Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
355 FXUS66 KSGX 142112 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 212 PM PDT Sat Sep 14 2024 .SYNOPSIS... A weak weather disturbance will move through Southern California and keep temperatures slightly below averages. The marine layer will remain deep providing cool conditions for the valley and coast. A stronger weather system is expected to arrive Sunday night and Monday and bring gusty winds and unseasonably cool air. Light precipitation is expected on Monday, except for deserts. A slight warming trends will start on Tuesday but another cool weather disturbance will enter southern California by Thursday. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Skies cleared to the coast and beaches, slowest for Orange County again but deep marine layer continues, up to 3500 feet MSL and as high as 4000 feet. A weak short wave trough is moving through today increasing southwest flow ahead of it and sustaining the deep marine air mass. High temperatures are several degrees below average except near average in deserts this weekend. Very dry air does exist still above 6000 feet, affecting the mountains. Dewpoint temps as low as teens above 7000 feet but those also recover during the daytime mixing into the 30s and 40s. An unseasonably strong upper trough will enter Socal during Sunday night Monday. The winds will be gusty and much stronger but due to the deep marine layer and even colder air mass the humidity will be considerably high and widespread light rainfall and even scattered showers with the trough passage on Monday. Wind gusts of 40 to 60 mph for wind prone mountains passes and ridges. 700 mb southwest wind flow is forecast to be 30 to 40 knots with temperatures down to 2C for San Gabriel mountains. Mixed out marine layer for Tuesday and Wednesday along with a modified warming air mass and light winds. The pattern looks to repeat itself for mid week, with a similar strong cold front crossing Socal by Thursday. This would also bring some precipitation in addition to the deep marine layer. By Friday this would shift to slight offshore flow and drying. This system has potential to close off and dig with time which induces the offshore wind. && .AVIATION... 142030Z...Coasts/Valleys...Hazy conditions continue due to FU from the Line and Bridge Fires in the San Bernardino Mountains. Low clouds have generally cleared the region, but are expected to build back in this evening beginning as early as 00-02z. Bases around 1800- 2300ft MSL and tops to 3500ft MSL will spread inland up to 30 miles, reaching the Inland Empire around 07z. Similar to previous nights, FU from the Line Fire may be trapped by the marine later and result in VIS reductions down to 3SM for KSBD. Clearing out will begin around 16z, from southeast to northwest, with coastal sites clearing by 19-20z Sunday. Mountains/Deserts...FU resulting in localized VIS restrictions near the San Bernardino County Mountains where the Line Fire and Bridge Fire are and the Santa Ana Mountains where the Airport Fire is will continue through Sunday. Strong west-northwest winds develop Sunday evening, with gusts up to 40kts possible through the mountain passes. && .MARINE... Some light precipitation will be possible Sunday night through Monday morning with less than 0.05" expected. Stronger winds will occur in the outer coastal waters Monday and Monday night with gusts 20-25 knots likely from the W/NW. Otherwise, no hazardous marine conditions are expected through Wednesday. && .FIRE WEATHER... Ongoing wildfires, Line, Airport and Bridge continue to be the main weather support. Increased southwest wind today, slightly, and persistent drier air above 6000 feet will be main concern into Sunday. For Sunday night and Monday stronger southwest to west winds but increasing humidity in upper elevations. Otherwise deep marine layer and cooler air mass is helping with containment. Fuel moistures that were record low are recovering quickly expect less on high terrain. && .CLIMATE... The upper troughs on Monday and Thursday are unseasonably cool in addition to some precipitation. This is after a record heat wave we experienced the first week of September. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Wind Advisory from 7 PM Sunday to 9 PM PDT Monday for Apple and Lucerne Valleys. PZ...None. && $$ PUBLIC/FIRE WEATHER...Tardy AVIATION/MARINE...Zuber