textproduct: San Joaquin Valley

KEY MESSAGES

1. Temperatures drop more on Today before a warmup begins on Tuesday.

2. A storm moving through California with produce unsettled weather, along with strong winds over the higher terrain of the Sierra Nevada and Tehachapi Range.

3. There is a 10 to 20 percent chance of an inch of snow above 9,000 feet through Wednesday night. Snow levels drop to around 6,500 feet overnight.

DISCUSSION

As the remnants of Tropical Storm Rachel continues to push inland, residue moisture will lingering across the region. Additionally, a strong storm moving down from the Gulf of Alaska will interact with this moisture, supporting afternoon showers primarily across the mountains. This storm is also bringing a significant surge of cold air into the region today; upper-air analysis showed the freezing line at around 4,000 feet over far Northern California as of 5:00 AM this Monday. This cold air will push further into Central California, with snow levels dropping from 9,000 feet this afternoon to near 6,000 feet tonight. The storm will exit the region on Tuesday as a warming and drying trend takes hold for the remainder of the week.

The Probability of Exceedance (PoE) of reaching 100 degrees is near zero percent outside of the Mojave Desert, though the PoE of reaching 90 degrees remains possible. The ongoing cold air surge will keep valley temperatures near or below seasonal averages through at least Thursday. The warming trend will be gradual, as the PoE for 90 degrees does not exceed 30 percent until Friday. By Saturday, PoE for 90 degrees rises to between 60 and 80 percent, while the PoE for 95 degrees remains below 10 percent. Expect temperatures in the lower 90s by Saturday before slight cooling trend begins on Sunday.

Ensemble model analysis indicates some uncertainty regarding the strength of a disturbance approaching the West Coast on Monday. While ensemble models acknowledge the existence of a developing disturbance with a signal toward cooler temperatures, its exact intensity remains uncertain. For now, the ensemble mean suggests the next storm will primarily affect the Pacific Northwest, bringing minor temperature and wind impacts to Central California.

AVIATION

VFR conditions will prevail for the next 24 hours. A slight chance of IFR conditions in rain and snow showers across the Sierra Nevada until 04Z Tuesday.

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.