Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/18/21

Area Forecast Discussion
National Weather Service La Crosse WI
952 PM CST Wed Feb 17 2021 .UPDATE... Issued at 952 PM CST Wed Feb 17 2021 Radar at 952 pm is...a mess regionally. Weak forcing on the 275K surface and shortwave trough activity passing through while the lowest levels have a dry air mass to battle. But, some light snow down to about 4SM is being reported here and there. Some dustings of snow out there as well, but very hard to predict where. Will continue to have iso-sct snow showers overnight in the forecast. Working on an update for higher snow chances Thu afternoon and eve along and north of I-94 mainly. I think the models are underdoing this negatively tilted shortwave trough moving the area. Mesomodels now starting to trend up in precipitation coverage since 00Z runs or so. It is becoming more dynamic into WI in the mid- afternoon and into the early eve...looking like a light amount, higher snow chance event. Now 50% chances in northcentral WI, decreasing southward...about a 20% uptick. && .SHORT TERM...(This evening through Thursday) Issued at 201 PM CST Wed Feb 17 2021 Early afternoon radar imagery showed light snow continuing across south-central Minnesota and into northwest Wisconsin, mainly driven by isentropic ascent. Farther southeast, certainly seeing the effects of a dry layer up to about 700 mb, as there are plenty of radar returns, but nothing in the way of ground truth other than a few passing flurries seen on MNDOT webcams. RAP guidance has been persistent in showing isentropic ascent tapering off as we go through the afternoon and that seems to be panning out as radar returns have decreased in intensity over the past 1-2 hours or so. It does pick up again overnight as some weak shortwave energy slides through, so could see some flurries continue across the entire area through Thursday, but the lift does remain quite weak, so wouldn`t expect much in the way of accumulation. Once all snow comes to an end, could see up to around 1/2" along our border with NWS Twin Cities and lesser amounts to the southeast. Should any pockets of stronger forcing develop, it wouldn`t take much to get near 1" given the 18-20 to 1 snow to liquid ratios, but again, guidance remains persistent in isentropic ascent tapering off for a time this afternoon. Otherwise, we continue our gradual warming trend on Thursday, with highs in the teens and 20s, though there is a chance clouds could keep them a bit lower. .LONG TERM...(Thursday night through Wednesday) Issued at 201 PM CST Wed Feb 17 2021 Although small, chances for snow remain off to the east of the Mississippi River Thursday night. Any lingering precipitation will continue to exit the region Thursday night as high pressure builds in from the west and the deeper longwave trough slides off into the eastern CONUS. The region continues its slow warm up with afternoon high temperatures in the teens on Friday. Low temperatures will dip into the single digits above and below zero. Additional warming is in store through the weekend as 850 mb temperatures rebound to near -5C by Sunday and surface winds become more southerly over the weekend. High temperatures are expected to increase into the upper 20s to low 30s. Additionally, above freezing temperatures are still on track over the first half of the work week, with overnight lows decreasing only into the teens and 20s above zero. The next best chance for precipitation comes on Sunday, but there has been a decreasing trend from previous model guidance runs. The 17.00z GEFS is on the more aggressive side with this system producing higher snowfall accumulations across the region. However, the 17.00z ECMWF EPS is on the lighter side with several members even keeping the area completely dry. The general idea is that a low pressure system will pass to the south of the region. The question is how far north of the system will the shield of accumulating snowfall advance. The differences and spread between models is partially due to how each handles the mid- to upper- level flow. While surface temperatures will increase under ridging this weekend, the ridge itself would be relatively weak and flattened. The flow would also be somewhat split as two shortwaves move eastward through the region. One shortwave looks to move through southern Canada, while the second progresses through the central CONUS. How these separate waves potentially interact as they progress eastward is one of the many issues introducing such a spread between the models and ensemble members. Will continue to stick with the blended model guidance with bringing in slight chances for snow for much of the area. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 558 PM CST Wed Feb 17 2021 Periods of light snow or flurries summarizes the TAF period. A lull will occur into the evening, before more light snow moves in from the west overnight. It could be MVFR visibility -SN, but for now confidence is not high enough to include that in the TAF. Ceilings will likely come into the MVFR category however. Will have to keep an eye on late afternoon and evening on Thursday as a bit stronger weather system moves through. It develops as it shifts east, which could bring MVFR SN in that period, with a bit higher probability to KLSE. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ UPDATE...Baumgardt SHORT TERM...CA LONG TERM...Peters AVIATION...Baumgardt
Area Forecast Discussion
National Weather Service Binghamton NY
