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   FOUS11 KWBC 020753   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   253 AM EST Fri Jan 2 2026   
      
   Valid 12Z Fri Jan 02 2026 - 12Z Mon Jan 05 2026   
      
   ...Great Lakes...   
   Days 1-3...   
      
   Ongoing lake effect snow (LES) Will continue in earnest today,   
   especially across the eastern U.P., and downwind of Lakes Erie and   
   Ontario. This LES will be driven by persistent CAA across the   
   lakes, leading to steep lapse rates and inversion depths that climb   
   towards 800mb, leading to 500-750 J/kg of lake-induced instability.   
   While the mean low-level flow will be a bit more W than NW, this   
   will help tap an upstream connection from Superior, across Huron,   
   and towards Lake Ontario, indicating the heaviest snowfall will   
   likely be along and south of the Tug Hill Plateau through D1 and   
   into D2 before winding down in response to brief shortwave ridging.   
   While periods of heavy snow are also likely in portions of the   
   northern L.P. and along the Chautauqua ridge, the persistence and   
   intensity of this snowfall should be less. This is reflected by WPC   
   probabilities for 4+ inches on D1 that area 30-50% in the eastern   
   U.P. and along the Chautauqua Ridge, but above 90% east of Lake   
   Ontario, where locally 2+ feet is likely on D1. During D2 the   
   intensity and coverage of LES wanes, but WPC probabilities for 4+   
   inches remain above 50% near Oswego, NY.   
      
   After a brief respite in response to the aforementioned shortwave   
   ridging, two separate, but fast moving, shortwaves will crest the   
   ridge to the west and dive rapidly from Saskatchewan/Alberta across   
   the Great Lakes. The first of these will race southeast Saturday   
   aftn/night, and while some enhanced ascent and subtly increased   
   moisture will result in light synoptic snowfall, additional   
   accumulations from eastern MN through western NY should be minimal.   
      
   A more substantial impulse will then drop southeast in a similar   
   fashion Sunday night, but this impulse will be accompanied by   
   greater moisture as it originates from the Pacific and ejects from   
   the Northern Plains rather than central Canada. This will again be   
   fast moving, but will have more pronounced synoptic lift in   
   response to height falls, PVA, LFQ jet diffluence, and more robust   
   850mb WAA leading to enhanced fgen. At this time, the speed of the   
   system is expected to limit total snowfall, but briefly heavy snow   
   rates thanks to idealized ascent into the DGZ could produce a   
   narrow swath of more than 4 inches as reflected by WPC   
   probabilities that are as high as 50-70% for 4+ inches from near   
   Duluth, MN eastward through much of the U.P and the neighboring   
   portions of WI.   
      
      
   ...Western U.S. Mountain Ranges...   
   Days 1-3...   
      
   An active period of weather continues across much of the West as   
   Pacific moisture repeatedly surges onshore in response to   
   persistent troughing offshore.   
      
   For D1, a brief period of ridging will blossom along the Pacific   
   Coast, but downstream into the Intermountain West a shortwave with   
   Pacific origin will lift steadily northeast while de-amplifying.   
   This will result in a stripe of precipitation arcing from the   
   Northern to the Central Rockies, and falling as snow above   
   6000-7000 ft. WPC probabilities D1 reach above 70% for 6+ inches   
   near the Tetons of WY and the Park Range of CO, with more   
   widespread elevated probabilities for 4+ inches across much of the   
   rest of the terrain in this region.   
      
   Then beginning late D1 and continuing into D3, much more pronounced   
   moisture begins to pivot onshore the Pacific Coast. This will be in   
   response to an impressive trough aligned just offshore, from which   
   a surface low will track northeast towards WA state by Sunday   
   morning, with a secondary wave tracking towards northern CA Sunday   
   aftn. While these surface lows will help enhance local ascent, in   
   general moisture will be pronounced across much of the West due to   
   increasing southerly flow downstream of the primary trough axis   
   pushing IVT well onshore with magnitudes above 500 kg/m/s. As is   
   typical with strong IVT plumes, they will be driven both by Pacific   
   jet energy and warm advection, resulting in elevated snow levels   
   climbing to 7000-9000 ft ahead of the first wave, and while they   
   will rise again with the secondary wave, they will generally be   
   much lower, 5000-7000 ft on D3, even lower, around 3500 ft, in the   
   Cascades and interior Northwest.   
      
   Any ascent forced through synoptic features or upslope enhancement   
   will cause rounds of heavy snowfall above these elevations both   
   Saturday and Sunday. WPC probabilities steadily increase and expand   
   through the weekend, with widespread high chances (>70%) for 4+   
   inches reaching from the Olympics, along the entirety of the   
   Cascades, the Shasta region, the Sierra, and through much of the   
   Northern/Central Rockies and into the Wasatch, by Monday morning.   
   While the heaviest snowfall is likely in the Sierra where many   
   locations above 6000 ft could experience 2-5 feet of snow, much of   
   the higher terrain of the West could receive 1-2 feet before   
   coverage wanes just beyond D3. This will likely bring considerable   
   impacts to the higher elevations due to generally low SLR snow,   
   with difficult travel likely across the Sierra Passes.   
      
      
   ...Central Plains...   
   Day 1...   
      
   A fast moving clipper rounding the western ridge and dropping   
   southeast over the Central Plains today will be of subtropical   
   origin. Although this feature will be progressive and of modest   
   amplitude as it weakens, it will produce sufficient ascent into a   
   moistening column to produce a narrow corridor of mixed   
   precipitation in the vicinity of northeast Nebraska. While total   
   precipitation will be modest, WPC probabilities indicate a 70-90%   
   chance of at least 0.01" of freezing rain, with locally up to 0.1"   
   of ice possible leading to hazardous travel.   
      
      
   Weiss   
      
      
      
   $$   
      
   = = =   
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   --- SBBSecho 3.28-Linux   
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