Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
122 FXUS66 KSGX 200919 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 219 AM PDT Sun Apr 20 2025 .SYNOPSIS... Dry and warmer through early next week with high temperatures near to around 5 degrees above normal inland by Monday. Gradual cooling follows Tuesday through Saturday. Areas of night and morning low clouds and fog continuing through next week, becoming more widespread towards the middle of the week as the marine layer deepens. Afternoon and evening winds will strengthen slightly across the mountains and deserts for the latter half of the week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... A few patches of low clouds have begun to develop just off the coast, otherwise skies are clear. Low clouds may briefly move into the coastal areas later this morning, but widespread coverage is not expected. Warmer today with highs near seasonal averages. We remain under weak cyclonic flow much of the week with a series of short waves passing by to the north. The marine layer will become more established and deepen each subsequent night. By Wednesday morning, the marine layer will be deep enough for low clouds to spread into the inland valleys. Persistent onshore flow will moderate temperatures west of the mountains where highs will remain near to slightly below normal through Tuesday. For the mountains and deserts, breezy westerly winds develop each afternoon and continue into the late evening along with highs slightly above normal. Ensembles have trended towards the more northern track of the upper low late in the week, bringing it into Pacific Northwest. This would result in less significant cooling Wednesday through Saturday and much lower precipitation chances, which are now below 5%. Friday and Saturday are currently forecast to be the coolest days of the week, with high temperatures around 3-5 degrees below normal. The marine layer will continue to deepen with widespread low clouds west of the mountains each night and morning for the latter half of the week. Depending on the timing of the short waves, we could see some patchy drizzle in the mornings. Breezy west winds will increase slightly across the mountains and deserts each afternoon and evening. By Sunday, ensemble solutions are 50/50 with digging the trough south through the Great Basin, which would result in continued cool weather, or a more progressive/further north track which would allow for some warming Sunday. && .AVIATION... 200930Z....Coasts/Valleys...Mostly clear skies prevailing over land though a few pockets of low stratus are lurking along the shore/beaches this morning. These clouds based around 700-1000ft MSL may bring occasional CIGs to the coastal TAF locations (with greatest confidence of occurrence at KSNA: 60%, followed by KSAN: 40%, and KCRQ: 20%) this morning. There is a 15% chance of patchy fog with visibility 1-2 SM developing along the coast, primarily on coastal mesas. Any low clouds or fog that develop/move onshore should clear by 16-18z, with VFR prevailing and breezy onshore winds through the afternoon. Higher confidence in more plentiful clouds filling in around 09-12z Monday, with bases likely near 1000-1500ft MSL. Mountains/Deserts...Clear skies with unrestricted VIS prevailing through Monday morning. && .MARINE... No hazardous marine conditions are expected through Thursday. && .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...SS AVIATION/MARINE...Munyan