111 FXUS66 KLOX 231701 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 1001 AM PDT Wed Oct 23 2019 .SYNOPSIS...23/852 AM. Weak to locally moderate Santa Ana winds will continue today over portions of Ventura and Los Angeles counties. Santa Ana winds will strengthen Thursday into Friday leading to critical fire weather conditions in many areas as well as hot temperatures near the coast. Temperatures will start cooling on Saturday into early next week. && .SHORT TERM (TDY-FRI)...23/947 AM. Another very warm Fall day across the region with highs in the mid 80s to mid 90s. This is 4-8 degrees cooler than yesterday and below records but still 10-15 degrees above normal. Primary weather feature in the short term is the strong Santa Ana expected for Thu/Fri which still looks on track. The GFS remains by far the weakest of the solutions but even the GFS MOS guidance is supporting at least advisory level winds across the usual favored Santa Ana wind areas of LA/Ventura Counties. Meanwhile, the NAM and ECMWF along with local hi resolution models are all advertising strong advisory level and some warning level winds down to lower elevations, possibly even the interior portion of the Oxnard coastal plain. So while there is a notable lack of cold air advection in place the strong upper level support and LAX-DAG gradients near or in excess of 8-9mb should be enough to drive down the core of strongest winds (50-55kt) between 850 and 900mb to the surface. Will likely be converting the high wind watches to the warnings for most of the areas currently in the watch, though am less confident in warning level winds in the San Fernando Valley. ***From previous discussion*** The trough will sharpen as it digs into the southern Rockies and into the Four Corners area tonight and Thursday. The upper high in the eastern Pacific will amplify just off the West Coast. This will set up a northerly flow pattern aloft across California. At the surface, low level gradients will turn sharply offshore tonight and Thu morning. The EC and WRF continue to show stronger offshore gradients than does that GFS, but the EC has been very consistent, so have placed a bit more faith in its solution. Along with the increasing offshore gradients, northeast winds at 850 mb increasing to about 55 knots across portions of L.A. and VTu Counties Thu morning, and there is a broad area of fairly strong subsidence. The only ingredient that is not completely ideal is that there is a lack of good cold advection, and for this reason, have refrained from upgrading the High Wind Watches to Warnings at this point. In the end, all the other factors may end making up for the lack of cold advection. Gradients will remain strongly offshore Thu night and Fri, but upper support should weaken. It appears that the most likely time period for High Wind Warning level winds would be Thu into Thu evening for areas under the High Wind Watch, but gusty, at least advisory level winds will linger through late Fri morning or early Fri afternoon. Have issued Wind Advisories for coastal sections of VTU County and for coastal sections of L.A. County (for areas mainly from Malibu to the Hollywood Hills) for very late tonight through early Fri afternoon, with the strongest winds expected Thu. Winds could actually get close to High Wind Warning levels across portions of the Ventura County Coastal Plain on Thu. There will likely be some cooling across the mountains, deserts and possibly the interior valleys on Thu, while there may be some warming near the immediate coast. There should be several degrees of warming in most areas on Fri which should be quite a hot day. Highs should rise well into the 90s across interior sections of the coastal plain and in the valleys. Red Flag Warnings are in effect from late tonight through Friday evening for most of L.A. and VTU Counties for the moderate to strong Santa Ana winds and very low relative humidities. .LONG TERM (SAT-TUE)...23/447 AM. An upper trough will drop into the northern Rockies on Sat, forcing the upper high over the region to the south and west into the Pacific. Offshore gradients will weaken quite a bit Sat morning, but there may still be some locally gusty NE winds, although well below advisory levels. Gradients may actually turn onshore during the afternoon. There should be several degrees of cooling, though temps should still be well above normal, and highs in the hottest valley locations may still reach 90 degrees. Beyond Sat, there are major differences in the models, and forecast confidence becomes much lower. The GFS is much more progressive, showing