766 FXUS66 KLOX 170107 AFDLOX Area Forecast Discussion...UPDATED National Weather Service Los Angeles/Oxnard CA 507 PM PST Sat Dec 16 2017 .SYNOPSIS... Winds will increase and shift overnight to the northeast over Los Angeles and Ventura counties. Temperatures will remain slightly above normal early next week. Below normal temperatures and another round of strong offshore flow will begin by Wednesday. && .SHORT TERM...(TDY-TUE) The strong and gusty NW to NE winds quickly developed as expected over the SBA County mtns and S coast this morning. Winds quickly ramped up with gusts reaching 65 mph at Montecito Hills, 55 mph at the Santa Barbara Botanic Gardens, and 53 mph at Tepusquet. With winds stronger than expected, had upgraded the Wind Advisory to a High Wind Warning for the SBA County mtns, but winds have already peaked and were below warning thresholds early this afternoon, so downgraded the warning to a Wind Advisory thru 6 PM for the zone update. A Wind Advisory will also continue for the SBA County S coast thru 6 PM. Needless to say, the strong N winds around Montecito has caused a significant flareup of the Thomas Fire in the hills above Montecito to near Santa Barbara, and will continue to affect the fire thru the afternoon. The Montecito Hills RAWS station was affected by the fire and was reported to have burned. The last report we received from the Montecito Hills RAWS was at 1647Z when winds were gusting to 62 mph. Skies over the forecast area this morning were mostly sunny except for areas of smoky skies from the S SBA County coast thru swrn VTU County. Gusty NW to N winds continued to affect the L.A./VTU County mtns and foothills this afternoon, with the strongest winds approaching advisory levels along the I-5 corridor. An upper level trof just E of the forecast area this afternoon will move off to the SE as it deepens into an upper level low over nwrn Mexico by this evening. The upper low will meander between nwrn Mexico into srn AZ tonight thru Sun then into New Mexico on Mon. As the upper level trof moves to SE and E of the area, upper level ridging will gradually build in thru the period. Upper level ridging will then persist over srn CA Mon night and Tue. The passage of the upper level trof will help to build surface high pressure into the Great Basin, and offshore pressure gradients will increase quickly thru tonight. The latest NAM was forecasting the LAX-DAG gradient to lower to -6.1 mb by 12Z Sun. In addition, mid and upper level support for gusty offshore winds will increase thru tonight, along with good cold air advection. These ingredients will support another round of gusty Santa Ana winds over swrn CA from this evening through Sun afternoon. The gusty winds will turn to the NE in the L.A./VTU mtns by early this evening then descend to the lower elevations including coastal areas thru the evening hours then continue into Sun afternoon. 850 mb winds up to 45 to 50 kt and 950 mb winds up to 45 kt are predicted by the latest NAM tonight into Sun morning. Gusts up to 55 mph are expected in the mtns including the Santa Monica Mtns, and gusts up to 40 to 50 mph are expected for the wind-prone vlys and coastal areas, including the Santa Clara River vly and other vlys and hills of sern VTU County, the Santa Clarita Vly, San Fernando Vly, and the VTU County coast and coast of L.A. County from Malibu to the Hollywood Hills. Wind advisories are in effect for these areas tonight thru Sun afternoon. Please see the latest Non-Precipitation Weather message (LAXNPWLOX) for further details on the High Wind Warning and Wind Advisories. For Sun night into Mon morning, there will continue to be gusty NE winds in the wind-prone areas of VTU/L.A. Counties, and winds may be close to advisory levels as times. However, upper-level support for widespread advisory-level winds will diminish. At this time, do not anticipate the Wind Advisories for L.A./VTU Counties to be extended into Mon, altho there is still a small chance of that happening. Winds will remain weakly offshore Mon night into Tue morning, then turn onshore by Tue afternoon. With all the dry offshore flow moving in again, skies will be mostly clear across the forecast area tonight thru Mon. Mostly clear skies should then continue into Tue, altho it cannot be completely ruled out that a few marine layer clouds may push to the Central Coast or the L.A. County coast by early Tue morning. Temps will be mainly near normal to slightly above normal over the region Sun thru Mon, with the coolest day for interior areas on Sun. Temps are expected to warm to several degrees above normal for all areas on Tue. .LONG TERM...(WED-SAT) There are some differences in medium range between the EC and GFS, especially Fri and Sat. There will be an upper level trof approaching srn CA from the N on Wed. This inside slider upper trof will pass mostly NE and E of the forecast area on Wed, altho the srn fringe of the trof will brush by. The EC is a bit more progressive with the upper trof, moving it well to the E for Thu. The GFS drops additional energy on the back side of the trof and develops and upper low over AZ on Thu and Thu night, then into nrn Baja on Fri before moving it E on Sat. Both the EC and GFS keep an upper ridge off the W coast Thu and Fri. The EC weakens this ridge on Sat as a broad upper trof moves into the Great Basin, while the GFS hangs onto the upper ridge along the W coast. Went with a general blend of the two models. Dry conditions will persist over swrn CA thru the period. The upper trof passing by late Wed and Thu will impart another Santa Ana wind event which could be quite strong from late Wed night thru Thu night. Gusty N winds will affect the SBA County mtns and S coast Wed evening then transition to NE and gusty over the the wind-prone areas of VTU/L.A. Counties. Winds are projected to be at least