956 PM EST Wed Feb 17 2021 .SYNOPSIS... A disorganized series of upper level disturbances and weak coastal lows will bring an extended period of light to moderate snow to parts of the region starting in the pre-dawn hours Thursday morning, and extending into Friday. Snowfall amounts through Friday evening will range from 2 to 5 inches over the Southern Tier of New York, with 3 to 6 inches in the Catskills and Northeast Pennsylvania. Expect lighter amounts elsewhere in Central New York. Colder air will push into the region behind this system, bringing scattered lake effect snow showers to the area Friday night through Saturday, with some light accumulations possible. Sunday will be a fair weather day with high pressure building in. But an active pattern will continue next week with rain and snow moving through the area on Monday, with lake effect snow showers likely through mid-week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... 955 pm Update... Water vapor imagery shows the beginning of a baorclinic leaf like pattern over the midwest to middle Mississippi Valley as the core of the upper level wave was moving through eastern Texas at this time. As the moisture heads northeast it is taking on the classic warm air advection look with anticyclonic curvature at upper levels. Indeed models all show strong warm air advection tonight through Thursday as the above mentioned upper level wave moves northeast to the eastern Great lakes by 00z Friday. The 850 mb low will take a similar track with its attendant warm air advection (or isentropic lift if you prefer that coordinate system). This overall will bring a modest amount of moisture northward as it is lifted leading to widespread snowfall. Moisture is rather limited with this feature as it eventually weakens over NY Thursday night and Friday. This occurs as a coastal low gets going well offshore with the bulk of the moisture. So in the sum we are expecting a longer duration light to occasionally moderate snowfall with the highest amounts in northeast PA/Catskills and southern tier of NY. Overall these areas will see generally 3"-6" with locally higher amounts in the Poconos and Catskills. Farther north, from the Finger Lakes, Syracuse and Oneida County we are expecting around 2-4" of snow. The snow will begin first in a band across northeast PA between 06z and 09z. This is in response to a surge of warm air advection which leads to some frontgenetic forcing. We are beginning our snow earlier in northeast PA as all models, hi-resolution and even synoptic scale are showing this band. So we will begin the winter weathr advisory sooner in these areas to account for earlier snow onset. Again, moisture looks limited so we are expecting basically 1- 3" before dawn northeast PA. This will affect the morning commute down there. Then the snow likely will back off until strong warm air advection arrives later in the morning into the afternoon. This will be the main surge of light to moderate snow. Then NAM12 and hi res CMC both show another low-level jet at 850 mb which enhances lift Thursday night associated with the upper level wave. This will be another period of snow of central NY and northeast PA. Then for Friday continued lifting aloft from PV advection and a fairly decent mid to upper level short wave will continue light snows which will taper to lake enhanced snow showers later Friday. Made some tweaks to POP to further refine timing and temperatures. As for snowfall forecasts 18z runs had the following snowfall: 18z Euro 4"-7" in southern central NY and northeast PA/Catskills and 1"-4" farther north. 18z GFSv15 (operational) widespread 6-9 inches south and east of a Cooperstown NY to BGM to Towanda PA line in the BGM forecast area. 2- 6" northwest to Finger Lakes. GFSv16 6-8" ne PA and Sullivan Co and 3" to 6" southern tier and 1- 4" farther north. The 00z HRRR run had 5"-8" northeast PA with highest amount over higher terrain and in the Poconos/Sullivan County. The rest of central NY even our northern areas around Syracuse had 2-5" of snow with the latest HRRR. The 00z NAM 4-7" in northeast PA/Catskills, 3-5" in southern tier and 2-4" farther north in central NY. The 18z Canadian had 3-6" in northeast PA and 2-5" southern tier and 1-2" farther north to the Finger lakes. So we see no big reason to change significantly change snow amounts as 18z guidance is in line with going forecast. Just added more snow between 06 and 12z Thursday. But offset this a bit so as to not change total snowfall in northeast PA. 355 PM update... Widespread sunshine allowed temperatures to in the lower elevations in the Southern Tier and NE PA to climb up into the upper-20s this afternoon. Some lake effect clouds and a few flurries persisted further to the north. Some flurries will be possible into early this evening over the northern Finger Lakes and wrapping around in the Syracuse and Tug Hill Plateau areas. While clouds will begin to increase from southwest to northeast over night, dry air and a mostly clear start will allow temperatures to drop off pretty quickly. Single digits and perhaps a few below-zero readings will be possible by early morning over Oneida County. Increasing isentropic lift ahead of the approaching system will allow light snow to overspread NE PA before dawn, but the onset time of snowfall may struggle north of the NY/PA border as precip fights drier air. Snowfall looks likely by the AM commute in NE PA, but we`ll be right on the edge in the Southern Tier. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/... 355 PM update... Light snow will continue to slowly progress northward Thursday morning, as isentropic lift steepens across the area. Meanwhile, a series of shortwave troughs embedded in southwesterly flow aloft will move up the east coast, with weak surface lows developing just offshore. None of the shortwaves are particularly strong, and none of the surface lows really get to take off as the stronger northern stream trough remains well back over the western Great Lakes. Later Thursday, 850-700 mb frontogenesis band associated with a weak coastal low will slide off just to our south and east, and we may see a bit of a lull in the light snowfall over much of the area, especially the further west you go. Much of our anticipated event total snowfall (especially northwest of the NE PA and the Cats) depends on subsequent waves moving up the eastern seaboard. The NAM and GFS continue to be more generous over our area Thursday night into Friday, while the Canadian and Euro are more stingy. The former models are a little stronger with the the shortwave troughs coming up from the southwest, and develop a slightly stronger low at the surface to around 700 mb. The stronger lift allows for another band of snow to flare up Thu night into Friday, perhaps lingering over the eastern part of the CWA well into the afternoon. I leaned a little towards the NCEP model solutions here, though the 12Z GFS ensembles still suggests about an even split. Without the expected Thursday night/Friday flare- up, snowfall amounts near, north, and west of BGM might only end up in the 1 to 3 inch range. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... 400 PM Update: A west-northwesterly flow will develop behind the departing storm system Friday night. This will lead to lake enhanced snow as moisture wraps around. This will be mainly concentrated along and north of the NY Thruway corridor, before shifting southward towards the Finger Lakes region the second half of the night. Lows Friday night will likely be in the mid teens to lower 20s. Continued lake effect snow showers are expected on Saturday, especially across the Finger Lakes region. Otherwise, mostly cloudy skies with highs in the mid to upper 20s are expected. High pressure approaches from the west Saturday night, which will gradually end any lingering lake effect snow showers. This high pressure system will lead to quiet weather on Sunday with partly sunny skies and highs in the upper 20s to lower 30s. Clouds increase from west to east Sunday night ahead of the next system. A shortwave trough sweeps across the Central US and into the Northeast, bringing snow to the area late Sunday night through Monday. As temperatures increase above freezing throughout the day on Monday, rain may mix in with the snow, especially in the valley locations. Another shortwave is expected to quickly move through the area on Tuesday, likely bringing another round of a mix of rain and snow. Highs Tuesday are currently expected to be in the mid 30s to lower 40s. Then a weak lake effect response is expected Tuesday night into Wednesday. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... VFR conditions expected at all terminals through the early morning hours Thursday. A storm system will bring quickly deteriorating conditions with light snow from south to north beginning Thursday morning for KAVP, KBGM, KELM, and KITH and Thursday afternoon for KSYR and KRME. An earlier arriving snowband for KAVP could bring visibility down to below airport minimums during the early morning hours. KAVP, KBGM, KELM, and KITH will see below alternate minimum restrictions by Thursday afternoon as snowfall becomes more widespread. KSYR drops to IFR late in the TAF period, and KELM will only fall to MVFR. Confidence remains fairly high that all terminals will see light snow during this period. Outlook... Thursday afternoon through Friday...Snow and associated restrictions likely from a passing storm system. Friday night through Saturday...System lifts out Friday night, but then lake effect snow showers appear likely for several NY terminals. Sunday...Mainly VFR Monday...Another system will likely bring light snow and associated restrictions. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...Winter Weather Advisory from 3 AM Thursday to 7 PM EST Friday for PAZ040-048-072. Winter Weather Advisory from 3 AM Thursday to 1 PM EST Friday for PAZ038-039. Winter Weather Advisory from 1 AM Thursday to 1 PM EST Friday for PAZ043-044-047. NY...Winter Weather Advisory from 3 AM Thursday to 7 PM EST Friday for NYZ062. Winter Weather Advisory from 6 AM Thursday to 1 PM EST Friday for NYZ024-055-056. Winter Weather Advisory from 6 AM Thursday to 7 PM EST Friday for NYZ057. && $$ SYNOPSIS...MPH NEAR TERM...DJN/MPH SHORT TERM...MPH LONG TERM...BJG/TAC AVIATION...BTL
Area Forecast Discussion
National Weather Service El Paso TX/Santa Teresa NM
437 PM MST Wed Feb 17 2021 .AVIATION...00Z TAF CYCLE Generally VFR conditions are expected for most locations through the period. However a passing disturbance this evening, overnight, and into the morning hours will create opportunity for brief and isolated MVFR to IRF conditions with isolated to scattered snow showers. The best probability is over the mountains across the Gila region and the Sacramento Mountains, as well as the lowlands between. The only terminal expecting precipitation this evening and overnight is TCS between 23Z- 10Z when -SN will be possible with brief VIS reductions to 2SM. CIGs for most of the area will be 080-120, with lower CIGs to 030-040 in any showers. West/ northwest surface winds at 14-18G24-28KT will subside and become northerly through the 03-08Z period. && .PREV DISCUSSION...205 PM MST Wed Feb 17 2021... .SYNOPSIS... An upper level disturbance will move across the Rocky Mountains today and tonight. This system will bring a few rain and snow showers to the region this afternoon and tonight along with chilly below normal temperatures Thursday and Friday. Westerly winds will produce warmer dry weather Saturday before another disturbance brings breezy to windy conditions Sunday with cooler temperatures again Monday. Warmer dry weather is forecasted for next Tuesday and Wednesday. && .DISCUSSION... .SHORT TERM...Rest of Today through Thursday... A secondary shortwave has rotated down along the backside of the weather system that we saw yesterday across the Borderland. Radar at the noon hour shows light scattered showers popping up across a good portion of the area, with quite a spread of cumulus clouds developing across the entire CWA. This is considerably more coverage than what the high resolution models have been showing all