![National Oceanic and Atmospheric Administration](/build/images/header/noaa.d87e0251.png)
![National Weather Service](/build/images/header/nws.4e6585d8.png)
![United States Department of Commerce](/build/images/header/doc.b38ba91a.png)
Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
123 FXUS66 KSGX 120903 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 203 AM PDT Mon Aug 12 2024 .SYNOPSIS... Monsoonal moisture will decrease through the early part of the week, with one more day of notable storm chances for portions of the southern mountains and deserts this afternoon. This will be followed by dry and seasonal weather through the week as a trough to the north brings in cooler and drier air. The marine layer will be deeper with patchy coastal low clouds and fog through the week as well. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Latest satellite imagery shows high clouds from yesterday`s storm activity dissipating, while low clouds offshore become more widespread as the marine layer deepens. Coastal areas have the potential to see these low clouds and fog occur later this morning. The marine layer will become more established by Tuesday into the weekend with higher terrain adjacent to the coast becoming shrouded in patchy fog each morning. The main story this week will be the influence from a lingering trough over Northern California. As the trough gains a bit more momentum today, drier southwest flow aloft will enter the region, pushing monsoonal air further east. With just enough moisture left in place, we will see one more day for a notable chance of thunderstorms. Chances are less than yesterday near 15 percent across the mountains of Riverside and San Diego counties, possibly moving into the Anza-Borrego desert in eastern SD Co. Latest hi- res models support another moisture intrusion along the mountain spine in northern Baja, with coverage of storms highest per latest HRRR output. PWAT ensemble members significantly lower by Tuesday through the work week as the trough to the north brings in dry southwest flow off the Pacific. This will keep daytime temperatures close to average with lower humidity. There will be minimal changes in daytime highs through Friday, with nighttime temperatures a bit more comfortable as well. By Friday into the weekend, a trough along the west coast of British Columbia will deepen. Ensemble model clusters agree on the trough becoming stronger by the weekend, but exact placement of where this sets up within proximity of the West Coast is still uncertain. Depending on how close this low pressure trough comes to us in SoCal, will determine how low we can go with temperatures and how high we reach in wind speeds. NBM paints highs near to slightly below average by the weekend. Breezier than normal conditions will occur across mountains and deserts as well, but exact details are still to be determined. High pressure off to the east will begin to influence our weather pattern by early next week, but uncertainty remains on how long it will be kept at bay. && .AVIATION... 120900Z...Coast/Valleys...Currently patchy low clouds with bases 900- 1100 ft MSL developing along Orange Co. coastal areas but are well offshore of San Diego Co. due to SCT-BKN clouds at 15-20k ft MSL. As high clouds dissipate, patchy low clouds will increase slightly in coverage with a 30-40% chance for CIG impacts at San Diego Co. coastal sites 12Z-15Z this morning. Low clouds that do come ashore will clear to the beaches 15Z-17Z. Otherwise, SCT-BKN clouds at or abv 10k ft MSL through tonight, clearing through Tue morning. More extensive low clouds with similar bases to tonight moving ashore 05Z- 07Z Tue. Mountains/Deserts...SCT-BKN clouds with bases at or abv 10,000 ft MSL through Tue morning. 10-15% chance for ISO TSRA 20Z Mon to 02Z Tue over mountains and deserts, but majority of activity expected to stay to S and E of region. Gusty and erratic winds possible near storms as well as MOD UDDFS. Storms that do develop moving from SE to NW. && .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...APR AVIATION/MARINE...CSP