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   FOUS11 KWBC 030716   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   216 AM EST Sat Jan 3 2026   
      
   Valid 12Z Sat Jan 03 2026 - 12Z Tue Jan 06 2026   
      
      
   ...Upper Midwest/Great Lakes...   
   Days 1-3...   
      
   Impressive lake effect snow (LES) will continue today, especially   
   across the U.P. of MI and downwind of Lakes Erie and Ontario. This   
   LES has already been impressive, with 24-36 hour snowfall of 1-3   
   feet or more in some areas east of Lake Ontario, and today's LES   
   will likely be heavy once again. Continued CAA, reinforced at least   
   slightly by a weak shortwave moving overhead, will maintain steep   
   lapse rates and lake-induced instability to support snowfall rates   
   of 1-2"/hr as reflected by HREF 1"/hr snowfall probabilities   
   above 40%. A more NNW wind shift behind this shortwave will cause   
   bands to drop a little south of the recent heavy snowfall, and   
   WPC probabilities for an additional 4+ inches peak above 70%   
   southeast of Lake Ontario, with lower potential (10-50% chance)   
   across the eastern U.P. of MI and near the southtowns of Buffalo,   
   NY to the Chautauqua Ridge.   
      
   Thereafter, brief shortwave ridging envelops the region before a   
   more significant shortwave crests the western ridge and races   
   eastward towards the Great Lakes. This impulse will be of Pacific   
   origin, and accompanying elevated moisture (PWs above 0.5" and the   
   90th climatological percentile) will track in tandem with this   
   feature. Forcing for ascent driven by height falls/PVA,   
   intensifying left-exit jet level diffluence, and strengthening WAA   
   will provide the impetus for heavy snowfall, with 1"/hr snowfall   
   rates likely within any banded structures. The system will remain   
   progressive, and the guidance has trended a little SW over the past   
   few runs, but accompanying NBM probabilities have been relatively   
   steady. This indicates increasing confidence for a narrow swath of   
   heavy snowfall, for which WPC probabilities indicate a moderate   
   risk (50-70%) for 4+ inches across the U.P. of MI D2 into D3, with   
   several inches likely as well from near Duluth, MN through the   
   northern L.P. of MI.   
      
   Additionally, on the southern edge of this precipitation swath,   
   some mixed freezing rain/sleet is likely as the warm nose edges   
   northward in response to the pronounced WAA. This could result in a   
   corridor of impactful icing from far eastern ND through   
   central/southern MN and into southern WI. Although WPC   
   probabilities for 0.1" of ice are less than 10%, some icy roadways   
   and hazardous travel are possible Sunday evening.   
      
      
   ...Western U.S. Mountain Ranges...   
   Days 1-3...   
      
   A persistent mid-level trough positioned west of the Pacific Coast   
   will periodically shed impulses northeast and onshore, with each   
   subsequent impulse spreading energy across most of the   
   Intermountain West.   
      
   This persistent trough will manifest with 850-500mb heights that   
   will remain at or below the 10th climatological percentile into   
   Monday before finally relaxing. As spokes of vorticity swing out   
   from this trough and push onshore (the first likely this aftn with   
   a secondary impulse lifting northeast on Sunday night), the   
   subtropical origin will expand anomalous moisture onshore thanks to   
   surges of elevated IVT. As is typical with this setup, the   
   corresponding WAA will help drive snow levels upward, but a series   
   of cold front accompanying the aforementioned impulses will temper   
   the overall warming, leading to a general slow drop in snow levels   
   through the period. By Tuesday, as the core of the trough finally   
   pivots towards CA, snow levels could be quite low in the Cascades   
   and Pacific Northwest, only 1500-2500 ft, and just 3000-5000 ft   
   elsewhere after being as high as 6000-8000 ft to start the forecast   
   period. This suggests that each wave of precipitation through the   
   forecast period will result in more expansive and impactful snow at   
   lower elevations.   
      
   During D1, the heaviest snowfall is expected in the Sierra and   
   northern CA terrain where WPC probabilities for 12+ inches reach   
   70-90+ percent, and 1-3 feet is likely above 6000 ft. WPC   
   probabilities for 6+ inches D1 of more than 50% cover a large   
   portion of the Intermountain West terrain as well, with locally 1   
   foot possible in parts of the Wind Rivers, Sawtooth/Salmon River   
   ranges, and Cascades. During D2, waves of precipitation continue,   
   and support another day of heavy snow, focused across the Sierra   
   and Shasta/Trinity area, with lighter accumulations elsewhere, but   
   still covering much of the terrain from the Wasatch/Uintas and   
   points north and west. Multiple feet of snow is again expected in   
   the Sierra (WPC probabilities for 12+ inches above 90%) with more   
   than 1 foot possible in the higher terrain of the northern   
   UT/western WY, and into ID. Finally on D3, precipitation intensity   
   wanes, but additional significant snowfall accumulations are likely   
   in much of the area as this prolonged event begins to wane.   
      
   With extremely heavy snow likely in the Sierra and northern CA   
   mountains, totaling 4-6+ feet in some areas, and snow levels   
   falling below pass levels, travel will become extremely challenging   
   into early next week, and extreme impacts are possible due to the   
   combination of heavy snow and low SLR.   
      
      
   Weiss   
      
   $$   
      
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