Area Forecast Discussion
Issued by NWS Los Angeles, CA

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914 FXUS66 KLOX 220523 AFDLOX Area Forecast Discussion...UPDATED National Weather Service Los Angeles/Oxnard CA 1023 PM PDT Sat Sep 21 2024 .SYNOPSIS...21/726 PM. A warmer and drier pattern will establish through Monday as high pressure aloft builds over the region. A warmer air mass will likely remain in place through much of next week away from the coast, with the hottest daytime temperatures forecast for Monday. Onshore flow will persist through the period, maintaining night through morning low clouds and fog for coastal areas and some of the valleys. && .SHORT TERM (SAT-TUE)...21/741 PM. ***UPDATE*** A quiet weather pattern is in store for Southwest California through the short term, and into much of next week. Building high pressure aloft will cause the marine layer to shrink somewhat tonight into Sunday morning, with less extensive low clouds than last night, and likely earlier clearing trends. Stratus tonight is expected to move over the coastal areas and the coastal valleys, and with weakening onshore flow, expect good clearing for all areas in the afternoon. High temperatures will rise 6 to 12 degrees away from the coast compared to today`s highs, with 2 to 5 degrees of warming near the coast. As the ridge aloft strengthens into Monday, the marine layer will shrink further, with overnight low clouds confined to coastal areas and temperatures will bump up another few degrees. Peak highs on Monday will be in the mid 90s to around 100 degrees in the warmest valleys. ***From Previous Discussion*** A slow clearing marine layer kept coast and valleys relatively cool today, mostly 60s and 70s, while interior areas warmed up considerably. At least some of that interior warming will migrate towards the valleys and coast Sunday into next week as building high pressure aloft and weakening onshore flow combine to dramatically lower the marine layer depth. Highs Sunday expected to rise 10 degrees over today across the valleys and 2-5 degrees closer to the coast. The marine layer, which was 3000` this morning south to 1000` north, is expected to be cut in half by Sunday and Monday, resulting in much earlier clearing at least for inland areas. Another 3-6 degrees of warming expected Monday bringing warmest valley highs to the mid to high 90s, roughly 4-8 degrees above normal. A slight increase in onshore flow is expected Tuesday afternoon that will cool temperatures a couple degrees across coast and valleys but either little change or slight warming across the interior. .LONG TERM (WED-SAT)...21/148 PM. Overall very quiet weather expected across southwest California the rest of next week with most of the ensemble based guidance maintaining temperatures at near to slightly above normal through the period. However, there is increasing spread in the ensemble solutions later next week resulting is decreasing confidence in the forecast. None of the solutions show rain south of the Bay area, but there are some solutions with a deeper trough along the West Coast Thu-Sat with cooler than normal temperatures. && .AVIATION...
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22/0522Z. At 0437Z at KLAX, the marine layer was 800 ft deep with an inversion up to 4100 ft and a maximum temperature of 22 C. High confidence in TAFs for KPRB, KPMD, and KWJF. Moderate confidence for all coasts and valleys. Arrival and clearing of cigs may be off by +/- 2 hours. Cigs may be off by 1 category at times, with periods of LIFR conditions possible for coastal sites from 12Z-17Z. There is a 30% chance of no cigs for KBUR and KVNY. KLAX...Moderate confidence in TAF. Arrival and clearing of cigs may be off by +/- 2 hours, and cigs may be off by 1 category at times. No significant east wind component expected. KBUR...Moderate confidence in TAF. Arrival and clearing of cigs may be off by +/- 2 hours, and there is a 30% chance of no cigs at all.
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&& .MARINE...21/807 PM. For the Outer Waters (Central Coast south to San Nicolas Island), moderate to high confidence in winds and seas remaining below Small Craft Advisory (SCA) level thru Wednesday, except for a 50% chance for low end SCA level wind gusts near Pt Conception Sunday evening thru late night. Then there a 30-50% chance of SCA level wind gusts beginning late Wednesday afternoon and evening, then higher confidence for Thursday and Friday, which will also lead to building steep seas. For the inner waters along the Central coast, high confidence in conds remaining below advisory levels through early Thursday, with moderate confidence in increasing winds in the afternoon Thursday and Friday. For the Inner waters south of Point Conception, moderate confidence in conditions remaining below SCA levels through Wednesday. Sunday afternoon, there is a 40% chance of local low end SCA gusts in the far western portion of the Santa Barbara Channel, the San Pedro Channel, and off the coast of Malibu. Additionally, there is a 30-40% chance of SCA level winds across the western areas Wednesday thru Friday in the afternoon thru evening hours. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC...MW/Smith AVIATION...Schoenfeld MARINE...Lewis/Schoenfeld SYNOPSIS...Smith weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox