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   FOUS11 KWBC 272050   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   350 PM EST Thu Nov 27 2025   
      
   Valid 00Z Fri Nov 28 2025 - 00Z Mon Dec 01 2025   
      
   ...Great Lakes...=20   
   Day 1...   
      
   Long duration lake effect snow (LES) event continues through=20   
   Friday with prolific snowfall totals in the favored snow belts for   
   NWly flow in northern MI and for WNWly flow off Lakes Erie and   
   Ontario.=20   
      
   Deep low remains over central Quebec through Friday before lifting   
   to Labrador. The mid level trough axis associated with the low is   
   currently over the eastern U.P. and will swing east over the   
   eastern Lakes tonight. Saturated DGZ zones will maintain efficient   
   snow production over the autumnally warm lakes. Ridging finally=20   
   spreads east over the region Friday night ending the LES.=20   
      
   For Michigan expect individual banding in NW flow over the eastern   
   U.P. with additional banding from added fetch from Lake Michigan=20   
   into the Tip of the Mitt will persist through Friday morning. Day=20   
   1 WPC snow probs for >8" additional are 40-70% in the same narrow=20   
   zones being impacted now.=20   
      
   Eastern Great Lakes see ideal multiple lake fetch in cyclonic flow as   
   seen in current radar mosaics with banding from Superior,=20   
   Michigan, Huron, and Ontario into the Tug Hill and fetch from   
   Superior, lower Michigan, and Erie into the Chautauqua Ridge of   
   western NY and east of Cleveland. WPC Day 1 snow probs for >8"   
   additional are 50-70% for these features, and over 80% on the   
   Chautauqua Ridge where probs for >12" are 50-70%.   
      
   Key Messages remain in effect for this system (link #1 below).   
      
      
   ...Northern High Plains through the Midwest into the Northeast...=20   
   Days 1-3...   
      
   ...Significant winter storm to impact large portions of the=20   
   Northern Plains, Midwest, and Great Lakes through this weekend...   
      
   A closed low along the WA coast this afternoon will shift southeast   
   tonight while opening, crossing the Northern Rockies Friday. This=20   
   wave is shunted on the southern trajectory from a northern stream   
   trough currently shifting south down the Canadian Rockies tonight.   
   This trough interaction and a strengthening upstream jet streak=20   
   will help spread moderate snow bands from Glacier NP through   
   northern MT tonight. Temperatures will be plenty cold for all snow   
   in the bands with some freezing rain potential on the southern   
   portions of precip over south-central MT overnight.=20   
      
   The frontogenetical banding quickly extends across the Dakotas   
   Friday morning, reaching western Iowa in the afternoon. This   
   banding is north of a developing lee-side low ahead of the merging   
   troughs that develops over eastern CO Friday and shifts east over   
   the KS/OK border as it further develops Friday night. This allows   
   the fgen band to transition into a deformation band around an   
   inverted trough extending from the surface low. Day 1.5 snow probs   
   for >6" are 30-60% from Northeast MT through central Iowa.=20   
      
   Thereafter, the system amplifies to become much more impressive=20   
   with expanding heavy precipitation through the central Midwest=20   
   Friday night through Saturday. The mid-level trough diving into the   
   Central Plains will sharpen, and as the vort swings into the base=20   
   of the longer wave trough it will force a negative tilt coincident=20   
   with the development of coupled jet streaks (one strengthening over   
   the Central Plains and another exiting the Great Lakes) to produce   
   strong ascent. This overlapping synoptic lift will help strengthen   
   a surface low developing in the lee of the CO Rockies and then=20   
   tracking east, and eventually northeast, from KS through IL and=20   
   into southern MI by 12Z Sunday.   
      
   Downstream of this surface low, warm and moist advection will   
   rapidly intensify as 850mb winds surging to above 50kts draw   
   elevated PWs northward from the Gulf, reflected by PW anomalies   
   surging above the 90th percentile according to NAEFS into KS/MO/IA.   
   This will be accompanied by a theta-e ridge lifting northward as   
   well, and although a true TROWAL is not currently progged, this   
   theta-e ridge will still promote additional moisture and some   
   elevated warm air to promote modest potential instability. This   
   intense WAA will help expand precipitation from the Dakotas and=20   
   Iowa Friday night, to encompass most of the Upper Midwest Saturday,   
   and then cross Lower Michigan Saturday night before surging up the   
   Interior Northeast Sunday.   
      
   Confidence continues to increase in the track of the low with a   
   preference for the northern end of the precip shield given to the   
   EC/GFS which are farther north (through central WI with 0.5" QPF) than   
   the CMC/UKMET. The broad precip shield and ample cold air will   
   result in pivoting heavy bands with the highest totals as of now   
   forecast over central IA where a foot is possible. As noted before   
   the DGZ depth will be a concern at times and with so much precip   
   from WAA, the ratios should be somewhat limited over IL/IN ahead of   
   the system.=20   
      
   Day 2/2.5 WPC snow probs for >8" are over 30% from far southeast   
   SD/northeast Neb across all but far southwest IA, southern MN,   
   central and southern WI, and northern IL. Day 3 probs for >8" are   
   20-40% for much of the L.P. of Michigan. Post-Thanksgiving travel=20   
   is likely to be extremely disrupted during this event.   
      
   Key Messages remain in effect for this system (Link #2 below).   
      
      
   ...Cascades and Northern Rockies...=20   
   Days 1-2...   
      
   Low crossing WA tonight with snow levels in the Cascades around   
   5000ft. Pacific moisture surges inland ahead with snow levels over   
   the northern Rockies of 4000-5000ft which decrease after snow   
   tapers behind a northern stream trough descending from the Canadian   
   Rockies. Day 1 snow probs for >6" are 40% in the high WA Cascades=20   
   and 50-80% across all western MT ranges into northern ID.=20   
      
   A combined upper trough shifts down the Rockies Friday with Day 1.5   
   snow probs for >6" 40-70% in the Tetons, Absarokas, Bighorns, and   
   ranges of north-central C0.=20   
      
      
   Jackson   
      
      
      
   ...Winter Storm Key Messages are in effect. Please see current=20   
    Key Messages below...   
      
   https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late=   
   stKeyMessage_1.png__;!!DZ3fjg!8umiVbKQN4ZSupkAbsvNAy8egWLsRvjnEIX-waL1s0UKs=   
   _UdFepA7tN5qL700FGj-H401SxDmvGxZyaBuiBN2o7Ywhc$=20   
      
   https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late=   
   stKeyMessage_2.png__;!!DZ3fjg!8umiVbKQN4ZSupkAbsvNAy8egWLsRvjnEIX-waL1s0UKs=   
   _UdFepA7tN5qL700FGj-H401SxDmvGxZyaBuiBN6Di-u1E$=20   
      
      
      
      
   $$   
      
   =3D =3D =3D   
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