Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
Issued by NWS San Joaquin Valley, CA
483 FXUS66 KHNX 040935 AFDHNX Area Forecast Discussion National Weather Service Hanford CA 235 AM PDT Tue Jun 4 2024 .KEY MESSAGES... 1. The Excessive Heat Warning has been extended through 8 PM Friday, due to continued daytime major(red) daytime HeatRisk on Friday. 2. The Heat Risk will be major(red) from Wednesday through Friday afternoon, which will affect anyone without effective cooling and/or adequate hydration. Impacts are likely in some health systems, heat-sensitive industries and infrastructure. 3. Temperatures are forecast to lower slightly on Saturday with more cooling into next week. Temperatures are forecast to still be a few degrees above normal by next Monday. 4. The anticipated heat for later this week could lead to increased snowmelt over the Sierra Nevada, resulting in colder and higher flows along rivers and waterways. && .DISCUSSION... Central California saw significant cloud cover on Monday resulting from the passage of a disturbance through the Pacific Northwest. While precipitation was confined to the Pacific Northwest, cool air filtered into the region as the disturbance kept High temperatures slightly below normal on Monday. In addition to the cooler air, the Central California Interior saw an increase in winds as speeds reached up to 60 mph in a few spots across the Mojave Desert. At this point, the air-mass over the region will take time to modify as the ridge of high pressure will now build over the West Coast. The trend for the next several days across the district will be the warming of temperature leading to a Heat-Wave later this week. A disturbance next weekend will slow down the heat as temperatures fall below 100 degrees for a day or two. Short-range High-Res Ensemble analysis is showing the disturbance pushing out of the area as the ridge will now take hold of the Southwest. Ensemble upper-air analysis begins the building of the West Coast Blocking High Pattern today as temperatures rebound back into the 90s. The ridge pattern will continue building over the West as Probability of Exceedance (PoE) of reaching 100 degrees ranges from 75 to 90 percent on Wednesday. PoE of 105 degrees remains below 40 percent for most of the San Joaquin Valley except for Fresno (where PoE is 50 percent). At the same time, Index values of extreme heat lean toward hot temperatures, yet, are not overly aggressive toward reaching extreme values. The ridge really takes hold of the West by Thursday. That at time, Ensemble Cluster Analysis shows a very strong ridge over the west. confidence is therefore high that High temperatures will reach dangerous levels. An Excessive Heat Warning has been issued as PoE of reaching 105 and above climbs to between 65 and 90 percent. While Friday does not the same percentage values as those on Thursday, PoE of reaching 105 degrees still range from 20 to 50 percent. Therefore, without the strong forcing of cooler air into the region on Friday, will maintain hot temperatures for an additional day. During this same time frame, Probability of Thunder does go up to near 15 percent across the Sierra Crest. Will mention a slight chance of mountain thundershowers (even under a ridge of high pressure) as moisture from melting snow adds humidity to the air. 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. The switch to a more westerly flow aloft will lead to a reduction in heat. At this point, the cooling will amount to a brief period of temperatures below 100 degrees. && AVIATION... 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... Wind Advisory until 5 AM PDT early this morning for CAZ338. Excessive Heat Warning from 11 AM Wednesday to 8 PM PDT Friday for CAZ300>317-319-321-332-337>339. && $$ Operations......Molina Support/IDSS....DS weather.gov/hanford