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   FOUS11 KWBC 252111   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   411 PM EST Tue Nov 25 2025   
      
   Valid 00Z Wed Nov 26 2025 - 00Z Sat Nov 29 2025   
      
      
   ...Significant winter storm/locally a Blizzard continues to impact   
   parts of the Upper Midwest/Great Lakes through Wednesday before=20   
   lake effect snow intensifies Wednesday night and lingers through=20   
   Thanksgiving and even Friday for the eastern Great Lakes...   
      
   ...Confidence increasing on a second winter storm to affect the   
   Northern Plains Friday and the Midwest/Great Lakes Friday night=20   
   into Sunday...   
      
   ...Key Messages for both systems are in effect and linked below...   
      
      
   ...Upper Midwest/Great Lakes...=20   
   Days 1-3...   
      
   Potent developing low over eastern South Dakota this afternoon will   
   continue to deepen/strengthen as it tracks east over Wisconsin   
   tonight and the northern L.P. of Michigan Wednesday. The trough   
   around this low takes on a negative tilt tonight as the downstream   
   SWly jet intensifies and a strong pressure gradient with a 1032mb   
   high over ND by Wednesday morning allows for a strong and broad   
   wind field that will allow Blizzard conditions as indicated by the   
   Blizzard Warnings over the U.P. of MI and in northeast SD. A=20   
   TROWAL forms on the western side of the storm as warmer air wraps=20   
   northward and westward around the low which aids dynamic banding,   
   but also results in a more marginal thermal environment tonight   
   over the eastern U.P. and Wednesday over the northern L.P. However,   
   areas on the back side of the low will see rapid cooling that   
   allows for heavy snow banding and eventually LES.=20   
      
   The system continues to strengthen/deepen through Thursday night as   
   it pushes in to Quebec and becomes rather sprawling. Powerful northerly   
   to northwesterly flow will transition the lake- enhanced snow to=20   
   lake effect snow over northern WI into the U.P. tonight into   
   Wednesday where the 850-lake temperature difference will be >15C=20   
   (-10 to -13C at 850mb and a lake temperature around 5C). Lake=20   
   effect snow will break out for the L.P. of MI Wednesday afternoon   
   and off the eastern Great Lakes late Wednesday night. The threat   
   for single-band LES exists over northern MI Thursday/Thursday night   
   and the eastern Great Lakes Thursday. Expect 850mb temperatures of   
   <-10C over Lakes Erie/Ontario SSTs around +10C, allowing intense=20   
   lake bands to persist on WSW to W to WNW flow as the cyclone shifts   
   north of the region. Single banded snow will drop southward and=20   
   become more multi-banded downwind of Lake Erie but may retain a=20   
   stronger single band off Lake Ontario. Multi- banded snow will=20   
   persist across the Upper Great Lakes as well through early Friday.=20   
      
   For the rest of the synoptic event, Day 1 WPC probabilities for >8"   
   are 50-90% from the northern MN/WI border through northern WI and   
   the western/central U.P. with potential for two feet centered on=20   
   the Porcupine Mtns. Day 1 snow probs for >4" greater than 40%=20   
   extend northeast from the Twin Cities across north-central WI.=20   
   Considerable LES is expected after the surface low passes late=20   
   tonight through Wednesday with Day 2 snow probs for >12" 50 to 80%=20   
   for most of the U.P. the northern L.P. west from I-75 (as well as=20   
   30% south of Grand Rapids). For Day 2.5 the snow probs for >8" are=20   
   50-90% southeast of Lake Erie (including the Chautauqua Ridge into   
   northwest PA) and over the Tug Hill.=20   
      
      
   ...Cascades through Northern Rockies...=20   
   Days 1-2...   
      
   A strong WNWly upper jet shifts across Washington State tonight   
   with sufficient Pacific Moisture for the Cascades (snow levels=20   
   around 4000ft rising to 5000ft) continuing for the Northern Rockies   
   into Wednesday where snow levels rise from 3000ft to 4000ft. Day 1   
   snow probs for >6" are 40-60% above these snow levels for the WA   
   Cascades, Bitterroots to the Absarokas.=20   
      
   High moisture plume ahead of the next wave tracks into Oregon   
   Wednesday with snow levels rising over 8000ft in OR Wednesday   
   afternoon with WA snow levels of 6000ft. Day 2 snow probs for >6"   
   are limited to the high WA Cascades.   
      
      
   ...Glacier NP through Dakotas to Iowa...=20   
   Day 3...   
      
   ...Increasing Winter Storm Threat Friday into/through the   
   Weekend...   
      
   The next winter storm to affect the central U.S. comes from a=20   
   Pacific shortwave low that crosses Washington State Thursday night=20   
   that combines with a shortwave trough that drops from the Canadian   
   Arctic Wednesday night, reaching Montana (and thus the connection   
   to the NW low) Thursday night. This combined longwave trough digs   
   across the northern Rockies Friday as lee-side surface cyclogenesis   
   occurs over eastern WY/CO. Confidence is increasing that a=20   
   resultant developing low pressure system then tracks east over the=20   
   central Plains Friday night with ample Gulf moisture allowing heavy   
   snow bands to set up across portions of the Midwest.   
      
   Of particular note for Thursday night/Friday is the Pacific   
   moisture combining with Gulf-sourced moisture with strong dynamics   
   ahead of the Pacific low (which opens Thursday night as the   
   northern stream trough approaches) allowing heavy snow bands to   
   develop over much of the MT Rockies and adjacent High Plains. Day=20   
   3 snow probabilities for >6" there are around 20% in a swath that   
   tracks just north over Great Falls with 40-80% values for any and   
   all terrain north of the Red Lodge portion of the Absarokas.=20   
      
   As the low develops Friday, a deformation axis of snow develops   
   across South Dakota and stretches into Iowa by 00Z Saturday. Day 3   
   snow probs for >4" are currently limited to 10-40% mainly in   
   eastern SD, but it's that banding that further develops and pivots   
   over the Midwest for much of Saturday.   
      
      
      
   The probability of significant ice across the CONUS is less than=20   
   10 percent.   
      
   Jackson   
      
      
   ...Winter Storm Key Messages are in effect for the ongoing system=20   
   over the Upper Midwest and Great Lakes (link one below) and new=20   
   Key Messages are in production for the next wave (link two below) that   
   reaches the Northern Plains Thursday night and crosses the Great=20   
   Lakes through Sunday...   
      
   https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late=   
   stKeyMessage_1.png__;!!DZ3fjg!4D5seMbfgWTVEv3GFrgjqqfSu-WjjwVo0HYX4BGYOLHZM=   
   ASgNnyhPvfDYvN7k7rjdLjy6M2Tn9Fe3jRAzRog-FLWKQk$=20   
      
   https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late=   
   stKeyMessage_2.png__;!!DZ3fjg!4D5seMbfgWTVEv3GFrgjqqfSu-WjjwVo0HYX4BGYOLHZM=   
   ASgNnyhPvfDYvN7k7rjdLjy6M2Tn9Fe3jRAzRogjtma3wE$=20   
      
      
      
   $$   
      
   =3D =3D =3D   
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