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   FOUS11 KWBC 152028   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   328 PM EST Mon Dec 15 2025   
      
   Valid 00Z Tue Dec 16 2025 - 00Z Fri Dec 19 2025   
      
      
   ...Great Lakes...   
   Day 1...   
      
   Warm advection around the northern periphery of a bubble of high   
   pressure centered over the Southeast U.S. will result in the   
   development of a single lake effect snow band off Lake Ontario this   
   evening, focused into the Tug Hill Plateau through the night   
   before tapering off Tuesday morning. Model soundings depict strong   
   and saturated lift within a deep DGZ, supporting moderate to heavy   
   snow across the Tug Hill. As a result, WPC probabilities are   
   moderate (40-60%) for snow accumulations >8", and high (>70%) for   
   accumulations >6".   
      
      
   ...Cascades and Northern Rockies...   
   Days 1-3...   
      
   After a shortwave trough brings a cold front through this evening,   
   which will lower snow levels amid lighter QPF to around 4000ft in   
   WA and 5000ft in northern OR, snow levels are progged to rise back   
   to 5000ft in WA and 6000ft in OR Tuesday as the next moisture surge   
   pushes inland. However, a sharper shortwave trough axis pushes   
   across the Cascades by 12Z Wednesday. This potent cold front brings   
   a sharp drop in snow levels after 06Z Wednesday to around 2000ft   
   in WA and 4000ft in OR. Again, the precip rates rapidly drop with   
   the snow levels, but there should be impactful snow at pass levels   
   including Snoqualmie. Low snow levels and precip rates persist then   
   through Wednesday night before another push of moisture and   
   mountain snow move in during the day on Thursday. The latest WPC   
   probabilities remains high for snowfall accumulations >8"   
   (particularly for the Washington Cascades) each day from 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 Tuesday night into Wednesday, followed by another   
   surge on Thursday, with falling snow levels. The latest WPC   
   probabilities for snowfall >8" are moderate to high (40-80%) for   
   the highest elevations of northern ID and western MT Day 1,   
   increasing to high (>70%) for a larger footprint of ranges across   
   ID, western MT, and western WY Day 2. Probabilities of >8" then   
   drop back to 30-70% for Day 3, with most confined to ID and WY.   
      
      
   ...Northern Plains and Upper Midwest...   
   Day 3...   
      
   A strong area of low pressure (minimum MSLP currently modeled   
   outside of climatology) progged to track eastward along the   
   U.S./Canada border roughly from Montana to the Upper Great Lakes   
   will support a swath of moderate to heavy snowfall within the   
   deformation zone / cold comma head across portions of the northern   
   Plains and Upper Midwest later Wednesday night into Thursday.   
   Relatively fast forward speed should put a cap on the overall   
   potential from an accumulation standpoint, but even so, the latest   
   WPC probabilities for snowfall >4" are moderate to high (40-70%)   
   across northeast ND and northern Minnesota, with odds of 10-30% for   
   >8". Regardless of snow accumulations, impacts could be more   
   notable than typical as a result of a very tight pressure gradient   
   and the potential for blowing and drifting snow due to strong gusty   
   winds.   
      
      
   The probability of significant icing is less than 10 percent.   
      
   Miller/Jackson   
      
      
   $$   
      
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