Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 11/21/21

Area Forecast Discussion
National Weather Service Louisville KY
920 PM EST Sat Nov 20 2021 .Forecast Update... Issued at 919 PM EST Sat Nov 20 2021 A warm advection band of light rain is lifting northeast through southwestern Indiana, but much of this is not hitting the ground and/or not measurable in the LMK CWA. 0105z SDF AMDAR sounding shows a massive layer of dry air persisting below 800 mb. Low-level forcing also remains weak, but the southwesterly LLJ will steadily increase off to the southwest overnight. Southern Indiana and KY counties along the river will see much greater rainfall coverage and accumulations from about 3 AM EST through the mid-morning hours. && .Short Term...(This evening through Sunday) Issued at 230 PM EST Sat Nov 20 2021 Not a bad November Saturday across the Ohio Valley, with seasonable temperatures and a decent amount of sunshine filtered by mid/high clouds in the return flow. Plenty of low-level dry air in place, which will keep us dry well into tonight. Upper-level shortwave trof over the Intermountain West will kick into the Plains by Sunday morning, with low-level jetting and isentropic lift touching off some light rain by daybreak over southern Illinois and Indiana. Will keep the evening dry but ramp POPs up to likely after midnight in southern Indiana with lesser chances over Kentucky cutting off sharply south of the Western Kentucky and Bluegrass Parkways. Low pressure intensifying between Lake Superior and James Bay will push a cold front toward the Ohio Valley on Sunday, with a well focused moisture feed along the front. PWAT values just north of 1 inch, but it`s a progressive enough front and instability is weak to nonexistent. Rainfall amounts will run around a half inch, perhaps touching 3/4 of an inch over toward Lake Cumberland. Lapse rates overall don`t support thunder, with only a small sliver of elevated instability developing over south-central Kentucky. Can`t completely rule it out but probabilities are too low to mention. .Long Term...(Sunday night through Saturday) Issued at 225 PM EST Sat Nov 20 2021 Sunday Night - Wednesday... Rain will be tapering off from west to east Sunday evening as the surface cold front exits off to the east. Under steady northwesterly flow, cooler air will advect into the region with low temperatures dipping into the upper 20s to lower 30s Monday morning. In the wake of Sunday`s system, deep upper troughing will remain over the eastern CONUS into Tuesday before broad ridging aloft progresses eastward over the area Wednesday. At the surface, high pressure initially located over the mid MS Valley will gradually drift towards the region, eventually moving off to the east Wednesday. Tuesday morning looks to be the coldest of the period as surface high pressure sits directly overhead, with lows dropping into the lower 20s and perhaps even into the upper teens. Temperatures will then gradually moderate towards normals as southerly flow takes hold on the back side of the high Wednesday, with afternoon temps warming into the lower to mid 50s. Thursday - Saturday... Pattern begins to change heading into Thursday as large upper trough pushes across the north-central CONUS, with a mid-level low potentially closing off over the southern Ontario/Upper Great Lakes region by Thursday night. At the surface, an area of low pressure will lift NE out of the Upper Midwest through central Ontario, sending another cold front towards the region. Overall there is general agreement amongst model guidance that the NE-SW oriented cold front will begin to push into southern IN by Thursday morning/early afternoon and continue across the area into the evening before exiting off to the east Thursday night. However, this is still a ways out so may continue to see minor shifts in the timing. Depending on how quickly moisture moves out of the area and colder air move in, may see some snowflakes mix in on the backside of the system. High pressure will once again push in behind the front resulting in mostly dry weather for Friday and Saturday. High temperatures will generally be in the 40s to lower 50s to end the week with lows in the mid 20s to lower 30s. && .Aviation...(00Z TAF Issuance) Issued at 650 PM EST Sat Nov 20 2021 IMPACTS: - VFR with increasing mid-level clouds tonight - Rain showers arrive around daybreak at SDF and HNB, early afternoon for BWG and LEX - Lower cig/vis Sunday afternoon with IFR likely DISCUSSION: SCT-BKN mid-level ceilings are forecast to thicken and gradually lower through the early morning hours of Sunday. HNB/SDF will see light rain showers move in 07-10z as the low-level jet increases from the southwest. Then from late morning through the afternoon, a band of showers will march east across the region accompanied by a significant lowering of ceilings. Expect lower vis to accompany the rain showers and low ceilings as well. S-SE winds will veer SW Sunday afternoon and W Sunday evening. CONFIDENCE: Medium-high on all elements. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...EBW Short Term...RAS Long Term...JML Aviation...EBW
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
