Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
965 FXUS66 KSGX 200331 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 831 PM PDT Thu Sep 19 2024 .SYNOPSIS... A low pressure system moving southward into the region will bring cooler and showery weather by into Friday. There is a chance for rain showers across most of the region, with a chance for thunderstorms from the Santa Ana mountains to the High Desert. The system will depart the area by the weekend, bringing drier weather with warming temperatures. Weak high pressure will then build into the region brining near to slightly above average temperatures with night/morning low clouds near the coast. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... At 8 PM the upper level low pressure system was currently off the coast of Point Conception. That low is expected to move south and east through Southern California tonight into Friday. As low clouds become more widespread across the coastal basin overnight, areas of drizzle and light rain will develop. Scattered light showers are most likely in San Diego county through the late morning hours. For the afternoon, forecast is still on track for shower and thunderstorm activity in the Inland Empire, San Bernardino mountains, Riverside mountains, and High Desert. Forecast for the weekend into early next week remains unchanged. From previous discussion issued at 2 PM 9/19/24... As the low moves closer to SoCal, expect light showers and marine layer drizzle across for areas west of the mountains to begin late tonight, highest confidence over San Diego County. Instability peaks near 200-400 J/kg Friday afternoon. Wrap-around moisture from the north will bring elevated showers and isolated thunderstorms Friday afternoon. Most areas will see dry weather or light showers with the best chance of thunderstorms occurring from the Santa Ana mountains to the Inland Empire northward toward the San Bernardino mountains and High Desert. Rain rates will near one quarter to below one half inch, so please continue to monitor this if you are near any recent burn scar locations. Rain totals will be light, away from where thunderstorms develop, with most locations seeing under one tenth of an inch. The system will depart by Saturday, leading to warming temperatures and sunnier conditions. Sunday will warm further as weak high pressure moves into the area with highs reaching near 90 degrees for inland valleys west of the mountains into the high desert. Mountain locations will rise into the 70s and 80s with near 100 degrees for the lower deserts. && .LONG TERM...(Next Week)... The ridge near the West Coast for the weekend will grow and amplify across across the west. The good news is that this will be strongest across the Pacific Northwest, with a weaker ridging pattern near our area. This will prompt temperatures to be near to slightly above average for the much of the week. The marine layer will be generally unchanged with night and morning low clouds to cover most coastal and western valley areas. Ensemble cluster models indicate a potential trough over the Pacific Northwest may be able to tamper down the high pressure a bit further by later next week. This would not change our weather pattern very much with continued dry and slightly above average temperatures. && .AVIATION... 200300Z...Coast to mountain slopes...Low clouds with bases 2000-3000 ft MSL have started to fill in the coastal basin. Low clouds are expected to fill in the coastal basin by 09Z. Cigs could be intermittent 15-21Z Fri, especially along the coast, with bases fluctuating between 2500 ft MSL and 3500-5000 ft. SCT low clouds with prevailing mid to high clouds expected after 21Z. Patchy, intermittent -RA or -DZ most likely along the coast and up against the coastal mountain slopes 06Z-21Z Fri. Vis reductions of 4- 6 SM and locally lower cigs possible in areas of -RA/DZ. From 20Z Fri-02Z Sat there is a 15-20% chance of TSRA over the eastern Santa Ana Mtns and Inland Empire. Erratic winds, local up/downdrafts, and reduced vis in locally heavy rain expected near thunderstorms. Cigs will redevelop after 06Z Sat, with BKN-OVC clouds 2500-3500 ft MSL. Mountain ridges to deserts...Mostly clear skies with unrestricted vis tonight. 20-30% chance for RA and TSRA over the San Bernardino mtns, Riverside mtns, and High Desert 20Z Fri-02Z Sat. Erratic winds, local up/downdrafts, and reduced vis in locally heavy rain expected near thunderstorms. && .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...CO/APR AVIATION/MARINE...CO