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   FOUS11 KWBC 230758   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   258 AM EST Sun Nov 23 2025   
      
   Valid 12Z Sun Nov 23 2025 - 12Z Wed Nov 26 2025   
      
      
   ...Southern Rockies...   
   Day 1...   
      
   An upper-low over central AZ this morning will move across the   
   Four Corners and through Colorado later today. Diffluent flow atop   
   a robust subtropical moisture feed will promote snow across the San   
   Juans and Sangre de Cristos, aided by upslope enhancement as the   
   upper low approaches. Snow levels will be high -- generally above   
   9000ft initially then dropping to around 7000ft as precipitation   
   ends early Monday. WPC probabilities for at least 8 inches of snow   
   are >50% above about 11,000ft in the more remote/higher ridge lines   
   of the San Juans and Sangre De Cristo range.   
      
   ...Pacific Northwest & Northern Rockies...   
   Days 1-2...   
      
   A Pacific disturbance embedded within quasi-zonal flow will usher   
   in a progressive, but potent, frontal system into WA/OR/ID and   
   northwestern MT this morning. 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   
   by early Monday as precipitation begins to taper off. 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, snow will also spread across northern ID into   
   western MT later today through Monday as moisture associated with   
   the Pacific system passes through. Minor snowfall accumulations   
   (1-4") are possible as far south as the Tetons and Big Horns. The   
   focus for the heaviest snowfall resides along the Lewis Range on   
   Monday as snowfall rates become enhanced by easterly upslope flow   
   due to strengthening high pressure over southwest Canada. Snowfall   
   rates nearing >1"/hr are possible at higher open passes (e.g.,   
   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 mostly Minor Impacts in the Lewis Range, the Bitterroots,   
   and the Crazy Mountains.   
      
   ...Northern Cascades/Olympic Peninsula...   
   Day 3...   
      
   The next Pacific system will move into western Washington on   
   Tuesday on a 120kt jet. Cold air in place could support some spotty   
   freezing rain along/east of the crest as warmer air aloft moves   
   in. Snow levels will slowly rise as the warm front lifts through   
   overnight into early Wednesday, but may be loathe to budge east of   
   the Cascades until later on Wednesday. With a fairly long moisture   
   fetch into the Pacific, precipitation amounts could be at least   
   modest, suggesting impactful snow even at Snoqualmie Pass. Through   
   12Z Wednesday, WPC probabilities of at least 6 inches of snow are   
   >50% above about 5000ft.   
      
      
   ...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   
   afternoon/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   
   some upslope enhancement may 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 (10-40%) in these areas generally above   
   1500-2000ft in the Adirondacks and Tug Hill, with the highest peaks   
   showing a slightly higher change (50-60%) of at least 4 inches of   
   snow. Still, some snow covered roads could make for slippery   
   driving conditions tonight and Monday morning.   
      
      
   ...Northern Plains...   
   Day 3...   
      
   The shortwave trough responsible for the snow across the Northern   
   Rockies to start the week moves into the northern High Plains on   
   Monday night. By early Tuesday, a sharpening of the jet will allow   
   the mid-level shortwave to deepen and close off (at least briefly)   
   as it remains progressive. WAA and lower-level FGEN will support a   
   stripe of light to modest snow across ND as a surface low deepens   
   along the ND/SD border. It will then continue to strengthen and   
   lift northeastward through MN into the western Great Lakes, with   
   sufficiently cold air on its northwest side for a broad area of   
   snow. The wrapped-up system could form a TROWAL across northern MN,   
   favoring a region of heavier snow. The models disagree on the   
   location and amount of QPF (and thus snow), but the potential   
   exists for an axis of appreciable snow late Tuesday into Wednesday   
   (and beyond for the western Great Lakes).   
      
   Through 12Z Wednesday, WPC probabilities for at least 4 inches of   
   snow are >50% from northeastern MT across much of ND and northern   
   MN. Within this region, probabilities for at least 8 inches of snow   
   are 30-50% over central ND and northern to northeastern MN.   
   Blowing snow may become a hazard as winds increase in response to   
   the deepening low pressure. 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.   
      
   Fracasso/Mullinax   
      
      
   $$   
      
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