920 FXUS66 KSGX 250941 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 241 AM PDT Fri Jul 25 2025 .SYNOPSIS... A weak trough of low pressure moving inland into California will bring cooling for today and Saturday with Saturday high temperatures as much as 10 to 15 degrees below average for the mountains and inland valleys. Strengthening high pressure to the east will bring a warming trend for Sunday through Wednesday with high temperatures on Wednesday within a few degrees of average. Night and morning coastal low clouds will spread into portions of the western valleys late each night. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .SHORT TERM (Today through Sunday)... A weak low pressure system moving inland into California will bring high temperatures a few degrees cooler today and another few degrees cooler on Saturday with high temperatures on Saturday as much as 10 to 15 degrees below average for the mountains and inland valleys. High temperatures on Saturday will range from around 70 near the coast to the upper 70s to mid 80s for the Inland Empire with 100 to 104 for the lower deserts. Strengthening high pressure to the east will bring a warming trend beginning on Sunday with Sunday high temperatures slightly warmer near the coast to a few to around 5 degrees warmer inland. High temperatures on Sunday will range from the lower 70s near the coast to the 80s and lower 90s for the Inland Empire with 102 to 106 for the lower deserts. A marine layer near 2000 feet deep early this morning will deepen to around 2500 feet for Saturday with night and morning coastal low clouds spreading into the western valleys in San Diego County early this morning and into southern and western portions of the Inland Empire for late tonight into Saturday morning. The marine layer will decrease in depth Saturday night into Sunday to 2000 to 2500 feet with coastal low clouds spreading into the western valleys late Saturday night. && .LONG TERM (Monday through Thursday)... The warming trend will continue through Tuesday with Tuesday high temperatures within a few degrees of average for most areas with the valleys still a few degrees below average. High temperatures on Tuesday will range from the lower to mid 70s near the coast to the upper 80s to upper 90s for the Inland Empire with 106 to 112 for the lower deserts. Not much change is expected for Wednesday with slight cooling on Thursday. The marine layer will slowly decrease in depth to 1500 to 2000 feet deep for Wednesday and Thursday with night and morning coastal low clouds spreading into portions of the western valleys late each night. There may be a minor intrusion of monsoonal moisture centered around Wednesday and Thursday. However, NBM daily chances for measurable rainfall for Big Bear have decreased to 5 percent or less for each day for Tuesday through Saturday of next week. Ensemble output for Imperial shows a greater influx of monsoonal moisture may occur by the middle of the following week, the first full week of August. && .AVIATION... 250915Z....Coasts/Valleys...Low clouds based right around 1500ft MSL (w/ tops near 2000ft MSL) have remained largely patchy across San Diego County this morning but are beginning to become more uniform. Patchy clouds spread into portions of Orange County for 12-17z, but won`t become consistently uniform as with SD County. These clouds scatter out by 16-17z this morning. Additionally, pockets of radiation fog have developed across some inland valleys, brining VIS to 1-3SM and locally under 1SM within these patches. Any fog will mix out by 14-16z this morning. Mostly clear skies persists through the late morning into the afternoon with low clouds redeveloping after 00z Saturday. These clouds will likely become uniform and spread into Orange County more quickly than this morning, eventually spreading into inland valleys and the Inland Empire by 06-09z Saturday. Bases will be relatively similar to this morning, around 1500 ft MSL. Mountains/Deserts...Mostly clear and VFR conditions through early Saturday morning. && .MARINE... Northwest wind gusts 15-20 kts over the waters today, weaker onshore flow follows this weekend into next week. No hazardous marine conditions are expected through Tuesday. && .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...17 AVIATION/MARINE...Munyan