advisory levels, with a chance some areas could have warning-level winds. The offshore flow will weaken some but continue Fri into Sat as well, especially over VTU/L.A. Counties. Skies will be mostly clear thru the period with temps generally a few degrees above normal except mostly near normal on Thu. && .AVIATION...17/0050z. At 23z, there was a deep moist layer up to around 2750 feet at KLAX. The top of the inversion was around 3700 feet with a temperature near 11 degrees Celsius. VFR conditions are expected throughout the period, except for a chance of MVFR conditions in smoke at coastal and valley terminals and a chance of VLIFR to LIFR conditions at KPRB. Periods of moderate to strong wind shear and turbulence are possible at all terminals through 20Z. KLAX...There is a 30 percent chance of MVFR conditions in smoke at KLAX. Moderate to strong wind shear and turbulence is expected between 08Z and 20Z. KBUR...There is a 20 percent chance of MVFR conditions in smoke at KLAX. Moderate to strong wind shear and turbulence is expected between 08Z and 20Z. && .MARINE...16/200 PM. Across the outer waters... Gale force NW winds will continue through late tonight. Small Craft Advisories (SCA) will have to be issued once the Gale Warning ends late tonight as winds will remain elevated through Sunday morning and seas through at least the afternoon. Winds will likely reach SCA levels again Wednesday. Across the inner waters north of Point Sal... SCA level winds will have a lull in the afternoon then elevate again and continue through late tonight. No lull is expected in the hazardous seas and there is a thirty percent chance that SCA conditions due to hazardous seas will linger through Sunday morning. Winds will likely reach SCA levels again Wednesday. Across the inner waters south of Point Conception... Winds will reach SCA levels across the western portion of the Santa Barbara Channel through this evening. The strongest winds will be near shore. SCA level NE winds are expected from Ventura to Anacapa Island south to Santa Monica and from San Pedro to Catalina Island tonight through Sunday. These winds will create choppy seas and short period wind waves which could affect Avalon and Two Harbors. SCA winds are possible again Wednesday. There will continue to be areas of smoke from the Thomas Fire over portions of the coastal waters, mainly from the waters west of Ventura County through the Santa Barbara Channel and over portions of the outer waters. Visibilities could locally drop to 2 NM or lower at times today in the inner waters. && .FIRE WEATHER...16/200 PM. Red Flag Warnings in effect until 10 pm this evening for the Santa Barbara County Mountains and South Coast. A Red Flag Warning is in effect for much of Los Angeles and Ventura Counties through from 9 PM tonight to 8 PM Sunday. Strong upper level winds behind the passage of an upper level disturbance combined with strengthening north-south pressure gradients caused a significant increase in winds across the Santa Barbara county mountains and south coast this morning, causing major impacts on the Thomas Fire. The SBA-Bakersfield gradient peaked at -6.2 mb this morning. Wind gusts of 35 to 50 mph were common this morning across these areas, with isolated gusts up to 65 mph observed in the Montecito Hills. While humidities have modified somewhat today, the strong north to northeast winds through this evening will continue to maintain dangerous Red Flag conditions for the Santa Barbara county mountains and south coast. As a result of these strong winds, there will be very rapid fire spread, long range spotting, and extreme fire behavior observed at the Thomas Fire and any new fire ignitions. In addition, there will be gusty north winds across the Ventura county mountains today, especially near the Highway 33 and Interstate 5 corridors which will impact the Ventura county portion of the Thomas Fire. For the remainder of Ventura and Los Angeles Counties, the Santa Ana winds are expected to begin this evening, then peak overnight into Sunday morning when gusts between 35 and 55 mph will be likely. A Red Flag Warning is in effect for tonight through Sunday evening for much of Los Angeles and Ventura Counties. There is the potential for another round of gusty Sundowner winds Wednesday into early Thursday, Another period of Sundowner winds will be possible for Santa Barbara county from Wednesday into Wednesday night, followed by a potential extended period of Santa Ana winds Thursday into next weekend. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...High Surf Advisory in effect until 9 AM PST Sunday for zones 34-35. (See LAXCFWLOX). Wind Advisory in effect until 6 PM PST this evening for zones 39-52. (See LAXNPWLOX). Wind Advisory in effect from 9 PM this evening to 3 PM PST Sunday for zones 40-41. (See LAXNPWLOX). Wind Advisory in effect until 3 PM PST Sunday for zones 44>46-53-54-88-547. (See LAXNPWLOX). Red Flag Warning in effect until 10 PM PST this evening for zones 239-252. (See LAXRFWLOX). Red Flag Warning in effect from 1 AM to 8 PM PST Sunday for zones 240-241. (See LAXRFWLOX). Red Flag Warning in effect from 9 PM this evening to 8 PM PST Sunday for zones 244>246-253-254-288-547-548. (See LAXRFWLOX). PZ...Small Craft Advisory in effect until 3 AM PST Sunday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 3 PM PST Sunday for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect from 3 AM to 3 PM PST Sunday for zone 655. (See LAXMWWLOX). Gale Warning in effect until 3 AM PST Sunday for zones 670-673-676. (See LAXMWWLOX). && .HAZARD POTENTIAL OUTLOOK...(TUE-SAT) Critical fire weather conditions are possible with gusty Sundowner winds Wednesday night and gusty offshore winds Thursday and Friday. && $$ PUBLIC...Sirard AVIATION...Hall MARINE...Kj FIRE WEATHER...Gomberg SYNOPSIS...TF weather.gov/losangeles