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   FOUS11 KWBC 302029   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   329 PM EST Sun Nov 30 2025   
      
   Valid 00Z Mon Dec 01 2025 - 00Z Thu Dec 04 2025   
      
      
   ...Great Lakes to the Interior Northeast...   
   Day 1...   
      
   The storm system responsible for the heavy and disruptive snowfall   
   that blanketed the Midwest and Great Lakes is tracking into Ontario   
   this afternoon. Cyclonic flow and CAA within WNW-NW winds will   
   reinvigorate the LES machine across the Upper Great Lakes, snow   
   belts of western MI and northern IN, and typical snow belts to the   
   east of Lakes Erie and Ontario. Snow bands will be capable of   
   producing anywhere between 1-2"/hr snowfall rates due to the   
   favorably unstable low-level profiles and a pivoting 850-700mb   
   trough over head this evening. WPC probabilities show moderate   
   chance probabilities (40-60%) for additional snowfall totals >4"=20   
   over far northwest PA and across the Tug Hill. An additional 1-4"   
   of snow is forecast in the Green and White Mountains before   
   tapering off by early Monday morning.   
      
      
   ...Central Rockies/Central Plains/Mid-South/OH Valley...   
   Days 1-2...   
      
   A 500mb positiviely-tilted trough is tracking through UT today and   
   will head for the CO/NM Rockies by early Monday morning. The   
   combination of height falls with a strengthening jet streak will=20   
   produce large scale ascent across the Central Rockies and Four=20   
   Corners today and into tonight. Heavy snowfall will be primarily   
   confined to the >10,000ft peaks of the CO/NM Rockies, although some   
   minor-to-moderate accumulations between 7,000-10,000ft are   
   possible.=20   
      
   As the upper trough tracks east towards the Central Plains tonight,   
   healthy 500mb PVA coupled with a strengthening 250mb jet streak   
   will foster healthy synoptic-scale divergence aloft. Guidance also   
   shows a strengthening 850-700mb WAA regime and corresponding 290K   
   isentropic ascent over the Central Plains that is likely to result   
   in a band of moderate-to-heavy snow tracking from northern KS early   
   Monday morning and across the heart of the Midwest by Monday   
   afternoon. Temperatures are cold enough aloft to support fluffy   
   SLRs (>15:1 in most cases) and it is progressive. WPC probabilities   
   show most accumulations will range between 1-4", given WPC   
   probabilities for >4" are low (10-30% at most in northeast   
   KS/northwest MO). However, there are some guidance members that   
   depict some localized totals >4" by the time the band of snow exits   
   to the east Monday evening. The same mechanism producing snow in=20   
   the Central Plains heads for the OH Valley and western PA. Snowfall   
   accumulations will generally range between 1-4" through Tuesday=20   
   morning.=20   
      
   Farther south, as low-level WAA and Gulf moisture spreads over and   
   air-mass that features sub-freezing temperatures and dry   
   dewpoints, freezing rain is expected to unfold from the   
   ArkLaTex eastward across central and southern AR and into western   
   TN. the plume of low-level moisture does not last long, but 290K   
   isentropic ascent sticks around long enough for some disruptive=20   
   ice accumulations in these areas on Monday. WPC probabilities show=20   
   low chances (10-30%) for ice accumulations than one-tenth of an=20   
   inch, but there are moderate chances (40-60%) for ice=20   
   accumulations over one-hundreth in central AR. The WSSI shows a=20   
   large swath of Minor Impacts across central AR and as far north as=20   
   the MO/AR border, but some localized Moderate Impacts in central AR   
   are possible.=20   
      
      
   ...Central Appalachians & Northeast...   
   Days 2-3...   
      
   ...Widespread hazardous snow and ice to blanket portions of the   
   Mid-Atlantic and Northeast Monday night and through Tuesday...   
      
   By Monday evening, the 500mb trough producing periods of snow over   
   the OH Valley will track across the Middle MS Valley Monday night   
   with a secondary disturbance tracking south of it towards the   
   Southeast. As a third disturbance approaches from the Great Lakes,   
   a strengthening 250mb jet streak over the Northeast will work with   
   a second 250mb jet streak over the South to creating a classic   
   "coupling jet streak" setup off the Mid-Atlantic coast. This will   
   be the basis for a strengthening winter storm that tracks initially   
   through the Southeast Monday night and up the East Coast by Tuesday   
   afternoon.   
      
