TZUTC: 0000   
   MSGID: 167234.weather@1:2320/105 2d95be59   
   PID: Synchronet 3.21a-Linux master/123f2d28a Jul 12 2025 GCC 12.2.0   
   TID: SBBSecho 3.28-Linux master/123f2d28a Jul 12 2025 GCC 12.2.0   
   BBSID: CAPCITY2   
   CHRS: ASCII 1   
   FORMAT: flowed   
   FOUS11 KWBC 012030   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   330 PM EST Mon Dec 1 2025   
      
   Valid 00Z Tue Dec 02 2025 - 00Z Fri Dec 05 2025   
      
      
   ...Central Plains through the Mid-Atlantic & Northeast...=20   
   Days 1-2...   
      
   ...Widespread moderate to heavy snow from the Central Plains to the   
   Northeast will impact travel early this week while treacherous   
   icing occurs across the Appalachians...   
      
   A positively-tilted upper trough will continue to move steadily   
   east of the Rockies, assuming a neutral tilt, with phasing streams   
   over the Plains early in the period. This trough will continue to=20   
   move east across the Midwest on Tuesday, reaching the East Coast=20   
   late in the day, before becoming negatively-tilted as it moves off=20   
   of the Mid Atlantic/Northeast coasts Tuesday night.=20   
      
   At the surface, low pressure will develop over the northern Gulf=20   
   tonight before energy transfers to low pressure along the=20   
   Southeast coast. Supported by a coupled upper jet, this low will=20   
   deepen quickly as it tracks north along the Mid Atlantic to the=20   
   Northeast coast on Tuesday. With the 12Z ECMWF now shifted north,=20   
   the general consensus of the deterministic runs and the ensemble=20   
   means show the low tracking near the 40N/70W benchmark around 00Z=20   
   Wednesday before continuing on a track east of the Canadian=20   
   Maritimes Wednesday morning.   
      
   Upper level forcing along with low-to-mid level frontogenesis will   
   continue to support light to moderate snow spreading east from the   
   mid Mississippi through the Ohio valleys tonight, with the latest=20   
   WPC probabilities indicating that accumulations for most areas will   
   remain under 4 inches.   
      
   As this band moves east into the Ohio Valley, it will merge with=20   
   the larger system developing near the Gulf as impressive moist=20   
   isentropic ascent supports a north-moving theta-e ridge and an=20   
   expanding precipitation shield. Strong 850mb WAA will provide=20   
   additional ascent, with the accompanying frontogenesis serving to=20   
   intensify omega into the DGZ. While the WAA will likely result in a   
   burst of moderate snowfall in many areas across the interior Mid=20   
   Atlantic into the Northeast, a lack of resupplying cold air as a=20   
   surface high to the north retreats will enable a quick transition=20   
   to mixed/rain, especially along and east of the I-95 corridor from   
   northern Virginia to Boston. The 12Z models trended slightly=20   
   warmer, further indicating that areas from DC to NYC will be=20   
   mostly, if not entirely, all rain. However, northwest of the I-95=20   
   corridor, the story remains much different, where a prolonged=20   
   period of moderate, to at times heavy snow, is likely, with 1+"/hr=20   
   rates spreading from Pennsylvania to Maine. This will create an=20   
   axis of snowfall for which WPC probabilities continue to show a=20   
   high risk (>70% chance) for 4+ inches from the Poconos through=20   
   Downeast Maine, with locally as much as 8-12 inches possible (50%=20   
   chance) across parts of the Catskills and from the Berkshires to=20   
   southern Maine, including the northern Worcester Hills and=20   
   Monadnock region.   
      
   South of the heavy snow axes, light ice accumulations will shift   
   northeast from southern Arkansas into eastern Tennessee and=20   
   Kentucky. WPC probabilities indicate that where ice does   
   accumulate it will remain under 0.10 inch for most areas.   
      
   Meanwhile, more significant icing is likely to develop starting=20   
   tonight across portions of the central and southern Appalachians as   
   isentropic ascent and accompanying WAA intensify. Subfreezing wet-   
   bulb temperatures will support an extended period of freezing rain   
   along the southern to central Appalachians from North Carolina to=20   
   western Maryland. Although the high to the north will be=20   
   retreating, this cold air may be more difficult to scour out,=20   
   especially in the more sheltered locations, leading to an extended=20   
   period of freezing rain with impactful ice accretions likely. WPC=20   
   probabilities show 50 percent or greater probabilities for at least   
   0.1 inch of ice from across parts of western North Carolina=20   
   northward along the southern Blue Ridge into southern West Virginia   
   and the Shenandoah region of Virginia, with a low chance (10-30%)=20   
   of up to 0.25 inch in isolated locations.   
      
