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   FOUS11 KWBC 052005   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   305 PM EST Fri Dec 5 2025   
      
   Valid 00Z Sat Dec 06 2025 - 00Z Tue Dec 09 2025   
      
      
   ...Pacific Northwest, Northern & Central Rockies...   
   Days 1-3...   
      
   A highly active storm track with several significant atmospheric   
   rivers into the Northwest will usher in copious amounts of Pacific   
   moisture from the Pacific Northwest on east into the Northern and   
   Central Rockies the next few days. A steady barrage of >90th   
   climatological percentile PWATs will stream across the Pacific   
   Northwest into the Great Basin and Rockies through Saturday, with   
   another round of >90th percentile PWATs arriving in the Pacific   
   Northwest Sunday into Monday. Synoptic-scale forcing for ascent   
   will be aided by a persistent NW-SE oriented 250mb jet streak with   
   its diffluent left exit region overhead. Snow levels over the   
   Pacific Northwest will dip as low as 3,000ft while the Northern   
   Rockies generally hover around 4,000ft. As height falls occur over   
   the Northwest through Saturday, snow levels will drop to as low as   
   2,000ft. That being said, the heaviest snowfall will be confined to   
   elevations above 5,000ft in the Bitterroots, Lewis Range, and   
   Sawtooth, above 6,000ft in the Tetons, Absaroka, Big Horns, Bear   
   River, and Wasatch Ranges, and above 7,000ft in the central WY/CO   
   Rockies. Snow looks to taper off across the Central Rockies by   
   Saturday evening, but the next atmospheric river will deliver   
   another plume of Pacific moisture and another round of heavy   
   mountain snowfall across the Pacific Northwest and northern Rockies   
   Sunday into Monday.   
      
   WPC probabilities continue to be impressive on Day 1 across the   
   higher terrain from Glacier NP through Yellowstone NP including   
   portions of the Sawtooth/Salmon River ranges, Absarokas, terrain of   
   NW WY, northern Utah, and into the Park Range of CO. Here, WPC   
   probabilities reach above 70% for 8+ inches, with locally higher   
   amounts of 1-2 feet generally above 6000 ft. Over the next few   
   days, WPC probabilities paint a wintry picture across many of the   
   Northern and Central Rockies, as well as the higher elevations of   
   the Cascades (above 5,000ft) with high chances (>70%) for   
   additional snowfall totals >18" in all of these listed ranges and   
   elevations through Sunday. In fact, the higher elevations of the   
   Lewis Range, Bitterroots, and Tetons have moderate-to-high chances   
   (50-80%) for snowfall totals >24". Moderate to heavy snow continues   
   later into Days 2 and 3 over the WA Cascades and northern Rockies,   
   though probabilities suggest less snowfall compared to the more   
   snowy stretches tonight into Saturday. The WSSI shows many areas of   
   Minor and Moderate Impacts across the Northern and Central   
   Rockies, including some locally Major Impacts. The Major Impact   
   potential areas (considerable disruptions; dangerous travel and   
   widespread closures) include areas along the Wasatch east of Salt   
   Lake City and the more remote areas of these Intermountain West   
   ranges. Residents in these mountain ranges should prepare for a   
   multi-day stretch of winter weather that results in difficult and   
   treacherous travel conditions.   
      
   ...Northern Plains & Midwest...   
   Days 1-2...   
      
   A fast-moving clipper system, aided by a slug of Pacific moisture   
   combined with strengthening low-level frontogenesis and warm   
   advection, will support a swath of moderate to heavy snow from the   
   northern Plains into the Midwest the next couple of days. The band   
   of snow first starts to develop across the Dakotas late tonight   
   into Saturday morning, then heads for southern MN and   
   northern/central IA as it intensifies late Saturday afternoon and   
   evening. The band then begins to weaken by early Sunday morning as   
   the snow reaches the Lower Great Lakes and OH Valley.   
      
   The latest WPC probabilities have increased with this forecast,   
   now supporting probabilities of 50-90% for snowfall totals >4" for   
   locations that banding (mentioned above) is most likely across the   
   Midwest. However, given the favorable synoptic and mesoscale   
   processes at play, a swath of heavier and more impactful snow still   
   remains on the table, as evident in the low-to-moderate chances   
   (30-50%) for snowfall totals >6" over northern/central IA. By   
   Sunday, low probabilities (10-40%) of >4" of snow extend into   
   southern Wisconsin and northern Illinois as the quick-moving wave   
   weakens on its track into the Lower Great Lakes and OH Valley.   
   Those in the Midwest should continue to monitor the forecast   
   closely as additional changes in the placement and totals of the   
   heaviest snowfall could still change over the next 24 hours.   
      
   ...Great Lakes & Northeast...   
   Days 1-3...   
      
   Periodic mid/upper level impulses rotating within a broad cyclonic   
   flow pattern will continue to support rounds of light-to-moderate   
   lake effect snowfall across the upper Great Lakes through Monday. A   
   cold frontal passage Saturday into early Sunday morning   
   revitalizes LES bands over the Michigan U.P. and downwind of Lake   
   Ontario over the Tug Hill. Then, the fast-moving clipper from the   
   Midwest races across the Great Lakes and Northeast later Sunday   
   into Monday, bringing more lake effect snow and likely a period of   
   steadier synoptic snow to interior portions of the Northeast and   
   northern New England. The latest 12Z guidance continues to suggest   
   a fairly flat mid/upper level shortwave as it passes over the   
   region, which would limit snowfall potential. That said, it would   
   not be surprising to see models trend a bit more amplified and more   
   snowy in future model cycles, so continue to monitor the forecast   
   in the coming days.   
      
   WPC probabilities show overall low chances (10-40%) of >4" of snow   
   across portions of northern Michigan downwind of Lake Superior and   
   Lake Michigan Saturday into Sunday. Low chances (10-30%) of >4" of   
   snow then extend downwind of Lake Erie and Lake Ontario and across   
   parts of northern New England Sunday into Monday.   
      
      
   Miller/Mullinax   
      
      
      
      
      
      
      
   $$   
      
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