Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
Issued by NWS San Joaquin Valley, CA
311 FXUS66 KHNX 241000 AFDHNX Area Forecast Discussion National Weather Service Hanford CA 300 AM PDT Mon Jun 24 2024 .KEY MESSAGES... 1. Temperatures will be around 10 to 15 degrees above average Today with widespread triple digit highs across the lower elevations. A Heat Advisory is in effect through Tuesday morning. 2. There is a 40 to 70 percent probability of high temperatures of at least 105 degrees or above across most of the San Joaquin Valley this afternoon. 3. Above average heat will continue this week, with 100 degree heat persisting for many locations through Wednesday. 4. There is a 10 to 20 percent probability for thunderstorms This afternoon and Tuesday afternoon along the Sierra Nevada crest from Yosemite National Park to Kings Canyon and Sequoia National Park. && .DISCUSSION... The Heat-Wave continues as triple digits and new record highs were observed on Sunday. Merced reached 108 degrees, which broke the old record of 107 degrees last set in 1939. The ridge of high pressure responsible for the weekend heat remains anchored over the South as the Heat-Wave will continue for at least one more day. The position of the ridge also allowed remnant moisture from Tropical Cyclone Alberto to surge northwest and into a large portion of the district. The increase in moisture allowed for afternoon convective development as isolated showers and thunderstorms popped-up before sunset. With little change expected today, will see heat and afternoon convection occur one more time. The development of a disturbance moving across the Pacific Northwest around the mid-week period will bring an end to the heat, but will increase the threat of thunderstorms across the area. The remainder of the week will see a cooling trend before warming begins early next week. High-Res Short-range Ensemble Probability of Exceedance (PoE) places a 40 to 70 percent chance of reaching 105 degrees across the San Joaquin Valley today. These percentages allow for higher confidence in maintaining the Heat Advisory today. In addition, ensemble mean instability does show enough energy to fire-off a slight chance of showers and thunderstorms (10-20 percent). Therefore, a repeat of Sunday will be observed this Monday. The only uncertainty will be the amount of cloud cover which can hinder afternoon heating. Yet, will allow the heat-wave to continue for one more day. Uncertainty in the heat exist on Tuesday as a disturbance pushes into the Pacific Northwest on Tuesday and Wednesday. High-Res Short-range ensemble and long-range ensembles showing the introduction of the short-wave trof moving ashore close to the mid-week period. While ensemble do drop the PoE of reaching 105, then also have 50-70 percent PoE of reaching 100 degrees. Therefore, while still hot, will re-evaluate the continuation of the Heat Advisory later today. However, confidence in convective activity is still high as stronger thunderstorm development will occur across the Sierra Nevada and locations eastward. While the initial onset of disturbances passage will occur on Tuesday and Wednesday, Central California will feel the full effect of the disturbance by Thursday. Ensemble Cluster Analysis is showing a strong signal toward having the disturbance cross the region between Thursday and Friday. As the disturbance moves through, more significant cooling and strong winds will develop. Messaging has started on windy conditions on Thursday as well as having temperature return to near normal conditions. Friday and the weekend will see a slow rise in temperatures as the lower elevations see triple digits toward the end of next weekend. && .AVIATION... A 10-20 percent chance of thunderstorm development from 20Z today through 02Z Tuesday across the Sierra Nevada and Kern Mountains. 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... Heat Advisory until 11 AM PDT Tuesday for CAZ300>317-319-321- 332. && $$ Operations.......Molina Support/IDSS.....JPK weather.gov/hanford