morning. The HRRR and NAM all kept the precip confined the mountains and perhaps the northern lowlands. The only exception is the very latest HRRR run which does now show a handful of spotty showers in Dona Ana and Otero County. Mesoanalysis shows a few hundred J/kg of CAPE over most of the Borderland, which is also different than the earlier model solutions that kept CAPE focused in the northwestern third of the CWA. Dewpoints are also a bit higher than what models thought they would be. Looking aloft, we do have a strong 500mb jet skirting around the Borderland today, which is likely helping develop these afternoon pop ups. Expect coverage to remain more scattered in nature, with the best chances for precip in the mountains and lowlands east of the Continental Divide. Radar may look scarier that what`s actually happening since some of these echos may just be virga and not actual rainfall reaching the ground. Either way, most areas shouldn`t be surprised if they see a few sprinkles on their windshields through the afternoon. Since there is a bit of CAPE and LIs are forecast to fall below 0 in spots, a rumble of thunder or two will also be possible during daytime heating. The lowland showers will remain as rain since temperatures are in the mid to upper 40s to even some lower 50s, with mountains likely seeing snow thanks to temps right around freezing. What models do agree on is any lowland activity diminishing as we get closer to sunset, then focusing the remainder of the precip over the Gila region and Sacramento Mountains. Once we lose the heating of the day, snow levels will start to drop to 3500-4000 feet. Again, models have most of the precip confined to the mountains at this time, but if any moisture does linger across the lowlands, some spots may see a rain/snow mix or perhaps some light flurries. No accumulations are anticipated in the lowlands. Rain amounts are expected to remain below 0.10". It looks as though the precip will linger in the Sacramento Mountains longer then originally thought, so the Sacs could see light snow showers all the way through mid-day Thursday before the precip finally exits the area. When all is said and done, the Sacramento Mountains and Gila region may see up to an inch or two of snow accumulation. Winds this afternoon have become a bit gusty, though not as strong as we saw yesterday. These winds are forecast to subside after sunset and gradually become north/northeasterly overnight as the backdoor cold front tries to make a short move west once again. Low temperatures will be below freezing for most everyone, and the Sacramento Mountains and Gila region will likely fall into the low teens to single digits thanks to the dense snow pack on the ground. Winds will remain easterly on Thursday, and clouds will clear out by the afternoon. With north/northwesterly flow aloft and easterly flow at the surface, temperatures will take a small tumble tomorrow, as forecast highs will be in the mid to upper 40s. && 32 Pegram .LONG TERM...Thursday Night through next Wednesday. By Thursday evening far west Texas and southern New Mexico will be located between deep upper trough in the plains and high amplitude ridge west of the divide. This will place the region in a deep subsiding northwest flow with transport of dry but cool air mass. So expect cold below normal morning lows Friday with high temperatures on Friday also around 10 degrees below normal despite the sunny skies. Westerly winds will advect dry but warmer air by Saturday pushing temperatures up to a little above normal. However a rather strong upper wave will move eastward into the central and southern rockies on Sunday. This system will cause low and mid level gradients to strengthen causing breezy to windy conditions across portions of the CWA. In addition an associated Pacific cold front will move across the CWA causing temperatures to cool around 5 degrees Sunday with slightly below normal temperatures on Monday. Despite strong upward forcing this system will lack sufficient moisture for significant rain or snow. Westerly winds will sustain dry weather conditions and produce warming temperatures next Tuesday and Wednesday. && .FIRE WEATHER... A few lowland rain showers and mountain snow showers will be possible through the afternoon and into the late evening hours. A couple of isolated lightning strikes will be possible mainly in the Gila region and Sierra County this afternoon, though a strike in the rest of the lowlands can`t be ruled out. The Sacramento Mountains will see snow linger through mid-day Thursday before all of the moisture finally exits the area. Snow amounts in the mountains will be 0.5-2 inches, and scattered rain amounts in the lowlands will be below 0.10". Gusty northwest winds will subside and become northerly overnight. Expecting light northeasterly winds on Thursday with cool temperatures. Min RHs this afternoon and tomorrow will be above 25- 35 percent, with 18-22 percent in NM fire zone 111. The Borderland will dry out for Friday and into early next week as westerly flow takes over. Aside from warming temperatures and patches of high clouds passing through, it will be a benign weather period. Min RHs will drop below 20 percent starting Friday. A weak trough may skirt the area on Sunday creating breezy northwesterly winds. Will have to watch this day for a chance of critical fire weather conditions as min RHs will drop into critical thresholds. Vent rates will be poor to fair Thursday and Friday, then good to very good Saturday and excellent on Sunday. && 32 Pegram && .PRELIMINARY POINT TEMPS/POPS... El Paso 32 47 25 55 / 10 0 0 0 Sierra Blanca 27 37 21 51 / 20 10 0 0 Las Cruces 28 46 22 54 / 10 0 0 0 Alamogordo 23 42 19 52 / 20 10 0 0 Cloudcroft 10 23 9 34 / 30 30 0 0 Truth or Consequences 27 46 23 54 / 40 0 0 0 Silver City 21 42 22 53 / 10 0 0 0 Deming 24 48 20 56 / 0 0 0 0 Lordsburg 23 50 22 58 / 0 0 0 0 