Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
217 FXUS66 KSGX 101628 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 928 AM PDT Fri May 10 2024 .SYNOPSIS... There is a slight chance of showers over the San Bernardino and Riverside County mountains this afternoon and evening. Areas of night and morning low clouds and fog will continue across portions of the coastal areas and valleys through the week. Gradual warming inland through Sunday followed by minor cooling Monday and Tuesday. Inland warming trend will resume on Wednesday. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Low clouds eventually filled nearly the entire coastal basin by sunrise, even though San Diego County was late to the cloud party. The Inland Empire and Orange County have started to clear pretty effectively already. There may be some intermittent cloudiness near the coast in San Diego County this afternoon, but you can count on mostly sunny skies for most areas later today. A weak upper level trough sits over the West today and Saturday. Today there is also a wave of mid level moisture and instability that will bring some clouds to the mountains and deserts, and isolated showers to the higher mountains this afternoon and evening. The trough begins to weaken and move out over the weekend. This will bring us a warming trend, and a shallower marine layer for Sunday into Monday. A new weak upper low from the northwest will float across SoCal Monday and Tuesday, which should deepen the marine layer and extend the coastal clouds. Today we`ll have max temps a few degrees below normal except inland valleys should reach a little above. We warm up this weekend, so that by Sunday max temps should be 0-8 degrees above normal. The 0-degree difference representing the coast and the 8-degree difference in the low desert, probably hitting 100 degrees. For the second half of next week, there is unsurprisingly a large spread in ensemble guidance. An amplified high-pressure ridge develops over the West, but with weak low pressure directly south of it, what we call a Rex Block. SoCal lies within the lower pressure embedded under the strong high pressure, so the forecast picture gets wishy-washy. A minority of members indicate some low pressure and moisture leading to showers, but a majority of members keep our weather dry. For now our forecast is dry with a warming trend, with uncertainty mainly concerned with how deep and dominant the marine layer will be. && .AVIATION... 101615Z...Coast/Valleys...Areas of low clouds with bases 1800-2200 ft MSL and tops to 3000 ft with local VIS 1-4 miles in BR, mainly in the valleys through 18Z, and local terrain obscurations in clouds. The valleys will clear through 18Z. Slower valley clearing KCRQ southward. Some patchy coastal BKN CIG near 2000 ft MSL lasting through this evening...then low clouds will spread farther inland Fri evening. Mountains/Deserts...SCT/BKN clouds will develop again Fri afternoon over the mountains with bases around 2000 ft MSL with local TCU possible. Otherwise, mostly clear skies will prevail through this evening with unrestricted VIS. && .MARINE... No hazardous marine conditions are expected through Tuesday. && .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...MM AVIATION/MARINE...Small