Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
450 FXUS66 KSGX 170425 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 930 PM PDT Sun Jun 16 2024 .SYNOPSIS... Areas of smoke will occur at least through Monday, mostly due to the Post Fire in the far northwest part of Los Angeles County. Otherwise, near to slightly below average temperatures will occur through the middle of the week as a trough of low pressure stays over the western US. This will also bring breezy conditions to the mountains and deserts along with greater low cloud coverage west of the mountains. High pressure will reemerge later this week, leading to above average temperatures away from the coast again. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Update... Areas of smoke covered the area due to several wildfires, with the Post Fire of extreme NW LA County being the most substantial one at over 14000 acres burned. Local west winds were gusting over 35 MPH in the mountains and deserts, with Whitewater West RAWS in San Gorgonio Pass registering 59 MPH around 7 PM. Areas of coastal low clouds were occurring as well, but otherwise fair weather prevailed. Inversion base of 1500-2000 ft MSL should allow at least some of the low clouds to make it into the valleys overnight. NKX sounding and surface observations showed dry air above that marine inversion, and a few locations had minimum RHs around 10 percent or even a little less today in the mountains and deserts. Unfortunately, north to northwest winds will continue in LA County and bring the smoke into our area through Monday, though HRRR Smoke model shows at least a decrease in the near-surface decreasing near the coast with the sea breeze early Monday afternoon, but smoke aloft will continue to bring hazy conditions. Monday should be the coolest day this week under the influence of the trough with slow warming on successive days even though troughiness remains through at least around Thursday. From previous discussion... Though the trough axis pushes east into the Northern Plains by the middle of the week, the troughing pattern will persist across the West. This is due to an amplified ridge that will build in across the eastern part of the country this week. While the heat turns up across the East, temperatures will be near to slightly below average here in Southern California. The marine layer will also be deeper, leading to greater low cloud coverage each night and morning for areas near and adjacent to the coast and locally into the Inland Empire. Minor day to day changes are expected in the weather pattern per latest model ensembles Tuesday through Thursday. The trough will weaken by Friday as high pressure expands into the desert southwest per latest cluster model guidance. Confidence is moderate to high that this will bring more warmer weather Friday into the weekend. NBM guidance shows not too much spread in ensembles, so this guidance is agreeable. Highs will start to climb near 5 to 10 degrees again by next weekend with a shallower marine layer. && .AVIATION... 170315Z...Coast/Valleys...Low clouds increasing in coverage near the coast at this hour. Bases are 1400-1700 ft MSL and tops are around 2200 ft MSL. CIG impacts currently only at KSAN but CIG impacts likely at KCRQ and KSNA around 06Z-08Z. Bases will likely stay above 1000 ft MSL and rise to near 2000 ft MSL after 12Z. Low clouds will spread 20-25 miles inland by 13Z obscuring higher terrain, with VIS 1-3SM where clouds and terrain intersect. There will be a 40-50 percent chance for CIGs at KONT and about a 30-40 percent chance at KSBD 12Z-15Z. Expect inland clearing 15Z-17Z and clearing to the coast 17Z-19Z Mountains/Deserts...SKC with unrestricted VIS through tonight. W-SW wind gusts of 20-35 knots, strongest through late tonight. WK-MOD up/downdrafts over/E of mtns. && .MARINE... Northwest wind gusts up to 20 knots will be possible in the outer waters again Monday afternoon. Otherwise, no hazardous marine conditions are expected through Friday. && .BEACHES... A combination of a west swell of around 5 feet/9 seconds in the outer waters and south swells of around 2 feet/16 seconds on Monday will bring surf of 3-6 feet along with a high rip current risk through Monday. The surf and rip current risk will gradually lower on Tuesday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement through Monday evening for Orange County Coastal Areas-San Diego County Coastal Areas. PZ...None. && $$ PUBLIC...Maxwell (Update)/APR (Previous Discussion) AVIATION/MARINE...PG