textproduct: San Joaquin Valley

KEY MESSAGES

1. A Flood Watch is in effect for the Sierra Nevada below 9,000 feet and foothills, mainly Yosemite, as well as Mariposa and Madera Counties from late Saturday until Monday.

2. A significant pattern change is expected to take place by this evening with precipitation likely for the Sierra Nevada and its foothills from Fresno County northwards. Moderate to briefly heavy precipitation is possible in these areas from Saturday evening into Sunday.

3. A second, stronger system is expected to arrive Tuesday, with a moderate risk for heavy precipitation throughout Central California, and a moderate risk for heavy snow in the Sierra Nevada expected from Christmas Eve through Friday of next week.

DISCUSSION

Precipitation begins as early as this evening, at least for our northern portions, such as Merced County to Yosemite NP. Additional moisture arrives by late Saturday towards Yosemite NP, as well as the Sierra and foothills in Madera and Mariposa Counties which will produce moderate to heavy rainfall at times until Monday. As of now, a 50-60 percent probability of at least one inch of rain in a 24 hour period ending Sunday morning exists in these areas, while about a 40-50 percent chance ending on Monday morning remains. Thus, have issued the Flood Watch for these locations. After Monday morning, we see a brief decrease in precipitation that could last into Tuesday morning. However, chances for precipitation do not completely diminish, but begin a gradual spread southward on Sunday into Tuesday.

On Tuesday, more widespread precipitation arrives, and the chances for at least one inch of rain per 24 hour period rises markedly for much of Central California. The best chances for two inches of rain per 24 hours are in the Sierra Nevada and foothills at elevations from 6,000 to 7,000 feet and below. The heaviest snow will fall at elevations above 8,000 feet on Tuesday onward, although the snow levels range from 6,000 to 7,000 feet during this time, with the higher levels of the range on Tuesday. There is around a 60-70 percent chance of snow above one foot in 24 hours beginning with the period from Tuesday morning until Wednesday morning. This continues each day until at least Christmas Day. Precipitation will also occur next Friday into next weekend, although uncertainty regarding amounts and exact timing of heavier precipitation increases. Any lull periods are possible during next week, although exact timing of these periods are also uncertain beyond early next week. In addition, with the initial surge of precipitation with the arrival of the Tuesday system, there could be increased winds. For example, Merced County shows around a 30-40 percent chance for a gust of 40 mph.

Above average precipitation (40-50 percent chance) and near to warmer than average temperatures are favored (up to 40 percent chance) in the latest 8-14 day outlook from the Climate Prediction Center, which includes December 26th through January 1st (next Friday through the following Thursday).

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 slight chance of showers towards MCE and MER after 06Z Saturday. IFR ceilings due to precipitation over the Sierra Nevada and adjacent foothills from Fresno County northward. Otherwise, VFR conditions will prevail over the next 24 hours.

AIR QUALITY ISSUES

On Friday December 19 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 high.

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 from Saturday afternoon through Monday afternoon for CAZ318-323>326.