Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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100 FXUS66 KLOX 131129 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 429 AM PDT Thu Jun 13 2024 .SYNOPSIS...12/725 PM. Low clouds and fog are expected through at least Friday morning across the coast and coastal valleys, with temperatures 3-6 degrees below normal. Gusty north winds are expected Friday into the weekend, mainly in the mountains and southern Santa Barbara County and adjacent coastal waters. Warming temperatures are expected Friday through weekend, with faster clearing of low clouds. && .SHORT TERM (TDY-SAT)...13/429 AM. A deep marine layer continued across the forecast area this morning, and was running around 2500 feet deep or so. Low clouds and fog were widespread in all coastal and valley areas with the exception of the far interior valleys of SLO County and the Cuyama Valley. Even in the far interior valleys of SLO County, there will likely be some low cloud infiltration this morning, and clouds will push into the lower coastal slopes from SLO County thru L.A. County. There will likely be some local drizzle as well, as model cross sections show some lift within the deep moist layer. An upper low centered about 200 NM SSW of KLAX early this morning will move eastward to near San Diego this afternoon. Strong onshore gradients will continue across the region. Clearing will be fairly slow today, with skies becoming mostly sunny by late morning in the valleys, but not until the afternoon across much of the coastal plain. In some immediate beach locations, skies will probably remain cloudy for much of the day once again. Max temps should be within a couple of degrees of those observed on Wed in most areas, except there will likely be cooling across far interior sections of SLO and SBA Counties. There will be some gusty west winds in the mtns and the Antelope Valley this afternoon and evening but they should remain below advisory levels. The upper low will continue to move eastward tonight and Fri, and a weak broad upper ridge will build into the region. The marine layer will likely begin to shrink in depth due to height rises, so expect less inland penetration of the low clouds tonight/Fri morning, with clouds likely below the coastal slopes, and possibly not even pushing into the Santa Clarita Valley. With weakening onshore flow, expect faster clearing in most areas Fri, with the sun probably making an appearance at most beach locations. Rising heights, weakening onshore gradients, and decent warming at 850 and 950 mb should lead to significant warming on Fri across interior areas. Max temps in most valley, mtn and desert locations will be 5 to 10 degrees warmer on Fri than they are today, and some locations, such as in the Salinas Valley, max temps may be 20 degrees or more higher than those reached today. N-S gradients will increase sharply late Fri into Fri night, and gusty NW to N winds will likely reach Wind Advisory levels across the southwestern SBA County coast, the western Santa Ynez Mountains, and through the I-5 Corridor. Low clouds should be less widespread, especially in the valleys and across SLO and SBA Counties Fri night/Sat morning, and in fact, may be confined to southern and eastern L.A. County. Gusty north winds will keep temps elevated Fri night in the mtns and foothills, especially across SBA County. A trough will move into the Pac NW Fri night and Sat, with a broad trough sagging southward down the West Coast. N-S gradients will continue to increase across the region Sat. Expect any low clouds to clear fairly quickly Sat. Falling heights may bring a bit of cooling to interior areas Sat, but strong N-S gradients will likely bring some warming to coastal and valley areas. Winds will remain gusty from the NW-N across southwestern SBA County and the I-5 Corridor, and will likely increase and become more widespread Sat afternoon, affecting the Central Coast, the interior mtns of SBA County and northern Ventura County, the Antelope Valley and foothills, and some L.A. County valley locations. N-S gradients will peak across the region Sat night, with models showing an offshore gradient of over 5 mb between KSBA and KSMX, and increasing offshore gradients between KSBA/KBFL and KLAX/KBFL. There will also be increasing W to NW flow at 500 mb, strengthening NW winds at 700 mb and N winds at 850 mb. At the same time, cold air advection will spread into the region late Sat, and subsidence will increase as well. This will bring the potential for NW to N winds to increase to damaging levels across much of southern SBA County including the foothills near the city of Santa Barbara and Montecito, the northern mtns of Ventura County, the I-5 Corridor, and the western Antelope Valley foothills. Have