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   FOUS11 KWBC 301835   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   135 PM EST Fri Jan 30 2026   
      
   Valid 00Z Sat Jan 31 2026 - 00Z Tue Feb 03 2026   
      
      
   ...Southern Appalachians, Mid-Atlantic, & Southern New England...=20   
   Days 1-2...   
      
   ...A major winter storm is expected to produce heavy snowfall and=20   
   blizzard conditions across the southern Mid-Atlantic...   
      
   The synoptic evolution continues to support a major winter storm,   
   primarily focused over the Carolinas, but questions about the   
   details continue.   
      
   The event begins this evening, as snow breaks out across the   
   southern Appalachians of NC/TN. This initial development of snow   
   will be in response to increasing synoptic ascent within strong   
   mid-level divergence downstream of a pivoting shortwave digging out   
   of the Great Lakes. As this shortwave dives southward out of the   
   Great Lakes, it will rapidly deepen into an impressive closed low   
   by 12Z Saturday over the Tennessee Valley, and then continue to   
   dive southeast, reaching the GA/SC coast by 00Z Sunday. This will   
   produce extreme anomalies of more than -5 sigma with respect to   
   500mb heights according to NAEFS across the Southeast/Gulf Coast,   
   indicative of how rare and extreme this setup will be. As the upper   
   low deepens and drops southward, forcing will intensify in response   
   to not only the mid-level divergence noted above, but additional   
   robust height falls, and increasing jet-level diffluence as a   
   downstream subtropical jet streaks strengthens across the Gulf and   
   then begins to arc poleward along the Southeast coast. This will   
   help generate surface cyclogenesis along the coast of the   
   Carolinas, with dual low-pressure systems progged, each one   
   deepening along the intense baroclinic gradient positioned offshore   
   owing to the recent extremely cold air blanketed across the eastern   
   CONUS.   
      
   The secondary surface low, which is likely to be the more intense   
   feature as it explosively intensifies Saturday night into Sunday   
   (maybe reaching into the 960s offshore) is progged to pivot more   
   east than northeast along the coast, so the heavy precipitation   
   should be generally confined to the Carolinas, southern VA, and   
   maybe Cape Cod as it pulls away. While there is continued   
   uncertainty into the exact amounts of precipitation due to dry air   
   aloft and intense mesoscale ascent that will drive bands of heavy   
   snow, there is high confidence in this overall synoptic evolution,   
   resulting in high confidence in the most impacted areas.   
      
   The column will be extremely cold, so other than possibly some   
   light rain along the coast to start the event, this will be an   
   all-snow scenario with above-climo SLRs, a rarity for this part of   
   the country. As noted above, the snow begins across the   
   Appalachians Friday evening and then expand rapidly to the south   
   and east as the upper low dives towards the Gulf and low pressure   
   development occurs offshore. This expansion of precipitation will   
   be driven primarily by increasing 850mb easterly flow, tapping into   
   the growing theta-e ridge offshore, with the resultant WAA leading   
   to the expanding snow shield, Some of this WAA could be intense as   
   reflected by strengthening 925-700mb fgen, well aligned into the   
   deep DGZ (>70% chance of at least 100mb of DGZ depth according to   
   the SREF). This will support not only expanding snowfall, but   
   intensifying snowfall such that by 00Z/Sunday at least moderate   
   snowfall rates should encompass nearly the entirety of the   
   Carolinas and into northeast GA and southern VA.=20   
      
   After 00Z Sunday is when the heaviest snow and most notable impacts   
   are expected as the low offshore deepens rapidly. This will pivot   
   winds to more N/NE across the region, and as a deformation axis   
   pivots west of the surface low and the cold conveyor sets up across   
   the Atlantic and into the eastern Carolinas, more intense ascent=20   
   and greater moisture should result in extreme (for this region)=20   
   snow rates. Cross-sections indicate a broad region of favorable=20   
   conditions for CSI, or even CI (thundersnow), and the HREF snow-=20   
   rate probabilities peak above 50% for 1"/hr suggesting at least a=20   
   potential for 2"/hr within a pivoting band somewhere in eastern NC=20   
   or SC, and this is additionally supported by the WPC prototype   
   snowband tool. These heavy snow rates will be accompanied by=20   
   strong winds that may gust 35-50 mph, higher at the coast and in=20   
   the mountains, suggesting near blizzard conditions in many areas.=20   
   While uncertainty remains into how dry air in the mid- level may=20   
   impact snow amounts on the broad scale, locally very significant=20   
   snowfall accumulations are likely, especially within these bands,=20   
   during D2. By Sunday afternoon the low will pull away bringing an=20   
   end to the snowfall and leaving just cold windy conditions in its=20   
   wake.   
      
