textproduct: San Joaquin Valley

UPDATE

Updated Aviation Section.

KEY MESSAGES

1. Warmup continues today before trending back to seasonal averages.

2. Monsoonal moisture brings 5 to 15 percent chance of thunderstorms over the Sierra Nevada Friday into Saturday.

3. Breezy conditions take place over typical wind-prone areas including San Luis Reservoir, Lake Isabella and the Mojave Desert Slopes.

DISCUSSION

Today's highs reached in the triple digits in many valley and desert locations. A modest lowering of temperatures is in store for Friday, but there is still a 65-75 percent chance of triple digits again on Friday in the San Joaquin Valley (mainly south of Fresno). Probabilities lower considerably from Fresno northward, as chances are about 40-50 percent at the highest for this portion of the valley. In the Mojave Desert, the chances for triple digits are near 100 percent and 50-60 percent for highs of 105 degrees or hotter. Triple digit heat will persist over the weekend into next week in this area as probabilities don't change significantly for maximum temperatures to reach at least 100 degrees. Temperatures lower slightly for Saturday as an upper-level trough passes over the Pacific Northwest, but highs in the San Joaquin Valley remain near the century mark, with a slightly lower probability of triple digit heat. However, chances of triple digits increase once again on Sunday and Monday in the San Joaquin Valley, or similar to Friday's (40 percent or less for Fresno County northward and 70-80 percent south of Fresno County). A broad ridge of high pressure will continue to build over the Desert Southwest into the Great Basin and Rocky Mountains, or a typical late summer pattern. Dry conditions continue into next week, except the higher elevations of the Sierra Nevada will see some monsoonal moisture by Friday afternoon. Although chances for thunderstorms remain minimal at 5-15 percent, mainly for Friday and Saturday.

Beyond early next week, we anticipate little change in the pattern. The ridge of high pressure persists over much of the Western U.S. Above average temperatures remain favored, per latest CPC outlooks, although chances are 40-50 percent for both the 6-10 day and 8-14 day periods, or the remainder of August into the first few days of September. Near average precipitation is shown for both periods, which means little or no precipitation for much of the region, given we are still in summer.

AVIATION

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

None.