Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
Issued by NWS San Joaquin Valley, CA
357 FXUS66 KHNX 171104 AFDHNX Area Forecast Discussion National Weather Service Hanford CA 404 AM PDT Tue Sep 17 2024 .KEY MESSAGES... 1. There is a 60 percent probability for 0.10 inches or more of rainfall in the San Joaquin Valley on Thursday and a 15 to 30 percent probability for 0.25 inches or more. 2. There is a 50 to 85 percent probability for 0.25 inches or more of rainfall across the Sierra Nevada from Fresno County north and less than a 50 percent probability south of Fresno County. There is a 25 percent probability for 0.50 inches or more of rainfall in Yosemite Valley on Thursday. 3. There is a 65 percent probability for 3 inches or more of snowfall at Tioga Pass on Thursday and a 45 percent probability for 4 inches or more. Snow levels will be around 10,000 feet. 4. There is up to a 30 percent chance for thunderstorms across the Sierra Nevada on Thursday, highest around Yosemite NP. There is a 10 percent chance for thunderstorms across the San Joaquin Valley on Thursday. 5. Temperatures will be 10 to 15 degrees below normal through Thursday before a weekend warmup. && .DISCUSSION... An unseasonably cool air mass has settled in over the central California interior as the upper low responsible lifts off to the northeast. High temperatures on Monday topped out around 15 to 20 degrees below climatological normals for this time of the year. Merced tied the record low maximum temperature for the date with 73 degrees, last set in 1908. Low temperatures this morning are forecast to be around 5 to 10 degrees below normal with generally lower 50s across the San Joaquin Valley. The probability for a low temperature less than 50 degrees is 20 to 50 percent. A large upper trough will remain across the region today with a drier northwesterly flow aloft over central California. The next upper low will drop south from the Gulf of Alaska today to just off the Pacific Northwest coast. The low settles near the SF Bay on Wednesday then moves over central California on Thursday. The low shifts east over Las Vegas on Friday and to the Four Corners region on Saturday as an upper ridge over the east Pacific gradually builds inland. The upper low will bring chances for precipitation Wednesday and Thursday. There is a 60 percent probability for 0.10 inches or more of rainfall in the San Joaquin Valley and a 15 to 30 percent probability for 0.25 inches or more. There is around a 50 to 85 percent probability for 0.25 inches or more of rainfall across the Sierra Nevada from Fresno County north and less than a 50 percent probability south of Fresno County. There is a 25 percent probability for 0.50 inches or more of rainfall across Yosemite Valley on Thursday. There is a 65 percent probability for 3 inches or more of snowfall at Tioga Pass on Thursday and a 45 percent probability for 4 inches or more. Snow levels will be around 10,000 feet. Instability will increase as the upper low moves over on Thursday. There is up to a 30 percent chance for thunderstorms across the Sierra Nevada on Thursday, highest around Yosemite NP. There is also around a 10 percent chance for thunderstorms across the San Joaquin Valley on Thursday. Some light wrap around showers may brush the Sierra Nevada on Friday as the upper low moves off to the east. Max temperatures will be around 10 to 15 degrees below normal today through Thursday with PoE for 80 degrees generally from 30 to 70 percent across the San Joaquin Valley. Temperatures warm to around 5 degrees below normal on Friday then to near normal on Saturday and around 5 degrees above normal on Sunday. The warming trend continues into early next week with highs nearing 10 degrees above normal. && .AVIATION... Areas of MVFR and local IFR visibilities near wildfires. Otherwise, VFR conditions will prevail across the central CA interior over 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. && $$ DCH weather.gov/hanford