FXUS66 KSGX 210057 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 557 PM PDT Fri Mar 20 2026 .SYNOPSIS... HeatRisk will decrease for the weekend, with minor cooling. Even with the cooling, temperatures will remain above average into next week. Patchy marine layer low clouds and fog will be present at times, most likely to impact the coastal waters and immediate coast. Areas of dense fog are possible Saturday morning. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... ...AVIATION/MARINE SECTIONS UPDATED... Multiple daily and monthly high and low temperature records were broken yesterday. The latest record report is headlined on our weather.gov/sandiego homepage. A climate section can be found below listing locations that are currently forecast to tie or break their monthly high temperature records today. Multiple locations have the potential to continue to hit daily temperature records through next week as well above average temperatures continue. Weakening high pressure aloft and strengthening onshore flow will bring 4 to 8 degrees of cooling Saturday. That will be most noticeable for locations west of the mountains, but even the deserts will cool 3 to 5 degrees. A weak low pressure system aloft will move east through Southern California into the Great Basin Sunday into Monday. That will bring an uptick in westerly winds Saturday and Sunday afternoon and evening over the mountains and into the deserts. Ridging aloft looks to rebuild early next week and strengthen into the middle of the week. This ridge isn't expected to be as strong as the one over Southern California this week, but it will be enough to maintain above average temperatures through next Friday. Widespread minor with areas of moderate HeatRisk will be present in the valleys and low desert for much of next week. As the ridge begins to break down today onshore flow will strengthen enough to bring patchy dense fog to the coastal waters and at the immediate coast Saturday morning. With the aforementioned passing weak low pressure onshore flow will increase further, making chances of dense fog less likely for Sunday morning. Low cloud and fog coverage on Sunday morning may reach into the western valleys. Weak offshore flow early next week may keep low clouds and fog patchy and more confined to the immediate coast again for early next week. && .AVIATION... 210000Z...Mostly clear skies and VFR conditions expected through 06Z. Patchy fog based 100-400 ft MSL with vis 1/2-3 SM expected to begin moving into the SD coast after 06Z, then into the OC coast after 09Z. Low clouds likely won't move any further than about 5 miles inland overnight. 30-40% chance for vis less than 1/2SM at coastal sites overnight. Fog clears to beaches 15-17Z. Elsewhere, VFR conditions through the TAF period. && .MARINE...Patchy fog with visibility under 1 nautical mile is expected to move over the coastal waters this evening and overnight, highest chances near the coastline. Otherwise, no hazardous marine conditions expected through Wednesday. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Heat Advisory until 8 PM PDT this evening for Orange County Coastal Areas-Orange County Inland Areas-Riverside County Mountains-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Coastal Areas-San Diego County Mountains-San Diego County Valleys-Santa Ana Mountains and Foothills. Extreme Heat Warning until 8 PM PDT Saturday for Coachella Valley-San Diego County Deserts-San Gorgonio Pass near Banning. PZ...None. && $$ PUBLIC...CO AVIATION/MARINE...CSPSGX-931564