Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
206 FXUS66 KSGX 170442 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 930 PM PDT Mon Sep 16 2024 .SYNOPSIS... Gusty southwest to west winds will continue through this evening. A few light showers will occur through early Tuesday morning, with areas of drizzle west of the mountains Wednesday morning. From Wednesday evening through Thursday or Friday, unsettled weather is expected again with additional chances of precipitation. Drier and warmer conditions will return by the weekend. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Update... Island band showers due to convergence downwind of Catalina Island were occurring from Oceanside to Escondido to San Pasqual Valley, while mostly cloudy skies prevailed from the mountains west to the coast. Most of the precipitation will be localized tonight with greatest concentration in San Diego County due to the island banding. The precip should end early Tuesday morning as the trough axis shifts east of the area and height gradients weaken. However, Tuesday will continue to be cool with only a slight warmup (mainly mountains and high deserts) as 850 MB temperatures only recover a few degrees C in the afternoon and a deep marine layer will continue, possibly remaining over 5000 feet deep through Tue night. Areas of moderately strong gusty winds continued in desert/desert slope areas, especially in Riverside and San Diego counties. The Whitewater observations had gusts to 54-55 MPH at mid-evening. The winds should slowly weaken overnight. From Previous Discussion... Weaker winds and mostly dry conditions are expected after Tuesday morning. A few degrees of warming are expected Tuesday west of the mountains and in the low desert with 5 to 10 degrees of warming in the mountains and High Desert. It looks like the marine layer will be deep enough on Wednesday morning to allow for areas of drizzle to develop west of the mountains and along the coastal mountain slopes. On Wednesday an upper level low will begin to dig south along the coast of the Pacific Northwest. Latest guidance has the low moving slower, now moving inland across Central and Southern California on Thursday. This system is expected to bring additional chances of precipitation to Southern California. Some showers or drizzle may develop late Wednesday night but the highest chances of precipitation are on Thursday. With the slowing of the trough, slight chances of showers have been added to the forecast for Friday morning. This system looks like a warmer one, so only minor fluctuations in temperatures are expected for Tuesday through Thursday. Current ensemble guidance does not have a very significant uptick in winds with ensembles indicating winds may be weaker than today. NBM chances of wind gusts greater than 45 mph are 35 to 45 percent for Wednesday and Thursday afternoon and evenings and confined to wind prone passes, like the San Gorgonio Pass. Due to the slow down of the trough, there is more uncertainty in the high temperature forecast for Friday. Some warming may occur compared to Thursday, but more substantial warming may not occur until the weekend. High temperatures will be several degrees warmer for Saturday with high temperatures for next Sunday warming to a few degrees above average for the deserts to around 5 degrees above average for the coast and valleys, mostly in the 90s for the inland valleys and 100 to 105 for the lower deserts. && .AVIATION... 170410Z...Coast and Valleys...Low clouds with bases varying 2500- 3500 feet MSL and tops to 5200 feet will continue through tonight. Brief periods of CIG impacts are possible...mainly at KSAN and KCRQ but timing is uncertain. Much of the terrain above 3000 ft MSL will be obscured with VIS reduces to 1 mile or less locally where clouds and terrain intersect. Clearing is expected to begin around 15Z Tuesday, starting at the coast and working inland scattering out last along the coastal mtn slopes. Smoke from the Line, Bridge and Airport fires will continue to reduce VIS in mountains, with hazy conditions over the Inland Empire and parts of the deserts. West-northwest winds will gust 40-50 knots through mountain passes, through tonight. Local moderate up/downdrafts east of mountain ridges. && .MARINE... Northwest gusts around 20 knots are expected in the outer waters this evening and again Wednesday afternoon and evening. Otherwise, no hazardous marine conditions are expected through Friday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Wind Advisory until midnight PDT tonight for San Diego County Deserts-San Gorgonio Pass Near Banning. PZ...None. && $$ PUBLIC...Maxwell (Update)/CO (Previous Discussion) AVIATION/MARINE...PG