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Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
067 FXUS66 KSGX 160422 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 922 PM PDT Sat Jun 15 2024 .SYNOPSIS... Areas of fog is possible along the coastal areas and far western valleys tonight into Sunday morning. A cooling trend will occur through Monday with gusty west winds across the mountains and deserts each afternoon and evening. Slow warming will occur Tuesday through next weekend as the West Coast trough weakens and high pressure begins to expand into So Cal. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Another hot day across the deserts, especially the lower deserts, where highs hit anywhere from 110-116 degrees. In fact, Ocotillo Wells tied with Blythe for the nation`s high with a high temp of 116 degrees, edging out Death Valley which had a high of 115. Despite the intense heat, no daily temperatures were broken. Given the cooling expect tomorrow, the Excessive Heat Warnings and Heat Advisory were allowed to expire earlier this evening. The 00Z KNKX sounding shows the marine inversion based near 1100 ft MSL. Given the approaching trough and the forecast development of a weak coastal eddy, the marine layer should deepen slightly overnight. Still expect fog along portions of the coast and onto the coastal mesas tonight into Sunday morning, where fog could be dense in spots. The upper level trough amplifies Sunday as a weak short wave moves through the mean flow, followed by a second stronger short wave on Monday. This will bring considerable cooling especially for inland areas on Sunday when high temps will be around 5-10 degrees lower than today, followed by another 5 degrees or so of cooling for Monday. By Monday, highs will be several degrees below seasonal normals, back down to the low 80s in the valleys, upper 80s in the high desert, and low 100s in the low desert. These waves will also generate stronger onshore flow with breezy west winds with gusts to around 35-50 mph in the mountains and deserts each afternoon into late evening, strongest below the San Gorgonio Pass and along I-8 near the Imperial County border. Minimum daytime humidity of around 10-15 percent in the deserts will also lead to elevated fire weather conditions each afternoon in the wind-prone areas, including the Hesperia Fire. Slow warming takes place Tuesday through Thursday as the trough along the West Coast weakens, followed by more significant warming Friday through next weekend as a broad upper level ridge of high pressure over much of the eastern two-thirds of the country begins to expand westward into CA. Nigh and morning low clouds will continue across portions of the coasts and valleys through the week. Both deterministic and ensemble guidance are hinting at the potential for a easterly wave to move across Baja California next weekend and monsoon moisture eventually being drawn up into So Cal. The upper high isn`t in a favorable spot (ridge axis directly overhead), so hard to say at this point if anything will come of it other than perhaps some muggy weather in the lower deserts and a few mid and high clouds. && .AVIATION... 160335Z...Coast/Valleys...FEW010 with unrestricted VIS at this time. Low clouds will increase in coverage and could spread 15-20 miles inland by 13Z. Bases will start out around 1000 ft MSL, briefly lower to near 700 ft MSL around 11Z then rise abv 1000 ft MSL by 15Z. CIG impacts most likely at coastal TAF sites 08Z-15Z with local VIS 1-3 miles in fog on higher coastal terrain. Low clouds expected to clear to the coast 7Z-20Z. Mountains/Deserts...SKC with unrestricted VIS through Sunday. Areas of wind gusts 25-35 kt from the west on the desert mountain slopes and into the deserts through Sun, along with weak to MOD UDDFS. && .MARINE... Northwest winds may gust to around 20 knots at times in the outer waters near San Clemente Island each afternoon and evening through Monday. Otherwise, no hazardous marine conditions are expected through Thursday. && .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...SS AVIATION/MARINE/BEACHES...PG