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   FOUS11 KWBC 012025   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   325 PM EST Thu Jan 1 2026   
      
   Valid 00Z Fri Jan 02 2026 - 00Z Mon Jan 05 2026   
      
   ...Great Lakes...   
   Days 1-3...   
      
   Persistent west-northwesterly flow continues across the Great   
   Lakes over the next few days. This is following in the wake of a   
   strong arctic front that exited the East Coast to kick off the new   
   year. This cyclonic flow pattern will be enhanced late tonight   
   into Friday as another shortwave passes through the flow, leading   
   to renewed CAA before another weak shortwave swings through on   
   Saturday and ridging finally develops by the end of the forecast   
   period.   
      
   The primary snowfall hazard will be associated with widespread   
   heavy lake effect snow (LES) in the favored W/NW snow belts. The   
   most intense LES will likely begin late tonight through Friday   
   night as 850mb temperatures plummet to as low as -15C to -20C,   
   across lakes that, while they have cooled, are mostly ice- free.   
   This will lead to impressive SBCAPE as high 5000-1000 J/kg to   
   support a long duration 1-2+"/hr LES event, especially downwind of   
   Lakes Erie and Ontario due to upstream connections. The heaviest   
   accumulations D1 and D2 are expected across the Chautauqua Ridge   
   and along/just barely south of the Tug Hill plateau before   
   shifting a little south into D1.5-D2. WPC probabilities are high   
   (>80%) for 6+ inches in these areas D1, continuing east of Lake   
   Ontario D2. Locally 2-4 feet of additional snow is possible east   
   of Lake Ontario before heavy LES wanes during late-D2 into D3.   
   Downwind of the other Great Lakes, WPC probabilities D1 feature a   
   low risk (20-40%) for 6+ inches in the eastern U.P., but this   
   wanes quickly during D2.   
      
      
   ...Western U.S. Mountain Ranges...   
   Days 1-3...   
      
   Shortwave with subtropical origins will cross over the central   
   Great Basin tonight and Central Rockies early Friday over an   
   expanding Rockies upper-level ridge that will help amplify an   
   eastern Pacific trough over the next few days. Downstream of this   
   initial shortwave/impulse, snow levels will remain elevated at   
   7000-9000 ft throughout much of the Great Basin, Four Corners and   
   central/northern Rockies before settling around 70000ft by the end   
   of D1. WPC probabilities D1 for 6+ inches of snow reach above 70%   
   in parts of the Wasatch, Central Rockies, and Tetons/Wyoming Range   
   of the Northern Rockies.   
      
   Then on D2-D3 a more pronounced surge of precipitation spreads   
   onshore CA once again as a deep trough amplifies offshore,   
   resulting in impressively amplified southerly flow. This will push   
   moisture onshore as IVT exceeds 500 kg/m/s (>80% chance). Once   
   again snow levels will be elevated within the accompanying WAA,   
   reaching as high as 8000 ft into the Sierra (although much lower   
   around 6000 ft across the Shasta/Trinity region). The pronounced   
   moisture will result in heavy snow again above these levels, and   
   with SLR expected to be low, it will be an impactful snowfall due   
   to snow load. Precipitation will also reach northward along the   
   West Coast mountains to the Cascades and inland across the Great   
   Basin towards the favorable upslope southwest facing terrain. Snow   
   levels will remain around 6000ft across these regions, with lower   
   levels (around 4000-5000ft) in the Cascades. WPC probabilities   
   D2-D3 are high (>70%) for more than 6 inches across the Sierra and   
   northern CA ranges, as well as the WA Cascades, Sawtooths of ID,   
   and Tetons of WY. More than two feet of snow is likely (70-90%)   
   over the next three days in the Sierra.   
      
      
   ...Columbia Basin and Gorge...   
   Day 1...   
      
   Increasing southerly mid-level flow over the Pacific Coast will   
   continue to spread moisture northward tonight, aided by a   
   weakening shortwave lifting from CA into the northern Great Basin.   
   As this moisture spreads into the Pacific Northwest, it will   
   overrun a slowly retreating ridge of high pressure, manifesting   
   with easterly winds draining into the Columbia Basin/Gorge to   
   maintain cold surface air. This setup is favorable for light   
   freezing rain with modest accretions as reflected by WPC   
   probabilities that reach 20-40% for 0.1 inches of ice after 00Z   
   this evening. Although amounts are generally light, impacted   
   travel is likely tonight into Friday morning due to slippery   
   roadways.   
      
      
   Weiss/Snell   
      
      
      
   $$   
      
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