the 15-20% range across the Valley each day and 9-15% in the Kern Desert. While wind is not expected to be a major concern, the heat and dry air will create elevated fire concerns, particularly Friday and into the weekend.

Despite the heat, water is still running cold and poses a risk to swimmers, both human and animal. Practice safety around lakes, rivers, and streams.

A compact shortwave may bring a minor dry lightning risk in the upper Sierra Nevadas on Friday.

AVIATION

VFR conditions expected across the central California interior 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

None.