Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
421 FXUS66 KSGX 292055 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 155 PM PDT Sat Jun 29 2024 .SYNOPSIS... Hot conditions across inland areas this weekend before slightly cooling develops on Monday. Slow warming sets in across inland areas starting on Tuesday, continuing into next weekend. Night and morning low clouds and fog will continue along the coast and far western valleys through much of next week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Skies have cleared across Southern California this afternoon and temperatures are rising quickly across inland areas. Highs look to top out near normal at the coast and 2-6 degrees above average across inland areas. Expect highs in the 70s at the coast, the 80s across the inland valleys and mountains, the 90s in the Inland Empire, the upper-90s across the High Desert and around 110 in the lower deserts. An interesting synoptic-scale pattern sets up this weekend as longwave troughing envelopes central California through the Pacific Northwest and a ridge builds across the Southern Plains, with increasing heights nudging westward into SoCal. Mid-level monsoonal moisture could make it into Imperial County and eastern Riverside County tomorrow, increasing mid-level cloud cover over the mountains and lower deserts. Some high-resolution guidance shows small precipitation chances south of the border in the mountains tomorrow afternoon, so we will continue to monitor trends to see if cells could pop in our mountains. Further warming is likely on Sunday across all areas. The trough axis weakens and moves eastward on Monday ahead of a strengthening ridge developing off the coast of the Pacific Northwest. A few degrees of cooling is anticipated on Monday as onshore flow strengthens. A weak, but present upper low looks to break off from the mean flow and settles to our southwest Monday into the middle of next week while the ridge impinges on the Pacific Northwest. Highs look to climb a degree or two each day Tuesday through Thursday, and moderate HeatRisk develops across most inland areas, with high a HeatRisk in the lower deserts. The presence of that weak low to the southwest could impact mid-level wind direction and potential moisture transport around midweek, so trends will continue to be monitored in regards to monsoonal thunderstorm chances in the mountains and deserts. Further warming is possible next weekend as global ensemble guidance shows the continuation of ridging over much of the western United States. The degree of warming will depend on the strength and location of the ridge. Regardless of forecast uncertainty, we look to be in for a long-duration heat wave through the first week of July. && .AVIATION... 291950Z...Coast/Valleys...Mostly clear with unrestricted VIS this afternoon. Low clouds returning to coastal TAF sites around 05-08Z Sunday, bases of 500-1000 FT MSL expected along with tops to near 1300 FT MSL. Scatter out timing similar to, if not slightly earlier than today, generally between 15-18z. Mountains/Deserts...Mostly clear skies with unrestricted VIS will continue through this evening. Westerly winds gusting locally 25-35 kt will return to the desert slopes and adjacent deserts and through San Gorgonio Pass this afternoon/evening. && .MARINE... No hazardous marine conditions are expected through Wednesday. && .BEACHES... A long-period SSW swell (from 190-210 degrees) of 2-3 feet at 16-18 seconds will arrive at the SoCal beaches as early as Wednesday morning. This may lead to elevated surf with breaking wave heights of 6-7 feet, mainly on south-and-southwest-facing beaches in Orange County. Rip current risks will accordingly increase as well. Elevated south swell looks to persist into late next week. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Excessive Heat Watch from Tuesday morning through Friday evening for Apple and Lucerne Valleys. Excessive Heat Warning from 10 AM Sunday to 8 PM PDT Friday for Coachella Valley-San Diego County Deserts-San Gorgonio Pass Near Banning. PZ...None. && $$ PUBLIC...EA AVIATION/MARINE...Adams