Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
481 FXUS66 KSGX 140413 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 913 PM PDT Sun Jul 13 2025 .SYNOPSIS... A little warmer inland Monday. Gradual cooling back to near seasonal averages expected for the middle to the end of the week. While chances are still low and uncertainty remains, confidence is increasing for the potential of monsoonal thunderstorms over the mountains late in the week. Marine layer low clouds and patchy fog will spread across the coastal areas and into the western valleys during the nights and mornings. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Satellite at 9 PM was showing low clouds along much of the coast. The 00Z sounding from KNKX showed the marine layer depth to be around 1500 ft with low clouds expected to make it into portions the valleys overnight. There is a potential for showers and thunderstorms over the mountains Thursday through Sunday. While uncertainty remains in the details, latest guidance is starting to indicate Friday and Saturday afternoons being the most likely days for shower and thunderstorm activity. From previous discussion... The dominant ridge will remain centered about 135 miles west southwest of San Diego through Monday. This will allow inland temperatures to rise by a few degrees above what they were the last couple of days. Temperatures Monday in the mountains and deserts will be several degrees above seasonal averages while west of the mountains, temperatures will be near to a few degrees below seasonal averages. This is mostly due to a relatively shallow but persistent marine layer, with low clouds and patchy fog in the coastal areas and western portions of the inland valleys each night and morning. On Monday, a couple of inverted troughs in the southeast flow on the southern side of the east-west oriented ridge axis will bring some monsoonal moisture into SoCal but the threat of afternoon convection will be low because the moisture will be limited and mostly above 10,000 ft, although a stray shower or tstm can`t be ruled out altogether. For Tuesday through the end of the week, model solutions begin to diverge significantly introducing more uncertainty into the forecast but in general, the dominant high pressure ridge will be weakened and displaced eastward towards the Four Corners as a low pressure system moves inland over the Pacific Northwest. During this time, temperatures will begin to trend generally lower even as conditions become drier for Tuesday and Wednesday. For Thursday through the weekend, an increasing number of solutions across model platforms are indicating an increase in monsoonal moisture with a corresponding increase in the chances for afternoon showers and thunderstorms, mainly in the mountains. This change in the pattern will likely continue the trend toward lower temperatures for the mountains and deserts. && .AVIATION... 140340Z....Coast/Valleys...Low clouds with bases 1000-1500 ft MSL and tops to 2000 ft MSL filling in along the coast through 08Z then spreading 20-25 mi inland by 11Z. Clouds likely reaching the far southern and western portions of the Inland Empire again with a 30% chance of CIGs at KONT 12-16Z. Clouds clearing inland 15-17Z and near the coast 17-19Z, though there is a 60% chance of CIGS continuing along the immediate coast of southern Orange County and San Diego County through the afternoon. Low clouds beginning to spread back into the coastal areas 15/00-03Z with similar bases and tops. Mountains/Deserts...Scattered shallow Cu possible over the mountain ridges Monday afternoon. Otherwise clear with unrestricted vis through Monday evening. && .MARINE... No hazardous marine conditions expected through Friday. && .BEACHES... A moderate period south-southwesterly swell (2-3 feet at 15-17 seconds) will generate elevated surf and a high risk of rip currents on Wednesday and Thursday. Surf of 3-5 feet expected with sets to 6 feet possible, primarily on southerly facing beaches. Swell and surf will begin to lower on 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...CO/PG AVIATION/MARINE/BEACHES...SS