textproduct: San Joaquin Valley

KEY MESSAGES

1. Storm system continues through Monday morning. Moderate to heavy rainfall expected for the lower elevations and snowfall for the Sierra Nevada above 6,000 feet.

2. A Winter Storm Warning for the Sierra Nevada above 6,000 feet remains in effect through Monday morning. A Flood Watch continues for the Sierra Foothills below 6,000 feet for the same time period.

3. Slight chance for thunderstorms developing across parts of the Sierra Nevada and adjacent foothills this afternoon. Brief heavy rain, small hail, gusty winds, and frequent lightning are possible with any thunderstorms.

4. Unsettled weather with mainly light precipitation remains Monday morning through Thursday, then there is a moderate chance of Tule fog to return to the Central Valley Thursday night.

DISCUSSION

Rain and snow chances continue today with another slight chance for thunderstorms. The chances for thunder are currently at 10-15 percent, mainly towards the Sierra Nevada foothills and elevations up to 6,000 feet in the Sierra. Confidence is high that most locations will receive at least another 0.25 inch of rain in the Central Valley and over an inch of precipitation in the Sierra Nevada and foothills through Monday morning (70-80 percent probability for these amounts).

Lingering showers persist beyond Monday morning, or until Thursday. Another low pressure system moves along the coast on late Monday into Tuesday. However, confidence is low to moderate that we will receive much more than a tenth of an inch of precipitation across the region during this time frame, as well as beyond Tuesday. High resolution models show the upper-level low moving southward well off the coast of California during Monday afternoon into Tuesday, so much of the precipitation may not reach much beyond the coastal ranges. Another shortwave trough passes over Northern California into the Great Basin, so any precipitation will be generally light and occur over mainly the mountains. Confidence is also low with this scenario.

Fog and stratus return to the Central Valley by Thursday night into Friday morning. Guidance is generally in agreement that high pressure will dominate over much of the Western U.S. for Friday and next weekend. In addition, the Climate Prediction Center shows increasing chances (now 60-70 percent chance) of below average precipitation in the latest 6-10 day outlook with a 40-50 percent chance of continued below average precipitation for the 8-14 day outlook.

AVIATION

Expect MVFR/IFR conditions at the TAF sites and much of the forecast area through the next 24 hours due to clouds and showers. A 10-15 percent chance of thunderstorms on Sunday afternoon (20Z Sun - 03Z Mon) exists over the Sierra Nevada and foothills. Otherwise, VFR conditions will prevail for the next 24 hours.

AIR QUALITY ISSUES

On Sunday January 4 2026, Fireplace/Wood Stove Burning Status is: Burning Discouraged in Fresno, Kern, Kings, Madera, Merced, and Tulare Counties, and in 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

Flood Watch through Monday afternoon for CAZ317>322-324-325. Winter Storm Warning until 10 AM PST Monday for CAZ323-326>331.