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   FOUS11 KWBC 152046   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   346 PM EST Thu Jan 15 2026   
      
   Valid 00Z Fri Jan 16 2026 - 00Z Mon Jan 19 2026   
      
   ...Central and Northern Plains into the Great Lakes...   
   Days 1-3...   
      
   Persistent longwave trough across the eastern CONUS will=20   
   repeatedly re-load through the weekend in response to multiple=20   
   embedded shortwave troughs and accompanying vorticity lobes=20   
   swinging through.=20   
      
   The first of these will be exiting the Northeast into   
   Atlantic Canada D1 as a closed low with the accompanying trough   
   axis extending into the Southeast. Behind this trough and the   
   accompanying cold front, strong CAA in its wake will drive   
   continued lake effect snow (LES), especially east of Lakes Erie=20   
   and Ontario before shortwave ridging develops Friday aftn shutting   
   off the LES. WPC probabilities D1 are modest for 4+ inches of   
   additional snow, highest southeast of Lake Ontario where it reaches   
   30-50%.   
      
   Immediately in the wake of this first impulse, a second shortwave   
   will dig out of Saskatchewan and race S/SE, reaching the Mid-   
   Mississippi Valley by D2 before continuing to rotate E/NE into New   
   England on Sunday. This shortwave will push a power arctic cold   
   front southward beneath it, and a clipper-type low is also expected   
   to track to the southeast across the Great Lakes during this time.   
   While the accompanying synoptic snow through WAA is likely to be   
   minimal, renewed CAA across the Lakes should result in additional   
   LES, with more widespread coverage as cold N/NW flow envelops the   
   entire region. A third shortwave is expected to cross into the   
   Great Lakes on Sunday with subsequent ascent and moisture leading=20   
   to more snowfall, but additional accumulations before 00Z Monday   
   should be minor. Before that time, however, 3-day snowfall   
   probabilities from WPC indicate a high risk (>70% chance) for at=20   
   least 8 inches across the western U.P. and much of the western=20   
   shore of the L.P. where locally 1-2 feet is possible. Lesser=20   
   amounts are expected east of Lake Ontario, but still modest=20   
   accumulations exceeding 8 inches have a low chance (10-30%) of=20   
   occurring.   
      
   In addition to the LES, the arctic cold front and post-frontal CAA   
   will provide sufficient ascent for widespread snow showers and   
   possible snow squalls across the Northern Plains, Upper Midwest,   
   and potentially into parts of the Great Lakes/Ohio Valley. This   
   will begin tonight across the Dakotas, and then persist through   
   Friday night while expanding southeast. While the setup does not   
   appear extremely favorable for strong snow squalls, linear bands   
   aligned perpendicular to the front within a region of elevated   
   0-2km fgen, increasing low-level moisture, and steepening lapse   
   rates where winds at the top of the PBL exceed 50 kts in some   
   areas, will support widespread snow showers (or squalls) with brief   
   heavy snow rates and gusty winds. While snowfall accumulations   
   across this region accompanying these squalls will be minimal, when   
   snow occurs it will fall heavily, and when combined with the strong   
   winds will create periodic near zero visibility and dangerous   
   driving. The alignment of these snow showers/squalls will also   
   support multiple rounds in some areas through D2.   
      
   Key Messages have been issued for these snow squalls, and they are   
   linked at the bottom of this discussion.   
      
      
   ...Ohio Valley, Mid-Atlantic, and Northeast...=20   
   Days 1-3...   
      
   Progressive flow within a reloading and persistent mid-level   
   longwave trough will create active winter weather across the area   
   through the weekend.   
      
   For D1, a low pressure system rapidly exiting into Atlantic Canada   
   will leave residual moisture and ascent across primarily Maine   
   where a theta-e ridge continues to pivot briefly tonight, with   
   increasing NW flow/upslope ascent occurring as the low pulls away.   
   Forecast soundings indicate a rapid drying of the DGZ tonight so   
   any moderate snow should wane quickly by Friday morning, but WPC   
   probabilities indicate a low risk (10-30%) for an additional 4+   
   inches of snow in northern ME.   
      
