textproduct: San Joaquin Valley

KEY MESSAGES

1. Triple digit heat continues for San Joaquin Valley and Mojave Desert.

2. Monsoonal moisture brings 10 to 20 percent chance of thunderstorms over the Sierra Nevada this afternoon.

3. 20-40% probability for extreme heat ending next week and starting September.

DISCUSSION

Upper level disturbance expected to swing around the ridge pattern today and cross into the Upper Inter-Mountain West on Sunday. While slight changes in temperatures and winds will be observed Today, the location of the upper level disturbance will be too far north to generate significant drops in the temperatures or strong winds. Therefore, with Probability of Exceedance (PoE) of reaching 100 degrees average at around 60 to 80 percent from Fresno To Bakersfield, respectively, will see minimal change as max temperatures sit around around 100 degrees each day. Areas north of Fresno will have PoE between 10 and 30 percent as upper 90s will be more representative of the region. This situation will result in mostly Minor Heat Risk with patches of Moderate Heat Risk for most of the next seven days. Afterward, the disturbance will exit the region with a rebound of the ridge ahead of another disturbance traveling through the Pacific Northwest. These transitory disturbance will prevent any big warm-up for the next five to seven days as the ridge pattern will not be allowed to amplify. Furthermore, PoE of 105 degrees remains at near zero outside of the west side of Kings County and the Kern County portion of the San Joaquin Valley.

The passage of the disturbance will also introduce an increase in the southwesterly to westerly wind component during the coming days. Currently, the flow is more southerly and is allowing for a northward surge of Monsoonal Moisture into the region. With the southwest winds aloft Today, enough orographic lift will exist to support thunderstorm development across the Sierra Nevada Crest. Latest ensemble probability of thunder is between a 10 and 20 percent chance of development this Afternoon from Yosemite to the Tulare and Kern County Line. By Sunday, the flow aloft becomes more westerly and forces the moisture to shift east and more into the Great Basin. Therefore, while convection is possible on Sunday, Central California will lose the ingredients for significant thunderstorm development as the probability of thunder drops to 5 to 10 percent. Probabilities continue to drop during the week as dry conditions prevail from Monday through at least Friday.

AVIATION

VFR conditions prevailing for the next 24 hours. 10-20% probability of afternoon thunderstorms from 18Z Saturday to 3Z Sunday along the Sierra Nevada crest down to 6,000 feet elevation.

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.