Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
032 FXUS66 KSGX 090416 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 916 PM PDT Wed Oct 8 2025 .SYNOPSIS... A low pressure system off the West Coast will draw tropical moisture from Priscilla northward into the area for Thursday through Saturday morning with increasing chances for showers and a chance for thunderstorms. Cooler with drying for Saturday through Monday. For Tuesday and Wednesday of next week, a low pressure system moving to near the West Coast will bring a chance of showers. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Patches of low clouds are beginning to develop along the coast as of 9 PM. Low clouds are expected to become more widespread overnight, reaching into portion of the valleys. Mid-level clouds from Tropical Cyclone Priscilla are expected to make their way into the area tomorrow morning. Areas of light to locally moderate rain are expected west of the mountains for much of the day Thursday, with the best chances currently looking to be in the afternoon. For the mountains and deserts, some light showers could develop Thursday morning with the potential for thunderstorms producing moderate to heavy rain in the afternoon and early evening hours. Areas of light rain may continue into Friday morning, with more widespread shower and thunderstorm activity expected Friday afternoon and continuing into Saturday morning. From previous discussion issued at 2 PM October 8... The latest track of Priscilla has remained similar to previous model runs, which shows that a majority of the moisture streaming up over the area from tomorrow through Friday to be located over San Diego County. For this reason, the mountains of San Diego will likely have the best chance of thunderstorms developing overhead during the afternoon. Otherwise, it will just likely be on and off showers falling from a relatively high based mid-level scattered to broken cloud deck for most of the areas tomorrow, with most of the coastal and inland areas likely receiving between 0.01-0.10" through Saturday. PWAT values are still pushing 200% of normal, so if a storm does develop, it could put down a heavy amount of rain in a short period of time, of possibly a half an inch or greater per hour. Given the higher PWATs, if there is a stronger shower or possible storm the develops and remains nearly stationary, it could cause some flash flooding problems, which is especially the case for Friday afternoon as the tropical depression moves closer to the CWA, with an increase of instability. By Saturday morning, the system will begin to pull away from the area and there will only be a slight chance of thunderstorms for the mountains and deserts. Saturday through the mid half of next week... The longwave trough with an area of low pressure upstream will continue to approach the region, and the tightening of the pressure gradient at the surface will cause winds to increase and become rather strong and gusty on Saturday for the high deserts, and areas prone to stronger winds due to gap flow. This will also allow for temperatures to begin to cool off, and this will continue going into the early part of next week, with the chance of rain as a series of troughs will bring about a chance of precipitation and also keep temperatures on the cooler side through the mid part of next week. && .AVIATION... 090300Z....Coasts/Valleys...A few low clouds with bases around 1000- 2000 feet MSL have started to develop along the coast and are expected to increase in coverage around 5-8Z and spread inland. Low clouds will start to scatter/clear at 14-16Z leaving a higher cloud deck around 10000 ft MSL. Vicinity showers are expected to develop as early as 14-15Z and last through the end of the TAF period. Mountains/Deserts...VFR conditions expected overnight and into the early morning. VCSH will begin to move in from the south after 15Z. Slight chance (15-25%) TSRA after 21Z for the San Bernardino, Riverside and San Diego mountains as well as the deserts but not enough confidence in location and intensity to include in the TAFs at this time. && .MARINE... Northwest wind gusts around 20 kt near San Clemente Island each afternoon/evening through Sat. There is a slight chance of thunderstorms Thursday and Friday in the afternoon/evening. Lightning, erratic winds, choppy seas, and/or reduced visibility in heavy rain likely in vicinity of any thunderstorms. && .BEACHES... There is a 5-15% chance of thunderstorms producing lightning Thursday and Friday. && .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 UPDATE...CO PREVIOUS DISCUSSION...Stewey AVIATION/MARINE/BEACHES...Villafane