Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
Issued by NWS San Joaquin Valley, CA
005 FXUS66 KHNX 060957 AFDHNX Area Forecast Discussion National Weather Service Hanford CA 257 AM PDT Thu Jun 6 2024 .KEY MESSAGES... 1. An Excessive Heat Warning remains in effect for the lower elevations from 11 AM today through 8 PM Friday. 2. The Heat Risk will be major (red) today and Friday afternoon, which will impact anyone without effective cooling and/or adequate hydration. Impacts are likely in some health systems, heat-sensitive industries and infrastructure. 3. Temperatures will lower slightly this weekend, but are forecast to still be around 5 to 10 degrees above normal. 4. The anticipated heat could lead to increased snowmelt over the Sierra Nevada, resulting in colder and higher flows along rivers and waterways. && .DISCUSSION... The Heat-Wave is on as the Central California Interior saw widespread 100 degree reading on Wednesday. With the axis of the ridge of high pressure now over the West Coast, temperatures will continue their warming trend as the region will see dangerous heat today. In addition, while surface pressure gradients will remain very weak and produce light up-slope winds, a surge of moisture down from the Pacific Northwest and snow-melt will help support convection this afternoon. Therefore, outside of the Sierra Nevada Crest, sunshine will dominate today as the Heat-Wave continues. A break-down of the ridge is expected this weekend as temperature rebound toward the middle of next week. High-Res Short range ensemble maintain a high probability of reaching dangerous heat (at and above 105 F) levels (60-70 percent) this afternoon. After breaking through the century mark Wednesday afternoon, confidence is high that reading near 105 degree will be attainable today. With this, will allow the Excessive Heat Warning to remain in effect through Friday. Short range ensembles also show mean instability values reaching levels that would support thunderstorms this afternoon over the mountains. Yet, without a strong forcing mechanism, convection will remain pulse-in-nature and drift east of the Sierra Crest before diminishing. Therefore, convection will do little to slow-down (or prevent) the heat-wave from occurring. Looking further our, longer range upper-air ensembles show the break- down of the ridge as index values and Probability of Exceedance (PoE) of reaching 105 degrees diminishes. Current list of PoE values of reaching 105 degrees and above across the San Joaquin Valley and Kern County Desert are included: THU FRI THU FRI Fresno: 71% 26% Merced: 51% 11% Bakersfield: 61% 26% Visalia: 66% 26% Hanford: 71% 41% Madera: 61% 16% Porterville: 61% 26% Delano: 66% 21% Reedley: 61% 16% Lemoore: 66% 26% China Lake: 100% 96% Edwards AFB: 91% 11% Inyokern: 100% 86% Mojave: 92% 0% Looking toward the weekend, uncertainty increases as an attempt is made in the ensemble solutions to push out the ridge. Confidence is not high enough to determine if strong cooling will enter the region. Yet, with a sharp drop in PoE values going into Friday, the trend is to continue the drop in values as the Heat-Wave end by Friday night. The switch to a more westerly flow aloft will lead to a reduction in heat as longer range ensemble temperature analysis place values in the upper 90s to near 100 degrees (below hazardous criteria). At this point, the cooling will amount to a brief period of temperatures below 100 degrees. By mid-week, temperatures start another warming trend. && .AVIATION... A 15-20 percent of thunderstorms over the Sierra Nevada Crest between 20Z and 02Z Friday. Otherwise, VFR conditions will prevail across the Central CA interior for 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... Excessive Heat Warning until 8 PM PDT Friday for CAZ300>317- 319-321-332-337>339. && $$ Operations......Molina Support/IDSS....DS weather.gov/hanford