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   FOUS11 KWBC 231947   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   247 PM EST Sun Nov 23 2025   
      
   Valid 00Z Mon Nov 24 2025 - 00Z Thu Nov 27 2025   
      
      
   ...Pacific Northwest & Northern Rockies...   
   Days 1-2...   
      
   A Pacific shortwave trough is escorting a progressive, but potent,   
   frontal system into WA/OR/ID and northwestern MT today. As the   
   cold front traverses the Pacific Northwest, snow levels around   
   5000-6000ft this afternoon will drop to as low as 2,000ft on the   
   windward side of the Cascades tonight as precipitation. Even as the   
   upper-level trough exits east, lingering upslope flow could keep   
   light snow in the forecast through Monday afternoon. This would   
   affect many of the passes with at least some snow, and WPC   
   probabilities for >4" of snow are between 30-50% in both Stevens   
   and Snoqualmie Passes.   
      
   Farther east, as the aforementioned plume of mid-level moisture   
   tracks eastward, snow will also spread across northern ID into   
   western MT this afternoon through Monday as moisture associated   
   with the Pacific system passes through. Measurable snowfall will   
   stretch as far south as the Tetons and Absaroka with the peaks of   
   the Tetons north of Jackson, WY sporting moderate-to-high chances   
   (50-70%) for snowfall totals >8". The focus for the heaviest   
   snowfall resides along the Lewis Range tonight and through Monday   
   as snowfall rates become enhanced by easterly upslope flow due to   
   strengthening high pressure over southwest Canada. Snowfall rates   
   >1"/hr are possible at higher open passes (including Marias Pass).   
   Snow should taper off across all of the northern Rockies by early   
   Tuesday morning. WPC probabilities for >8" of snowfall are >70%   
   across the Lewis Range above 5,000ft. In the highest elevations of   
   the Lewis Range (>6,000ft), WPC probabilities show moderate chances   
   (40-70%) for snowfall totals >12". The WSSI does show Moderate   
   Impacts (hazardous travel conditions) in the Lewis Range, the   
   Bitterroots, the Crazy Mountains, and peaks of the MT Absaroka.   
      
   ...Northern Cascades/Olympic Peninsula...   
   Days 2.5-3...   
      
   Following a brief lull in the action on Monday night and Tuesday   
   morning, the next Pacific system moves into western WA on Tuesday   
   at the nose of an 140kt 250mb jet. Unlike the storm system this   
   weekend, Canadian high pressure will provide a colder air-mass out   
   ahead of this next Pacific storm system that will support some   
   spotty freezing rain along the leeward slopes/valleys of the   
   Cascades and in the valleys of the Columbia River Basin over   
   northern WA. Snow levels will gradually rise as the warm front   
   lifts through Tuesday night into early Wednesday, but the surface   
   front will takes longer to cross the Cascades rather than the more   
   robust 700mb WAA nose that support the potential for icy   
   conditions east of the Cascades. Thanks to a longwave trough firmly   
   entrenched over the North Pacific, an extended moisture fetch into   
   the the Pacific Northwest provides a favorable setup for multiple   
   days worth of accumulating snow and ice that continues through   
   Wednesday afternoon. Through 00Z Thursday, WPC probabilities of at   
   least 6 inches of snow are >50% above about 4000ft, with as much as   
   4-6" of snowfall possible near Snoqualmie Pass.   
      
   ...Northeast...   
   Day 1...   
      
   A clipper system rotating beneath the base of an broad upper-low   
   over Quebec will push quickly through northern NY/New England this   
   evening and exit to the east by Monday morning. QPF and the   
   resulting snowfall will be somewhat limited due to its fast   
   movement and the clipper being relatively moisture-starved, but   
   upslope enhancement will allow for anywhere between 1-4" of snow   
   across the Tug Hill, Adirondacks, and the Green and northern White   
   Mountains. WPC probabilities for at least 4 inches of snow remain   
   on the lower side (10-30%) in these areas generally above   
   1500-2000ft in the Adirondacks and Tug Hill. Despite the minor   
   accumulations, this system would still support snow covered roads   
   that could make for slippery driving conditions tonight and Monday   
   morning.   
      
   ...Northern Plains & Upper Midwest...   
   Days 2-3...   
      
   The shortwave trough responsible for the snow across the Northern   
   Rockies to start the week moves into the northern High Plains by   
   Monday night. An 850mb low will form along a strengthening   
   925-850mb front over central ND, while a narrow inverted trough   
   axis forms on its western flank. By 12Z Tuesday, areas from   
   northeast MT to central ND will be enveloped in a band of   
   moderate-to-heavy snow that also includes increasingly gusty winds   
   as low pressure strengthens. As the low moves east, the TROWAL on   
   the western flank of the storm is likely to produce at least 1"/hr   
   snowfall rates during the daytime hours Tuesday, which combined   
   with wind gusts approaching 30 mph will cause poor visibility.   
   However, areas not beneath the deformation axis will struggle to   
   accumulate given marginal boundary layer temperatures and lesser   
   SLRs. Expect a tight gradient in snowfall totals, where beneath the   
   TROWAL WPC probabilities over central ND show low-to- moderate   
   chances (30-50%) for snowfall totals >6" through Tuesday evening.   
   Across northeast ND and southern ND, those probabilities drop to   
   low chances (10-30%) for >6".   
      
   By Tuesday evening, the winter storm will strengthen as most   
   guidance agrees that a closed 500 low develops as it heads for   
   central MN. The 500mb low will be embedded within a broad 500mb   
   trough that takes on a negative tilt, fur The heaviest snowfall is   
   likely to occur just north of the 700mb low track, which places   
   northern MN in the sweet spot for heavier totals. Beneath the   
   strengthening TROWAL, snowfall rates of 1-2"/hr are possible late   
   Tuesday afternoon and into Tuesday night. As the storm tracks into   
   northern WI Tuesday night, ENErly winds will accelerate off Lake   
   Superior and introduce more low-level moisture and convergence over   
   the MN Arrowhead. Snowfall rates of 1-2"/hr are anticipated and   
   should accumulate efficiently do the bulk of the snow in northern   
   MN coming over night. Snow will also fall heavily over northwest WI   
   and the western Michigan U.P. Tuesday night and continue into   
   Wednesday as CAA over Lake Superior kick up lake-enhanced snowfall.   
      
   WPC probabilities for >6" of snow are >50% across north-central MN   
   with low-to-moderate chance probabilities (30-50%) for >12" of   
   snowfall in the MN Arrowhead. The area most likely to see >12"   
   snowfall amounts are portions of Michigan's far western U.P.,   
   including the Porcupine Mountains, where WPC probabilities show   
   moderate chances (40-60%) for >12" of snowfall. Across much of ND,   
   most snowfall amounts will range between 2-6", but on which end of   
   those amounts portions of the state witness will depend heavily on   
   the placement of the banded areas of snowfall. Interests in the   
   Northern Plains and Upper Midwest should keep a close eye on the   
   forecasts from their NWS WFOs and WPC in the coming days given this   
   storm could prove a headache for those traveling in the lead up to   
   Thanksgiving.   
      
      
   The probability of significant ice across the CONUS is less than   
   10 percent.   
      
   Mullinax   
      
      
      
      
      
   $$   
      
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