Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
547 FXUS66 KSGX 192027 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 127 PM PDT Sun May 19 2024 .SYNOPSIS... A large-scale trough over western North America will persist through this week. Temperatures will remain below seasonal averages with gusty winds across the mountains and deserts. A closed upper level low will move across the region on Monday, which will bring the coolest and windiest conditions overall. Low clouds will continue nights and mornings, retreating back to the coast each afternoon. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... This afternoon, the marine layer low clouds have cleared to about 25 miles offshore and much like yesterday, will return to the coast in a couple of hours then spread inland to the coastal slopes by about 5 am Monday. The marine layer will likely deepen, with enough moisture to produce patchy drizzle late tonight and early Monday morning, although accumulations are unlikely. Onshore flow continues with sfc pressure gradients 4.2 mb SAN-DAG and 6.2 mb SAN-IPL currently producing westerly winds gusting 30-40 mph and up to 55 mph in the windiest locations. From previous discussion... A closed upper low currently about 900 miles southwest of San Diego will be drawn into the mean flow and become an open wave over SoCal on Monday as a large-scale trough to the north deepens. This will bring additional cooling to the region and Monday will likely be the coolest day of the week. Temperatures will be near 5 degrees below average across the coastal areas with up to 10 degrees below average for inland areas. It will also strengthen the westerly winds, especially in the mtns and adjacent desert areas where chances are good for wind gusts over 40 mph and over 55 mph in wind-prone mountain passes. The San Gorgonio Pass will have a 70-80% chance of wind gusts exceeding 55 mph. The trough over the West Coast will continue, though not as amplified as Monday. Rising heights will lead to some warmer conditions and somewhat weaker winds over inland regions. Little day-to-day variations in temperatures, winds and marine layer clouds can be expected from Tuesday through the end of the week, where we will see slightly below average temperatures and May Gray conditions west of the mountains in the morning with general clearing toward the coast by the afternoons. As we get into next weekend, the consensus of model solutions shows the dominant trough weakening and a building ridge of high pressure centered over eastern Mexico. At this time, it seems likely that the weather over SoCal will continue to be dominated by troughing over western North America. && .AVIATION... 191935Z...Coast/Valleys...Full clearing this morning including beaches. Low clouds will return this evening, partially late today 23Z-02Z with sea breeze and lowering sun angle. Ceilings should be similar in the 1000 to 2000 ft AGL range. A weather disturbance will lift the marine layer Monday morning and lead to clearing again. The tops near 3000 ft MSL overnight and Monday morning. Mountains/Deserts...Clear with unrestricted vis through Monday morning. Wind increasing with peak gusts 25 to 30 kt. There is low chance of 35 kt gust at TRM and PSP from 23 to 04Z. Blowing dust is possible. Strongest winds are in the mountain passes and foothills of the Coachella valley with gust to 40 kt. Winds are enhanced by a passing weather system on Monday. && .MARINE... No hazardous marine conditions through Thursday except for offshore waters with wind gusts 20 knots for Monday. && .BEACHES... A series of southwest swells of 2-3 ft at 16-18 seconds from 200-220 degrees will build through Monday, producing above normal surf of 3- 5 ft with locally higher sets on exposed SW facing beaches, as well as a high risk of rip currents at all beaches. A Beach Hazards Statement is in effect through Monday evening. Swell and surf will slowly lower on Wednesday and Thursday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement through Monday evening for Orange County Coastal Areas-San Diego County Coastal Areas. PZ...None. && $$ PUBLIC...PG AVIATION/MARINE/BEACHES...Tardy