textproduct: San Joaquin Valley

UPDATE

Update aviation section and added fire weather section.

KEY MESSAGES

1. Extreme Heat will continue to be the major weather concern over the weekend and early next week. Extreme Heat Warnings have been issued and extended through 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 each afternoon through next week, with chances of 20 to 30% this weekend.

DISCUSSION

The hot and dry conditions will continue until Monday as the ridge over Utah stays in place. With it, the San Joaquin Valley will continue to see hot temperatures, with Sunday afternoon expected to be the peak of the heat. The Probability of Exceedance (PoE) for 105 degrees is currently between 60-75% for much of the SJV. On the more extreme end of maximum temperatures, there is a 10% PoE for 109 for the northern half of the San Joaquin Valley. Kern County, Bakersfield included, will be well above 105 degrees. The PoE for 110 in Bakersfield is 50-60%. The more extreme models are hinting at a 10% probability of exceeding 111 degrees on Sunday. As for the Mojave desert...well...it's hot out there. There's a 70% chance of reaching 110 degrees tomorrow in Ridgecrest. Good news! After Sunday that PoE for 110 degrees will begin to drop off for the Mojave Desert, as there is a 10% chance on Monday and drops off completely on Tuesday. There's also a chance for thunderstorms in the Sierra Nevada crest everyday until at least Saturday. These chances will range between 10-20%.

Tuesday is looking to be the date of most change during this upcoming week. The ridge over Utah begins to shift eastward thanks to an upper-level trough beginning to push in through the Pacific Northwest and Northern California. While temperatures will still be warm, they are expected to drop to the low 100s for the San Joaquin Valley. By Thursday, we will see climatological normal temperatures. Wahoo! This is again thanks to the upper-level trough, as by Thursday it will be digging into Northern California.

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 from 21Z Sunday until 03Z Monday across the Sierra Nevada Crest.

FIRE WEATHER

Hottest temperatures with the current heat wave will be observed this afternoon, resulting in lowered minRH values around 15 to 20 percent in the San Joaquin Valley, Sierra Foothills, and high Sierras where thunderstorms do not occur. Desert minRH values will be around 10 percent. The hot, dry conditions bring elevated fire concerns especially to those areas where the hottest temperatures occur, including the Mojave Desert, the lee of the Coastal Range, and the western San Joaquin Valley. Downsloping winds into this latter area due to onshore flow will also be a contributing factor. The hot conditions across central California will also raise mixing heights across the region; for the higher terrain and desert areas, heights will rise above 9000 feet, causing concern for plume-dominated fires. In addition, monsoon moisture tracking over the Sierra Nevada will bring a threat for dry lightning to occur this afternoon.

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>317-319- 321-332-334>339.