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   FOUS11 KWBC 250750   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   250 AM EST Tue Nov 25 2025   
      
   Valid 12Z Tue Nov 25 2025 - 12Z Fri Nov 28 2025   
      
      
   ...Significant winter storm to impact parts of the Northern Plains   
   and Upper Midwest/Great Lakes through Wednesday before lake effect   
   snow intensifies on Thanksgiving. Key Messages have been issued=20   
   for this storm...   
      
      
   ...Northern Plains/Upper Midwest/Great Lakes...   
   Days 1-3...   
      
   Shortwave trough moving through the northern Plains this morning=20   
   will continue eastward today. The sharpening upper jet across the=20   
   US/Canada supports a strengthening area of low pressure that will=20   
   move from the Plains to the Upper Midwest and western Great Lakes=20   
   over the next couple of days. An inverted trough over ND will act=20   
   as a focus for modest snow this morning, then translate east-   
   southeastward today as the surface low deepens over southeastern=20   
   MN. Trend in recent guidance was to bring this swath of light to=20   
   moderate snow farther south than just 12hrs ago, down the I-94=20   
   corridor into the Twin Cities. As the mid- level shortwave starts=20   
   to then close off, a TROWAL should form on the western side of the=20   
   storm as warmer air wraps northward and westward around the low.=20   
   This could allow for >1"/hr snowfall rates along with gusty winds=20   
   over 30mph, causing some blowing/drifting snow and low visibility=20   
   at times. By tonight into early Wednesday, the low will lift toward   
   the U.P. with northeasterly flow off Lake Superior, aiding in=20   
   enhancing moisture into the region just north of the 850mb low=20   
   (eastern central MN into northern WI).=20   
      
   By Wednesday night into early Thursday, the system will reach its=20   
   peak intensity over Ontario and take the bulk of its snow with it.=20   
   However, northerly to northwesterly flow will transition the lake-=20   
   enhanced snow to lake effect snow over northern WI into the U.P.=20   
   where the 850-lake temperature difference will be >15C (-10 to   
   -14C at 850mb and a lake temperature around 5C). Lake effect snow=20   
    will eventually break out across the rest of the Great Lakes by=20   
    Thursday morning and continue through the day and into Friday=20   
    morning. With 850mb temperatures < -10C and Lakes Erie/Ontario=20   
    SSTs around +10C, intense lake bands will persist on WSW to W to=20   
    WNW flow as the cyclone pulls farther away from the region. Single   
    banded snow will drop southward and become more multi-banded=20   
    downwind of Lake Erie but may retain a stronger single band off=20   
    Lake Ontario. Multi-banded snow will persist across the Upper=20   
    Great Lakes as well through early Friday.=20   
      
   For the synoptic event D1, WPC probabilities for at least 6 inches   
   of snow are >30% from southeastern ND and northeastern SD eastward   
   across much of central MN from the Twin Cities northward to the=20   
   Arrowhead. Higher probabilities >70% exist across central MN and=20   
   northern WI to the U.P. of Michigan. After the surface low passes=20   
   and the snow becomes driven by lake effect (mostly D2-3), WPC=20   
   probabilities for at least 12 inches of snow are >50% from near=20   
   Ironwood eastward across the northern portion of the U.P. near the=20   
   Huron Mountains. This region is also where major impacts due to=20   
   snow amounts are possible as three day snow totals could be in=20   
   excess of two feet. Over northwestern Lower Michigan, lake effect=20   
   snow could yield in excess of a foot of snow as well (probabilities   
   are >50% just east of Traverse City). Residents and visitors in=20   
   the Upper Midwest/Great Lakes are advised to check the latest=20   
   forecast before traveling this week.   
      
   Lake effect snow will pick up in earnest over western and northern   
   NYS on Thursday (Thanksgiving) and continue into Friday. WPC=20   
   probabilities for at least 8 inches of snow are >70% over=20   
   northeastern OH, northwestern PA, and western NY as well as the Tug   
   Hill Plateau downwind of Lake Ontario. Areas that see stronger=20   
   snow bands hold the longest may see totals in excess of 18 inches,=20   
   especially over northwestern PA where WPC probabilities are already   
   >50%.=20   
      
   ...Pacific Northwest/Northern Rockies...   
   Days 1-3...   
      
   An active North Pacific jet will send in two systems into the=20   
   Pacific Northwest and northern Rockies over the next three days.=20   
   The first will be today as the upper jet dips south across=20   
   Washington and a cold front (with a leading warm front) move in=20   
   from the west/southwest. Another system will form west of 140W=20   
   tomorrow and travel along the lead stationary/moisture boundary=20   
   into Washington on Thursday. Snow levels will start low today with=20   
   colder air in place but then rise on Wednesday as milder air wins=20   
   out across the region. The second system will push into the Rockies   
   late Thurs/early Fri.   
      
   For D1, colder sheltered locations along/east of the Cascades may=20   
   see some freezing rain as moisture moves in from the west.=20   
   Otherwise, snow levels initially near 2000-4000ft (north to south)=20   
   along the Cascades will slowly rise over the northern WA Cascades=20   
   but rise much quicker over the southern WA/northern OR Cascades to=20   
   over 6000ft by early Wednesday. Thereafter, snow levels will rise=20   
   well above 5000-6000ft Thursday as the second system moves in. WPC=20   
   probabilities of at least 6 inches of snow D1 are >50% above about=20   
   3000-4000ft in the WA Cascades (which includes Stevens and=20   
   Snoqualmie Passes). For D2-3, WPC probabilities for at least 8=20   
   inches of snow are >50% above about 5000ft. Farther east, much of=20   
   northwestern MT above 6000ft or so across the Lewis and Flathead=20   
   Ranges show probabilities of at least 8 inches of snow above 50%.   
      
      
   The probability of significant ice across the CONUS is less than=20   
   10 percent.   
      
   Fracasso   
      
   ...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!4LDjCV1VJ-Jt_mbQyvEw7p95f8ihrIq4NbocPm8O4o_KN=   
   9w-OXp-MvmkFlPWbEc22b1dUNJdhbzUHBf4SUOwBb9sSDw$=20   
      
      
      
   $$   
      
   =3D =3D =3D   
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