Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
Issued by NWS San Joaquin Valley, CA
682 FXUS66 KHNX 171705 AFDHNX Area Forecast Discussion National Weather Service Hanford CA 1005 AM PDT Sun Aug 17 2025 .KEY MESSAGES... 1. The cooling trend is expected to continue until Monday, and both the Central Valley and Kern County desert will continue to see a Minor Heat Risk through Tuesday. 2. A slight (10-20%) chance of afternoon and evening showers and thunderstorms exists in the higher elevations of the Sierra Nevada today. Otherwise, chances for isolated mountain and desert thunderstorms are in store later this week. 3. A warming trend returns by the middle of the week with triple digit heat in the warmest locations. The potential for Major Heat Risk returns by Thursday in the Kern County desert and enters into the Central Valley by Friday. 4. Elevated fire risk with minimum relative humidity expected to be less than 10 percent in the Mojave Desert with breezy winds in the afternoon to evening. && .DISCUSSION...Another mild day, at least for mid-August, is expected today following a relatively cool morning. Highs will remain in the 90`s at the warmest locations in our forecast area, although a triple digit won`t be out of the question for the Indian Wells Valley in northeastern Kern County. A dry southwest flow and upper-level trough over the Pacific Northwest will keep convection over the Sierra Nevada at bay, but it`s possible that the high country of Yosemite NP might see a storm or two this afternoon and evening. Things might become somewhat more interesting later this week, but in the meantime, expect a warming trend after Monday. By Wednesday, widespread triple digit heat returns to the desert, while triple digits return to the Central Valley by Thursday. This is due to the ridge of high pressure retrograding back to the West Coast states. Further heating will occur Friday into next weekend, prompting a Major Heat Risk for both the Central Valley and Kern County desert (which could begin as early as Thursday in this particular region). There is some uncertainty regarding the desert heat could be an influx of monsoonal moisture which might mitigate some heating, although there is a high probability (60-90 percent) of highs at least 105 degrees starting Thursday. At least for now, the past couple of runs of the ensemble guidance has been creeping up the temepratures for later in the week and next weekend. Many San Joaquin Valley locations will potentially see the hottest temperatures this year so far, and the chances for highs to reach at least 105 degrees are a bit higher than during the previous heat event (currently 30-60 percent as early as Day 6, or Friday). There is also some uncertainty regarding how high temperatures in the Central Valley will reach, including in our northern zones. Based on the uncertainty and in consensus with neighboring forecast offices, will hold off on issuing heat products for now. For the time being, enjoy the break from the heat. The latest CPC (Climate Prediction Center) 6-10 temperature outlook continues to favor above average temperatures at a 50 to 60 percent probability, while the 8-14 day outlook shows near average temperatures. So, it does appear there could be some relief from the heat by the end of the month. && .AVIATION... 18Z Update: VFR conditions are expected in the San Joaquin Valley for the next 24 hours. There is a slight, or 10-15 percent, chance of mountain obscuring showers and thunderstorms over the higher elevations of the Sierra Nevada, mainly towards Yosemite NP, from 20Z Sunday through 03Z Monday. && .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... None. && $$ BSO/JPK weather.gov/hanford