Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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646 FXUS66 KLOX 241644 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 944 AM PDT Tue Sep 24 2024 .SYNOPSIS...24/934 AM. Low clouds and fog will continue across coastal areas through the week with some afternoon clearing and below normal temperatures. Valley temperatures will begin a cool down today be at or below normal the rest of the week. Far interior areas will remain above normal. Otherwise, a quiet weather pattern will continue. && .SHORT TERM (TDY-THU)...24/942 AM. ***UPDATE*** A solid coastal marine layer, about 1700 feet deep in LA County sloping down to around 1100 feet along the Central Coast, is making late September feel more like mid June. This will be a quiet week of weather with below normal temperatures across coast and valleys, but several degrees above normal in the Antelope Valley. A weak but stubborn upper low will linger just a few hundred miles west of the coast, maintaining a weak cyclonic flow aloft that will provide a favorable pattern for stratus development. This pattern may continue well into next week with very little day to day changes in temperatures as well. ***From Previous Discussion*** An unexpected eddy spun up just before midnight and has lifted the marine layer a few hundred feet enough to bring plenty of low clouds to the vlys and also to eliminate most of the dense fog. The deeper marine air intrusion will also bring noticeable cooling to the vlys. Low clouds will hug the coast and many beaches will remain cloudy all day. Not much change in the cloud pattern for Wed and Thu skies will be clear save for the night through morning low clouds which will extend into the vlys. Hgts will fall through the two day period as a long wave trof develops in the east pac and moves closer to the coast. Look for 2 to 4 degrees of cooling Wed and 1 to 2 degrees on Thu. Max temps will take on an early July like distribution with the interior sections running 4 to 8 degrees above normal and the csts and vlys (swaddled in marine air) will end up 3 to 6 degrees below normal. .LONG TERM (FRI-MON)...24/327 AM. The benign weather will continue late this week and into the weekend. Hgts rise a few dam on Friday as a weak upper high pushes into the state from the east. Look for 2 to 4 degrees of warming across the board. A cooling trend will develop on Saturday and continue into Sunday as troffing spreads over the state and onshore flow increases. The night through morning low clouds will penetrate a little deeper into the vlys and will persist a little longer at the beaches. There will be stronger afternoon west winds across the mtns and the Antelope Vly. Look for 2 to 4 degrees of cooling on Saturday and 1 to 2 degrees on Sunday. The csts/vlys will end up 4 to 8 degrees below normal while the interior will remain 3 to 6 degrees above normal. Not the best confidence in the forecast for early next week but the most likely scenario is for high pressure to move closer to the state from the east and kicking off a slow warming trend. && .AVIATION...24/1252Z. At 12Z at KLAX, the marine layer was 1700 ft deep. The top of the inversion was near 2700 ft with a temperature of 28 deg C. High confidence in desert and KPRB TAFs. Low to moderate confidence in remainder of TAFs. Low clouds were widespread in coastal areas and have pushed into the San Gabriel Valley, portions of the San Fernando Valley, and portions of the Ventura County valleys. Conds were mostly LIFR to VLIFR. Expect skies to clear by mid morning in the valleys, and late morning across interior sections of the coastal plain. Cigs will likely continue into the afternoon near the coast, and possibly all day. Expect widespread low clouds in coastal and lower valley areas tonight, with IFR to LIFR conds expected, and local VLIFR conds. KLAX...Low confidence in TAF. There is a 40% chance that cigs will scatter out between 20Z and 03Z. High confidence in no significant easterly wind component. KBUR...Moderate confidence in TAF. There is a 20% chance that cigs will linger until 18Z. There is a 20-30% chance that cigs will not arrive tonight until after 08Z. && .MARINE...24/850 AM. For the Outer Waters (Central Coast south to San Nicolas Island), moderate to high confidence in the forceast. High confidence in the northern zone (10 to 60 NM off the Central Coast) remaining below Small Craft Advisory (SCA) level thru Thursday, then there is a 40-50% chance of SCA winds and seas Thurs afternoon thru evening. In the two Southern Zones (Pt Sal to San Nicolas Islands), moderate confidence in conditions remaining sub advisory level thru tomorrow afternoon, then there is a 40-60% chance of SCA level winds form Pt Conception to San Nicolas Island in the afternoon thru evening tomorrow and Thurs. Then, moderate confidence in the Outer Waters remaining sub advisory Friday thru the weekend. For the Inner Waters along the Central Coast, high confidence in conditions remaining sub advisory level thru the period, with highest chances (20-30%) of SCA conditions Thurs afternoon thru evening. For the Inner Waters south of Pt Conception, moderate confidence in winds and seas remaining below SCA level thru tomorrow morning. Local gusts to 25 kt are possible (20-30%) this afternoon thru evening in the Santa Barbara Channel and from Anacapa Island to Pt Dume. Higher confidence in more widespread SCA level winds in this area and the San Pedro Channel tomorrow afternoon thru evening. Then, moderate confidence in winds remaining sub advisory thru the weekend. A shallow marine layer will bring at least patchy dense fog thru tomorrow, especially in the afternoon thru evening hours. Please refer to our marine weather statement for more information. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC...MW/Rorke AVIATION...DB MARINE...Lewis SYNOPSIS...MW weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox