textproduct: San Joaquin Valley

UPDATE

Updated Aviation Section.

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

Today's temperatures ranged from average to 5 degrees above, with the San Joaquin River serving as the invisible dividing line from north to south respectively. The latest National Blend of Models (NBM) run at 1Z Saturday indicates more or less the same will continue this weekend into the start of next week, with moderate to high (>50%) probability for triple digit afternoon highs staying south of the San Joaquin River. Likewise, afternoon highs above 105 in the Mojave Desert will be confined below 2,500 feet elevation. Minor to Moderate risk of heat illness continues to be the main weather threat for the region.

Beyond central California, an upper level trough just off the Pacific Northwest coast will track inland overnight into Saturday morning. For us, this will provide just enough moisture transport from the south- southwest for thunderstorms to enter back into the forecast. As of the last NBM run, there is a 10-15% probability of afternoon thunderstorms along the Sierra Nevada crest down to 6,000 feet Saturday. By Sunday, as the upper level trough moves deeper into Canada, upper level flow returns to more benign westerlies that will bring thunderstorm probabilities back down to <10%.

Looking towards the end of August, the Climate Prediction Center continues to highlight a higher likelihood of above average temperatures (50-70% probability) in the 6-10 Day Temperature Outlook, as well as a slight risk (20-40% probability) of extreme heat across our area. Meanwhile, the Weather Prediction Center continues to show about average temperatures in their Day 3-7 forecasts. Whether extreme heat is waiting for us in September remain to be seen in the coming discussions.

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.