textproduct: San Joaquin Valley

UPDATE

Aviation and Air Quality Sections Updated

KEY MESSAGES

1. Fog, while dense at times, and low clouds will continue each night and morning across the San Joaquin Valley into the foothills up to 1,500 feet through Tuesday.

2. Above average temperatures will continue across the mountains and desert until Tuesday, as the high pressure pattern persists over the region.

3. Precipitation makes its return to Central California by the middle of the week after having a dry start to December.

DISCUSSION

The consistent stable pattern over the southwest will continue through at least the beginning of next week, with strong ridging keeping the low stratus clouds in place for the center of the San Joaquin Valley with dense fog on the edge of the Valley from elevations of 500 feet to 1500 feet. This stratus will also lower further down during the nighttime hours and lead to fog in the Valley itself.

A small pattern change is likely in store for Central California, with the ridging over the Southwest weakening somewhat as a small trough passes through the Pacific Northwest. This weaking may lead to slight troughing in Northern California into Central California, which may lead to a small amount of precipitation for the northern-most Counties in our CWA, mainly in Mariposa County and Yosemite Nation Park. This small disturbance may also provide elevated winds aloft to break the inversion over the Valley and lead to the stratus deck clearing out, though it's unclear if those winds will be strong enough.

The next potential system is expected to move through the region by Friday afternoon into the weekend, with most long term ensemble models, including the Euro, GFS and Canadian, all indicating precipitation from the next weekend onwards into day 14 on the 28th of December. This kind of agreement shows a confidence form these ensembles that precipitation may occur, even if the amount is not agreed upon just yet. This time period will be watched closely for consistency over model runs, which would strengthen the confidence in that forecast.

AVIATION

IFR to LIFR ceilings and visibilities are expected to prevail for much of the San Joaquin Valley during the next 24 hours, with a 40 to 60 percent chance of VLIFR in dense fog returning after 06Z Monday. IFR to LIFR conditions will also persist in the coastal ranges, Sierra foothills, and the Kern County mountains due to low clouds. Otherwise, VFR conditions will prevail in the Sierra Nevada and in the Kern County mountain and desert areas over the next 24 hours.

AIR QUALITY ISSUES

ISSUED: 12/14/2025 13:32 EXPIRES: 12/15/2025 23:59

On Monday December 15 2025, Fireplace/Wood Stove Burning Status is: No Burning Unless Registered in Fresno, Kern, and Madera Counties. Burning Discouraged in Kings, 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 medium. 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.