Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
Issued by NWS San Joaquin Valley, CA
345 FXUS66 KHNX 171220 AAA AFDHNX Area Forecast Discussion National Weather Service Hanford CA 520 AM PDT Mon Aug 17 2026 .UPDATE... Updated aviation section. && .KEY MESSAGES... 1. Temperatures will gradually warm this week and rise back to around 5 degrees above average by the middle of the week. 2. Breezy conditions take place over typical wind-prone areas including San Luis Reservoir, Lake Isabella and the Mojave Desert Slopes through this week. && .DISCUSSION... Seasonable temperatures remain expected over central California into the upcoming week as the region is located between two large-scale air masses. A low pressure system to the west over the eastern Pacific is pushing upper level moisture over most of Claifornia, resulting in high cloud cover but with little is any precipitation. Meanwhile, a high pressure ridge is centered over the southern United States which is expected to slowly shift westward, building to a peak between Wednesday and Thursday. Both of these days there is a 65 to 75 percent probability for maximum temperatures to exceed 100 degrees across the San Joaquin Valley, with greater probabilitiies between 90 and 100 percent in the Mojave Desert. These warmer temperatures will cause widespread Minor Heat Risk with increasing areas of Moderate Heat Risk across the lower elevations midweek. These heat impacts are due in part to the expected overnight temperatures, especially in the urban and foothill areas, where there is at least a 75 percent probability for overnight lows to exceed 70 degrees. However, in the remaining valley areas, there is less than a 10 percent probability for overnight minimums to exceed 70. Due to the rising temperatures, relative humidities across central California will be on the downtrend. Minimum values will approach a low of 15 to 20 percent in the San Joaquin Valley midweek, with similar values in the Sierra Nevada, but single- digits in the Mojave Desert. However, moderate to good overnight recoveries are expected; values of 50 to 60 percent will be present across much of the region. Winds across central California are primarily expected to be light and diurnal except for the most wind-prone areas including San Luis Reservoir, Lake Isabella, and the Mojave Desert Slopes in the lee of the Tehachapi Range. && .AVIATION... VFR conditions will prevail for the next 24 hours. && .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. && $$ public/aviation...McCoy/CM weather.gov/hanford