textproduct: San Joaquin Valley

KEY MESSAGES

1. The Heat Wave will continue to be the major weather concern as the Extreme Heat Warnings will be in effect until Monday evening.

2. Persistent hot and dry conditions will also continue to promote the potential for wildfires with cured fuels.

3. Potential for thunderstorms over the Sierra Nevada crest continues for this afternoon and evening, with chances of 20 to 30% today and additional chances Tuesday through next weekend.

DISCUSSION

Heat Dome sitting over the West as temperatures continue to heat-up this late this weekend. Many San Joaquin Valley locations observed triple digit heat Today with values reaching 110 degrees across a wide area with reading up to 104 degrees at places like Chowchilla and Merced. Probability of Exceedance (PoE) of reaching 105 degrees will start to decrease on Tuesday as a downward trend will be see later this week. For now, the extreme heat is upon us with a transition starting on Tuesday. By Wednesday, the PoE of reaching 105 degrees drops to near zero and the PoE of 100 degrees drops to near zero percent on Thursday. Therefore, with PoE showing that downward trend through out the week across the San Joaquin Valley, relief from the heat will be felt later this week. Furthermore, the Kern Desert will be right in step with the Valley as temperatures value fall below 100 degrees by this Friday.

With the High Pressure Heat Dome well over the Southwest, the flow aloft is now turning more southeasterly. This turn in the wind flow will has allowed a surge of Monsoonal Moisture to push closer to the Central California Interior. At the moment, moisture will be confined to the Sierra Crest and portions of Kern County. Ensemble forecast does show a up-tick in the precipitation spread across the the Sierra Crest. While the lower end of the spread for the period from Monday through Wednesday is zero (0.00) the upper end shows a chance (10 percent) of receiving a wetting rain (0.10-0.20). Therefore, while the probabilities are low for Monday, they do increase going into Wednesday as a better surge of Monsoon Moisture pushes into the Sierra Nevada Crest. Therefore, will expect an up-tick on convection from very isolated on Monday to widely scattered by Wednesday.

AVIATION

VFR conditions will prevail for the next 24 hours with light northwest winds during the day and variable winds overnight. Thunderstorms will have a 10-20 percent chance from 21Z Monday until 03Z Tuesday across the Sierra Nevada Crest.

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 8 PM PDT Monday for CAZ300>319-321- 332-334>339.