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 shifting east as temperature began a cooling trend that will exist for the rest of the week. Confidence is high that temperatures will start cooling as the Probability of Exceedance (PoE) of reaching 105 degree drops to below 10 percent. While the PoE of reaching 100 degrees still sits at 70-90 percent for areas from Fresno County southward across the San Joaquin Valley, the PoE of that will also drop throughout the week. Therefore, the Extreme Heat Warnings were allowed to expire this evening as our attention turns toward the intrusion of monsoonal moisture moving through the Desert Southwest.

The high pressure area over the Desert Southwest (Four Corners Area) will allow for a good southeast flow aloft to push moisture toward California. Ensemble precip-water analysis does show an increasing trend in values surging into the area over the next few days. 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 have been low, they do increase going into Tuesday with better chances Wednesday as the surge of Monsoon Moisture pushes deeper across the Sierra Nevada Crest. Therefore, will expect an up-tick on convection from very isolated on Tuesday to widely scattered by Wednesday. Furthermore, the surge may be strong enough on Wednesday to push some moisture in the San Joaquin Valley. While probabilities area low, the chance of foothill convection may increase as an isolated storm over the valley floor is not out of the question.

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 Tuesday until 03Z Wednesday 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

None.