Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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491 FXUS66 KLOX 131226 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 526 AM PDT Thu Jun 13 2024 .SYNOPSIS...13/451 AM. Low clouds and fog in coastal and valley areas will clear slowly today. Expect less in the way of clouds tonight, with faster clearing Friday. Gusty north winds are likely Friday through the weekend, with damaging gusts possible in portions of Santa Barbara County and the mountains Saturday night into early Sunday. It will be much warmer Friday, especially inland. A bit more warming is possible Saturday. Night through morning clouds will be minimal Friday night through Sun. A cooling trend is expected Sunday and Monday, with a gradual increase in night and morning low clouds and fog. Minor changes are then expected through midweek. && .SHORT TERM (TDY-SAT)...13/525 AM. A deep marine layer continued across the forecast area this morning, 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 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 Wed in most areas, except there will likely be cooling across far interior sections of SLO/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 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 thru the I-5 Corridor. Low clouds should be less widespread, especially in the valleys and across SLO/SBA Counties Fri night/Sat morning, and in fact, may be confined to southern and eastern L.A. County. Gusty N winds will keep temps elevated Fri night in the mtns/foothills, especially in SBA County. An upper low will move into the Pac NW Fri night/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. This will be especially true for the south coast of SBA County. 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-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. This will bring the potential for NW-N winds to increase to damaging levels across much of southern SBA County including the foothills near the cities of Santa Barbara and Montecito, the northern mtns of VTU 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 60-70 mph in the more wind prone locations in these areas. .LONG TERM (SUN-WED)...13/514 AM. The powerful NW winds across SLO/SBA Counties and the coastal waters will gin up a good eddy circulation across the inner waters late Sat night/Sun. This will set up the age-old battle between the NW flow and the eddy, making for a difficult cloud forecast for Sat night/Sun morning. If the northerly flow wins out, some gusty winds will affect the L.A. County valleys, and clouds will be confined to southern L.A. County. There may also be clouds across southern portions of the Central Coast due to northerly upslope flow against the northern slopes of the Santa Ynez Range. If the eddy wins, low clouds will push farther north and west, possibly into the valleys of L.A./VTU Counties. Not only will cloud cover be dependent on the outcome of the eddy/NW flow battle, but so will max temps Sun. In general, expect a few degrees of cooling Sun as heights fall, but cooling will be more significant and widespread in areas south of Pt Conception if the eddy becomes the dominant player. N-S gradients will remain steep across SLO/SBA Counties Sun into Mon morning, so advisory level NW winds are likely in southern SBA County again late Sun afternoon into Sun night. Low clouds should become more widespread south of Pt Conception late Sun night/Mon morning. There should several degrees of cooling in most areas Mon as heights continue to fall. An upper low will move thru the Pac NW Mon and into the northern Rocky Mountains Tue, with a sharpening trough across CA. The trough axis will be located right across the region Tue, then it will move to the east Wed. N-S gradients will remain decently offshore across SLO/SBA Counties Mon night, then actually increase Tue night. This should keep gusty N winds late each afternoon/evening across southern SBA County Mon thru Wed. Expect night thru morning low clouds to remain fairly minimal across SLo and SBA Counties, with clouds in most coastal and valley areas of L.A./VTU Counties. Expect minor changes in max temps Tue with some warming possible Wed as heights begin to rise. && .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 AVIATION...RAT MARINE...RAT SYNOPSIS...DB weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox