Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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244 FXUS66 KLOX 181657 AFDLOX Area Forecast Discussion...UPDATED National Weather Service Los Angeles/Oxnard CA 957 AM PDT Wed Sep 18 2024 .SYNOPSIS...18/204 AM. Much cooler than normal temperatures will continue through Friday before warmer conditions return for the weekend. There is a chance of showers and thunderstorms Wednesday night through Friday (especially over the mountains) as a low pressure system moves into the area. && .SHORT TERM (TDY-FRI)...18/948 AM. ***UPDATE*** The forecast is well on-track, and no changes have been made to the ongoing forecast. ***From Previous Discussion*** Not much to talk about today. A cool upper low will start its way down the CA coast. Hgts will lower and the upper flow will become more SW. There is not much of marine inversion south of Pt Conception and low clouds there will be patchy at best. Better onshore flow has brought plenty of low clouds to the Central Coast these clouds will likely stay through the morning. The low`s approach is now fcst to be a little slower and no rain is forecast through the afternoon. Max temps will be similar to Tuesday`s chilly readings with the csts and vlys only seeing temps in the upper 60s and 70s. While the coasts will be 4 to 8 degrees blo normal the rest of the area will be 8 to 16 degrees blo norms. The upper low will continue to march down the coast tonight and by dawn it will be just to the north SLO county. A chance of rain will develop over SLO and northern SBA counties overnight. Rainfall amounts if any will be under .05 inches. On Thursday and overnight into Friday the upper low will slowly move from west to east over the area. There is little disagreement among the mdls and ensembles about how far south the low will go with the consensus being a more northerly track across the northern half of SBA/VTA/LA counties. Most of the area will have a chc of a rain shower anytime of the day with the least chc across eastern LA County. The cold core (-21C at 500 mb which is some of the coldest 500 mb temps ever recorded) of the low will move over the area in the afternoon. The instability that will result from this will increase the chc of showers to 70 percent and will also bring a 20 percent chc of TSTMs to the interior of SLO county and the northern mtns of SBA/VTA/LA counties. This system does not have much moisture to work with and most areas away from the area of maximum instability will likely see a trace to a tenth of an inch. The area of maximum instability however could see a a quarter to half inch of rain with a 10 percent possibilty of an inch. Look for a 3 to 6 degree drop in temps as hgts plummet and partly to mostly cloudy skies restrict the sunshine. Max temps will be January like with the csts and vlys peaking only in the 60s and lower 70s (10 to 20 degrees blo normal. With the low moving to the east the threat of showers will be confined to LA county and there is a 20 percent chc they will linger into Friday morning there. Otherwise skies will clear out as the marine inversion will be obliterated. Friday morning`s lows will be on the chilly side with many people waking up to temps in the lower 50s or perhaps even the upper 40s. Friday will turning into a sunny day everywhere by late morning and with rising hgts max temps will rebound 6 to 12 degrees. Even with this warming max temps will come in 5 to 10 degrees blo normal. .LONG TERM (SAT-TUE)...18/317 AM. Good confidence in a rapid reversal of temperatures for the weekend. Hgts will quickly rise to 586-588 dam. There will only be weak onshore flow and even some weak offshore flow in the morning. Stratus will most likely be confined to the Central Coast. Max temps will jump 5 to 10 on Saturday with an additional 3 or 6 degrees of warming on tap for Sunday. By Sunday temps will be 3 to 6 degrees above normal with 70s at beaches 80s a little further inland and 90s in the vlys, lower elevation mtns and inland areas. Monday looks to be the warmest day of the next 7 with an additional 1 to 2 degrees of warming likely. Max temps will fall Tuesday as broad troffing affects the western CONUS and onshore flow increases. The marine layer cloud pattern may start to make a comeback as well. && .AVIATION...18/1133Z. At 1130Z at KLAX, There was a 5000 ft deep moist layer with no inversion. Good confidence in TAFs for KSBA, KPMD, and KWJF. Fairly good confidence in TAFs for KOXR, KCMA, KBUR, and KVNY with a 20 percent chc of MVFR cigs through 16Z Wed, and again after 06Z Thu. Moderate confidence in KPRB, KSBP, and KSMX TAFs through 03Z, then low confidence. There is a 20 percent chc of high MVFR cigs lifting to VFR with VCSH after 06Z. Low confidence in the remainder of the TAFs with a 25 percent chc of no low clouds. Cigs are very patchy in nature and could dissipate and reform frequently until settling in by 14Z Wed. There is a 30 percent chc of MVFR cigs after 08Z Thurs. KLAX...Low confidence in TAF. There is a 25 percent chc of no low clouds. If low clouds do form, they may scatter and reform frequently. There is a 20 percent chc of BKN025 cigs 08Z-16Z Thurs. No significant east wind component is expected. KBUR...Moderate to high confidence in TAF. There is a 20% chance of BKN020 conds through 16Z. && .MARINE...18/313 AM. For the Outer Waters, Small Craft Advisory (SCA) winds are lingering across the waters north of Point Sal (Zone PZZ670) early this morning, but expect winds to continue to weaken through the morning so allowed the advisory to expire. SCA winds will continue across the southern two zones south of Point Sal to San Nicolas Island (PZZ673 and PZZ676) through late tonight and accompanied by steep and choppy seas. For Thursday and Friday through this weekend, SCA headlines will be unlikely, though a few spots of marginal SCA winds cannot be ruled out (30% chance) from areas around San Miguel and Santa Rosa Islands toward Pt. Conception each afternoon and evening. For the Inner Waters north of Pt. Sal, SCA conditions are not expected through the period. For the Inner Waters south of Pt. Conception, SCA winds are expected across portions of the Santa Barbara Channel -- especially the western two-thirds -- this afternoon and evening, accompanied by steep and choppy seas. For Thursday and Friday through this weekend, SCA headlines will be unlikely, though a few spots of marginal SCA winds cannot be ruled out (30% chance) over the Los Angeles and Orange County waters within 20 NM from shore. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...Small Craft Advisory in effect from 3 PM this afternoon to 3 AM PDT Thursday for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Thursday for zones 673-676. (See LAXMWWLOX). && $$ PUBLIC...Rorke/Cohen AVIATION...Lund MARINE...Cohen/Lund SYNOPSIS...MW weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox