Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
Issued by NWS San Joaquin Valley, CA
347 FXUS66 KHNX 111753 AFDHNX Area Forecast Discussion National Weather Service Hanford CA 1053 AM PDT Mon Aug 11 2025 && .KEY MESSAGES... 1. This heat wave event is expected to reach it`s hottest day today, with a slight 1 to 2 degree decrease on Tuesday. This slow cooling trend is expected to continue through this weekend. 2. The Heat Advisory remains in effect for the San Joaquin Valley through 11 PM tonight, with a 25 to 55 percent chance for highs of 105 or higher this afternoon. 3. The Extreme Heat Warning for the Mojave Desert will remain in effect until 5 AM tomorrow morning, with an 80 percent chance for highs of 110 or higher at Ridgecrest and a 15 to 25 percent chance in the rest of the desert region. 4. Minor fire risk with widespread minimum relative humidity between 15 and 25 percent for the non-desert areas. Minimum relative humidity expected to be less than 10 percent in the Mojave Desert with breezy winds in the afternoon to evening. && .DISCUSSION... A large high pressure ridge is currently centered off the west coast, which is leading to increased 500mb heights over California. This has lead to the above normal temperatures we have been seeing for the last few days, and these temps or expected to continue through today and somewhat into tomorrow. The reason we may see a slight decrease in highs (of a couple degrees), is due to the ridge being split by a weak disturbance over the Oregon coast. This will then lead to the ridge being pushed to the east as a trough moves in from the west. This will lead to our temperatures coming down to around normal once again by Wednesday. This gradual cooling trend is expected to last through the weekend, where highs may become below normal, which would be in the mid to high 90`s for the Valley and a few degrees above the triple digits for the Desert. Relative humidity is expected to see a similar shift as we move through the week and begin to cool down by the weekend. Minimum RH`s today are expected to be in the 15 to 25 percent range for the Valley and single digits in the desert. And due to these low RH`s and high temperatures, a minor fire risk exists for the region. As we come under the influence of the trough later this week, RH`s in the afternoon are expected to slowly recover, with values in the Valley of 25 to 40 percent, though the desert may remain in the single digits. This trough is also expected to lead to slightly breezier winds in the Valley and along the Mojave Desert Slopes, though those currently aren`t expected to be high enough for an Advisory. These winds will keep the minor fire risk in place due to the dry fine fuels that are still abundant throughout the region. && .AVIATION... 18Z Update: VFR conditions are expected in the San Joaquin Valley for the next 24 hours. && .AIR QUALITY ISSUES... None. && .CERTAINTY... The level of certainty for days 1 and 2 is medium. 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 Warning until 5 AM PDT Tuesday for CAZ337>339. Heat Advisory until 11 PM PDT this evening for CAZ300>317-319- 321. && $$ Public/Aviation/Fire Weather...EW DSS/PIO........................JPK weather.gov/hanford