Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
031 FXUS66 KSGX 172036 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 136 PM PDT Thu Jul 17 2025 .SYNOPSIS... Monsoonal moisture will be present through Saturday, before dry conditions return for early next week. This will bring chances of showers and thunderstorms to the mountains and locally into the High Desert through Saturday. Below average temperatures expected for the end of this week into next week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Radar at 1 PM was showing a couple isolated showers moving east to west across the valleys towards the coast. So far, no rainfall accumulation has been recorded. The only lightning being detected at this time is south of the border in Baja. Additional showers and potentially a thunderstorm or two may still develop this afternoon over the mountains. Most of the convection looks to stay elevated, which translates to limited impacts at the surface, especially when it comes to rainfall. The reasonable worst case scenario rainfall rate for this afternoon is 0.40 inches per hour, with those amounts expected to be quite isolated to the mountains if they do occur. An upper level low will move north and east from Baja into southeastern California overnight. This could generate some light showers across the area overnight and early Friday morning. A few isolated lightning strikes are possible from the coast to the deserts. Even with some decrease in precipitable water Friday, thunderstorm chances look higher due to better diurnal heating Friday afternoon. High resolutions model guidance is indicating thunderstorms developing over the mountains and locally into the High Desert. Areas of moderate to heavy rain look more likely with thunderstorm activity Friday. Rainfall rates are expected to be 0.30 to 0.50 inches per hour, locally up to 0.75 inches an hour. Frequent lightning, locally gusty winds, and areas of flooding look to be the main impacts. High resolution guidance is indicating isolated lighter showers and thunderstorms may develop over the mountains Saturday afternoon, but peak rainfall rates look to be around 0.25 inches per hour. Dry conditions are expected to return Sunday and continue into the middle of next week. High temperatures for Friday will be a few degrees cooler west of the mountains and a few degrees warmer in the deserts. Warming will continue for the deserts into Sunday. Even with the warming through Sunday, high temperatures for the deserts and elsewhere are expected to be near to slightly below average for this time of year. Night and morning coastal low clouds will spread into portions of the western valleys late each night. && .AVIATION... 172035Z....Coast/Valleys...SCT-BKN clouds AOA 10K ft MSL continuing into the afternoon in the valleys and VCTY KSAN. ISO TSRA possible across the region later this afternoon and evening until around 02Z. Cigs returning across areas up to 15 miles inland after 01Z. Highest confidence in BKN-OVC cigs will be across San Diego County, closer to 06Z VCTY KSNA. Cigs clearing to the coast 17-19Z with SCT-BKN clouds AOA 10K ft MSL with storm chances more confined to the Inland Empire, especially VCTY KSBD. Mountains/Deserts...SCT-BKN clouds 10000-15000 feet today. ISO-SCT SHRA/TSRA over the mtns until 02Z, many rain showers elevated. Highest chances through late this afternoon, but an isolated storm is possible overnight. Associated wind gusts, UDDFS, and VIS restrictions possible with any storm that develops. Similar clouds and storm chances tomorrow, greatest chance near Big Bear. && .MARINE... Chance of thunderstorms across the inner coastal waters through tonight. Otherwise, no hazardous marine weather expected through the middle of next week. && .BEACHES... A moderate period south-southwesterly swell (2-3 feet at 15-16 seconds) will continue to generate elevated surf and a high risk of rip currents through tonight. 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 night. Chance of lightning and thunderstorms at the beaches through tonight. && .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 AVIATION/MARINE/BEACHES...APR