Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
263 FXUS66 KSGX 010341 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 841 PM PDT Tue Apr 30 2024 .SYNOPSIS... Fair and seasonal weather will continue this week. The marine layer will provide coastal clouds nights and mornings, more extensive on Wednesday morning. It will turn warmer on Thursday before low pressure and onshore flow increase this weekend. That will bring a cooling trend, more coastal clouds and brisk westerly winds in the mountains and deserts Saturday through Monday. There is a slight chance of showers Saturday night and Sunday morning. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .Evening Update... Low clouds formed late this afternoon across portions of the coast, with greater coverage expanding across this region. Low clouds will continue to push inland through the night, filling much of the coastal basin by morning per latest HREF guidance. A troughing pattern will remain in place through the weekend with sunny and comfortable days during the work week. Model ensemble guidance shows some members with light precip amounts by the weekend across the region, but confidence remains low on how much, if any, will fall. Otherwise, no forecast updates this evening. .Previous Discussion (144 PM Tuesday)... Coastal clouds cleared quite well today and it`s a little cooler than this time yesterday. A low pressure trough will swing down into the northwestern U.S. tonight and Wednesday. The increased onshore flow will boost westerly winds in our mountains and deserts this evening, with top localized gusts achieving 35-50 mph, such as in the San Gorgonio Pass. The trough will also strengthen our coastal eddy and extend low clouds farther inland by Wednesday morning. Low clouds and fog should cover most or all of the coastal basin west of the mountains. A brief ridge builds up Thursday, with a hint of offshore flow, which will generate our highest max temperatures of the week: low 80s in the Inland Empire and high desert, low-mid 90s in the low desert, 70s across much of the coastal basin, 60s at the coast, and upper 50s to mid 70s in the mountains. These numbers are near or slightly above normal away from the coast. A longwave trough sags southward Friday and Saturday, increasing our onshore flow again, increasing westerly winds and deepening our marine layer for the weekend. A more defined low pressure trough will swing through CA Sunday. Some ensemble members, mostly from the GEFS indicate some rain, mainly Sunday morning, from the coast to the mountains. Euro ensemble members show a much lower chance of rain, and Canadian members fall in between. We introduced a slight chance of measurable rain late Saturday night through Sunday morning. With more confidence you can count on cooler weather, breezier onshore winds, and more clouds this weekend, particularly Sunday. Some weak high pressure returns Monday and Tuesday to reverse the cooler, cloudier trend back toward a warmer, sunnier normal. && .AVIATION... 010325Z...Coasts/Valleys...Low clouds with bases around 1500 ft MSL and tops to 2300 ft MSL increasing in coverage at this hour. CIG impacts currently at KSAN and CRQ, likely at KSNA by 06Z, and at KONT and KSBD after 10Z. Low clouds likely to spread inland to the mtn foothills by 14Z. Bases and tops will rise by about 200 feet obscuring higher terrain, with VIS restrictions where clouds and terrain intersect. Inland clearing expected 15Z-17Z and clearing to the coast 17Z-19Z. Elsewhere, clear skies with unrestricted VIS through Wednesday. && .MARINE... No hazardous marine conditions are expected through Friday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ Evening Update/Previous Discussion...APR/MM AVIATION/MARINE...PG