Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
901 FXUS66 KSGX 111127 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 427 AM PDT Thu Jul 11 2024 .SYNOPSIS... The heat will continue for inland areas today followed by a gradual slow cooling trend for Friday through Tuesday of next week. Night and morning coastal low clouds will continue to spread into portions of the western valleys late each night. Monsoonal moisture will begin to arrive on Friday and peak over the weekend with a chance of afternoon and early thunderstorms for the mountains and deserts for Saturday and Sunday, followed by drying 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 Saturday)... The marine layer remains around 1200 feet deep with the coverage and inland extent about the same as 24 hours ago with coverage across much of the Orange County coastal plain and for San Diego County inland into portions of the far western valleys. In San Diego County, there could be some locally dense fog into this morning for the mesas into the far western valleys. Satellite imagery also shows some mid clouds moving northwestward across the area. In the late Wednesday afternoon sounding from NKX, there was a shallow saturated layer between 400 and 450 mb. With the incoming 12Z sounding, there is just a shallow moist layer around 450 mb. Slight cooling is expected for portions of the inland valleys today, but for most areas high temperatures will be within a few degrees of those on Wednesday. A gradual slow cooling trend is expected to begin on Friday and continue through around Tuesday of next week. Some monsoonal moisture may begin to arrive on Friday with a greater influx on Saturday with precipitable water values greatest over the weekend. The guidance hasn`t changed much for Friday with a less than 15 percent chance for showers and thunderstorms during the afternoon and early evening, mainly over the San Bernardino Mountains. Chances are greatest for Saturday afternoon and early evening at 25 to 35 percent in the mountains and 15 to 25 percent in the deserts. && .LONG TERM (Sunday through Wednesday)... NBM shows a decrease of about 5 to 10 percent in the chances for afternoon and early evening showers and thunderstorms on Sunday with a drying trend continuing into the middle of next week. With the cooling trend, high temperatures on Tuesday will be a few degrees above average in the deserts to around 5 degrees below average in the inland valleys, around 110 in the lower deserts and in the mid 80s to mid 90s for the Inland Empire. Not much change is expected for Wednesday. Areas of night and morning coastal low clouds will continue to spread inland into portions of the western valleys late each night. && .AVIATION... 110945Z...Coast/Valleys...Low clouds increasing in coverage and spreading locally 15-20 miles inland by 15Z. Bases are 400-800 ft MSL with tops around 1200 ft MSL. Areas of fog with VIS 2-4 miles, locally 1 mile on higher coastal terrain and portions of the inland valleys. Expect inland clearing 17Z-19Z and clearing to the coast 19Z-21Z. Low clouds returning to coastal TAF sites after 02Z Friday with similar bases and tops. Mountains/Deserts...SCT-BKN at or abv 18,000 ft MSL with unrestricted VIS through this afternoon. Localized VIS reductions down to 3SM due to smoke in the San Bernardino Mountains VCNTY the Vista fire. Winds generally light, but periods of northwest winds gusting up to 30kts around San Gorgonio Pass through Thursday evening. && .MARINE... No hazardous marine conditions are expected through Sunday. && .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 9 PM PDT this evening for San Bernardino and Riverside County Valleys-The Inland Empire- San Diego County Mountains-San Diego County Valleys. Heat Advisory until 9 PM PDT this evening for Orange County Inland Areas-Riverside County Mountains-San Bernardino County Mountains-Santa Ana Mountains and Foothills. Excessive Heat Warning until 9 PM PDT Friday for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts- San Gorgonio Pass Near Banning. PZ...None. && $$ PUBLIC...17 AVIATION/MARINE...PG