Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
402 FXUS66 KSGX 042018 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 118 PM PDT Sat May 4 2024 .SYNOPSIS... Cloudy and cool conditions expected this weekend with periods of gusty winds in the mountains and deserts and periods of showers in and west of the mountains. Strongest winds and most likely time of precipitation is tonight into early Sunday morning. Winds will weaken slightly during the day Sunday but remain elevated into Sunday evening. Dry conditions are expected by Sunday afternoon. Dry and gradually warming conditions expected for much of next week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Visible satellite imagery at 1 PM was showing the low cloud deck slowly breaking up, with high clouds moving into Orange and San Bernardino counties. High clouds will become more widespread through the afternoon ahead of a low pressure system that will move inland across northern California. This low will dig into the Great Basin into Sunday, bringing cold and windy conditions with periods of showers to Southern California. Gusty southwest to west winds are expected over the mountains, through passes, and into portions of the deserts. Winds will slowly increase in strength through this afternoon and evening, peaking late tonight into early Sunday morning. Winds will weaken slightly through the day Sunday but remain elevated into Sunday night. Peak wind gusts will be 50 to 65 mph with isolated gusts to 70 mph possible through the San Gorgonio Pass and on the desert foothills of the San Bernardino Mountains. Another round of weaker but still gusty west winds will occur Monday afternoon and evening. Peak gusts of 40 to 50 mph expected over the mountains and into portions of the deserts. Winds will taper off into Tuesday morning, but periods of enhanced winds in the mountains and deserts may continue in the afternoons and evenings most days next week. The trough axis of the low and associated cold front are expected to quickly pass through Southern California tonight into early Sunday. Periods of mostly light rainfall are expected for areas in and west of the mountains as the front passes. As far as rainfall totals go generally less than 0.15 inch expected for the coasts/valleys with local amounts around 0.25 inch near the foothills. Orographics will enhance precipitation along the coastal slopes of the mountains with amounts of 0.25 to 0.50 inch, upwards of 0.75 inch on the southwest facing slopes of the San Bernardino Mountains. Amounts in the High Desert, if any, will be a couple hundredths of an inch, with no precipitation expected in the low deserts. Precipitation will come to an end by early Sunday afternoon. Snow levels will begin near 7500-8000 ft tonight, falling to around 5500-6000 ft behind the cold front as precipitation tapers off. Any snow accumulation will be limited to an inch or less. High temperatures on Sunday will be 15-20 degrees below normal for inland areas and 5-10 degrees below normal near the coast. Cool conditions expected Monday morning before temperatures rebound during the day. Low temperatures Monday morning will be quite chilly, with lows in the mid to upper 30s for the High Desert, mid- 20s to mid-30s for the mountains, and the low 40s for some valley locations. Conditions are expected to gradually warm Tuesday into much of next week, although there is some uncertainty in the forecast for the middle to end of the week. By Wednesday, ensembles are pretty much split half and half on warmer vs cooler scenarios. By Thursday, the cooler scenario with the low retrograding much further SW is the outlier containing only 7 percent of global ensemble members. Given the large uncertainty the current forecast follows NBM for temperatures which shows a very subtle warming trend through the week. && .AVIATION... 041930Z...Coasts/Valleys/Foothills...Low clouds cover the region west of the mtns, with bases in one layer SCT-BKN 1500-2500 FT MSL, and another BKN-OVC 2500-4000 FT MSL. VIS reduced to 1-3SM where low clouds and terrain intersect, obscuring higher terrain. Expect only partial and intermittent clearing over most areas west of the mountains today. Scattered -SHRA beginning as early as 02-03z Sun at the coast, but more likely between 06-09z for Orange County/Inland Empire and 09-12z for San Diego County. Briefly lower CIGs and slightly reduced VIS down to as low as 3 SM in -SHRA. Gradually clearing then for Sunday after 18-20z. Elsewhere...Clear skies with unrestricted VIS this morning, with increasing high clouds AOA 15,000 FL MSL later today. Mountains/Deserts...W-SW winds developing after 20z, with the strongest winds after 00z Sun. Expect W-SW winds 20-35 kt with gusts of 45-60 kt. Areas of MOD-STG up/downdrafts and LLWS over/east of mtns. && .MARINE... Gusty northwest wind gusts of 25 to 30 knots will occur this evening through Sunday evening, which will generate hazardous boating conditions, especially in the outer waters. Northwest wind gusts up to 20 knots will be possible over the outer waters each afternoon and evening for Monday through the middle of next week. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Wind Advisory until 8 PM PDT Sunday for Apple and Lucerne Valleys-San Bernardino County Mountains-San Gorgonio Pass Near Banning. Wind Advisory until 8 PM PDT Sunday for Coachella Valley- Riverside County Mountains-San Diego County Deserts-San Diego County Mountains. PZ...Small Craft Advisory from 3 AM to 10 PM PDT Sunday for Coastal Waters from San Mateo Point to the Mexican Border and out to 30 nm. Small Craft Advisory from 6 PM this evening to 3 AM PDT Monday for Waters from San Mateo Point to the Mexican Border Extending 30 to 60 nm out including San Clemente Island. && $$ PUBLIC...CO AVIATION/MARINE...Adams