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   FOUS11 KWBC 221903   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   203 PM EST Sat Nov 22 2025   
      
   Valid 00Z Sun Nov 23 2025 - 00Z Wed Nov 26 2025   
      
      
   ...Southern Rockies...   
   Days 1-2...   
      
   An upper-low over Baja California will move northeast today and   
   tonight, spreading rain and high mountain snow across AZ then into   
   CO/NM tomorrow. Healthy subtropical moisture directed at the   
   Southern Rockies will at the same time be co-located beneath   
   diffluent flow aloft. Upslope enhancement into some of the   
   mountain ranges such as the Gila Mountains, the San Juans, and the   
   Sangre De Cristo will aid in producing periods of moderate-to-heavy   
   snow across these mountain ranges. The upper low will cross over   
   the Four Corners region on Sunday and deliver heavier snowfall to   
   the San Juans and Sangre de Cristos, but primarily in the   
   higher/remote elevations. Snow tapers off by Monday as the upper   
   low tracks into the central Great Plains.   
      
   Due to the lack of a cold antecedent air-mass, snow levels will   
   struggle to fall much lower than 7,000ft. Elevations above 9,000ft   
   in the Mogollon Rim and Gila Mountains and the more remote   
   elevations above 10,000ft in the San Juans and Sangre De Cristos   
   are the most likely candidates to see the heaviest snowfall amounts.   
   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 1-3...   
      
   A Pacific disturbance embedded within quasi-zonal flow will usher   
   in a progressive, but potent, frontal system into WA/OR/ID and   
   northwestern MT Sunday. As the cold front traverses the Pacific   
   Northwest, snow levels around 5000-6000ft Sunday 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. WPC   
   probabilities for >4" of snow do range between 40-60% in both   
   Stevens and Snoqualmie Passes, with potentially upwards of 6"   
   possible. A brief lull in mountain snow Monday night and into   
   Tuesday morning concludes by Tuesday afternoon when the next   
   Pacific storm system delivers another round of mountain snow to   
   the Cascades and Olympics with snow levels as low as 2,500ft.   
   Additional snowfall totals of 1-4" are possible through Tuesday   
   afternoon with more snow still to come into the middle of the week.   
      
   Farther east, snow will also spread across northern ID into   
   western MT late Sunday and 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. 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,   
   the Crazy Mountains with some localized Moderate Impacts (hazardous   
   driving conditions) in the higher peaks of the Lewis Range.   
      
   ...Northeast...   
   Day 2...   
      
   A clipper system rotating beneath the base of an broad upper-low   
   over Quebec will push quickly through northern NY/New England   
   Sunday 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 both 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. Still, some   
   snow covered roads could make for slippery driving conditions   
   Sunday night 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. There are ongoing differences on model guidance in   
   terms of the speed/strength of this feature as it enters the   
   northern High Plains. Most guidance does agree, however, that as   
   the 500mb trough tracks over the Dakotas, a compact 500mb low   
   develops and with an inverted low-to-mid level trough on the low's   
   western flank. This becomes effectively a TROWAL that helps to   
   focus a narrow band of 850-700mb FGEN and WAA that, when combined   
   with sufficient lef-texit region jet streak dynamics, gives rise to   
   a band of moderate-to-heavy snow starting over eastern MT Monday   
   night. As the 500mb low forms over the Dakotas on Tuesday, EC-AIFS   
   shows the TROWAL develops a formidable band of heavy snow over the   
   Dakotas Tuesday morning that then tracks into central MN by   
   Tuesday afternoon.   
      
   It is worth noting guidance over the last 12-24 hours is still   
   trying to synthesize a better forecast track with this developing   
   storm system, and the placement of where the heavier snowfall   
   occurs is still coming into focus. This is also looking like a   
   fairly progressive system, but could still pack a punch with   
   snowfall rates >1"/hr in play as it tracks through the northern   
   High Plains and Upper Midwest through Tuesday night. At this   
   moment, WPC probabilities are focusing on ND (20-50% chances for   
   >4" of snow) as the most likely to witness impactful snowfall, as   
   well as gusty winds that greatly reduce visibilities. Heavy snow   
   will likely translate into northern MN by Tuesday evening, and SD   
   could also contend with wind blown snow that causes travel delays.   
   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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