Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
Issued by NWS San Joaquin Valley, CA
221 FXUS66 KHNX 171114 AFDHNX Area Forecast Discussion National Weather Service Hanford CA 414 AM PDT Wed Jul 17 2024 && .KEY MESSAGES... 1. The high risk of grass fires in the valley continues, with fire behavior enhanced even with low wind speeds. 2. Periods of afternoon thunderstorms in the Sierra Nevada continue this week. The greatest chances will be this weekend with a 15 to 20 percent probability. 3. There is a 60 to 80 percent chance of afternoon highs to reach or exceed 105 degrees in the San Joaquin Valley beginning next Monday. Chances remain above 60 percent at least through next Wednesday. && .DISCUSSION... Cooler temperatures will continue across central California today as an upper level trough influences the region while it progresses into the Pacific northwest. Ensemble guidance from the National Blend of Models expresses less than a 20 percent chance for temperatures to exceed 100 degrees across the San Joaquin Valley this afternoon. These probabilities will increase later this week as an upper level ridge, currently located over the desert southwest, is expected to track westward towards the Great Basin. The subsiding and stagnant air aloft will again result in temperatures around ten degrees above normal for central California by the start of next week. There is a 60 to 80 percent chance for temperature to reach or exceed 105 degrees, with a 20 to 40 percent chance to reach or exceed 110 by midweek. In addition to the warmer temperatures, the shift from the aforementioned ridge over the western United States will bring a chance for afternoon thunderstorms along the Sierra Nevada through the remainder of this week. The anticyclonic rotation around the upper level high will result in winds aloft from the south, causing moisture from the Pacific to entrain across the region. The triple-degree heat and topography will provide enough convective energy for thunderstorm development across the crests. The highest chances will be this weekend with a 15 to 20 percent probability. Increased lightning activity with these storms paired with drier fuels may result in an enhanced risk for fire danger in the mountain areas, even with low wind speeds. There is around a 30 percent chance for one tenth of an inch of rainfall at the highest elevations of the Sierra on Thursday, however through the weekend probabilities are less than fifteen percent. This further reflects the enhanced fire danger as these potential thunderstorms have a greater chance of having dry lightning associated with them. Long-term cluster analysis indicates a continuation of the ridge above central California through next week, with ensemble guidance suggesting at least a 70 percent chance of temperatures exceeding 100 degrees through next Friday. && .AVIATION...Areas of MVFR and local IFR visibility will continue in and around wildfires. Otherwise, VFR conditions will prevail across the central CA interior over the next 24 hours. && .AIR QUALITY ISSUES... ISSUED: 07/16/2024 14:50 EXPIRES: 07/17/2024 23:59 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...SM IDSS..............ab weather.gov/hanford