   The primary ingredients are generally agreed upon on all guidance,   
   although how they come together and where the storm tracks is=20   
   still coming into focus. High pressure over the Northeast will=20   
   initially provide a sufficiently cold air-mass to support wintry=20   
   precipitation at the onset from the Central Appalachians on north=20   
   and east, but it will be exiting off Atlantic Canada on Tuesday. As   
   925-700mb WAA advances north Monday night and into Tuesday, any=20   
   initial snow over the Central Appalachians will changeover to a=20   
   sleet/freezing rain mix, then all freezing rain. Cold air damming=20   
   (CAD) will linger long enough in the higher terrain to support=20   
   disruptive ice accumulations that result in slick travel conditions   
   Monday night and into Tuesday morning. WPC probabilities show >50%   
   chances for ice accumulations over a tenth of an inch from the=20   
   Blue Ridge of western NC on north through the mountains of western=20   
   VA and eastern WV. There are some low-chance probabilities (10-30%)   
   for over a quarter inch of ice from VA's Skyline Drive on south and west   
   to the WV/VA border. The latest WSSI does depict Minor to Moderate   
   Impacts in these regions with a focus on treacherous travel=20   
   conditions.   
      
   Farther north over the Mid-Atlantic, precipitation is likely to   
   start out as snow over northern VA/MD, southern PA, and on north   
   towards the NYC metro Tuesday morning. Guidance then begins to   
   disagree on the handling of the transition and northward expansion   
   of the snow-wintry mix area. Low-level SErly flow is strong enough   
   to where most areas along I-95 should flip over to plain rain on   
   Thursday morning, but farther inland over the Piedmont of VA,   
   northern MD, and Lower Susquehanna Valley, low-lvel cold may stick   
   around long enough for a wintry mix to hang around longer. This is   
   likely to be the region's first accumulating snowfall, so there are   
   likely to detrimental impacts to travel even if snowfall and ice   
   accumulations are minor (1-3" of snow for these areas, up to a=20   
   tenth of an inch of ice in western MD and northwest VA). However,=20   
   from the Lehigh Valley and Poconos on north and east through=20   
   northwest NJ, the Catskills, and into interior southern New=20   
   England, snow is likely to remain the primary precip type.   
      
   The storm by Tuesday afternoon will begin to develop a closed lower   
   over the Delaware Valley that deepens south of Long Island by   
   Tuesday evening. To the north and east of the 850mb low, a   
   consolidated 850-700mb FGEN area will develop and result in a band   
   of heavy snow somewhere from northeast PA and southern NY (north of   
   NYC) through southern New England. Snowfall rates within this band   
   are likely to at least top 1"/hr. There still remains some   
   uncertainty on where this band sets up, but probabilistic guidance   
   is showing increase odds on a snowfall swath of >6" from the   
   Poconos and Catskills on north and east. The higher terrain across   
   New England (Berkshires, Worcester Hills, Green, Whites, Downeast   
   Maine) are the most favored for locally heavy snowfall as WPC=20   
   probabilities shows low-to-moderate chances (30-50%) for over 12"=20   
   in some spots. The latest WSSI does depict Moderate Impacts due to   
   snow from western MA and northern CT to southern NH and southern=20   
   ME with locally Major Impacts possible.=20   
      
   In summary, this is going to be the first accumulating snow of the   
   season for many areas from southern PA to areas just west of I-95,   
   potentially including the Boston metro area should more southern   
   guidance come to fruition. Expect travel delays on Tuesday and into   
   Tuesday night in affected areas. High pressure and dry conditions   
   return to the Northeast by early Wednesday morning.=20   
      
   Key Messages remain in effect for this system and are linked below   
   (Key Message #3)   
      
      
   Mullinax   
      
      
      
   ...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!4a3u3xvT3-hHMgEuVV19WxvIhLYs9AwNztPM6v7_Rvx-N=   
   fA7rqvdw0CdltnXbH7K29K2qwndPvJ_PXi1VPNvhwlFOkk$=20   
      
      
      
   $$   
      
   =3D =3D =3D   
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