West El Paso Metro 33 47 28 55 / 10 0 0 0 Dell City 24 39 16 53 / 30 20 0 0 Fort Hancock 29 44 20 57 / 20 0 0 0 Loma Linda 27 39 23 48 / 10 0 0 0 Fabens 30 47 23 56 / 10 0 0 0 Santa Teresa 28 46 22 53 / 10 0 0 0 White Sands HQ 30 45 27 53 / 10 0 0 0 Jornada Range 24 45 21 53 / 10 0 0 0 Hatch 27 48 22 56 / 10 0 0 0 Columbus 29 49 24 56 / 0 0 0 0 Orogrande 26 43 19 51 / 20 10 0 0 Mayhill 14 31 13 48 / 30 30 0 0 Mescalero 13 32 10 43 / 30 30 0 0 Timberon 12 29 9 42 / 30 30 0 0 Winston 12 40 11 53 / 30 0 0 0 Hillsboro 22 44 19 56 / 20 0 0 0 Spaceport 24 44 20 53 / 30 0 0 0 Lake Roberts 14 40 15 54 / 30 0 0 0 Hurley 18 45 17 54 / 0 0 0 0 Cliff 22 49 21 58 / 0 0 0 0 Mule Creek 21 45 24 55 / 20 0 0 0 Faywood 24 45 23 54 / 0 0 0 0 Animas 24 50 21 60 / 0 0 0 0 Hachita 22 50 19 58 / 0 0 0 0 Antelope Wells 26 49 24 58 / 20 0 0 0 Cloverdale 28 47 28 58 / 10 0 0 0 && .EPZ WATCHES/WARNINGS/ADVISORIES... NM...None. TX...None. && $$ 32/05/14
National Weather Service Morristown TN
1005 PM EST Wed Feb 17 2021 .UPDATE... EVENING UPDATE. && .DISCUSSION... Doppler radar and surface observations indicate that precip has begun reaching the ground across the southern Plateau and southern Valley, and we have received public reports of sleet in Cleveland and 0.3 inches of snow in Whitwell. The potential for snow and sleet will spread north and east through Midnight as isentropic upglide continues to strengthen along with strengthening warm, moist advection ahead of the approaching shortwave. Surface temps are generally in the mid 30`s to near 40, but dew points in the 20`s will lead to evaporative cooling as the airmass saturates, which will support the wintry precip. RAP soundings show a warm nose developing near 850 mb as WAA increases, so snow/sleet mix will gradually change to more of a sleet scenario then eventually all rain as the warmer air makes it back to the surface. This will occur fairly quickly from S to N, and the HREF precip types support this idea with much of the S Plateau and S Valley through SW NC expected to be rain by 07Z while the middle Valley changes to rain in the 07-09Z timeframe and the N Plateau through the N Valley and NE TN into SW VA changes to rain in the 09-12Z timeframe (perhaps later in SW VA). The previous forecast and headlines look good, so the only change was to issue an SPS for Bradley, McMinn, NW Monroe, and W Polk Counties through 07Z to cover the current mixed precip. Garuckas && .AVIATION... 00Z TAF DISCUSSION. Showers will overspread the TAF sites this evening with periods of MVFR first developing at CHA then reaching TYS and TRI late this evening or early tonight. Cigs and vis will fall to primarily IFR with periods of MVFR overnight as precipitation becomes steadier. A mix of snow and sleet will occur at TYS and TRI before dawn with light accumulations possible before changing to all rain Thursday morning. Showers will become more scattered Thursday, but reduced cigs and vis will prevail much of the day. Garuckas && .PREV DISCUSSION... /ISSUED 349 PM EST Wed Feb 17 2021/ SHORT TERM...(This Evening through Thursday)... Key Messages... 1) A wintry mix of snow, sleet, and possibly freezing rain Plateau and Mountains can be expected across the region from this evening through early Thursday morning. Wintry mix will transition to all rain by around daybreak Thursday. Greatest accumulations from the Plateau, northeast Tennessee into southwest Virginia. 2) Very challenging forecast on precipitation type. Initial precipitation will be influenced by wet bulb cooling due to dry airmass and eventually strong dynamic forcing between 04-09Z. However, models also depict strong strong warm air advection/isentropic lift which will fight to change precipitation to rain. Model soundings show warm air winning out over most of the area by daybreak. 3) The strong system will also produce widespread rainfall amounts of 1 to 1 1/2 inches with localized 2 inches+. Given the soggy soil conditions, most of this will be runoff which may cause some localized flooding issues. 4) Temperatures warming into the 40s across much of the valley Thursday with another round of rain with frontal passage in the afternoon. Now for the particulars... For this evening and tonight, strong jet structure will move across the Tennessee valley and southern Appalachians. Some models are so a 300mb jet of 165-170kts over the Ohio valley. Models show very strong upper divergence with the jet configuration between 04-09Z. The Ageostrophic Vertical Circulation with the jet will produce dynamic cooling as well as the wet bulb cooling due to initial dry airmass. A period of heavy snow (some sleet) is possible across the Plateau, western sections of the Tennessee valley, northeast Tennessee, and southwest Virginia. The strong warm air advection and isentropic lift will produce widespread precipitation. Eventually the warm air advection will win out with model soundings show precipitation transitioning to rain area-wide soon after daybreak. For Thursday, the strong dyanmics will move east of the area with a break in the widespread precipitation ending by mid-morning. However, another wave of jet energy and frontal passage will produce another round of rain in the afternoon. LONG TERM...