textproduct: San Joaquin Valley

KEY MESSAGES

1. Heat Advisory now in effect for the majority of the area until 11 PM Tuesday.

2. Widespread Moderate Heat Risk, including triple-digit heat, in the lower elevations Thursday until next weekend. Some pockets of Major Heat Risk, particularly near urban areas.

3. Hot and dry conditions will create increased fire risk in eastern Kern and Tulare Counties this weekend.

4, Chance for thunderstorms in the Sierra Nevada the next few days, which may include dry lightning.

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

DISCUSSION

High pressure ridge holding strong off the Pacific Coast as Central Californias Heat Wave continues this Saturday. While ensemble upper-air analysis does show a pattern shift toward a more zonal flow (westerlies) over the Pacific Northwest, this shift is showing minimal changes over Central California. Therefore, will see little relief from the heat as high pressure remains in-place through the middle of next week.

Current ensemble surface temperature analysis has Probability of Exceedance (PoE) of San Joaquin Valley (SJV) temperatures reaching 100 deg in the 75 to 95 percent range (with higher percentage values over the Kern County portion of the SJV). These percentages will be the expected values from this Saturday through at least Wednesday of next week. Yet, the PoE of 105 deg is only 10 to 20 percent for foothill locations on either side of the SJV for the same period. Therefore, with the 75th and 90th percentiles in the 102-106 deg range across the SJV, confidence is high that the heat wave will continue through at least Wednesday. Ensemble PoE of reaching 100 deg on Thursday does show a drop-off as percentages fall below 20 percent Valley-wide.

The latter part of next week shows a closed low attempting to cross Northern and Central California for a possible threat of mountain thunderstorms. The disturbance will also introduce a cool-down and stronger winds over the favored locations of the district. Beforehand, an area of weakness will drop through the area (centered along the coast) with weak lift and some surge of moisture ahead of it to generate mountain showers and thunderstorms on Sunday. Ensemble thunderstorm probabilities do show an up-tick in percentages along the Sierra Crest near Yosemite on Sunday (compared to Today) and again of Thursday.

AVIATION

VFR conditions expected in the San Joaquin Valley for the next 24 hours. Surface Wind G25KTS will have a 30-40 percent probability of occurrence over Kern County after 00Z Sunday.

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

Heat Advisory until 11 PM PDT Tuesday for CAZ300>321-332.