Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
058 FXUS66 KSGX 230423 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 923 PM PDT Sun Sep 22 2024 .SYNOPSIS... Warming trend for early this week. The marine layer will become shallower over the next two to three days, becoming confined to the coast and portions of the western valleys. For the middle to end of the week, minor daily fluctuations in high temperatures are expected. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... No Significant changes to the forecast this evening as widespread stable conditions dominate the evening hours. Low marine stratus has already worked into a large swath of the San Diego County coast, and some sections of Orange County are developing fog/low stratus at the moment. This is expected to push inland roughly 15-20 miles overnight. From previous discussion... Numerical models are in good agreement through Wednesday with respect to the synoptic pattern. Cyclonic flow aloft in a stretched trough will evolve in a relatively weak Rex Block by Tuesday, with a closed upper low centered about 100 miles west of San Diego and an upper high centered just off the southern Oregon coast. By Wednesday, a low/trough deepens off the west coast as a strong low pressure system moves into the Gulf of Alaska. This will displace the upper high to a position near the Four Corners. Solutions begin to diverge on Thu and the spread increases significantly as we approach next weekend. However, it seems likely that some form of low/trough will persist near SoCal through the forecast period. High temperatures today will reach the mid to upper 70s in the coastal areas, the 80s to low 90s in the valleys, 70s to low 80s in the mountains, low 90s in the High Desert, and 100 to 105 degrees in the low desert. Additional warming is expected for Monday, with most places 3 to 5 degrees warmer than today. For Tuesday, temps will be similar to Monday with only a degree or two difference in most locations. At this time, it`s most likely that there will be only slight day-to-day temp variations from Wed through Friday with more of a cooling trend for next weekend. However, the spread in model solutions continue to inject significant uncertainty in the forecast. The marine layer will become shallower through Wednesday, with low clouds and fog becoming mostly confined to the coastal areas, inland Orange County and the western portions of the San Diego County valleys. The marine layer may recover slightly (or significantly) for the middle to end of the week if - as some model solutions suggest - the trough deepening off the west coast were to shift eastward even a little. This would put Socal under southwest winds aloft in cyclonic flow. && .AVIATION... 220330Z...Coasts/Valleys...Low marine stratus has built into most of coastal San Diego County this evening, based around 1000-1400 ft MSL with tops to about 2000-2300 ft MSL. This will continue to move into coastal sites through 06Z this evening, moving inland 15-20 mi overnight. Local vis reductions 1-3 SM expected for higher coastal terrain and valleys. Clouds scatter out 16-18Z, retreating to beaches. Low clouds with similar bases and tops redeveloping along the coast 04-07Z Tue. Mountains/Deserts...Mostly clear skies with unrestricted VIS expected through Monday evening. && .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...Suk AVIATION/MARINE...CSP