627 FXUS66 KSGX 050416 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 916 PM PDT Wed Jun 4 2025 .SYNOPSIS... Drizzle will be possible tonight through early tomorrow morning for portions of the coastal and inland areas of San Diego and Orange counties, and within the IE. Drier conditions returning tomorrow into next week, with a warming trend through the weekend. High temperatures will peak Sunday and Monday at a few to around 5 degrees above average for coastal areas and 5 to 10 degrees above average for the mountains and deserts. Night and morning coastal low clouds will cover much of the valleys into Thursday, then not spread as far into the valleys for the weekend into early next week as the marine layer becomes shallower. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Update: All showers and thunderstorms have now made their way out of the CWA. There could be some drizzle for the coastal and inland areas throughout the night. This will clear out for the inland areas and most of the coastal areas by later in the morning tomorrow. High pressure will be building back in over the region, although some overall troughing will keep the onshore flow going strong throughout the rest of the week, although further subsidence from the building high pressure is going to allow for the marine layer to become more thin and shallow beginning tomorrow night, and therefore will not extend as far inland. There will be a gradual warming trend going into the weekend. There will be an upper level low which could help to hold down the temperatures slightly going into the weekend. Models are still having a hard time on the placement of this. The subtropical ridge will be building over Mexico beginning this weekend into early next week, which depending on where the ridge axis establishes itself, could result in warmer temperatures early next week, otherwise more troughing upstream advancing slowly towards the region will result in a slight cooldown towards the mid part of next week. (Previous discussion submitted at 140 PM): This afternoon...Satellite imagery shows cumulus cloud buildups over the local mtns but radar is yet to detect any precipitation, except over the mtns of northern Baja. There is still time for showers/tstms to develop this afternoon/evening in our local mtns. Any convective activity will likely dissipate around 7 pm. The marine layer low clouds are very slow to clear and continue to cover the coastal areas and the western portions of the San Diego County valleys. From previous discussion... The atmosphere over SoCal will steadily become drier today through tomorrow for decreasing chances of afternoon showers/tstms as conditions become more stable. In spite of broad troughing over the western US through Friday with a closed upper low developing off the CA coast on Sat, temperatures will slowly rise through the weekend. Friday high temperatures will be mostly within a few degrees of average, ranging from around 70 near the coast to the 80s for the Inland Empire, with 100 to 104 for the lower deserts. As we move into the weekend, the sub-tropical high over northern Mexico will build over AZ and extreme southeastern CA. Slow warming will continue through the weekend with the heat peaking on Sunday and Monday. High temperatures for Sunday will range from a few to around 5 degrees above average for coastal areas and 5 to 10 degrees above average for the mountains and deserts. High temperatures on Sunday will range from the lower 70s near the coast to the mid 80s to mid 90s for the Inland Empire, with 105 to 110 for the lower deserts. The marine layer will become shallower with night and morning coastal low clouds not spreading as far into the valleys. Not unexpectedly, model solutions diverge as we move into next week so there is measurable uncertainty in the forecast details. In general, we will see the sub-tropical ridge expand westward but remain to our south with weak ridging over the west coast. We can expect dry conditions to persist through the middle of next week with a shallower marine layer modifying temperatures near the coast. Inland temperatures will remain mostly several degrees above average. && .AVIATION... 050330Z....Coast/Valleys...Low clouds based 1500-2000 feet MSL have pushed into most of San Diego/Orange Counties and southern IE already. Expecting the rest of the IE to fill in overnight with minor vis restrictions possible (3-5 SM) as bases lower slightly. Clearing Thu morning 15-17Z for inland areas, 18-20Z for Orange County coast, and only partial clearing for San Diego County coastal areas 19-21Z, with KCRQ and KSAN likely remaining under cloud cover all day once again. Low clouds push inland again after 00z Friday with bases continuing to hover between 1000-2000 ft MSL. Mountains/Deserts...Generally SKC with a typical diurnal wind pattern through Thursday. ISO SHRA/TSRA based at 10000 feet MSL possible over the San Bernardino County mountains and high desert after 21z Thursday. && .MARINE... No hazardous marine conditions are expected today 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. && $$ UPDATE...Stewey PUBLIC...PG AVIATION/MARINE...KW