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Forecast Discussion for San Diego, CA
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000 FXUS66 KSGX 251800 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 1000 AM PST Mon Jan 25 2021 .SYNOPSIS...A cold low pressure system is currently over the region, will continue to bring areas of showers, strong gusty winds, and low elevation snow into this evening with Tuesday and Wednesday a little warmer. Light precipitation may return as early as late Tuesday night or Wednesday for areas bordering Los Angeles County, though widespread precipitation is looking increasingly likely closer to late Thursday into Friday with drier conditions for the weekend. Wednesday and Thursday will be a little warmer, cooler on Friday, then warming to around 5 degrees below average for Sunday. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .Morning Update... The forecast remains on track this morning as winds continue to be very gusty at the beaches, especially in San diego County, where current gusts are above 50 MPH in some spots. Westerly winds will continue to increase later this morning, peaking early in the afternoon. Winds will slowly ease for Orange County into the Inland Empire later this afternoon, but winds will continue to howl for San Diego County into the deserts for the first half of the night. Please see High Wind Warnings and Wind Advisory products for more details. Showers will continue to become more widespread the southern areas of our forecast area, especially in San Diego County later this morning into the afternoon, with snow levels going down to around 2,000 feet. A Winter Weather Advisory has been issued for areas above 1500 feet across the Inland Empire and above 2000 feet in San Diego County. Hi-res models continue to show a slow sagging of the moisture down to the south through tonight. Rain totals look to be around one quarter of an inch in the San Diego metro. Snow showers will continue for most areas, tapering off north to south this afternoon into tonight. Thank you to all those who have provided your snow reports! Many locations across the San Bernardino`s have picked up over a foot of fresh powder with this latest system. High elevation locations in the San Diego County mountains could receive over one foot of snow when all is said and done with this storm system. A brief reprieve looks to be had Tuesday into Wednesday. Another storm looks to make it into our area by Thursday night into Friday. This will have a bit higher elevation snow, and more widespread precipitation. .SHORT TERM (Today through Wednesday night)... A cold low pressure system from the northwest will move quickly through southern California today, moving into Arizona tonight. It will bring showers, low elevation snow, strong gusty winds, and cold temperatures today with the precipitation ending from the northwest tonight and early Tuesday. There is also a slight chance of thunderstorms today, mainly for the coast and valleys. There will be strong gusty winds today into tonight with the ECMWF EFI exceeding the 90th percentile across the coastal waters into the adjacent coastal areas and the 80th percentile for portions of the lower deserts from San Diego County into Imperial County. At the coast, gusts will exceed 45 mph at times and could briefly reach 55 to 60 mph at times in bands of showers as stronger winds aloft are brought down to the surface. There was a gust to 46 mph at 900 feet near Laguna Beach with the passage of a band of showers at 3:20 AM and subsequent gusts to 45 to 50 mph at Solana Beach and Mission Beach, Upstream, there have been gusts to 59 mph at 1570 feet on Catalina Island and 76 mph at Santa Barbara Island. For the mountains and deserts of San Diego County, cross sections show winds exceeding 50 knots with the strongest and most widespread winds from late morning through the afternoon with the cross sections showing the potential for occasional stronger gusts downstream over the deserts from mountain waves. These occasional stronger gusts may continue overnight into early Tuesday. Snow levels near 3500 to 4000 feet early this morning will lower to 2500 to 3000 feet this afternoon and 2000 to 2500 feet tonight with the lower snow levels toward the north. Snowfall of a few inches is possible down to around 3500 feet with 4 to 8 inches above 4000 feet and 8 to 14 inches above 5000 feet. Snowfall could reach 18 inches on the higher peaks in the San Bernardino Mountains and the Riverside County mountains and could locally exceed 18 inches on the highest peaks in the San Diego County mountains. There will be slow warming for Tuesday and Wednesday, but with temperatures remaining well below average. The next low pressure system moving