Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
Issued by NWS San Joaquin Valley, CA
766 FXUS66 KHNX 010814 AFDHNX Area Forecast Discussion National Weather Service Hanford CA 114 AM PDT Mon Jul 1 2024 && .KEY MESSAGES... 1. Above average temperatures continue on Monday, then rapidly warm up to as much as 15 degrees above normal by Wednesday. This is a dangerous, prolonged heat wave that will last several days with Extreme Heat Risk through this week of Fourth of July. 2. An Excessive Heat Warning has been issued for Tuesday July 2nd through Tuesday July 9th. This may need to be extended beyond July 9th in future forecast cycles. 3. The risk of grass fires will continue to increase with herbaceous fuel loading at or near 120% of normal. A long period of excessive heat, minimum relative humidities near 15% and poor overnight relative humidity recoveries will add to the grass fire risk. && .DISCUSSION... Temperatures across Central California will continue to trend upwards as a very strong 600 decameter ridge of high pressure in the Eastern Pacific nudges eastward. Afternoon highs across the San Joaquin Valley will be a degree or two above the century mark - about 5 degrees above average for the date. Afternoon highs will trend several degrees higher on Tuesday as the ridge`s influence shifts eastward. Tuesday will be the first day of widespread Major Heat Risk across much of Central California, and this situation unfortunately worsens through the week. Wednesday in particular will be sweltering hot for afternoon highs. Major to areas of Extreme Heat Risk will be prevalent through Central California. NBM probabilities generally depict a 40-60% chance of afternoon highs reaching at least 110 degrees in the San Joaquin Valley. Warm overnight lows in the low 70s in rural areas and upper 70s in urban areas are projected to occur Wednesday morning through the end of the forecast period, including the Fourth of July. Major to Extreme heat risk is forecast to continue through the weekend as this very strong of ridge of high pressure remains in control over the Golden State. Ensemble guidance indicates the ridge axis will be nearly directly overhead by Saturday, suggesting that Saturday is potentially the hottest day of the heat wave. NBM probabilities are consistently showing a 50-60% chance of highs being at or above 110 degrees on Saturday in the valley, with locations in the Mojave Desert such as China Lake having a 56% chance of seeing afternoon highs reaching or exceeding 115 degrees. Either way, this heat wave will easily bring the hottest temperatures the forecast areas as seen year to date. Ensemble guidance shows this ridge of high pressure meandering over CA/NV after this weekend. This scenario implies a prolonged period of afternoon highs and morning low temperatures being well above average going well into the extended period of the forecast. If this scenario is to be realized, additional extensions of the Excessive Heat Warning may be prudent. && .AVIATION... Continued areas of MVFR and local IFR visibility due to smoke at and around the Fresno County fires will continue in the Sierra Nevada and adjacent foothills. Otherwise, VFR conditions will prevail across the central California interior for the next 24 hours. && .FIRE WEATHER... Fuel moistures are typically at their lowest and Energy Release Component is typically the highest through July. Near record low 100 hour and 1000 hour fuel moisture are forecast to occur during the peak of the heatwave next week, especially in the Central Valley. Additionally, ERC is forecast to approach record highs. This will create an increased risk for grass fires, especially on the 4th of July. && .AIR QUALITY ISSUES... Air Quality Alert due to smoke impacts from wildfires. See AQAHNX for more details. && .CERTAINTY... The level of certainty for days 1 and 2 is high. The level of certainty for days 3 through 7 is high. 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 from 11 AM to 8 AM PDT Tuesday for CAZ300>322-324-332-334-336>339. && $$ ab weather.gov/hanford