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   FOUS11 KWBC 160835   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   335 AM EST Tue Dec 16 2025   
      
   Valid 12Z Tue Dec 16 2025 - 12Z Fri Dec 19 2025   
      
      
   ...Cascades and Northern Rockies...   
   Days 1-3...   
      
   Snow levels on the WA Cascades rise from 4000ft to 5500ft through   
   this evening under brief ridging until a sharp shortwave trough   
   axis pushes across the Cascades by 12Z Wednesday on the head of a   
   170ft WNWly jet. This potent cold front brings a sharp drop in   
   snow levels tonight, reaching 2000ft in WA and 4000ft in OR early   
   Wednesday. The precip rates rapidly drop with the snow levels, but   
   there should be impactful snow at pass levels including   
   Snoqualmie. Low snow levels and moderate precip rates persist into   
   Thursday before an intense push of moisture and height rises move   
   in, particularly into Oregon. The latest WPC probabilities remain   
   high for snowfall accumulations >8" (particularly for the   
   Washington Cascades) each of days 1-3, with 72-hour probabilities   
   through Thursday remaining high for accumulations >24".   
      
   Moisture and windy conditions will progress eastward over the   
   Northern Rockies today, followed more surges tonight and Thursday,   
   with falling snow levels. The latest WPC probabilities for   
   snowfall >8" are moderate to high (40-80%) for the highest   
   elevations of central and northern ID and western MT Day 1,   
   expanding south through western Wyoming with 40-80% probs on Day   
   2, and then an increase over similar areas of MD/ID/WY on Day 3   
   with to 50-90%.   
      
      
   ...Northern Plains, Upper Midwest, Great Lakes...   
   Day 3...   
      
   Strong low pressure tracks eastward along the U.S./Canada border   
   roughly from Montana to Lake Superior Wednesday through Thursday. A   
   wintry mix is possible in the warm air advection ahead of the   
   system over the Upper Midwest Wednesday night, but the main concern   
   is the leading axis of heavy snow on the cold conveyor belt that   
   connects to a wrap around deformation band with an intense pressure   
   gradient and high wind/blizzard threat. Fairly fast forward motion   
   and the likelihood that most of the leading bands should be north   
   of the border limits the overall snowfall for the U.S. That said,   
   Day 2.5 WPC probabilities for snowfall >4" remain moderate   
   (40-70%) from northeast ND through far northern Minnesota, with   
   10-30% for >8" in the northern Arrowhead. In general, the wind   
   field should be worst south of the new snow, but over the Dakotas   
   and Minnesota which has a decent snowpack that could be driven into   
   ground blizzard conditions. Please stay tuned on this wind-whipped   
   forecast.   
      
      
   The probability of significant icing is less than 10 percent.   
      
   Jackson   
      
      
      
   $$   
      
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