029 FXUS66 KHNX 091801 AFDHNX Area Forecast Discussion National Weather Service Hanford CA 1101 AM PDT Wed Jul 9 2025 .KEY MESSAGES... 1. Temperatures near season averages across the region today before a gradual warm up into the triple digits later this week. 2. Low RH values 15 to 25 percent will stretch across much of the San Joaquin Valley and Sierra Nevada with values 5 to 10 percent in the Mojave Desert. RH will decrease over the region later in the week with warming temperatures. && .DISCUSSION... Upper level disturbance riding over Northern California is now pushing into the Great Basin and out of the area. This shift will allow the ridge of high pressure over the Desert Southwest to retrograde and shift back toward the West Coast in the coming days. While the ridge of high pressure will build over the West Coast by the end of the week, the ridge is expected to remain flat with minimal amplification. Therefore, while triple digit heat toward the end of the week, the intensity of the heat will be such that values will remain well below any records for the period. In addition, the flow around the flat ridge will prevent any significant monsoonal moisture push to surge toward Central California as the region remains dry during the upcoming heat event. Therefore, by the start of the weekend, a heat wave will reach Central California with some overnight recovery as minimum temperatures bottom out in the mid 60s. Little change in seen as the ridge pattern will remain into early next week. While the ridge pattern builds back onto the West Coast, ensemble Probability of Exceedance (PoE) of reaching 100 degrees remains below 30% today. Thursday marks the transition period at which time the PoE jumps up to a range between 50% and 90%, with the higher end on the west side of the San Joaquin Valley along the Interstate-5 corridor. At that point, triple digits are mostly scattered with less of a chance over the Highway-99 corridor. Also, by Thursday, the Kern Desert maxs out its PoE with values above 90% for the duration of the period. Friday shows both the San Joaquin Valley and Kern Desert having probabilities in the 90% and above range. At that point, confidence in widespread triple digits increases for the start of the next heat wave. While Thursday will see some highs reaching 100 degrees, Friday has a higher likelihood of having values reach the 103 degree and above mark. By Friday and the weekend, PoE of 103 degrees is in the range of 70% to 90% which increases confidence in having a heat wave. Little change in PoE values is observed through early next week as triple digit temperatures will exist through day 7. The ridge pattern solution will favor some heat as the flow around the ridge will hinder monsoonal moisture from reaching Central California. Therefore, dry and hot will be the main message during the short term as light diurnal winds will also be seen during the period. && .AVIATION... 18Z Update: VFR conditions will prevail for the next 24 hours across the Central California Interior. && .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. && $$ Public/Aviation....Molina weather.gov/hanford