Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
052 FXUS66 KSGX 170334 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 834 PM PDT Fri Aug 16 2024 .SYNOPSIS... After a thunderstorm in the Anza Borrego Desert this evening, dry and seasonal conditions are expected for the weekend. Monsoonal moisture will increase Tuesday and Wednesday, with the best chance of thunderstorms Wednesday and lesser chances Tuesday and Thursday. A warming trend is expected Sunday through Tuesday. Night and morning low clouds and fog are expected to reach into valleys tonight, and will be less extensive thereafter. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Another fair and benign evening in our SoCal weather... wait a minute. What`s this? A thunderstorm complex out in the Anza Borrego Desert! It`s so remote it has missed every rain gauge so far, but we have detected lightning and a wind gusts of 37 mph from it. Surely some locally heavy rain has fallen over the Vallecito Mountains. It has made the view east from San Diego quite interesting and beautiful. It was the one isolated case that had just enough instability to punch through a stable convective cap we`ve had in our atmosphere today. This feature is quieting down and we`ll return to our regularly scheduled quiet weather evening. The marine layer has gotten a boost from our coastal eddy today. The low clouds have moved ashore already across coastal areas, farther inland in northern San Diego County. This is looking like fingers of clouds and fog could reach into inland valleys by sunrise. Saturday will be relatively cooler than today especially west of the mountains, thanks mostly to the robust eddy and deeper marine layer. A low pressure trough to our north will begin to retreat as a high pressure ridge to our east expands westward early next week. This will bring a notable warming trend, likely peaking Tuesday. Temperatures will rise to 100-105 in the Inland Empire and the high desert, and 110-115 in the low desert. The higher pressure will diminish the marine layer low cloud presence. Monsoonal moisture will not be sufficient to produce thunderstorms through Monday, but increases Tuesday and appears to peak Wednesday. There is a slight chance of thunderstorms Tuesday in the mountains and a better chance Wednesday in both the mountains and deserts. The trough seems to take its turn to dominate Thursday and Friday. This would sweep away the monsoonal moisture and help deepen the marine layer for more coastal clouds. It will also bring a cooling trend heading into next weekend. && .AVIATION... 170330Z...Coast/Valleys...Marine clouds currently along the coasts based around 1000-1200ft MSL should gradually lower through 12z to around 700-900ft MSL, with tops to 1300-1500ft MSL. VIS reductions are anticipated for the valleys and higher coastal terrain, falling as low as 1-3SM, possibly even less than 1SM at times, and visibilities along the immediate coast may fall to around 4-6SM. Clearing should occur by 16-18z on Saturday, with VFR prevailing through Saturday evening. Patchy low clouds should redevelop late Saturday evening. Mountains/Deserts...A lone thunderstorm over the Borrego Desert has dissipated, otherwise, mostly clear skies and unrestricted VIS should prevail through Saturday afternoon. && .MARINE... No hazardous marine conditions are expected through Wednesday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ PUBLIC...MM AVIATION/MARINE...Munyan