Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
Issued by NWS San Joaquin Valley, CA
211 FXUS66 KHNX 120922 AFDHNX Area Forecast Discussion National Weather Service Hanford CA 222 AM PDT Sun Oct 12 2025 && .KEY MESSAGES... 1. Winter Storm Warning in effect from 11 AM Monday through 5 PM Wednesday. 2. Portions of the Sierra Foothills and the Valley is under a Marginal (5-15 percent) Risk of Excessive Rainfall Monday and Tuesday. 3. There is a 10 to 40 percent chance of at least a foot of snow between 6,000 and 7,000 feet and a 60 to 95 percent chance of at least a foot of snow above 7,000 feet through 5 PM Tuesday. 4. The San Joaquin Valley has a 25 to 75 percent chance of at least an inch of rain in 24 hours ending Tuesday at 5 PM. The Sierra foothills have a 20 to 45 percent chance of at least 2 inches of rain in 24 hours ending at 5 PM Tuesday. 5. Drier and calmer conditions will prevail Thursday into the weekend. && .DISCUSSION... The trough that is currently sitting over the Great Basin continues to move away today. However, the cooler temperatures will continue today along with the winds decreasing throughout the day. The big story is the next trough which will slide down the coast today into tomorrow. This stronger trough is bringing much colder air that snow levels will drop to 6,000 to 6,500 feet. However, moisture is the biggest concern as latest models show a 60 to 80 percent chance of Integrated Water Vapor Transport values of 250 kg/(m*s), which is stronger than what was forecast yesterday. This large amount of moisture will be responsible for a 25 to 75 percent chance of at least an inch of rain in 24 hours for the San Joaquin Valley ending at 5 PM Tuesday. In the Sierra foothills, there is a 20 to 45 percent chance of at least 2 inches of rain in 24 hours ending at 5 PM Tuesday. These heavy rain amounts have led the WPC to issue portions of the San Joaquin Valley under a Marginal (5-15 percent) Risk of Excessive Rainfall for Monday and Tuesday. The heavy rain amounts bring a major concern of debris flows and flooding at burn scars. Snow is the big concern with this storm as latest probabilities have a 10 to 40 percent chance of at least a foot of snow between 6,000 and 7,000 feet and a 60 to 95 percent chance of at least a foot of snow above 7,000 feet through 5 PM Tuesday. The large amounts have warranted the upgrading of the Winter Storm Watch to a Warning for the Sierra Nevada. Rain and snow will decrease on Wednesday and will move out by the late afternoon as the trough slides east. Drier conditions will prevail into next weekend as a ridge of high pressure begins to move in on Friday into Saturday which will bring temperatures back up in the Valley. && .AVIATION... VFR conditions are expected to prevail through the forecast period. && .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... Wind Advisory until 5 AM PDT early this morning for CAZ337>339. Winter Storm Warning from 11 AM Monday to 5 PM PDT Wednesday for CAZ323-326>331. && $$ JPK weather.gov/hanford