textproduct: San Joaquin Valley

KEY MESSAGES

1. Temperatures will continue to cool down, and chances for precipitation last until Thursday evening. There is also a 10-20 percent chance of thunderstorms for the period.

2. There remains an 80-90% chance of an additional half inch in the Sierra Nevada with a 40-50% chance of an additional quarter inch of rainfall in the remaining portions of the forecast area until Thursday evening.

3. Snowfall is likely above 8,000 feet in elevation with a 50-60% chance of at least 4 inches of snowfall (probabilities increase further at higher elevations) through Thursday evening.

4. Seasonal temperatures and mainly dry conditions take place Saturday until the middle of next week.

DISCUSSION

Additional light to moderate showers have been developing in the San Joaquin Valley during the last hour or so. Light to moderate rain has also been falling in the Kern County mountains since this afternoon. Another band of precipitation is moving inland from the Central CA coast, so expect shower coverage to increase through tonight. The upper-level low remains off the coast of Pt. Conception, per latest satellite imagery. This feature is forecast to move inland over Southern CA during Thursday. Additional chances for showers and a slight (10-20 percent) chance for isolated thunderstorms will also occur until Thursday afternoon into the early evening hours. Confidence is high that the Sierra Nevada will receive at least another half an inch of rain until Thursday evening, with a moderate probability of at least 0.25 inch elsewhere in our forecast area. In addition, there is a 20-30 percent chance of additional precipitation from Thursday evening through Friday afternoon, mainly in the Sierra Nevada. Snow chances also remain for the higher elevations of the Sierra Nevada through Thursday evening, and the chances for at least four inches of accumulation are at 50 to 60 percent, mainly above 8,000 feet.

By Friday evening, precipitation will end, and dry conditions return. Temperatures will remain relatively cool on Saturday, although a minor warming trend occurs over the weekend into early next week. Highs are projected to reach the mid to upper 70s at the warmest spots which will be close to seasonal averages for late October. Despite this, the chances for highs below 80 degrees are currently at 80-90 percent for this period. While our forecast is dry for this weekend until next Wednesday, long range models suggest a slight chance for precipitation later next week or the following weekend.

AVIATION

IFR with mountain obscurations over the Sierra Nevada in RA/SN showers. Elsewhere, MVFR conditions with IFR at times in SHRA. Isolated thunderstorms have a 10-20 percent chance to develop until Thursday afternoon across the forecast area. Winds up to 10 kts at the TAF sites, mainly from the east. 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

Flood Watch through Thursday evening for CAZ308-309-313-314- 316-332>339. Winter Weather Advisory until 11 AM PDT Thursday for CAZ323- 326>328-330-331.