textproduct: San Joaquin Valley

KEY MESSAGES

1. Extreme Heat will continue to be the major weather concern over the weekend and early next week. Extreme Heat Warnings and Heat Advisories have been extended through the upcoming weekend to account for this.

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 increases this afternoon and continues for each afternoon through the weekend, peaking this weekend with chances of 10 to 20%.

DISCUSSION

Heat Dome now well in control of the West as temperatures continue to heat-up this weekend. Many San Joaquin Valley locations observed triple digit heat Today with values reaching 110 degrees across the Kern County Desert. Probability of Exceedance (PoE) of reaching 105 degrees will increase to percentage in the range of 70-85 percent through Sunday. Therefore, confidence is high that the Valley will continue to see heat advisory conditions through this weekend. In addition, with PoE of reaching 110 degrees across the Kern Desert up to 70 percent, will maintain the extreme heat warning for the same time period. While little relief will be seen through the early part of next week, POE does shows a decrease toward next Thursday. With that, heat will be the biggest concern for at least the next five days.

With the High Pressure Heat Dome over the Southwest, the flow aloft is now turning more southeasterly. This turn in the wind flow will allow for a surge of Monsoonal Moisture 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 probabilities with the Sierra Crest having the best percentages in the 20-30 percent range. Yet, while an increase in the west wind will taper off convection early next week, a disturbance pushing through California near the mid-week period will provide enough support for additional chances of convection over the Crest. The same disturbance will help to lower temperatures as well.

AVIATION

VFR conditions will prevail for the next 24 hours with light northwest winds during the day and variable winds overnight. Convection will have a 20-30 percent chance after 20Z Saturday 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 Sunday for CAZ337>339. Heat Advisory until 8 PM PDT Sunday for CAZ300>317-319-321-332- 334>336.