   Thereafter, the mid-level trough begins to re-amplify in response   
   to a shortwave diving through the Great Lakes and elongating into   
   the Ohio Valley and Central Plains. This evolution will drive an   
   arctic cold front sharply east, reaching the Mid-Atlantic states by   
   the end of D2 /00Z Sunday/. A shortwave downstream of this front   
   may help develop a wave of low pressure which will bring some light   
   to moderate snowfall to New England, although WPC probabilities for   
   more than 2" of snow D2 are only around 30%, highest in the higher   
   elevations of the Catskills and Berkshires. More substantial   
   snowfall is likely through lift along the front, followed by   
   impressive upslope snow into the Central Appalachians, as well as   
   parts of western PA. Steepening lapse rates will keep the DGZ   
   relatively shallow, but sufficient ascent into the moistened column   
   will result in periods of moderate to heavy snowfall which may   
   accumulate to more than 4 inches in parts of WV and PA as reflected   
   by WPC probabilities reaching 30-50%.   
      
   Then during D3 /00Z Sunday to 00Z Monday/ an elongated lobe of   
   vorticity will swing into New England, while a secondary and   
   sharpening shortwave dives into the primary longwave trough across   
   the Mississippi Valley. While the lead impulse may cause some light   
   snow across Maine (WPC probabilities for 4+ inches 10-30%), the   
   more challenging and bigger concern will be what happens with   
   moisture spreading northward from the Southeast the latter half of   
   D3. While uncertainty is significant, there is at least modest   
   confidence that light precipitation will spread far enough   
   northwest to bring snowfall to parts of the Mid-Atlantic coast from   
   eastern VA through coastal NJ, and potentially onto Long Island and   
   Cape Cod. Current WPC probabilities are modest (30-50% for 1"), but   
   trends will need to be monitored as the system develops in the next   
   few days.   
      
      
   ...Southeast...   
   Day 3...   
      
   A complex forecast scenario is evolving for portions of the   
   Southeast beginning around 00Z Sunday and persisting through D3. An   
   arctic cold front will push into the area Saturday and then=20   
   progress rapidly to the Atlantic Coast by Sunday morning. As this   
   front pushes east, a sharpening upper shortwave trough will rotate   
   near the Gulf Coast, potentially taking on a negative tilt late in   
   the forecast period (although there is a lot of uncertainty into   
   the amplitude of this feature). At the same time, a downstream jet   
   streak will amplify to become powerful over the Mid-Atlantic and   
   Northeast, leading to weak surface cyclogenesis along the Gulf   
   Coast. As this wave develops, moisture will spread northward, and   
   while the column will initially be too warm for wintry   
   precipitation, rapid cooling behind the front will allow for a   
   changeover from rain to snow.=20   
      
   The speed at which this occurs, as well as how much moisture can=20   
   remain in the column after transition, will play the most important   
   role into any possible snowfall accumulations. The GFS continues=20   
   to be the most robust with the transition and available moisture=20   
   for snow, while the EC and CMC are weaker and drier. Evaluation of=20   
   the D3 clusters suggests that both the CMC and GFS ensembles are=20   
   under-dispersive (with the CMC members nearly uniformly deeper=20   
   with the trough, while the GFS members are nearly uniformly faster=20   
   at 500mb), suggesting the EC members and their variety of=20   
   solutions results in a more accurate solutions via the ECENS mean.   
   While there is still a lot of uncertainty, confidence is increasing   
   for at least mixed rain/snow from the Florida Panhandle northeast   
   through southeast Virginia. While the threat for significant   
   accumulations appears small, and WSE plumes only have a handful of   
   members producing >1" of snow, the WPC probabilities have increased   
   and suggest a 10-30% chance for 1" of snow from southern AL through   
   the NC Piedmont and into the coastal Mid-Atlantic states. Forecast   
   changes are almost certain, so those potentially impacted should   
   remain apprised of the latest forecast through the next few days.   
      
      
   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!6RNjUAou4g17Px_u1pNFlRzORKhcuzmoTm4odAbI2R7Ol=   
   g8xKox0NZQc9EVJ7SQwiAS7NX09bAHxt-zgZW50whtt9wE$=20   
      
      
      
   $$   
      
   =3D =3D =3D   
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