Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
783 FXUS66 KSGX 150415 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 915 PM PDT Mon Jul 14 2025 .SYNOPSIS... Cooler for tomorrow into Wednesday, with high temperatures as much as 8 to 12 degrees below average for the valleys and near seasonal averages for the deserts. For Thursday and Friday, a weak upper level low pressure from the south will bring an increase in monsoonal moisture with a chance of afternoon showers and thunderstorms, mainly for the mountains and high desert with the better chances on Friday. Chances will slowly decrease during the weekend as the monsoonal moisture slowly decreases. Night and morning coastal low clouds will spread into the western valleys late each night. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... This evening...The marine layer remains at a fairly consistent depth and low clouds are increasing in coverage over the coastal areas and spreading inland. High-resolution models indicate that the low clouds will spread as much as 15-20 miles inland by sunrise before clearing back to the coast in similar fashion to today. High temperatures today were generally near or a little below seasonal averages, even in the inland valleys and lower deserts. From previous discussion... The dominant high pressure ridge remains in place, although there is now more influence from the troughing upstream which has allowed for a cooldown to begin today that will continue into Wednesday, with temperatures gradually dropping off and becoming 10 to 15 degrees cooler than the seasonal average for the inland valleys as the onshore flow becomes more enhanced. For the high deserts and the lower deserts which are prone to gap flow winds, during the afternoon, winds will begin to strengthen and become gusty during the afternoon hours, although should remain below the threshold of wind advisory criteria. By Wednesday, highs will only make it into the low to mid 80s for most locations within the Inland Empire (IE). The marine layer will also continue to slightly lift and thicken up for the overnight hours during this period in the forecast, with a very slight chance of there being some very light drizzle, especially for the inland areas during the early morning hours. There could also be some patchy fog as well within some of the wind-sheltered inland areas. A weak upper level low south of the region will begin to slide more to the north on Thursday. In the meantime, there will be an area of high pressure centered over Arizona. This will allow for mid to upper level winds to turn more southeasterly and result in some of the monsoonal moisture from Mexico to be advected up over SOCAL along with some weak upper level disturbances that will allow for a chance of thunderstorms over the mountains and deserts beginning on Thursday. There could be a hindrance to thunderstorm development on Thursday though, depending on how much mid-level cloud coverage moves over during the morning hours, which might inhibit daytime heating. By Friday, there will be more moisture advected up over the area and further north, although the mid- level flow will still be very weak out of the southeast at the 700 mb level. This is alluding to there being the best chance of thunderstorms on this day during the afternoon hours. In addition, given the weak mid-level flow, some of these storms may become stationary (or nearly stationary), which may lead to potential flash flooding issues, especially if one of these storms becomes situated right over a burn scar area. By Saturday, the U/L low is going to begin to propagate further towards the northeast and draw some of the moisture further towards the east in the process. The ridge is also going to slightly build into the weekend. As the U/L continues to move out of the region and the mid level flow turns back to being more out of the southwest, that will help to suppress thunderstorm development as drier air aloft replaces the more moist and unstable southeasterly flow, allowing for a lessening of probability of storms over the mountains and deserts for both days, especially Sunday. The drying and slight warming trend will continue into early next week. && .AVIATION... 150335Z....Coast/Valleys...Low clouds near 1000-1500 ft MSL will slowly move inland this evening, further into the valleys overnight. Confidence is moderate to high on timing for low clouds to move into VCTY KONT around 11Z Tue. Other areas of the Inland Empire will see vis restrictions 4-6SM in HZ/BR 10-16Z Tue. Clouds will scatter back to the coast with slightly better chances of clearing (65% chance at KSAN, higher at KSNA). Cigs of similar bases returning to most of the same areas by Tuesday night. Mountains/Deserts...Mostly clear skies with unrestricted VIS through Tuesday night. && .MARINE... No hazardous marine conditions expected through Saturday. && .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 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...PG AVIATION/MARINE/BEACHES...APR