Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
524 FXUS66 KSGX 261029 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 329 AM PDT Wed Jun 26 2024 .SYNOPSIS... There will be overall slight cooling of high temperatures through Friday with a little greater cooling of low temperatures. Night and morning coastal low clouds will increase in coverage and spread gradually farther into the valleys through Friday. There will be warming for the weekend with Sunday high temperatures around 5 to locally 10 degrees above average, to around 115 for the lower deserts and around 100 for the most inland valleys. This may be followed by very slight cooling into the middle of next week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .SHORT TERM (Today through Friday)... Satellite imagery shows some mid clouds spreading northwestward across the area. Though still fairly patchy, there`s greater coverage of low clouds over the coastal waters and into portions of coastal San Diego County into the western valleys. The local NAM-bounded WRF shows a weak coastal eddy for tonight into Thursday morning and again for Thursday night into Friday morning with night and morning coastal low clouds becoming more widespread and spreading farther into the valleys. High temperatures for the coast into the valleys will be a few degrees cooler today, otherwise just a slight overall cooling trend in high temperatures through Friday along with some drying for late in the week. && .LONG TERM (Saturday through Tuesday)... With the drying, temperatures for Friday night will not be quite as warm. High temperatures will warm for Saturday and Sunday with Sunday high temperatures around 5 to locally 10 degrees above average, to around 115 in the lower deserts and around 100 for the far inland valleys. With the drying and with the resulting overnight temperatures not being quite as warm, the heat risk for the deserts may decrease just enough to fall below Excessive Heat Warning criteria for Friday and Saturday. However, with the warming during the weekend, excessive heat could return for the deserts on Sunday and continue at least into the middle of next week. && .AVIATION... 260850Z...Coast/Valleys...Areas of stratus with bases 1300-1800 ft MSL and tops to 2000 ft MSL continuing to develop across the coastal areas and far western valleys this morning. There is a 30-40 percent chance of CIGS at KSNA 12-15Z. Clouds clearing to the coast 15-18Z. More widespread low clouds redeveloping this evening, beginning to move back into the coastal areas after 27/02Z and spreading 15-20 mi inland by Thu morning. Little change in bases/tops tonight. Otherwise FEW-SCT clouds at/above 15,000 ft MSL through Thu morning. Mountains/Deserts...SCT Cu with bases near 10,000 ft MSL developing across the mountain crests this afternoon, dissipating by sunset. Otherwise FEW-SCT clouds at/above 15,000 ft MSL through Thu morning. West winds with sfc gusts 25-40 kt developing across the mountains and deserts this afternoon and evening, strongest through the passes. MOD up/downdrafts over and east of the mountains. && .MARINE... No hazardous marine conditions are expected through Sunday. && .CLIMATE... Precipitable water is the water through the entire depth of the atmosphere above a location if that water were all precipitated out as rain. For San Diego for June, the existing record for highest precipitable water from a sounding occurred on June 9th, 2015 for the 12Z NKX sounding at 1.75 inch. The second greatest was for a sounding on June 30th at 1.61 inch. The climatological average for San Diego increases from 0.70 inch at the beginning of June to 0.84 inch at the end of June. Beginning on June 23rd of this year, there have now been 5 soundings from NKX that have exceeded the previously second highest precipitable water for June, but not quite reached the record of 1.75 inch. Those soundings have had PW values of 1.7, 1.7, 1.69, 1.68, and 1.65 inches. This is probably most notable in that there is nothing in the existing climatological record of sustained precipitable water values this high for the month of June. The main impact has probably been in keeping overnight temperatures warmer. Over the past three days, there have been 28 daily records tied or broken for warmest low temperature. Soundings for San Diego go back to around 1956. .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Excessive Heat Warning until 8 PM PDT Thursday for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts- San Gorgonio Pass Near Banning. PZ...None. && $$ PUBLIC/CLIMATE...17 AVIATION/MARINE...SS