textproduct: San Joaquin Valley

KEY MESSAGES

1. Slight chance for thunderstorms across the Sierra Nevada Friday, increasing chances on Saturday.

2. Above average temperatures across the CWA on Friday and Saturday.

3. A closed-low enters the area over the weekend to early next week with the best probability for weather impacts Sunday through Tuesday.

DISCUSSION

A building shortwave ridge will lead to above normal temperatures both today and into tomorrow, with highs near 90 degrees in the Valley both days. This ridge will also be short- lived as it is expected to be pushed east by Saturday afternoon into the evening, which may also lead to thunderstorm development as a cut-off low approaches from the west.

This cut-off will continue to increase thunderstorm probabilities for each afternoon it is aloft, through at least Tuesday afternoon. These chances will be concentrated to the Sierra Nevada and it's foothills and currently have values of 10-20%, with higher chances along the crest of the range. The initial wave will also lead to a rapid decrease in temperatures beginning on Sunday and peaking on Tuesday with the Valley likely to see highs in the lower 70's, which would be about 10 degrees below normal for this time of yer. As the cut- off gets closer to the region, rain chances for the mountains and foothills increase, with the highest probabilities on Monday into Tuesday. These values are currently 25-50% for at least a quarter inch of rainfall over 24 hours. There is also a 15-25% chance for a tenth of an inch of rainfall in the Valley, mainly on the east side adjacent to the foothills.

After this cut-off exits the area, another ridge is expected to build in its place, leading to another warming trend for the region likely to push highs about 10 degrees above normal by next Friday.

AVIATION

VFR conditions will prevail for the next 24 hours over Central California.

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.