   Key Messages remain in effect for this system and are linked below   
   (Key Message #3)   
      
      
   ...Northern to Southern Rockies...=20   
   Days 1-3...   
      
   A shortwave will dig south out of British Columbia into the   
   northwestern U.S. overnight. This shortwave will continue to move=20   
   southeast Tuesday into Wednesday, and may become more amplified as   
   it drops through the Great Basin in response to secondary=20   
   vorticity maxima digging through its base. This will result in a=20   
   slowing and amplification of the trough, with downstream ascent=20   
   maximizing through height falls, PVA, and downstream intensifying=20   
   jet energy.=20   
      
   Available moisture will generally be modest as reflected by near-   
   normal PW anomalies, but the overlapped synoptic lift will be more   
   than sufficient to wring this out as periods of moderate to heavy   
   snowfall across much of the terrain. At the same time, a wave of   
   low pressure is progged to drop southeast coincident with the   
   shortwave trough, and a secondary front will also push south out of   
   Canada to cool the column while additionally leading to localized   
   upslope flow. Despite a shallow DGZ noted in regional forecast   
   soundings, the best ascent may maximize within this snow growth   
   region to enhance snowfall, and this suggests a broad swath of   
   moderate snow is likely Tuesday and Wednesday across much of the   
   Rockies.   
      
   WPC probabilities for 4+ inches Day 1 are highest from northwestern   
   Montana to northwestern Wyoming and northern Idaho, with local=20   
   maxima in snowfall above 8 inches possible across the higher   
   terrain. By Day 2, the heaviest snow pivots southeast reaching the   
   central Rockies, notably the Colorado ranges, where most of the   
   higher probabilities for accumulations above 4 inches are=20   
   centered. The southern shift is expected to continue into Day 3,=20   
   with the Sangre de Cristos in northern New Mexico the focus for the   
   higher probabilities for amounts over 4 inches.   
      
   ...Great Lakes & Northeast...   
   Day 3...   
      
   A strong arctic front will race across the Great Lakes Wednesday,   
   likely reaching Upstate NY by Thursday morning before continuing   
   into New England. The signals appear favorable for snow squalls=20   
   along this front as it dives southeast. The trends in the GFS SnSq=20   
   parameter remain fairly muted, however the NAM ramps up notably   
   across parts of Pennsylvania and Upstate NY into New England on   
   Thursday. While snowfall accumulations will be minimal, snow=20   
   squalls can cause dangerous driving due to briefly heavy snow rates   
   and gusty winds, so this event will need to be monitored as it=20   
   gets closer.   
      
   Pereira/Weiss   
      
   ...Winter Storm Key Messages are in effect. Please see current=20   
    Key Messages below...   
      
   https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late=   
   stKeyMessage_3.png__;!!DZ3fjg!6oXhXucCqMO6rFQZw4LhD3-riI-5FAbKI4WO1sf2hP8LT=   
   oEz6p5IVVzBv2VrbH0G1tj2lmGYpsUo2RcvZ2Kbm3cNMKo$=20   
      
      
   $$   
      
   =3D =3D =3D   
   To unsubscribe from WX-STORM and you already have a login, go to   
   https://lists.illinois.edu and use the "Unsubscribe" link.  Otherwise email   
   Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.   
      
   --- SBBSecho 3.28-Linux   
    * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)   
   SEEN-BY: 1/19 100 16/0 19/10 37 104/119 105/81 106/201 114/10 120/302   
   SEEN-BY: 123/130 128/187 129/14 142/104 153/757 7715 154/10 30 50   
   SEEN-BY: 154/110 700 201/0 203/0 218/700 840 220/10 20 30 90 221/1   
   SEEN-BY: 221/6 360 226/18 30 44 50 227/114 229/110 134 206 300 307   
   SEEN-BY: 229/317 400 426 428 470 664 700 705 240/5832 266/512 280/5003   
   SEEN-BY: 291/111 301/1 320/119 219 319 2119 322/757 762 326/101 335/364   
   SEEN-BY: 341/66 342/200 396/45 423/81 460/58 633/280 712/848 902/26   
   SEEN-BY: 2320/0 105 304 3634/12 5020/400 5075/35   
   PATH: 2320/105 154/10 221/6 1 320/219 229/426