issued a High Wind Watch from Sat evening thru Sun morning, for the potential for wind gusts of 60 to 70 mph in some of the wind prone locations in these areas. .LONG TERM (SUN-WED)...12/230 PM. Sunday will be an interesting day as there will still be strong northerly winds continuing across the western counties, adjacent coastal waters, and the northern mountains. However, models have been consistent showing the development of a coastal eddy circulation developing off the coast of LA and Orange Counties and significant cooling at least for LA/Ventura County coast and valley areas. And most of the models are even showing several degrees of cooling across inland areas of LA/Ventura Counties as well. Will likely still see advisory level Sundowner winds again Sunday into Monday for the Santa Barbara area but probably not quite as warm as the previous couple days. With the eddy developing later in the weekend will likely see marine layer stratus moving up from the south and into coastal LA/Ventura Counties. Northerly flow expected to remain quite strong across the offshore coastal waters through the middle of next week, which will keep at least a threat of Sundowner winds going for southern Santa Barbara Counties going into next week as well. For this reason, stratus coverage should be confined to just LA/Ventura Counties at least for the first half of the week. Temperatures in these areas will drop back to normal or slightly below normal levels. For SLO and northern Santa Barbara Counties, gusty northwest winds will continue, especially near the coast, but little or no marine layer stratus is expected. Temperatures will generally be within a few degrees of normal. && .AVIATION...13/1123Z. At 0930Z at KLAX, the marine layer was 1600 ft deep. The top of the inversion was at 2900 ft with a temperature of 22 C. For 12Z TAF package, high confidence in deserts TAFs, but low to moderate confidence in coastal/valley TAFs. Timing of dissipation of CIG/VSBY restrictions could be +/- 2 hours of current forecasts...with a 30-40% chance that coastal sites south of Point Conception may not clear this afternoon. For tonight, high confidence in return of CIG/VSBY restrictions to coastal/valley sites, but only moderate confidence in timing and flight category. KLAX...Moderate confidence in 12Z TAF. Timing of dissipation of CIG/VSBY restrictions today could be +/- 2 hours of current 20Z forecast (with a 30% chance that CIG/VSBY restrictions will not dissipate). For tonight, timing of return of CIG/VSBY restrictions could be +/- 2 hours of current forecast with a 40% chance conditions could drop to LIFR levels. No significant easterly wind component is expected. KBUR...Moderate confidence in 12Z TAF. Timing of dissipation of CIG/VSBY restrictions today could be +/- 2 hours of current 18Z forecast. Timing of return of LIFR conditions could be +/- 2 hours of current 08Z forecast. && .MARINE...13/411 AM. For the Outer Waters, moderate to high confidence in current forecast. Small Craft Advisory (SCA) level winds will develop late tonight and Friday morning then will increase to Gale force levels from Friday afternoon through Monday. Seas will peak in the 12 to 15 foot range this weekend. GALE WATCHES are currently in effect from Friday afternoon through Monday, but these will likely upgraded to warnings this afternoon or tonight. Additionally, there is a 20% percent chance of Storm Force gusts (48 knots or greater) Friday night through Sunday night. For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. Today through Friday morning, winds and seas will remain below SCA levels. From Friday afternoon through Monday, a combinations of SCA level winds and seas can be expected. Additionally, there is a 30-40% chance of Gale force winds Saturday night through Sunday night. For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. For the Santa Barbara Channel, high confidence in SCA level winds developing Friday afternoon and continuing through Monday with a 40% chance of Gale force winds across the western half of the Santa Barbara Channel Saturday through Sunday. For the rest of the southern Inner Waters, there is a 30-40% chance of SCA level winds Saturday and Sunday. Across all the coastal waters, steep and dangerous seas can be expected this weekend. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...High Wind Watch in effect from Saturday evening through Sunday morning for zones 349>353-377-378-381. (See LAXNPWLOX). PZ...Small Craft Advisory in effect from 2 AM to 2 PM PDT Friday for zones 670-673-676. (See LAXMWWLOX). Gale Watch in effect from Friday afternoon through Monday afternoon for zones 670-673-676. (See LAXMWWLOX). && $$ PUBLIC...DB/MW AVIATION...RAT MARINE...RAT SYNOPSIS...MW/Smith weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox