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   FOUS11 KWBC 021934   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   234 PM EST Fri Jan 2 2026   
      
   Valid 00Z Sat Jan 03 2026 - 00Z Tue Jan 06 2026   
      
   ...Central Plains...   
   Day 1...   
      
   A fast moving clipper rounding the western ridge and dropping   
   southeast over the Central Plains today will have sufficient 290K   
   isentropic ascent and 850mb WAA to foster precipitation over   
   eastern NE and as far east the lower MO River Valley. Soundings   
   show a pronounced warm nose between 850-750mb to cause a wintry mix   
   with surface-850mb temps sub-freezing. WPC probabilities indicate   
   a 70-90% chance of at least 0.01" of freezing rain, with locally up   
   to 0.1" of ice possible leading to hazardous travel. The WSSI does   
   depict Minor Impacts from Ainsworth on south and east to US routes   
   30 and 81 near Columbus, suggesting hazardous travel is a concern   
   in these areas through this evening. There is the potential for   
   some travel impacts all the way to the MO River, including the   
   Omaha metro area this evening.   
      
      
   ...Lake Effect Snow...   
   Days 1-2...   
      
   Ongoing lake effect snow (LES) will continue this afternoon,   
   especially across the eastern U.P., and downwind of Lakes Erie and   
   Ontario. This LES will be driven by persistent CAA across the   
   lakes, leading to steep lapse rates and inversion depths that climb   
   towards 800mb, leading to 500-750 J/kg of lake-induced   
   instability. While the mean low-level flow will be a bit more W   
   than NW, this will help tap an upstream connection from Superior,   
   across Huron, and towards Lake Ontario, indicating the heaviest   
   snowfall will likely be along and south of the Tug Hill Plateau   
   through D1 and into D2 before winding down in response to brief   
   shortwave ridging. While periods of heavy snow are also likely in   
   portions of the northern L.P. and along the Chautauqua ridge, the   
   persistence and intensity of this snowfall should be less. This is   
   reflected by WPC probabilities showing moderate-to-high chances   
   (50-70%) for 4+ inches through Saturday over the eastern U.P. and   
   along the Chautauqua Ridge. The heaviest snowfall will be downwind   
   of Lake Ontario through Saturday with additional snowfall totals of   
   12-20" around Oswego, NY.   
      
   After a brief respite in response to the aforementioned shortwave   
   ridging, two separate, but fast moving, shortwaves will crest the   
   ridge to the west and dive rapidly from Saskatchewan/Alberta across   
   the Great Lakes. The first of these will race southeast Saturday   
   aftn/night, and while some enhanced ascent and subtly increased   
   moisture will result in light synoptic snowfall, additional   
   accumulations from eastern MN through western NY should be minimal.   
      
      
   ...Upper Midwest...   
   Days 2-3...   
      
   One of the 500mb disturbances responsible for heavy mountain snow   
   in the West will round the ridge axis over the southern Plains and   
   head for the Upper Midwest on Sunday. The Upper Midwest lies   
   beneath a coupling 250mb jet streak structure that coincides with   
   500mb PVA and 700mb Q-vector convergence Sunday afternoon that then   
   moves over the Great Lakes Sunday night. In addition to the synoptic-   
   scale ascent aloft, strengthening 850-700mb WAA and FGEN will give   
   rise to a band of heavy snow from northern MN and northern WI   
   Sunday afternoon to the Upper Great Lakes Sunday night. There is   
   likely to be a >0C warm nose in southern ND, central MN, and   
   southern WI that leads to an icy wintry mix. As the 500mb vort max   
   moves east Sunday night, it will run into a stronger confluent zone   
   over Ontario that shears out the disturbance and leads to   
   lessening snowfall rates. By Monday morning, periods of snow will   
   envelope Upstate NY and reach as far inland as the northern   
   Appalachians, but snow will generally be on the lighter side with   
   the upper-level forcing weakening.   
      
   WPC probabilities show low-to-moderate chances (30-50)% for 24-hour   
   snowfall totals >4" over the heart of MI's Upper Peninsula.   
   Localized totals >6" are likely, especially given the favorable   
   meteorological drivers that are at play. Many deterministic   
   members do show a swath of >6" of snow, but given the wide cast of   
   potential QPF totals and the different placement of the band, it is   
   leading to greater dispersion in ensemble mean guidance. At this   
   time, residents from northern MN and northern WI to the MI U.P. and   
   tip of MI's Mitten should prepare for at least Minor Impacts.   
   WPC's WSSI-P does show low-to-moderate chances (30-50%) for Minor   
   Impacts in the Lower MI U.P. and northeast WI. The WSSI-P also   
   shows low chances (10-30%) for Minor Impacts (hazardous travel   
   conditions) over western WI and central MN due to ice   
   accumulations.   
      
      
   ...Western U.S. Mountain Ranges...   
   Days 1-3...   
      
   An active weather pattern continues across much of the West as   
   repeated rounds of Pacific moisture surge onshore and advance   
   eastward across the Rockies.   
      
   An anchored troughing pattern along the west coast of North   
   America is forecast to continue for several more days. This   
   anomalous longwave trough, paired with a strong ridge over Mexico,   
   is supporting steadfast SWrly flow out of the Pacific that is   
   supplying copious amounts of moisture over the western-third of the   
   CONUS. As snow over the central Rockies dissipates this afternoon,   
   an upper-level ridge axis over the Great Basin will slide east   
   thanks to the approach of a large upper-low west of CA. An   
   expansive IVT, with moisture originating out of the subtropics,   
   will surpass 500 kg/m/s and extend almost the full length of the   
   U.S. West Coast tonight. This moisture plume will be heaviest along   
   the track of a frontal system (low 980s low west of OR) that slams   
   into the West Coast tonight and early Saturday morning. While this   
   system has a good deal of moisture at its disposal, their is a   
   significant lack of a continental polar (cP) air-mass ahead of the   
   storm. Still, the combination of upslope enhancement and persistent   
   500mb PVA when paired with the onslaught of Pacific moisture will   
   foster mountain snow throughout much of the West this week.   
      
   Snow levels throughout CA will initially be in the 7000-9000ft   
   range ahead of this first system (higher snow levels farther   
   south), but as subsequent upper- level disturbances approach as   
   they round the base of the longwave trough positioned off the West   
   Coast, 500-700mb height falls and CAA should result in snow levels   
   coming down to the 5000-7000ft late Saturday and to close out the   
   weekend. Snow levels will be a little lower in the Pacific   
   Northwest and northern Rockies, but most snowfall will still reside   
   in the more remote reaches of these mountains ranges with some   
   welcomed snow to ski resorts in these regions. That said, the   
   bigger impacts will be in the Sierra Nevada where low SLR's and   
   steadily lowering snow levels should prompt heavy snow for many of   
   the mountain range's passes.   
      
   Snowfall totals above 6,000ft in the Sierra Nevada, over the next   
   three days, are likely to range between 2-5 feet with localized   
   amounts in the higher peaks of the southern Sierra Nevada topping 6   
   feet. The WSSI is lit up with Major to even Extreme Impacts due to   
   Snow Amount, with the I-80 portion beginning near Truckee on west   
   to around mile marker 158, likely to see significant travel   
   impacts beginning Saturday night and continuing into Sunday.   
   Farther north, WPC probabilities show high chances (>70%) for   
   snowfall totals >4" in the Cascades, Olympics, and on south to the   
   Siskiyou/Shasta mountains of northern CA. Farther east, snowfall on   
   the order of 8-12" are likely in the Lewis Range, Blue, and   
   Sawtooth Mountains above 6000ft, the Tetons, Absaroka, and Bear   
   River above 7000ft, and the Wind River and Uinta/Wasatch above   
   8,000ft. The Sawtooth, Tetons, Wind River, and Bear River Ranges   
   all sport high chances (>70%) for snowfall totals >12" with some   
   localized totals topping 24" expected.   
      
      
   Mullinax/Weiss   
      
      
      
   $$   
      
   = = =   
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   --- SBBSecho 3.28-Linux   
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