612 AM PST Sat Nov 20 2021 .SYNOPSIS...20/327 AM. An offshore flow pattern in place across the area will bring a warming and drying trend through Monday. Gusty offshore winds are likely for portions of the area through the weekend and into early Monday. Cooler conditions are forecast for Tuesday and Wednesday as a weak weather system moves over the region. A few showers are possible, but mainly a cooling trend is expected. An another Santa Ana wind event is possible between Thanksgiving Day and Saturday. && .SHORT TERM (TDY-MON)...20/451 AM. The latest water vapor imagery shows what`s left of a frontal boundary pushing south through Monterey County early this morning. This mainly dry front will push south while continuing to wash out. Ahead of the boundary, a well-entrenched marine layer stratus pattern is in place. KLAX AMDAR soundings indicate a 1500 foot deep marine layer depth currently, which agrees well with NAM BUFR time height sections. As BUFR time height section suggest and surface observations verify, it is likely shallower along the Central Coast. Dense fog has developed across most coastal and valley areas north of Point Conception and a dense fog advisory was added through 9 am this morning. A dense fog advisory was also added for the San Fernando and San Gabriel Valleys as low clouds and fog have also turned dense in these areas similar to last night. Farther upstream, infrared satellite imagery and nighttime microphysics RGBs show offshore flow starting to establish over the San Francisco Bay area. Offshore flow will establish across portion of the region later today making for a tricky temperature forecast for the coast and lower valleys. These areas could remain mired in the depth of the marine layer and keep the air mass on the cooler side today. The forecast goes warmer than forecast guidance for the valleys, foothills, and mountains but remains near to slightly cooler than forecast guidance for the coastal locales. Northeast low-level flow developing later this morning will likely drive weather pattern through the weekend. Gusty Santa Lucia winds will develop later this morning as the offshore push establishes up north then takes a firmer hold across Los Angeles and Ventura Counties tonight. Wind advisories were added for gusty Santa Lucia winds from late this morning through Sunday morning, and for gusty Santa Ana winds from late tonight through Monday afternoon. There is some concern that winds could reach damaging levels in some spots late tonight and into Sunday morning. Deterministic 00Z NAM-WRF solutions put 950 mb and 850 mb winds on the upper- threshold for high wind warning levels, but 06Z solutions have backed off. EPS ensemble members also indicate a similar stance for K3A6 keeping gusts between 45 and 55 mph. A few perturbations do increase winds above 55 mph to around 60 mph. Confidence is highest with a high-end advisory moderate Santa Ana wind event, but this will need to be monitored by future shifts for strengthening. Temperatures remain on the warm side of forecast guidance for Sunday and Monday and toward the higher end of EPS ensemble members for the Southland, including KBUR, KCMA, KCQT, KLAX, and KLGB. Temperature across most of the coastal and valley locations will likely range between the upper 70s and upper 80s on Sunday. Some cooling is possible on Monday, but it will depend much upon how quick the flow pattern transition from offshore to onshore. Ensemble members lean cooler in the EPS for most sites, local knowledge might trump the coarseness of the ensemble model resolution. Local knowledge suggest that transition days can be tricky and it is best to take a warmer stance south of Point Conception. .LONG TERM (TUE-FRI)...20/450 AM. A upper-level trough near 30N and 135W this morning will likely phase with a shortwave dropping down the state this evening and consolidate offshore to the southwest of Los Angeles over the weekend. This trough will then lift northeast into the region. Local knowledge suggests that the forecast models struggle with troughing to the southwest of the region and the forecast should lean wetter. Deterministic models hint at a sizable cloud mass moving northeast with it, but ensemble members are struggling pick up on it in the QPF values. A few members of CMC ensembles do bring measurable rain to the KEMT, KPOC, and KAVX. PoPs were nudged higher for Monday night and into Tuesday across Los Angeles County as the trough lifts out, then a quick hitter shortwave drops in behind it between Tuesday night and Wednesday. A cooler air mass will spread in behind the shortwave for Wednesday and temperatures forecast break away from NBM values for this period. Future shifts will need monitor this portion of the forecast period for any changes as this portion of the forecast could become impactful. Almost all ensemble members of the EPS and GEFS indicate offshore flow developing between Thanksgiving Day and the end of the week. Deterministic solutions give credence to a possibly stronger event than previously surmised as decent northeast winds develop at the middle levels of the atmosphere. With still much variation in the across the CMC, GEFS, and EPS ensemble, confidence sits highest in offshore flow developing and a warming and drying trend establishing, but less confidence exists in the timing and strength of the event. && .AVIATION...20/1411Z. At 