(Thursday night through Tuesday)... By Thursday night the precipitation will be pulling out to the northeast as the strong trough over the central US begins to finally swing through into the eastern half of the country. Have trimmed back precipitation chances Thursday night into Friday as some models are speeding up the exit of the precip. If precipitation is able to linger into the early overnight hours Thursday night temperatures will drop enough that we could see another round of light snow. Accumulations with any snow Thursday night and Friday morning are expected to be very light if they do occur as the moisture will be mostly gone and QPF should be light. We`ll finally take a break from wintery precipitation over the weekend, with the biggest story being cold temperatures in the morning, specifically Saturday morning. This will be the time when the cold air from the northwest will have the greatest impact and low temperatures are expected to be in the low 20`s into the teens across all of the area. Winds are expected to be light as the surface high begins to build in with winds likely remaining below 5 mph, so am not anticipating a wind chill advisory being needed. But these will still be some of the coldest temperatures of the season regardless. Trough begins to weaken it`s grip and with the drier air from the west/northwest we`ll actually get to see the sun for the majority of the weekend. This will help with a warming trend and temperatures are expected to finally warm up into the 50`s on Sunday, although we`re still going to be running a few degrees below normal it`s probably going to feel very nice out in the sun. Another trough and front are expected to quickly swing through the area early in the week on Monday. Models have trended a bit colder with this system from previous runs so we could see a bit of snow in the higher elevations Monday morning mixed in with the rain (which should be the dominant precipitation type). This system will quickly move through and we get back to a warming trend behind it. The current forecast calls for temps in the upper 50`s and possibly 60`s (and sunny) on Wednesday. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 34 45 29 42 22 / 100 60 20 10 0 Knoxville McGhee Tyson Airport, TN 33 42 30 38 21 / 100 90 40 10 0 Oak Ridge, TN 33 43 28 38 20 / 100 70 30 10 0 Tri Cities Airport, TN 32 43 31 37 19 / 100 100 60 20 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...Winter Weather Advisory until 7 AM EST Thursday for Cherokee- Clay. TN...Winter Storm Warning until 1 PM EST Thursday for Anderson-Blount Smoky Mountains-Campbell-Claiborne-Cocke Smoky Mountains- Hancock-Hawkins-Johnson-Morgan-Scott-Sevier Smoky Mountains- Southeast Carter-Southeast Greene-Southeast Monroe-Unicoi- Union. Winter Weather Advisory until 7 AM EST Thursday for East Polk- Grainger-Hamblen-Hamilton-Jefferson-Knox-Loudon-Meigs-North Sevier-Northwest Blount-Northwest Cocke-Rhea-Roane. Winter Weather Advisory until 10 AM EST Thursday for Northwest Carter-Northwest Greene-Sullivan-Washington. Winter Storm Warning until 9 AM CST Thursday for Bledsoe-Marion- Sequatchie. VA...Winter Storm Warning until 1 PM EST Thursday for Lee-Russell- Scott-Washington-Wise. && $$
Area Forecast Discussion
National Weather Service Pendleton OR
756 PM PST Wed Feb 17 2021 .SHORT TERM...Tonight and Thursday...A ridge of high pressure will be passing over the region tonight ahead of the next weather system expected to move off the Pacific Thursday in a westerly flow. Will see some increasing clouds overnight and the potential for some patchy fog around the Columbia Basin. Precipitation will begin move over the Cascades late in the morning then impact the entire forecast area through the afternoon and evening. The westerly flow will somewhat shelter the Cascade east slopes and Basin with the least precipitation while the Cascade crest and eastern mountains will see the most. Winter Weather Advisories have been issued covering Thursday afternoon through midday Friday for the Cascades and northern Blue Mountains. There will also be the potential for some freezing rain in portions of the Columbia Basin Thursday night. && .PREV DISCUSSION... /issued 215 PM PST Wed Feb 17 2021/ SHORT TERM...Tonight through Friday night...WSR-88D continues to pick up weak returns over the Blues and Wallowas, so will keep isolated snow showers or snow flurries for this area through the evening. Otherwise, no precipitation is expected through early Thursday morning. Patchy dense freezing fog was observed this morning in the Tri-Cities area, and believe the areal coverage will be greater tonight. This is supported by the HRRR visibility progs that show fog as far south as the Lower Columbia Basin of Oregon and near Prosser as well as the eastern Columbia River Gorge. Southerly downslope winds along the Blue Mtn Foothills may keep this area fog free tonight. A shortwave trough will travel across WA/OR Thursday and Thursday night. There is a weak warm front associated with the trough that will increase snow levels to around 3000 feet over eastern OR and far southern WA but only around 1500-2000 feet for areas north of the Tri-Cities and Prosser. Precipitation will develop along the Cascades early Thursday morning then gradually spread eastward over the remainder of the forecast area Thursday afternoon and evening. One forecast challenge has been whether there may be light freezing rain or sleet over the Columbia Basin where persistent fog and low clouds may keep temperatures just around the freezing mark. Using the NBM Conditional Probability for -FZRA as a guideline, will introduce a chance of freezing rain for the Lower Columbia Basin from the Tri-Cities south to the Blue Mountain Foothills. Confidence isn`t high to go likely, but a chance. The wintry mix will not last long as a westerly flow will follow the shortwave trough which is not favorable for precipitation across the Columbia Basin and surrounding valleys. Winter Weather Advisories are in effect for the east slopes of the WA/OR Cascades and the northern Blue Mountains from Thursday morning through Friday afternoon. There will be a prolonged period of a westerly flow Friday and Friday night bringing numerous snow showers in the advisory locations. The Wallowa Valley, Grande Ronde Valley, and the Ochoco-John Day Highlands will likely receive 1-3 inches of snow which do not meet advisory criteria. The lower elevations, including Central Oregon, will have up to 1 inch of new snow. No wind concerns during the short term, although it will be windy in the Grande Ronde