Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
771 FXUS66 KSGX 042140 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 200 PM PST Wed Dec 4 2024 .SYNOPSIS... High pressure aloft and developing weak offshore flow will bring well above average high temperatures in inland areas through this weekend. Areas of night and morning low clouds and fog, locally dense, will occur in coastal areas through Friday morning. A low pressure system from the northwest will bring cooling early next week with gusty west to northwest winds in the mountains and deserts initially around Sunday and a possible Santa Ana Wind event Monday or Tuesday from the mountains west to near the coast. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Skies were sunny at early afternoon across the region as the low clouds and fog all dissipated over land. With the marine layer getting more shallow tonight, there could then be patchy dense fog over higher coastal terrain, and perhaps even near the immediate coast, with any dense fog that forms Thursday night being restricted to near the immediate coast before the marine layer will likely become minimal. A closed low aloft will likely remain over Arizona through Friday and then only very slowly drift to the east as a high pressure ridge extends from the East Pacific through California and the Great Basin. This will be an offshore flow pattern, though high-resolution models indicate any Santa Ana winds to be weak to locally moderate. Through Thursday night, most of the winds appear to be along the mountain ridges, but some of the gusty winds could come down into the valleys, especially the Inland Empire, Friday through Saturday. Current gust potential is to around 40 MPH in the windiest locations south of Cajon Pass. Humidity will be low with some 10-15 percent values mainly Saturday for elevated to locally near critical fire weather conditions. It should be quite mild across the region with highs Friday-Saturday around 80 or even a little above at most lower elevation locations away from the immediate coast. A cooling trend will occur early next week with a long-wave trough moving southeast from the Pacific coast off of British Columbia through much of the western US. This should be a dry trough for SoCal, but it could be accompanied by a moderate Santa Ana wind event Monday and/or Tuesday due to a surface high pressure center developing in the Great Basin and cold air advection from the northeast. && .AVIATION... 042100Z....Coasts/Valleys...Mostly clear skies and VFR prevails through this evening until until low clouds move back ashore after 01z, with high confidence in CIGs at the coastal terminals starting by 05-07z. These clouds should reach 5-10 miles of inland extent tonight, with bases around 500-1000ft MSL. Reduced VIS 1-5SM possible, especially on mesas and higher coastal terrain. Clouds look to scatter/clear around 17-19z Thursday morning, giving way to mostly clear skies and VFR conditions. Otherwise...VFR and mostly clear skies prevails through Thursday afternoon. && .MARINE... Patchy fog under 2SM possible over the waters Thursday night into Friday morning, otherwise, no hazardous marine weather conditions are expected through Monday. && .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...Maxwell AVIATION/MARINE...Munyan