Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
994 FXUS66 KSGX 010421 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 921 PM PDT Fri May 31 2024 .SYNOPSIS... A weak trough over the Southwest and a Catalina Eddy over the coastal waters will keep a deep marine layer in place through early next week. High temperatures will be a few degrees below average west of the mountains, and a few degrees above average in the mountains and deserts. High pressure building over the West next week will bring warmer days Wednesday and Thursday. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Evening update... Low clouds have quickly spread back into the valleys this evening and have even begun sneaking into the far southern portions of the Inland Empire. The 00Z KNKX sounding shows the marine inversion based near 2400 ft MSL, similar to this morning. Low clouds will fill in across much of the coastal basin again tonight, then clear back to the coast by early Saturday afternoon. Elsewhere skies will remain clear with breezy west winds through the passes diminishing overnight. Previous discussion... This low cloud pattern will repeat Sunday and Monday as a weak trough over the West and a Catalina Eddy over the coastal waters combine forces to the keep a deep marine layer in place. There may be patchy morning drizzle each day, the most widespread on Monday morning when the marine layer will the deepest. Sunday and Monday will be the coolest days as that will be when the trough axis passes. Highs will be in the mid to upper 60s near the coast, the 70s and low 80s in the valleys, the 70s in the mountains, near 90 in the high deserts and from 100-105 in the lower deserts. The trough will also produce gusty west winds with gusts to around 25 to 40 mph each afternoon and evening in the mountains and deserts this weekend. On Tuesday the trough moves east, replaced by weak ridging and warmer days Wednesday and Thursday when highs will be in the upper 60s and low 70s near the coast, the 80s in the valleys, near 90 in the eastern sections of the Inland Empire, the 80s in the mountains, from 95-100 in the high deserts and from 105-110 in the lower deserts. The marine layer will become more shallow during this period with less inland extent each night and morning. && .AVIATION... 010325Z...Coast/Valleys...Areas of low clouds extend about 20 miles inland at this hour. Bases are 1500-2000 ft MSL and tops are around 2700 ft MSL, with CIG impacts currently at KSAN, KCRQ and KSNA. CIG impacts likely at KONT after 08Z, reaching up to 35 miles inland by 12Z. About a 50 percent chance for CIGs at KSBD 10Z-16Z. Bases will likely lower to 1000-1500 ft MSL with tops to 2500 feet, obscuring higher terrain. Areas of vis 2-4 miles with local vis below 1 mile 06Z-17Z Sat. Expect inland clearing 16Z-19Z, with only partial clearing at the coast. Mountains/Deserts...Clear skies with unrestricted VIS will continue through Sat. West winds will develop after 22Z Sat on the desert slopes and into the deserts, including near San Gorgonio Pass with gusts 25-35 kt and weak-moderate UDDFS. && .MARINE... No hazardous marine conditions are expected through Wednesday. && .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/Moede AVIATION/MARINE...PG