textproduct: San Joaquin Valley

KEY MESSAGES

1. One more day of below average temperatures for central California before a warming trend begins Monday, lasting through Thursday.

2. Medium probability (40 to 50 percent) for High Heat Risk in the San Joaquin Valley on Thursday; 70 to 80 percent probability for triple-digits.

3. Medium probability (50 to 60 percent) for measurable rainfall in the Sierra Nevada on Wednesday.

DISCUSSION

Clouds and moisture are tracking over the southern portion of central California, being forced to the northeast by a low pressure trough currently centered over Oregon. Light precipation has occurred so far today in the eastern Kern Mountains and Desert areas, with between 0.02-0.08" being observed at most locations; Mojave has received 0.20". Precipitation chances will gradually decrease as the focus of this moisture pushes further east into Nevada. Meanwhile, clear conditions are present over all locations north of Kern County, leading to warmer temperatures in the upper 80s for the Central Valley. For this afternoon, there is an 80 to 90 percent probability for valley temperatures to exceed 85 degrees.

For the Labor Day holiday, expect additional warmer temperatures closer to season averages. This is due to the aforementioned trough continuing its path eastward into the northern Great Plains. In its wake, there will be a return to west-east zonal flow, supporting the near-average temperatures. However, as the week progresses, a high pressure ridge is progged to gradually build westward, raising temperatures back above averages. The ridge looks to reach its greatest strength on Thursday, where there is a 70 to 80 percent probability for triple-digits in the San Joaquin Valley once again.

Tropical moisture from the remnants of Marie still appears to push into the region midweek, however chances have begun to downtrend for much of the region to receive precipitation. This is most likely due to the influence of the high having a greater hold over the region and keeping the moisture at bay off the coast. Still, there is a 50 to 60 percent probability for measurable rainfall in the Sierra Nevada on Wednesday, but less than 10 percent for the valley and most of the foothill communities. The high-end scenario from the NBM (1 in 10 chance of occurrence) for this event has trended down towards 0.5"-0.75" for the Sierra, the greatest of these totals around Mount Whitney.

AVIATION

VFR conditions expected 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

None.