   The exception will be across far southeast Massachusetts and onto=20   
   Cape Cod and the Islands where, despite a subtle southeast trend in   
   today's model guidance, periods of moderate snow are still expected   
   due to onshore flow and sufficient synoptic ascent into the   
   moistening column. A period of moderate snowfall is likely, with   
   some local enhancement south of Boston and on the Outer Cape due to   
   ocean influences, Sunday aftn/eve.   
      
   WPC probabilities for the event are quite robust for both the   
   Appalachians and eastern North Carolina, where they are above 50%   
   for 8+ inches, and 30-50% for 12+ inches. The greatest potential=20   
   for more than 12 inches appears to be eastern NC where the=20   
   deformation band may pivot, but a widespread 4-8" snowfall appears=20   
   likely from southern VA through northern SC, with impactful=20   
   accumulations expected in areas like Richmond, VA, Charlotte and=20   
   Raleigh, NC, Columbia, SC, and even into Atlanta, GA. Farther=20   
   northeast, WPC probabilities are 30-50% for 4+ inches across the=20   
   Cape and Islands.   
      
   Key Messages are in effect for this storm, and are linked below   
   (Key Message #2).=20   
      
      
   ...Great Lakes...   
   Day 1...   
      
   Potent shortwave diving southward within broad cyclonic flow into=20   
   the Tennessee Valley Saturday morning will rapidly sharpen the   
   eastern CONUS trough leaving pronounced CAA on northerly flow in   
   its wake. This will result in continued lake effect snow (LES),   
   especially in the favored north snow belts south of Lake Ontario   
   and especially south of Lake Michigan where the long fetch of the   
   lake will be maximized to produce a narrow band of heavy snowfall.   
   Although the lakes are cooling and have much higher ice coverage   
   than a week or two ago, frigid 850mb temperatures moving overhead   
   will create strong delta-Ts to support snowfall rates that have a   
   30-40% chance (from the HREF) of exceeding 1"/hr, greatest across   
   NW Indiana. While some light accumulations are likely south of Lake   
   Ontario, WPC probabilities for 4+ inches are confined to NW IN   
   where they reach 30-50%.   
      
      
   ...Northern Plains through the Upper Midwest and Great Lakes...=20   
   Days 1-3...   
      
   A shortwave emerging from the Pacific will crest the ridge over the   
   Pacific Northwest and then dive slowly southeast into the Northern   
   Plains and then amplify into a deeper trough as it moves into the   
   Great Lakes and then elongate towards the Tennessee Valley. This   
   feature will generally be of modest amplitude and remain   
   progressive, so large scale forcing for ascent will be modest and   
   driven by mid-level divergence downstream of the trough overlapping   
   modest warm advection/isentropic ascent. The result of this will be   
   axes of both light freezing rain and snow in many areas from   
   eastern MT through the western Great Lakes. WPC probabilities for   
   2"+ of snowfall are as high as 30-50% D2 across central/northern   
   MN, and similar for parts of the U.P. and western L.P. of MI D3.   
   For freezing rain, WPC probabilities are as high as 30% for 0.1"=20   
   in western ND on D1, but are generally less than 10% elsewhere=20   
   through the period. However, light freezing rain accreting above=20   
   0.01" is possible for much of Montana and the Dakotas.   
      
   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_1.png__;!!DZ3fjg!_zv2HEUaCxHmrxcjxPpQ_d45hb_EFdwDQXzo01Egj7qkP=   
   UXe0KoqO0O81tc8GJAqH6nRw9ZPdRN7lhhSqjXZph7rlAQ$=20   
      
   https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late=   
   stKeyMessage_2.png__;!!DZ3fjg!_zv2HEUaCxHmrxcjxPpQ_d45hb_EFdwDQXzo01Egj7qkP=   
   UXe0KoqO0O81tc8GJAqH6nRw9ZPdRN7lhhSqjXZerjYTzs$=20   
      
      
      
   $$   
      
   =3D =3D =3D   
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