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   FOUS11 KWBC 310710   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   210 AM EST Sat Jan 31 2026   
      
   Valid 12Z Sat Jan 31 2026 - 12Z 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...   
      
   Sharp mid-level trough over the mid-MS Valley early this morning=20   
   will close off into a potent upper low over Middle TN by 12Z. The=20   
   pattern over the East Coast will feature an increasingly amplified=20   
   pattern (e.g., strengthening S-shaped upper jet) that will support=20   
   explosive cyclogenesis off the Carolina coast this=20   
   evening/overnight. With an arctic air mass already in place, nearly   
   all of the precipitation will be snow even at onset. The system=20   
   will quickly lift up the coast (outside the 40/70 benchmark) and=20   
   clip southeastern New England as it races into Atlantic Canada=20   
   tomorrow.=20   
      
   First part of the system is underway over the southern=20   
   Appalachians with light to modest snow over the Smokeys into SW VA=20   
   beneath lower-level FGEN and incoming height falls/PVA. Snow will=20   
   expand southward today over WNC and Upstate SC as well as northeast   
   GA as the upper low tracks over ATL to CHS by this evening. To its   
   north, near the path of the developing 850mb low, the snow could=20   
   fall heavy at times today with 1"/hr rates possible (10-40% chance=20   
   per the CAM guidance) into the Charlotte metro. As the upper low=20   
   reaches the coast around 06Z Sun, banded snow could sink=20   
   southeastward into northeastern SC (Myrtle Beach/The Grand Strand).   
   By this time, the coastal low will have begun its rapid=20   
   intensification, which leads into the other part of the system.=20   
      
   With the coastal low intensifying through the 990s to 970s mb, N=20   
   to NE flow at the surface over eastern and northeastern NC into=20   
   extreme southeastern VA will increase as snow continues to fall.=20   
   The increasing 850mb northeasterly/easterly flow, tapping into the=20   
   growing theta-e ridge offshore, coupled with WAA and strengthening=20   
   925-700mb FGEN, will support >1"/hr rates over eastern NC after 00Z   
   Sun. Deformation axis should pivot west of the surface low and the   
   cold conveyor sets up across the Atlantic and into the eastern=20   
   Carolinas to support those rates. Cross-sections indicate a broad=20   
   region of favorable conditions for CSI, or even CI (thundersnow),=20   
   which is not unusual in highly dynamic and rapidly intensifying=20   
   systems. The column is quite cold, and SLRs should be well above=20   
   climo with a deep DGZ (>13:1 to near 20:1). These heavy snow rates=20   
   will be accompanied by strong winds that may gust 35-50 mph, higher   
   at the coast, suggesting near-blizzard conditions in many areas.   
      
   One question in the forecast, per the 00Z guidance, is what=20   
   happens in between these two main drivers of heavier snow areas;=20   
   i.e., in the I-85/95 corridors in NC. Some CAM guidance shows an=20   
   extreme min (near zero snow) while other guidance shows at least=20   
   several inches. CAM guidance could be overdoing the mesoscale=20   
   response of oscillatory subsidence/lift surrounding the system, but   
   it certainly is unusual to see this much spread just before the=20   
   start of the event. Trimmed down the amounts here from the previous   
   forecast but not to the extent of the 00Z CAMs.=20   
      
   By Sunday afternoon the low will pull away bringing an end to the=20   
   snowfall and leaving just cold windy conditions in its wake. To the   
   northeast, despite a track just outside the 40/70 benchmark, the=20   
   expansive system will likely clip far southeast Massachusetts=20   
   (southeast of I-95) and Cape Cod and the Islands where periods of=20   
   moderate snow are expected due to onshore flow and sufficient=20   
   synoptic ascent into the moistening column. A period of moderate=20   
   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 at least 6 inches of snow are >50% over much   
   of western NC, across the border to upstate SC, southeastward to=20   
   the coast, and the northeastward up the coast into extreme=20   
   southeastern VA. Lower probabilities around 30% exist along the VA=20   
   border and over southwestern SC. Mesoscale bands will likely=20   
   enhance snowfall over some areas resulting in >10-12" snow. A=20   
   broader area of light snow is expected surrounding the system, with   
   WPC probabilities for at least 1" of snow >50% as far west as=20   
   Atlanta, south to near Savannah, and on the north side up to=20   
   Richmond, VA and Salisbury, MD on the DelMarVa. In MA, WPC=20   
   probabilities for at least 4 inches of snow are >30% over the Cape=20   
   and Martha's Vineyard but >50% over Nantucket.=20   
      
      
   Key Messages are in effect for this storm, and are linked below=20   
   (Key Message #2).=20   
      
      
   ...Northern Plains through the Upper Midwest and Great Lakes...=20   
   Days 1-3...   
      
   And advancing warm front over the western High Plains this morning   
   will continue eastward, bringing the chance for some snow and=20   
   freezing rain as milder Pacific air overruns the cold surface. The=20   
   system will continue eastward Sunday into the western Great Lakes=20   
   and through MI to the eastern Great Lakes Monday. Amounts will be=20   
   light, generally 1-3", as the system remains progressive. WPC=20   
   probabilities for at least 4" are around 10% over portions of the=20   
   Red River Valley (ND/MN border) and perhaps the Keweenaw Peninsula=20   
   wit some lake enhancement after the front moves to the east.=20   
      
      
   Fracasso/Weiss   
      
      
   ...Winter Storm Key Messages are in effect. Please see current Key   
   Messages below...   
      
   https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late=   
   stKeyMessage_1.png__;!!DZ3fjg!4XEwcjZbPCsaopLdDZHr3UrVyP5HfOPX16r-Ffei8ZPsV=   
   DY7_6OXc-aU-DKV2da-bl6n6tCr8zwqm953Cu8HX5EO-2M$=20   
      
   https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late=   
   stKeyMessage_2.png__;!!DZ3fjg!4XEwcjZbPCsaopLdDZHr3UrVyP5HfOPX16r-Ffei8ZPsV=   
   DY7_6OXc-aU-DKV2da-bl6n6tCr8zwqm953Cu8H32009l4$=20   
      
      
      
   $$   
      
   =3D =3D =3D   
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