textproduct: San Joaquin Valley

UPDATE

Updated aviation section.

KEY MESSAGES

1. The heat trend continues with temperatures about 10-15 degrees above average for the next several days.

2. Moderate to Major Heat Risk in the Central Valley through Wednesday. Heat Advisory has been extended further to 11 PM Wednesday.

3. Dry and calm conditions will persist for the week ahead.

DISCUSSION

Near record temperatures across Central California as the Heat Dome continues to dominate our weather. Heat Advisory remains in effect as triple digit heat expected through mid-week. For this Sunday, High temperatures were about a degree or two from reaching record values. While not reaching the 90th percentile, this Sundays max temperatures fell closer to the 75th percentile. Looking forward, an area of weakness (minor disturbance) will cross California on Monday with an increase in the westerly flow and an influx of monsoon type moisture pushing up from the Desert Southwest. Therefore, while not much of a cool-down, Central California will see a slight change high range from the upper 90s to near 100 degrees and convection develops over the Sierra Nevada Crest.

Probability of Exceedance (PoE) of reaching 100 degrees on Monday, as the heat dome weakens slightly, will lower by 10 to 20 percent. Highs are expected to settle in the mid to upper 90s with fewer locations reaching the triple digit mark. The passing disturbance will offer only minor relief (a 1 to 3 degree drop at best) before the Heat Dome begins rebounding on Tuesday. Temperatures will remain steady in the mid to upper 90s across the valley for most of the week, with isolated triple digits in typical hot spots. High confidence remains for maintaining the Heat Advisory through Wednesday.

Ensemble model analysis is still showing a stronger storm approaching the West Coast late Friday into Saturday. This stronger storm is expected to bring relief, as temperatures analysis is still lowering the 90th percentile high temperatures back more into the lower to mid 90s. Ensemble model analysis also indicate a chance for showers over the Sierra Nevada near Yosemite on Friday and Saturday.

AVIATION

Isolated MVFR conditions in showers along the Sierra Crest between 18Z Mon and 06Z Tue. Otherwise, VFR conditions will prevail for the next 24 hours.

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 Wednesday for CAZ300>322.