Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
581 FXUS66 KSGX 140946 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 246 AM PDT Sun Jul 14 2024 .SYNOPSIS... Hot weather will continue inland through the week. Monsoon moisture will bring another chance of thunderstorms this afternoon in the mountains and high desert, with a slight chance Monday afternoon. Drying will occur midweek before another increase in moisture brings a renewed chance of mountain and desert thunderstorms next weekend. Night and morning low clouds will continue for the coastal areas into the far western valleys. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Low clouds are very slow to develops near the coast this morning, but should eventually fill in across the coastal areas by sunrise. Elsewhere there are a few mid level clouds. A gulf surge is well on the way in the lower deserts. At 2 am, Imperial had a decent SE winds and dew points climbing to 75 degrees, while Thermal is calm with a 73 degree dew point. Hi-res guidance shows this moisture not completely mixing out today, which will help keep temperatures down but the Heat Index high. The Excessive Heat Warning for the low deserts FINALLY expires this evening. The weather for this week will be dominated by the stubborn upper level high over the Desert Southwest and Great Basin. Sufficient mid level moisture sticks around today and to a lesser extent Monday for afternoon thunderstorms over the mountains and high desert with lower chances across the lower deserts. Mid-level flow is very weak at only around 5-10 kt, so storms will mostly remain anchored across convergence boundaries over the mountain crests and onto the desert slopes as the sea breeze progresses inland, as well as along the sea breeze arc in the high deserts, ending by evening as we lose daytime heating. Highs today and Monday will be near seasonal normals. The upper level high currently over the Four Corners region slowly shifts westward towards the Great Basin and amplifies through Friday. This will bring some drying in the mid levels along with hotter and more stable conditions. While we may see a few clouds over the mountains each afternoon, precipitation/thunderstorm chances will be less than 15 percent for Tuesday through Friday. Minor warming is expected each day, peaking around Friday. Widespread moderate to locally high HeatRisk is expected in return for inland areas for Thursday and Friday, possibly into Saturday depending on when and how much monsoon moisture returns. The upper high begins to break down next weekend, which may allow for enough instability for afternoon thunderstorms over the mountains once again as well as some cooling. Coastal areas will remain temperate through the week with a continuation of low clouds and patchy fog each night and morning. && .AVIATION... 140900Z...Coast/Valleys...Patchy low clouds are slowly developing along the coast and are expected to reach into portions of the western valleys through 14Z. Bases are expected to be 700-1200 ft MSL with tops to 1500 ft MSL. Local VIS 1-3 miles will occur over higher coastal terrain through 16Z Sun, with local terrain obscured. Most areas will clear 15Z-17Z Sun. 15-20% chance local BKN/OVC conditions will linger near beaches through Sun afternoon. Otherwise, unrestricted VIS and generally SCT clouds at/above 10000 ft MSL will prevail, with areas of low clouds expected to move inland 02-06Z Mon. Bases are expected to be similar at 700-1200 ft MSL. Mountains/Deserts...There is a slight chance of TSRA 20Z Sun-03Z Mon with CB bases around 10000 ft MSL and tops to 40000 ft MSL. Highest chances of TSRA will be in the mtns (20-30%) with lesser chances in the deserts (15-20%). Strong UDDFS and local sfc gusts to 40 kt expected where storms develop. Local smoke will occur in the San Gabriel Mountains. Otherwise, unrestricted VIS and generally SCT clouds at/above 12000 ft MSL will prevail through early Mon. && .MARINE... No hazardous marine conditions are expected through Friday. && .BEACHES... A SSW swell of 3 ft/18-19 sec/210 deg will impact mainly Orange County beaches Tuesday through Thursday. The period will gradually decrease to 15 sec by Thursday. This will bring elevated surf (sets to 6-7 feet) and high risk of dangerous rip currents to south-facing beaches. && .FIRE WEATHER... A Red Flag Warning for dry lightning continues through 9 PM this evening for the Riverside and San Bernardino County Mountains and the high desert. Scattered thunderstorms are expected in these areas this afternoon and early evening. For any storm that develops, wetting rain is expected, but isolated dry lighting is likely outside of the rain core. In addition, strong and erratic winds, possibly reaching 35 to 50 mph, will create brief but critical fire weather conditions should any lightning starts occur. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Red Flag Warning until 9 PM PDT this evening for Riverside County Mountains-Including The San Jacinto Ranger District Of The San Bernardino National Forest-San Bernardino County Mountains-Including The Mountain Top And Front Country Ranger Districts Of The San Bernardino National Forest-San Gorgonio Pass Near Banning-Victor Valley -Apple Valley - Lucerne Valley -Johnson Valley. Excessive Heat Warning until 9 PM PDT this evening for Coachella Valley-San Diego County Deserts. PZ...None. && $$ PUBLIC/FIRE WEATHER...SS AVIATION/MARINE...CO