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   FOUS11 KWBC 260648   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   148 AM EST Fri Dec 26 2025   
      
   Valid 12Z Fri Dec 26 2025 - 12Z Mon Dec 29 2025   
      
   *** Continued Heavy Snow on the Sierra Nevada through Friday ***   
      
   *** Heavy Wintry Mix tonight through Friday night from the Great   
    Lakes through the Northeast and Mid-Atlantic ***   
      
   ...Great Lakes to Northeast...   
   Days 1 & 3... Maximum impact level from WSSI: Moderate=20   
      
   Current UA analysis pin-points our shortwave that be involved in   
   the next winter focused disturbance over the northern and eastern   
   CONUS. Forecast is for the shortwave trough to push through=20   
   northern Lower MI with a sfc reflection developing over IN/OH this   
   morning. Major player in the forecast evolution will also be the   
   attendant 850mb low which will migrate over Lower MI, cutting east   
   to BUF leading to persistent southwesterly flow within the upper   
   portion of the boundary layer. The sfc low will weaken as it=20   
   approaches the Appalachians, getting too far behind the mid- level=20   
   shortwave, and ultimately jumping into the Atlantic by 12Z Sat.=20   
      
   =46rom Friday to Saturday morning, a variety of ptypes are expected=20   
   over the region (central Appalachians/Mid- Atlantic to the=20   
   Northeast) thanks to the WAA regime progged between 925-800mb. The   
   stubborn cold surface air will hold tight over Lower MI and=20   
   especially into the Laurel Highlands in western PA where=20   
   significant freezing rain is possible. WPC probabilities of at=20   
   least 0.10" icing are high (>70%) from central to southeast MI,=20   
   including Detroit, as well as into western PA/western MD. 40 to 70%   
   probabilities of at least 0.25" icing exist over southeast MI down   
   through northwest PA into the Laurel Highlands. Light icing is=20   
   likely on either side of this zone of maximum probabilities -- on=20   
   the south side along the I-66 corridor (DC) and into eastern WV. To   
   the north/northeast, deeper cold air at the surface will allow for   
   sleet to be a dominant ptype over central/eastern PA with up to an   
   inch of sleet possible.=20   
      
   To the north, from central NYS through northeast PA into the=20   
   Catskills/Poconos and to the NYC Metro area, an axis of moderate to   
   locally heavy snow is likely, driven by the stronger height falls=20   
   at the nose of the incoming 130-135kt jet. 00z model suite is in   
   agreement on the axis of heaviest snowfall aligning over the area=20   
   from Central and Southern NY state down through the Lower Hudson=20   
   to NYC and 50-75 miles on either side seeing at least 4" with >6"=20   
   becoming a greater likelihood around the Catskills into the Lower=20   
   Hudson Valley to the north of NYC.=20   
      
   WPC probabilities for at least 4 inches of snow are still >50% in   
   a zone bounded between I-890/Rt 17/I-476 to the west, the southern   
   Adirondacks on the north side, Berkshires/I-91 to the east, and=20   
   into the NYC Metro/Long Island to the south. Probabilities for at   
   least 6" are now between 50-90% for that area of central NY state=20   
   down through southern NY, including the Catskills/Lower Hudson/NYC=20   
   corridor south and east of I-88. Though the system will be=20   
   progressive, combination of higher SLRs and upslope could yield=20   
   more than 8 inches of snow into the southern Catskills where areal=20   
   average maxima is currently positioned and latest WPC probabilities   
   for >8" now upwards of 40-70%.=20   
      
   On D3, another surface cyclone will intensify and move northeast   
   through the Upper Midwest and Great Lakes. Ensemble means show a   
   rapid CAA pattern within the northwest side of the cyclone leading   
   to snowfall breaking out across northeastern MN into northern WI   
   and the Michigan U.P. Best chance for at least 4" of snow lies over   
   the western U.P. due to lake effect threat kicking in downwind of   
   Lake Superior. WPC probabilities for >4" are now between 50-90%   
   across all of the central and western U.P. with the highest   
   probabilities across the Iron Range over into the Keweenaw   
   Peninsula.=20   
      
   Kleebauer   
      
      
   ...California/Sierra Nevada...=20   
   Day 1... Maximum impact level from WSSI: Extreme   
      
   *** Heavy Snow Continues on the Sierra Nevada through this morning***   
      
   Final push of moderate to heavy snowfall forecast across the Sierra   
   Nevada today with the heaviest likely to occur this morning before   
   slowly waning as our AR event finally comes to an end. Prior,   
   expect heavy snow rates between 2-3"/hr at times leading to   
   additional accumulations between 1-2ft above 9000ft MSL. WPC   
   probabilities for >12" are still between 50-80% for much of the   
   northern and central Sierra Nevada with the highest probabilities   
   co-located with the area near Mammoth up to just south of I-80.   
   Storm totals will approach 4-6ft or more after the full event is   
   complete leading to significant impacts to travel even after the   
   event has completed.=20   
      
   Kleebauer   
      
      
   ...Pacific Northwest, Great Basin and Rockies...=20   
   Days 1-3... Maximum impact level from WSSI: Moderate to Major   
      
   Deep low pressure off CA will continue to infuse moisture across=20   
   the West with a separate trough pushing down the BC coast Friday=20   
   and over the northern Rockies Saturday providing a final focus for=20   
   precipitation and ending the active pattern.=20   
      
   Moderate to locally heavy snow for the length of the Cascades will   
   occur through today into early Saturday morning with snow levels=20   
   dropping on the WA Cascades from 3000ft to 1000ft and over the OR=20   
   Cascades to 2000ft. Snow probs for >8" are 50-90% on the WA/OR=20   
   Cascades including for the Snoqualmie and Santiam passes.   
      
   Moisture from the leading edge of the AR from the Pacific will   
   continue to maintain a prolonged moderate to heavy snow forecast=20   
   until the cold frontal passage later this evening. Snow levels=20   
   drop from 6000/7000ft to 3000/4000ft through this time leading to=20   
   increasing travel impacts. Snow probs for >8" are 50-90% over the=20   
   Sawtooths, northern ID/western MT ranges, western WY ranges, the=20   
   higher central NV ranges, and the Wasatch.   
      
   The progression of the cold front is notable with the Day 2 snow=20   
   probs for >8" limited to the Wasatch and 50-80% for northern and=20   
   western CO Ranges.   
      
   Jackson/Kleebauer   
      
      
   ...Winter Storm Key Messages are in effect. Please see current=20   
    Key Messages below...   
      
   https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late=   
   stKeyMessage_1.png__;!!DZ3fjg!5w3TbUg8Y9oJAqQvGcX7aMFVDpRF8TwGKKw-v-VfCNlHR=   
   jP15638ILZXRJ6yNkbDkKwnNrS8Qi7kz_kEq-Rg3Pm5YCc$=20   
      
   https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late=   
   stKeyMessage_2.png__;!!DZ3fjg!5w3TbUg8Y9oJAqQvGcX7aMFVDpRF8TwGKKw-v-VfCNlHR=   
   jP15638ILZXRJ6yNkbDkKwnNrS8Qi7kz_kEq-Rg9_jxf4A$=20   
      
      
      
   $$   
      
   =3D =3D =3D   
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