southward off the California coast could bring some light precipitation at times for areas bordering Los Angeles County to the east, but the more widespread and heavier precipitation may not extend much past Santa Barbara County through much of the day on Thursday. && .LONG TERM (Thursday through Sunday)... The next round of more widespread precipitation may move through southwestern California Thursday night and Friday, with precipitation ending from the northwest Friday night and early Saturday, Snow levels are not expected to be as low as early this week, but could still fall to around 4500 feet on Friday. Rainfall could range from around 1.5 inch at the coast to 2 to 3 inches in the mountains with locally greater amounts with amounts decreasing from north to south. Next weekend would be dry and a little warmer, but with Sunday high temperatures remaining around 5 degrees below average. && .HYDROLOGY... For Orange County into southwestern San Bernardino and western Riverside Counties, rainfall (and liquid equivalent above the snow level) will range from one quarter to one half inch at the coast to 1 to 2 inches in the mountains with one quarter inch or less in the deserts. For San Diego County, rainfall will range from one half to three quarters of an inch near the coast to 2 to 3 inches in the mountains with locally greater amounts. Snow levels will lower to 2000 to 3000 feet this afternoon and tonight, closer to 1500 feet in the Inland Empire. Snowfall of a few inches is possible down to around 3500 feet with 4 to 8 inches above 4000 feet and 8 to 14 inches above 5000 feet. Snowfall could reach 18 inches on the higher peaks in the San Bernardino Mountains and the Riverside Mountains and could locally exceed 18 inches on the highest peaks in the San Diego County mountains. Rainfall rates in bands of heavier showers and isolated thunderstorms could briefly exceed four tenths of an inch per hour with fast cell movement being a limiting factor. Isolated thunder is possible today, mainly for portions of the southern coast and valleys, with the greatest instability for this afternoon over the coastal waters into adjacent coastal areas. Local ponding of water and urban flooding is possible near these heavier showers, especially if they repeatedly track across the same area, but overall the threat of flooding is low and runoff is expected be limited. The next low pressure system moving southward off the California coast could bring some light precipitation at times for areas bordering Los Angeles County to the east, but the more widespread and heavier precipitation may not extend much past Santa Barbara County through much of the day on Thursday. The next round of more widespread precipitation may move through southwestern California Thursday night and Friday, with precipitation ending from the northwest Friday night and early Saturday, Snow levels are not expected to be as low as early this week, but could still fall to around 4500 feet on Friday. Rainfall could range from around 1.5 inch at the coast to 2 to 3 inches in the mountains with locally greater amounts with amounts decreasing from north to south. Runoff potential would be greater due to deeper layer atmospheric moisture, already moistened ground, melting snow, and higher snow levels. && .AVIATION... 251630Z...Coast/Valleys...Strong winds are the biggest issue through this evening. Expect sustained 20-30 kt winds with gusts 35-45 kts at KSAN through this evening, with AWW in effect until 06Z. At KCRQ/KSNA, occasional gusts of 25-30 kts are expected. The peak winds are expected to occur 18-02Z. Winds will gradually begin to decrease after 04Z tonight. Scattered SHRA with occasional ceilings of 2500 feet MSL and brief reduction in visibilities to 2-5SM. Best chance at KSAN/KCRQ. Isolated TSRA possible but timing/coverage too low to mention in TAFs. SHRA to taper off near KSNA and KONT after 20Z, with occasional scatter out, but SHRA and BKN clouds continuing at KCRQ and KSAN through 08Z. Showers ending overnight into Tuesday with greater scattering out. Mountains...Expect wind gusts in excess of 40 kts to create low visibility along with MOD/STG UDDFS at times. Periods of +SHSN can be expected through this evening with occasional terrain obscuration. Deserts...Strong winds expected this afternoon. Sustained 20-30 kts with occasional gusts to 40 kts expected especially from 18-02Z followed by a significant decrease in wind speeds overnight tonight. Expect SCT-BKN clouds 3000-6000 feet MSL with periods of -RA this morning, tapering off after 18Z. && .MARINE... Gales and hazardous seas will combine with a few thunderstorms to generate extremely hazardous conditions today through this evening. A Gale Warning and a Marine Weather Statement contain the hazard details. Thunderstorms will become less likely tonight and Tuesday, while wind and sea conditions gradually improve Tuesday. No additional marine hazards are expected Tuesday night through Thursday. The next storm could produce hazardous wind conditions Thursday night and Friday. && .BEACHES... Very large swells will generate high surf today through Tuesday. There is also a small chance of thunderstorms and beach lightning today. Check the High Surf Advisory and Surf Zone Forecast for details. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Winter Storm Warning until 10 PM PST this evening for Riverside County Mountains-San Bernardino County Mountains-San Diego County Mountains. High Wind Warning from 6 AM this morning to 7 AM PST Tuesday for San Diego County Deserts. Wind Advisory from 6 AM this morning to 10 PM PST this evening for Apple and Lucerne Valleys-Orange County Coastal Areas- Orange County Inland Areas-San Diego County Valleys-San Gorgonio Pass Near Banning. Winter Weather Advisory until 10 AM PST this morning for Santa Ana Mountains and Foothills. High Wind Warning from 6 AM this morning to 10 PM PST this evening for San Diego County Coastal Areas. High Surf Advisory from 6 AM this morning to 6 PM PST Tuesday for Orange County Coastal Areas-San Diego County Coastal Areas. PZ...Gale Warning until 10 PM PST Tuesday for Coastal Waters from San Mateo Point to the Mexican Border and out to 30 nm-Waters from San Mateo point to the Mexican Border Extending 30 to 60 nm out including San Clemente Island. && $$ PUBLIC/HYDROLOGY...17 AVIATION/MARINE/BEACHES...MM.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .SYNOPSIS... && .SHORT TERM... && .LONG TERM... && .AVIATION... 251630Z...Coast/Valleys...Strong winds are the biggest issue through this evening. Expect sustained 20-30 kt winds with gusts 35-45 kts at KSAN through this evening, with AWW in effect until 06Z. At KCRQ/KSNA, occasional gusts of 25-30 kts are expected. The peak winds are expected to occur 18-02Z. Winds will gradually begin to decrease after 04Z tonight. Scattered SHRA with occasional ceilings of 2500 feet MSL and brief reduction in visibilities to 2-5SM. Best chance at KSAN/KCRQ. Isolated TSRA possible but timing/coverage too low to mention in TAFs. SHRA to taper off near KSNA and KONT after 20Z, with occasional scatter out, but SHRA and BKN clouds continuing at KCRQ and KSAN through 08Z. Showers ending overnight into Tuesday with greater scattering out. Mountains...Expect wind gusts in excess of 40 kts to create low visibility along with MOD/STG UDDFS at times. Periods of +SHSN can be expected through this evening with occasional terrain obscuration. Deserts...Strong winds expected this afternoon. Sustained 20-30 kts with occasional gusts to 40 kts expected especially from 18-02Z followed by a significant decrease in wind speeds overnight tonight. Expect SCT-BKN clouds 3000-6000 feet MSL with periods of -RA this morning, tapering off after 18Z. && .AVIATION... && .MARINE... Gales and hazardous seas will combine with a few thunderstorms to generate extremely hazardous conditions today through this evening. A Gale Warning and a Marine Weather Statement contain the hazard details. Thunderstorms will become less likely tonight and Tuesday, while wind and sea conditions gradually improve Tuesday. No additional marine hazards are expected Tuesday night through Thursday. The next storm could produce hazardous wind conditions Thursday night and Friday. && .MARINE... && .BEACHES... && .HYDROLOGY... && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Winter Storm Warning until 10 PM PST this evening for Riverside County Mountains-San Bernardino County Mountains-San Diego County Mountains. High Wind Warning until 7 AM PST Tuesday for San Diego County Deserts. Winter Weather Advisory until 10 AM PST this morning for Apple and Lucerne Valleys-Santa Ana Mountains and Foothills. Wind Advisory until 10 PM PST this evening for Apple and Lucerne Valleys-Orange County Coastal Areas-Orange County Inland Areas-San Diego County Valleys-San Gorgonio Pass Near Banning. Winter Weather Advisory until 6 AM PST Tuesday for San Bernardino and Riverside County Valleys-The Inland Empire- San Diego County Valleys. High Wind Warning until 10 PM PST this evening for San Diego County Coastal Areas. High Surf Advisory until 6 PM PST Tuesday for Orange County Coastal Areas-San Diego County Coastal Areas. PZ...Gale Warning until 10 PM PST Tuesday for Coastal Waters from San Mateo Point to the Mexican Border and out to 30 nm-Waters from San Mateo point to the Mexican Border Extending 30 to 60 nm out including San Clemente Island. && $$ PUBLIC...APR AVIATION/MARINE/BEACHES...Moreland |
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