


Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
Issued by NWS San Joaquin Valley, CA
796 FXUS66 KHNX 192310 AFDHNX Area Forecast Discussion National Weather Service Hanford CA 410 PM PDT Tue Aug 19 2025 .UPDATE... Updated Aviation Section. && .KEY MESSAGES... 1. A significant 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. An Extreme Heat Watch has been issued for these areas. 2. There is a 10 to 30 percent chance for thunderstorms this weekend with an influx of monsoonal moisture, with the greatest chances along the Sierra crest. 3. Elevated fire risk with minimum relative humidity expected to be less than 10 percent in the Mojave Desert and Kern County mountains with breezy winds in the afternoon to evening. A Fire Weather Watch for low humidity and locally breezy winds has been issued for the Ft Tejon area from Wednesday until Saturday. && .DISCUSSION... A strong warming trend is expected over central California towards the end of this week as an area of high pressure gradually builds in over the region. Near-average highs today and Wednesday will give way to triple-digit temperatures approaching ten degrees above season averages, with some areas nearing record highs during the weekend. Much of the San Joaquin Valley has a 50 to 80 percent probability to exceed 105 degrees Friday, and a 20 to 70 percent chance on Saturday, with the greatest of these in the southern valley and urban areas. For the urban and foothill areas, minimum temperatures will also be well above normals, with a 30 to 90 percent chance to exceed 75 degrees Friday through Sunday. As a result, an Extreme Heat Watch has been issued valid from 11 AM PDT Friday through 8 AM PDT Sunday. An Extreme Heat Watch has also been issued for the Mojave Desert valid 11 AM PDT Thursday through 8 AM PDT Sunday due to prolonged heat. There is a 40 to 95 percent probability to exceed 105 degrees Friday and Saturday, with a 45 to 80 percent chance on Sunday. There is a 20 to 60 percent probability to exceed 75 degrees in the open desert areas, including Edwards and California City, but with a greater chance at 85 to 100 percent for Mojave, Ridgecrest, and Inyokern. Monsoonal moisture associated with the aforementioned area of high pressure is also expected to entrain over the region this weekend. The mid-level moisture and warming temperatures across the area will allow for thunderstorm development across the Sierra Nevada, with the best chances being Saturday and Sunday afternoons at 15 to 30 percent across the higher elevations of Fresno and Tulare counties. && .AVIATION... 00Z Update: VFR conditions are expected in the San Joaquin Valley for the next 24 hours. && .FIRE WEATHER... Warming temperatures across the region will cause minimum relative humidity to lower for much of the lower elevations of the area (the influx of moisture in the mid levels will cause RH to increase in the Sierra). Widespread minimums 15 to 20 percent are expected for the San Joaquin Valley and Kern County mountains and less than 15 percent in the Kern Desert. Lowering RHs paired with stronger southerly wind gusts near 25 mph in Frazier Park and Fort Tejon has led to the issuance of a Fire Weather Watch as these conditions can cause rapid fire spread if development occurs. && .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... Extreme Heat Watch from Thursday morning through Sunday morning for CAZ337>339. Extreme Heat Watch from Friday morning through Sunday morning for CAZ300>316-332. Fire Weather Watch from Wednesday morning through Saturday evening for CAZ597. && $$ public/aviation...McCoy idss..............EW weather.gov/hanford