the trough dropping through the Rockies on Sunday, and moving into the Midwest on Monday and Tue, while an upper high builds into the West Coast. This would bring some additional cooling on Sunday, followed by some warming early next week. The 00Z operational run of the EC, on the other hand, shows the upper trough digging sharply to the west across Nevada on Sunday, evolving into a closed low over Central CA by early Mon. It is then forecast to drift into AZ on Tue. This is a much colder solution, and even would threaten at least eastern sections of the forecast area with some showers on Mon. With this feature, the EC has NOT be consistent. Therefore, have kept the current forecast as is, leaning towards the GFS next week given its better consistency. However, confidence is low. && .AVIATION...23/1659Z. At 1607Z, there was no marine layer at KLAX. High confidence in CAVU 18z TAFs. There will be a 30% chance for LLWS and UDDF across airfields across L.A. and Ventura County Coast and valley locations, especially after 12z Thu. KLAX...VFR conditions are expected through the 30-hour period. There is a 30% chance for easterly wind component to exceed 8 knots. KBUR...VFR conditions are expected through the period at this time. There is a 30 percent chance of wind shear and turbulence starting 10z Thu. && .MARINE...23/922 AM. Outer Waters...Winds will remain below Small Craft Advisory thresholds through at least this weekend. There is a 30% chance that SCA level gusts could occur across the western portion of the northern outer waters of zones (PZZ670-673) this afternoon through early evening. The exception would be the northern portion of the southern waters (PZZ676) where the potential for easterly Gale force gusts could occur across the northern portion Thursday morning through mid afternoon hours. Inner Waters N of Point Sal...Not anticipating any winds reaching SCA levels through this weekend. Inner Waters S of Point Conception...Winds will remain below wind advisory levels through late Wednesday evening. A strong Santa Ana wind event will develop pre dawn on Thursday. Northeast winds could strengthen quickly to Gale Force winds as early as 8 AM between Ventura and Malibu and out to the Channel Islands. A Gale Watch remains in effect early Thursday morning through the mid afternoon hours. Gusts to 35 knots will be possible in areas mentioned. Otherwise expect moderate to strong SCA level winds across the San Pedro Channel to Catalina Island. Mariners should be prepared for possibly choppy seas across east facing harbors including Avalon Harbor Thursday. There is a 60% chance that SCA level gusts will continue through Friday morning for the same areas. && .FIRE WEATHER...23/914 AM. Tonight through Friday, a moderate to strong Santa Ana wind event remains on track. Peak wind gusts between 45 and 65 mph are expected for much of Los Angeles and Ventura Counties, where a Red Flag Warning remains in effect. Santa Barbara and San Luis Obispo Counties will see elevated to brief critical conditions, with peak winds of 20 to 40 mph, but a Red Flag Warning is not anticipated. Humidities will lower to 2 to 9 percent and temperatures will remain well above normal with highs generally in the 90s. This has all the ingredients of a dangerous fire weather scenario, similar to or worse than the recent October 10-11 event that produced the Saddleridge Fire. The fuels and vegetation are critically dry. The expected weather will create an environment ripe for large and dangerous fire growth, especially Thursday and Friday. We urge everyone to be extremely cautious with any potential fire ignition sources. Fires have started from things like cigarettes, camp fires, welding or brush clearing equipment, and dragging towing chains. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Wind Advisory in effect from 5 AM Thursday to 3 PM PDT Friday for zones 40-41. (See LAXNPWLOX). High Wind Watch in effect from late tonight through Friday morning for zones 44>46-53-54-88-547. (See LAXNPWLOX). Red Flag Warning in effect from 1 AM Thursday to 10 PM PDT Friday for zones 240-241-244>246-253-254-288-547-548. (See LAXRFWLOX). PZ...Gale Watch in effect from late tonight through Thursday afternoon for zones 650-655-676. (See LAXMWWLOX). && .HAZARD POTENTIAL OUTLOOK (FRI-TUE). Hot and dry conditions along with strong Santa Ana winds are expected Friday, especially LA/Ventura Counties. Fire weather conditions will be critical to extreme. && $$ PUBLIC...MW/DB AVIATION...Sweet/Kaplan MARINE...Sweet/Kaplan FIRE...Kittell SYNOPSIS...Stewart weather.gov/losangeles