Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
Issued by NWS San Joaquin Valley, CA
899 FXUS66 KHNX 091930 AFDHNX Area Forecast Discussion National Weather Service Hanford CA 1230 PM PDT Tue Jul 9 2024 .KEY MESSAGES... 1. A long-duration, rare heat wave with an Extreme HeatRisk will continue through late this week will have many impacts on all of our citizens and all sectors of the community. 2. An Excessive Heat Warning remains in effect until Saturday, July 13 at 10 AM. A Heat Advisory remains in effect for Yosemite NP through Wednesday at 10 AM. 3. The high risk of grass fires will continue with herbaceous fuel loading at or near 120% of normal exhibiting behavior typically not experienced with low wind speeds. 4. Chance of afternoon thunderstorms returns to the higher elevations of the Sierra Nevada this weekend as high level moisture spreads over the district. && .DISCUSSION... The heatwave that has been impacting Central California continues today due to high pressure aloft. The longevity of this heatwave has been quite impressive, with Fresno now seeing 7 consecutive days of high temperatures over 105 degrees... and that trend does not appear to be at an end soon. In fact, the entire forecast area has been stubbornly 15 degrees above normal... with the last few days in particular being exceptionally hot. With overnight lows also being in the 75-80 degree range, this heat is quite dangerous. Major to Extreme HeatRisk continues across the San Joaquin Valley this week, with the hottest days projected to be Wednesday and Thursday. Here are NBM probabilities for afternoon highs reaching or exceeding 110*F for select locations in the forecast area on Thursday: Merced: 45% Madera: 45% Fresno: 55% Hanford: 45% Visalia: 60% Bakersfield: 60% Ridgecrest: 85% Afternoon highs begin to gradually nudge downwards Friday as the high pressure ridge moves east over Central California, and a upper low becomes more prominent off the CA Coastline. This situation will allow for some upper moisture to begin reaching the forecast area on Saturday. Blended model guidance shows that Saturday afternoon has the potential for thunderstorms in the Sierra Nevada. Models are not real keen on there being much in the way of precip either, since the moisture will be mostly confined to the upper levels. This does raise some additional concerns about new fire starts in the Sierra Nevada on Saturday, especially considering the fuels are drying out. A similar situation looks conceivable on Sunday. NBM guidance continues to show a slow drift downward in Max and Min T`s on Monday and Tuesday of next week and the ridge of high pressure flattens, and shifts further eastward towards the Four Corners region. && .AVIATION...Areas of MVFR and local IFR visibility will continue in and around wildfires. Otherwise, VFR conditions will prevail across the central CA interior for the next 24 hours. && .FIRE WEATHER...The danger of fire starts across the entire area remains very high, even though the winds are mostly reduced, due to near record high temperatures combines with low daytime relative humidity with poor overnight recovery. By the weekend, gusty winds allow the West Side Hills and Mojave Slopes to enter back into the fire weather picture alongside high temperatures and poor RH recoveries. Additionally, concerns due to thunderstorms in the Sierra Nevada may lead to new fire starts Saturday and Sunday afternoon. && .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... Excessive Heat Warning until 10 AM PDT Saturday for CAZ300>322- 324-325-332-334>339. Heat Advisory until 10 AM PDT Wednesday for CAZ323. && $$ ab weather.gov/hanford