Area Forecast Discussion
Issued by NWS San Diego, CA

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000 FXUS66 KSGX 240933 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 233 AM PDT Wed May 24 2017 .SYNOPSIS... Cooler weather is in the forecast through Friday as a weak trough of low pressure moves through the region. Low clouds will spread farther inland each day as the marine layer deepens. It will be windy in parts of the mountains and deserts. There is a slight chance of light showers from the coast to the foothills Thursday night into Friday morning. High pressure will rebuild over the West this holiday weekend for warmer weather and a shallower marine layer. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Coastal low clouds have been slowly advancing overnight, but not much if at all into the valleys. Some high clouds will continue to move across our sky coming from a weak low over the Pacific to our west. A fair and cooler day is expected as a low pressure trough bears down from the north and merges with that Pacific low today and tonight. That will deepen the marine layer and extend the low clouds into the valleys. It will also boost winds in the mountains and deserts. Small portions of this region will have strong winds. An advisory is in effect for gusty pockets in the northern Coachella Valley and the Anza Borrego Desert late this afternoon into Friday morning. The trough will deepen further Thursday and a shortwave will move through Southern California Thursday night into Friday morning. As the marine layer gets stretched out in the vertical, some light showers could result. Friday will be unseasonably cool with highs in the 60s west of the mountains, 50s and 60s in the mountains, and 70s and 80s in the deserts. The trough moves off and allows for some half-hearted ridge to build through the holiday weekend. The marine layer will gradually shallow while daytime temps will gradually rebound to slightly above average on Memorial Day. That means 70s near the coast and in the mountains, 80s and lower 90s in the inland valleys and high desert, and back over the century mark in the lower deserts. A weak trough appears on the horizon next week which would bring slightly cooler weather and more extensive coastal clouds. && .AVIATION... 240900Z...Coast/Valleys...Widespread stratus near the coast and about 10 SM inland with bases 400-800 ft MSL continuing through mid morning. Areas of vis 3-5 SM over higher coastal terrain and down to 1SM on coastal mesas/western valleys. Stratus clearing to the coast 16-18Z. Bases lifting to 1000-1500 this evening, reaching the coastal airports 03-06Z and spreading into the inland valleys overnight. Mountains/Deserts...A few high clouds and unrestricted vis through Thu morning. Onshore winds becoming strong after 00Z this evening with gusts through the mountains and along the desert slopes up to 45 KTS along with mdt up/downdrafts...and patchy blowing dust/sand in the deserts. && .MARINE... No hazardous marine weather is expected through Sunday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Wind Advisory from 5 PM this afternoon to 8 AM PDT Friday for San Diego County Deserts-San Gorgonio Pass Near Banning. PZ...None. && $$ PUBLIC...MM AVIATION/MARINE...Brotherton is the U.S. government's official web portal to all federal, state and local government web resources and services.