Valley Thursday and Thursday night. Wister LONG TERM...Saturday through Wednesday...A progressive pattern with an overall west to northwest flow will prevail through much of the extended period. On Saturday a weak trough will move across the area in a northwest flow, which will cause mainly upslope mountain snow and occasional light valley rain or snow. QPF amounts are not too impressive with this disturbance, but there could be a substantial amount of upslope snow in the northeast mountains, and the Cascades, especially near the crest. Then on Sunday weak upper ridging will develop. However, there will be a shortwave trough that will move in and flatten the ridge by afternoon. There will still be some lingering upslope mountain snow showers. This pattern will persist through Monday night. Then a westerly jet stream will increase over the PacNW with a faster zonal flow on Tuesday. During this time, the upslope snow showers over the northeast mountains will taper off and end, and the flow over the Cascades will bring some spill over precipitation near the crest. Elsewhere will be dry. A new trough will then develop and amplify with the trough axis over areas west of the Cascades in OR/WA on Wednesday. The dynamic lift with the associated vorticity advection and increased moisture with the trough will cause precipitation to develop again in the eastern and northeast mountains. Precipitation will increase over Oregon, but the northern areas will stay mostly dry (mainly the WA Lower Columbia Basin, and the Yakima/Kittitas Valleys). There will be a warming trend Saturday through Monday, with Monday peaking out in the 40s and 50s...and then temperatures will cool slightly after that. It will be breezy to locally windy through most of the extended period due to the fast progressive flow pattern. The longer range models are in pretty good agreement through the extended period with each other and with the various ensembles. 88 AVIATION...00Z TAFs...VFR conditions will prevail this evening at all terminals. However, there could be periods of low clouds and light fog over KALW, KPSC and KYKM. Flying conditions will deteriorate on Thursday afternoon from west to east as another weather system moves into the region, with periods of MVFR and possible IFR conditions as clouds lower and visibility decreases in precipitation at all terminals. The exception will be at KPSC and KYKM which will be in the drier northern areas. Winds will be light tonight and under 5-10 kts, but a southeast gradient will cause winds to increase along the Blue Mountains and Foothills and also in the Ochoco-John Day highlands with possibly locally breezy winds by late Thursday afternoon. 88 && .PRELIMINARY POINT TEMPS/POPS... PDT 24 36 33 42 / 0 30 70 20 ALW 26 37 33 43 / 0 20 70 30 PSC 25 34 29 43 / 0 40 60 10 YKM 26 34 25 42 / 0 60 50 10 HRI 26 36 31 44 / 0 40 70 10 ELN 26 32 27 41 / 0 60 50 20 RDM 21 41 31 44 / 0 70 60 20 LGD 18 33 31 40 / 0 30 80 50 GCD 19 39 32 45 / 0 60 90 30 DLS 32 36 35 47 / 0 90 70 30 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Winter Weather Advisory from 10 AM Thursday to 1 PM PST Friday for ORZ502-509. WA...Winter Weather Advisory from 10 AM Thursday to 1 PM PST Friday for WAZ030-520. && $$ SHORT TERM...91 LONG TERM....91 AVIATION...74
Area Forecast Discussion...UPDATED
National Weather Service Shreveport LA
945 PM CST Wed Feb 17 2021 .UPDATE... The significant winter storm has now exited the entirety of the Four State region and has laid down significant accumulations of snow, and/or sleet, and/or ice (depending on where you live). We are becoming increasingly confident the deeper baroclinic zone aloft (925 to 700 mb) will juxtapose with the right entrance region of a strong upper level jet to squeeze out an additional light wintry mix (mainly fzra/snow) from late tonight and possibly into early afternoon from mainly Deep East Texas into North and Central LA and the Arklamiss. Additional ice and/or snow accumulations are possible in these areas, but they should be very light. Nevertheless, any additional accumulations will ensure already bad travel conditions will not be improving at all. For the above reasoning, the prior Winter Storm Warning in effect for the whole region through midday tomorrow was kept going in outlined areas where additional wintry precipitation is possible. However, since no additional wintry precipitation is anticipated northwest of the outlined zones, we have canceled the Winter Storm Warning in Arklatex zones basically along and northwest of the I-30 corridor. Of course most of those areas are already covered with snow and impacts from this locally heavy snow will continue and travel will be treacherous. Otherwise, low temperatures were lowered in most areas tonight to match trends and will range from the upper teens northwest to upper 20s southeast. Stay safe and try to stay warm everyone. Warmer and sunnier times are eventually coming. /50/ && .PREV DISCUSSION... /issued 645 PM CST Wed Feb 17 2021/ AVIATION... IFR cigs will persist across much of the region through the overnight hours, with areas of a wintry mix expected to diminish through 03Z across Srn AR/N LA. However, additional snow and ice accumulations are expected at the TXK and ELD terminals, with lighter icing accumulations at MLU. Some slow improvements to cigs are expected overnight across portions of NE TX/SW AR with MVFR cigs returning, although this improvement is not expected for areas farther SE until mid/late morning through the afternoon Thursday. However, areas of a light wintry mix may redevelop late tonight through much of the morning Thursday across portions of Deep E TX into NCntrl LA, possibly affecting the LFK/MLU terminals. However, any additional icing will be minimal over these areas. Conditions will continue to improve gradually late in the TAF period and beyond, although MVFR cigs looks to hang on for a better part