000 FXUS66 KSGX 282027 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 127 PM PDT Sun Apr 28 2024 .SYNOPSIS... Warm and dry conditions continue through much of this week. Marine layer low clouds and fog will likely be confined to the coast and the western coastal valleys during this time. The mountains and deserts will also experience breezy winds from the west each afternoon and evening. There is a chance for some weak Santa Ana winds on Thursday, followed by another round of cooler and breezier weather by next weekend. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... At 1 PM PDT, a 1030 mb surface high was over the Eastern Pacific as a weak 500mb ridge was building in over the region. Subsidence has allowed for steadily warming temperatures and a more shallow marine layer over the past few days. This trend will continue today, especially following the clearing of most low clouds at the coast by about 9 AM this morning. Highs today will remain near seasonal normals. Monday and Tuesday will see this warming trend continue, with highs climbing generally 1 to 3 degrees each day. With this warming trend, the marine layer will become more shallow with low clouds and fog becoming more and more confined to the immediate coast and the western coastal valleys each morning. There will be a coastal eddy at times, which will likely help to keep the marine layer from eroding entirely. Early this week, a 500mb trough will move across the Northwestern US and Western Canada. The amplitude of this trough will not be strong enough to bring significant changes to sensible weather in SoCal, but will be strong enough to maintain a slightly stronger pressure gradient across our region. This will generally favor gusty winds in the mountains and deserts each afternoon and evening, fairly typical for this time of year. Peak gusts each day today through Tuesday will generally be in the 20-40 mph range, strongest over ridgelines, below passes, and through wind-prone canyons. Wednesday will see a slightly stronger 500mb trough move across the Western US, which will bring a bit of cooling as well as slightly stronger winds and a deeper marine layer. It will not be a significant or abrupt cooldown as temperatures are still expected to remain near to slightly above average for early May. What may be of bigger impact is the potential for offshore flow/Santa Anas behind the trough passage on Thursday. At the moment, this looks to be a weak Santa Ana event that will be most noticeable immediately below mountain passes and in the coastal mountain foothills, with gusts generally at or below 30 mph. The forecast then becomes a bit murky for the weekend. Global ensembles are in some agreement on the approach of another weak trough, but the timing and amplitude of said trough remain uncertain. Regardless, a switch to some cooler and breezier weather with a deepening marine layer looks fairly likely for next weekend, queuing up the “May Gray” we are all so used to. && .AVIATION... 282020Z...Coast/Valleys...Clear skies with only few low clouds near 1,800 feet AGL. Expect similar clouds returning with ceiling developing late tonight between 07 to 10 UTC mainly for KCRQ to KSAN. Marine layer slightly lower tonight so IFR ceiling possible at KCRQ. Mountains/Deserts...Clear through today. Northwest winds 10 to 15 kt in deserts after 00 UTC and locally in mountains through 01 UTC. && .MARINE... No hazardous marine conditions are expected through Wednesday. && .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...Adams AVIATION/MARINE...Tardy
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