textproduct: San Joaquin Valley

UPDATE

Updated Key Messages, Aviation, and Air Quality Issues.

KEY MESSAGES

1. Will see drying conditions through Tuesday as clouds linger over Central California, mainly across the Sierra Nevada, the adjacent foothills, and the Kern County mountains.

2. Dense fog returns to the Central Valley each night and morning through Tuesday.

3. Next round of storms will move in Wednesday leading to a wet start for 2026.

DISCUSSION

We find ourselves today near the middle of the trough but all the moisture plumes now well to our South after a very wet Christmas. Latest model ensembles give an encouraging sign as the trough slides east today as a ridge moves in over the weekend bringing drier conditions. However, the ensembles agree that part of the trough will still break off and slide off to the southwest over the Pacific leading to the formation of a rex block. This will help bring a stable pattern which brings a return of fog to the Valley. Tonight we are looking at a 20 to 30 percent chance of visibilities below a mile for much of the Valley based on the 12Z model runs. The rest of the weekend into early next week looks to be below average as there is a less than 25 percent chance of highs of at least 55 degrees in the Valley in the latest NBM run.

However, any plans for New Years will be recommended to be indoors as a trough begins sliding in on Wednesday and picks up the cutoff low that is from the rex block. Model ensembles differ as to how much moisture will be drawn in from this storm especially of water vapor transport values of at least 250 kg/(m/s). Any moisture will be more favored to move in from Kern County northward. There is a 60 to 70 percent chance of at least a tenth of an inch of rain each day on Thursday and Friday for the Valley. In the Sierra Nevada, there is a 10 to 30 percent chance of a foot of snow or more for Friday and next Saturday.

AVIATION

There is a 20 to 30 percent chance of IFR to LIFR conditions tonight due to fog in the San Joaquin Valley from 09Z-18Z Sunday. Otherwise, VFR conditions will persist for the next 24 hours.

AIR QUALITY ISSUES

On Sunday December 28, 2025, Fireplace/Wood Stove Burning Status is: No Burning Unless Registered in Fresno and Kern Counties. Burning Discouraged in Kings, Madera, Merced, and Tulare Counties, and Kern (Greater Frazier Park Area) and Sequoia National Park and Forest.

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.