Area Forecast Discussion
Issued by NWS San Diego, CA

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000 FXUS66 KSGX 241115 AFDSGX AREA FORECAST DISCUSSION National Weather Service San Diego CA 415 AM PDT SUN JUL 24 2016 .SYNOPSIS... The cooling that began Saturday will continue today with the greatest cooling in the valleys. Slowly warmer inland for Tuesday through Thursday with some mid and high clouds at times and some afternoon clouds over the mountains. A little cooler inland for Friday through next weekend with an influx of monsoonal moisture bringing a slight chance of afternoon thunderstorms near the mountains. Areas of night and morning coastal low clouds and fog will spread locally into the western valleys at times. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... High pressure aloft will weaken slightly through Monday... strengthen slightly for Tuesday through Thursday...then weaken into next weekend as a trough of low pressure develops near the West Coast. The cooling that began Saturday as a result of weakening high pressure aloft and a coastal eddy will continue for most areas today with the greatest cooling in the valleys. The circulation center of a coastal eddy has moved far enough to the southwest of San Nicolas Island...such that the most widespread stratus coverage is mostly beyond the offshore islands with patchier coverage toward the coast with not much inland spread of the stratus. Satellite imagery and lightning detection data shows a large convective complex over northwest Mexico. The GFS initializes this reasonably well and takes the bulk of the mid and high level moisture westward across northern Baja through tonight...possibly just grazing far southern California. The vertical distribution of this moisture is less than optimal for convective development in Southern California with most of it 600 mb and above and the bulk of it from 500 to 300 mb. An influx of monsoonal moisture for late in the week could be more favorably distributed for afternoon convection over the mountains...extending down to around 700 mb. With the developing trough of low pressure near the West Coast for next weekend... drier southwest flow aloft should not be too far away to the northwest. && .AVIATION... 240900Z...Coast...Areas of stratus will continue this morning near the coast and up to about 15 miles inland. Bases will be 500-900 ft MSL with tops to 1300 ft MSL. Vis restrictions 1-3 SM over the higher coastal terrain and near the coast, possibly including the San Diego County mesas, VCNTY KCRQ, KMYF and KSDM. Most areas will clear out between 16Z-18Z this morning although a few patches BKN conditions possibly continuing near the beaches through this afternoon. Coastal stratus will likely reform this evening with bases a bit higher than this morning, more widespread, and spreading up to 20 SM inland overnight through early Monday morning. Valleys/Mountains/Deserts...Some smoke will occur in San Bernardino County from the Sand Fire of LA County, but most vis will remain above 5 SM. Otherwise, increasing clouds above 15000 ft MSL with unrestricted vis will continue through this evening. && .MARINE... No hazardous marine weather is expected through Thursday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX Watches/Warnings/Advisories... CA...Heat Advisory until 8 PM PDT this evening for Apple and Lucerne Valleys-Coachella Valley-Riverside County Mountains-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Deserts- San Diego County Mountains-San Diego County Valleys-San Gorgonio Pass Near Banning. PZ...None. && $$ PUBLIC...17 AVIATION/MARINE...JMB is the U.S. government's official web portal to all federal, state and local government web resources and services.