1230Z at KLAX, the marine layer was 1600 feet deep. The top of the inversion was around 3200 feet with a temperature of 15C. Widespread low clouds in all coastal and most valley areas. Conds were mostly LIFR to VLIFR, except IFR to low MVFR across coastal sections of L.A. and VTU Counties. Expect skies to clear by mid to late morning in the valleys, and by noon near the coast. There is a chance that clouds could linger once again at some beaches into the afternoon. Low clouds may return to some coastal areas this evening, with generally IFR to LIFR conds, but will likely clear overnight as flow turns offshore. Gusty NE winds will begin to affect the mtns and valleys of L.A. and VTU Counties by late evening with mdt to stg UDDF and some LLWS. KLAX...Moderate confidence in the 12Z TAF. There is a 20-30% chance that cigs will slip into the IFR category thru 16Z. There is a 20% chance that cigs will could linger through 21Z. There is a 20% chance that skies will remain clear tonight. KBUR...Moderate confidence in the 12Z TAF. There is a 20% chance that cigs will scatter out as early as 16Z. There is 20% chance that there will be a period of IFR cigs between 06Z and 10Z tonight. && .MARINE...20/527 AM. For the outer waters, fairly high confidence in the forecast. Winds are expected to drop below Small Craft Advisory (SCA) levels later this morning. There is a 30% chance that SCA level winds will continue into this evening. There is a 30% chance of SCA level NE winds across portions south of San Miguel Island and north of San Nicolas Island on Sun. Otherwise, SCA conds are not expected Sun thru Mon. SCA level NW winds are likely Tue thru Wed. For the Inner Waters north of Pt. Sal, moderate confidence in the forecast. There is a 20-30% chance of SCA level NE winds near shore late tonight Sun morning. SCA level NW winds are expected Tue, then there is a 40% chance of SCA level NW winds Wed. For the Inner Waters south of Pt. Conception, moderate to high confidence in the forecast. Late tonight and Sun, and again late Sun night/Mon morning, SCA level NE winds are likely from the eastern Santa Barbara Channel south to Santa Monica. There is a 20-30% chance of SCA level NE winds affecting Avalon Harbor. There is a 40% chance of SCA level W-NW winds across western SBA Channel Tue afternoon and evening. Otherwise, winds and seas will remain below SCA levels Mon afternoon thru Wed. && .FIRE WEATHER...20/455 AM. A Red Flag Warning remains in effect for the Sunday/Monday time period due to increased confidence of Red Flag conditions in these areas. A Fire Weather Watch remains in effect for Sunday across the mountains of Santa Barbara and San Luis Obispo counties due to less certainty in these areas reaching Red Flag thresholds. Northeast to east Santa Ana winds are still on track to increase late Saturday Night into Sunday, with the peak winds expected Sunday morning and afternoon. During this peak, offshore wind gusts of 35 to 55 mph are expected across Los Angeles and Ventura Counties, except isolated gusts up to 60 mph in favored mountains and foothills. In addition, wind gusts of 30 to 40 mph could extend into the mountains of Santa Barbara and San Luis Obispo counties on Sunday. Gusty Santa Ana winds are expected to continue into Monday morning, however wind gust speeds are expected to be 10 to 15 mph less than Sunday. Humidities are expected to fall to around 15 to 20 percent by mid morning Sunday, potentially lowering to between 8 and 15 percent by Sunday afternoon and evening, and again on Monday. Temperatures generally look to peak between 75 and 85 degrees. The potential for Red Flag conditions is around 80 percent for Los Angeles and Ventura Counties, resulting in the upgrade to the Red Flag Warning. The confidence in Red Flag Warning conditions for the mountains of Santa Barbara and San Luis Obispo counties remains around 50 percent, resulting in less certainty in an upgrade to Red Flag Warning for those areas. Conditions are expected to improve Monday night into Tuesday. There is the potential for another round of weak to moderate offshore winds and dry conditions Wednesday through Friday. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Dense Fog Advisory in effect until 9 AM PST this morning for zones 34>37-46-547. (See LAXNPWLOX). Wind Advisory in effect until 8 AM PST Sunday for zone 34. (See LAXNPWLOX). Wind Advisory in effect from 3 AM Sunday to noon PST Monday for zones 40-41. (See LAXNPWLOX). Wind Advisory in effect from 9 PM this evening to 3 PM PST Monday for zones 44>46-53-54-88-547. (See LAXNPWLOX). Red Flag Warning in effect from 9 AM Sunday to 3 PM PST Monday for zones 240-241-244>246-253-254-288-547-548. (See LAXRFWLOX). Fire Weather Watch in effect from Sunday morning through Sunday evening for zones 251-252. (See LAXRFWLOX). PZ...Small Craft Advisory in effect from 3 AM Sunday to noon PST Monday for zones 650-655. (See LAXMWWLOX). Small Craft Advisory in effect until 9 AM PST this morning for zones 670-673-676. (See LAXMWWLOX). && .HAZARD POTENTIAL OUTLOOK (MON-FRI). Critical fire weather conditions and gusty Santa Ana winds are likely into Monday. Another Santa Ana wind event is possible for the latter half of week. && $$ PUBLIC...Hall AVIATION...DB MARINE...DB FIRE...Hall/Gomberg SYNOPSIS...Hall