of the day before lifting/scattering out. NNE winds 6-10kts will continue through the end of the TAF period. /15/ PREV DISCUSSION... /issued 413 PM CST Wed Feb 17 2021/ SHORT TERM.../Today through Thursday Night/ The 2nd winter storm of the week has been fully impacting the Four State Region today, but will be winding down from southwest to northeast through late afternoon into early this evening. Some of the snow amounts, in particular, have been very impressive across AR portions of the CWA and we will be doing reports through the evening to highlight event totals, so look for those. Even though there will be a relatively quick downward trend in activity over the next handful of hours, there could still be lingering light FZRA potential tonight in portions of the region, although recent model runs have made this seemed less likely. The final portion of trough energy may also squeeze out some more very light freezing drizzle or flurries tomorrow in the region, but any additional impact from this is also looking far less likely. The current Winter Storm Warning does not expire until noon tomorrow to cover those lingering threats and we may cancel the warning early later this evening, choosing not to change parameters of the warning right now to avoid confusion when the event is still ongoing. Otherwise, the HRRR model has been doing a pretty good job handling the mixed precipitation details pretty well with mostly sleet, occasionally heavy, in a tight corridor from GGG, to SHV, to ELD - with mostly snow north of this corridor and mostly FZRA south of this corridor. We have also seen some slight shift north of these pcpn type boundaries this afternoon, although not a great deal of further change is expected before most everything exits to the east/northeast later this evening. Additional ice accumulations (from freezing rain) of up to a quarter inch are probably more limited to Central Louisiana with additional snow accumulations greater than 2 inches probably more limited southwestern AR. Less additional snow/sleet/frza rain accumulations are expected elsewhere according to p-type boundaries described above. Interestingly, temperatures warmed far above model expectations in central portions of the CWA where latent heating processes at the surface due to freezing rain have warmed temperatures to, or near, freezing. But these areas will likely not get above freezing before starting to fall off again tonight. Locations across Deep East TX and Central LA have just barely topped the freezing mark, but will fall below freezing again tonight. For tomorrow, a solid reinforcement of below normal temperatures will be coming in the wake of this system and some patchy and light wintry pcpn types could accompany this in at least SE portion of the CWA, as alluded to above. There should be at least some patchy sunshine by afternoon in the northwestern half of the CWA juxtaposed with temperatures probably a little above freezing and, if this occurs, would get a touch of melting going on. But roads will remain a mess in most areas as lows tomorrow night should be in the chilly teens in most areas and will efficiently freeze any liquid or slush on road surfaces. A hard freeze warning will be considered for future package covering tomorrow night, but we decided to hold off on that product for now to keep the message simple. /50/ LONG TERM.../Friday through Wednesday night/ Friday morning will see a 1036mb high over the Rio Grande valley that will slowly edge eastward and weaken down to 1030mb or so in E TX by nightfall. We are still looking at loads of lingering ice getting into the weekend with more record lows perhaps to start and then highs on Friday only in the low to mid 30s with sunshine helping to melt ice off structures anyway. The weekend will be chilly to start with more mid to upper teens, but rebounding on Saturday as winds shift to southerly on the back side of this still 1030mb air mass axis crossing the MS river. High temps on Saturday will get into the lower 40s north of I-20 and upper 40s south. Then the clouds will begin to increase overnight into early Sunday blanketing in more heat and keeping lows closer to average for late February. The clouds will continue lowering during the mid to late day with highs ranging from near 50 north to 60 south. Most of us along I-20 only in the lower 50s with rain not far behind the clouds for I-30 in the afternoon and then spreading down area-wide by nightfall. This is a weaker Pacific airmass of 1028mb that will push another cool front through overnight Sunday. The upper trough arriving overnight will be cooling temps aloft which will allow for a brief window for a mix to end predawn, mainly along and north of I-20. This will only be how the overnight light rainfall ends, due to timing of predawn hour and the drier NW flow deepening under the passing trough. NO additional ice accumulation is expected anywhere in our area with this few hour window of transistion before quickly ending. Hopefully travel will have greatly improved over the weekend and this tail end trace will not affect that process in the least, as we continue with sfc winds the will back from NW to SW late in the day. The rest of the work week look very nice with average 60s for highs and 40s for lows and southwest winds and sunshine. /24/ && .PRELIMINARY POINT TEMPS/POPS... SHV 23 34 18 37 / 20 30 0 0 MLU 26 33 19 36 / 40 40 0 0 DEQ 19 37 11 36 / 20 10 0 0 TXK 22 35 14 34 / 40 10 0 0 ELD 21 34 15 36 / 60 20 0 0 TYR 21 33 13 32 / 10 10 0 0 GGG 21 34 14 35 / 20 20 0 0 LFK 25 36 19 40 / 30 30 0 0 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...Winter Storm Warning until noon CST Thursday for ARZ060-061- 070>073. LA...Winter Storm Warning until noon CST Thursday for LAZ001>006- 010>014-017>022. OK...None. TX...Winter Storm Warning until noon CST Thursday for TXZ112-125-126- 136>138-149>153-165>167. && $$ 50/15/24