Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
622 FXUS66 KSGX 162039 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 139 PM PDT Wed Jul 16 2025 .SYNOPSIS... A weak low pressure system from the south will bring an increase in monsoonal moisture on Thursday and Friday with a chance for mainly afternoon showers and thunderstorms, mainly for the mountains. Dry and seasonal weather will return for the weekend and early next week. Coastal low clouds will continue to spread into western valleys during the nights and mornings. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Classic July weather will continue this coming week, but with an added twist Thursday and Friday. Monsoon moisture has begun to increase today, coming from the south where a weak upper low resides off the central Baja Coast. Precipitable water of 1.08 inch this morning should increase by Thursday morning to around 1.50 inch, along with a wave of unstable air. This will bring some interesting altocumulus and probably some virga across the region, but no credible chance of measurable showers. The legit chances of precipitation will need the surface heating and the higher terrain to get enough lift to trigger any thunderstorms. Right now the chances are slight and mainly in the mountains and the high desert east of I-15 during the afternoon and early evening. There is still a lot of moisture spinning across the entire region Thursday night and Friday morning, and there is a very slight chance of measuring showers, sprinkles more likely, west of the mountains. The moisture decreases a little Friday, but the chance of afternoon tstorms continues in the mountains and high desert. We`ll adjust time, space and intensity of any chance of precip as needed, but for now, rain intensity doesn`t appear problematic (~0.40/hour max in the San Bern Mtns). All this action doesn`t seem to phase the marine layer very much. Copy and paste this morning`s cloud coverage into western valleys for each upcoming night and morning. Temperatures will be dampened by the higher humidity and cloud cover Thursday, but only by a few degrees. The upper low moves into SoCal Friday, then shifts eastward and dissolves Saturday and takes any meaningful chance of precip with it. Dry weather continues for Sunday through at least Wednesday as an upper trough in the Pac NW region sets up dry southwest flow across SoCal. And we`ll be back to our regularly scheduled July weather: marine layer clouds into western valleys each night and morning and temps near or slightly below normal. && .AVIATION... 162030Z....Coast/Valleys...SKC currently at the coast and over neashore waters. Clouds redevelop over nearshore water in the next few hours and begin to push inland again after 00z Thursday with similar bases. Similar inland extent with most of SD/Orange County valleys filling in by 12z. Clouds may push into the western/southern IE with 40% chance of reaching KONT. Low clouds scatter to the coast by around 18-19z. Slight chance a shower or storm may drift into the IE after 20z. Mountains/Deserts...Cumulus near 10000 feet possible over the mountains through 01z. Increasing clouds AOA 15000 feet overnight and into Thursday morning. ISO-SCT SHRA/TSRA over the mtns after 18z Thursday. Slight chance TSRA for the deserts. Associated wind gusts, UDDFS, and VIS restrictions possible with any storm that develops. && .MARINE... No hazardous marine conditions are expected through Sunday. && .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 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...MM AVIATION/MARINE/BEACHES...KW