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   FOUS11 KWBC 272009   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   309 PM EST Tue Jan 27 2026   
      
   Valid 00Z Wed Jan 28 2026 - 00Z Sat Jan 31 2026   
      
      
   ...Great Lakes...   
   Days 1-3...   
      
   The seemingly endless cyclonic flow that has kept the LES machine=20   
   cranking over snow belts of the Great Lakes looks to continue   
   through the remainder of the work-week. Frigid 850mb temperatures=20   
   will persist with temperatures around -18 to -24C, which are below   
   the 10th climatological percentile. According to GLERL, Lake Erie=20   
   is essentially ice covered, so available moisture will be limited=20   
   there while Lakes Superior and Ontario remain largely open. W-NWrly   
   low-level winds will continue through Wednesday before the approach   
   of a sharp 500mb shortwave pivots through and shifts winds more out   
   of the N-NNW by Thursday. Northerly flow continues Friday as high   
   pressure builds in over the Northern Plains. 72-hour WPC   
   probabilities depict high chances (>70%) for snowfall totals >4"   
   over the northern tier of the Michigan U.P. and down wind of Lake=20   
   Ontario to the south of an over the Tug Hill. The area with the=20   
   best odds of seeing over a foot of snow over the next few days are=20   
   near the Oswego, NY area where WPC probabilities for over a foot of   
   snow are in the moderate range of probabilities (40-60%).=20   
      
      
   ...Cascades & Olympics...   
   Days 1-3...   
      
   A series of storm systems tracking into the Gulf of Alaska will   
   direct rounds of moisture and WAA at western WA through the   
   remainder of the week. Strong upslope flow should support locally   
   heavy snowfall totals as low as 4,000ft, but most heavy snow will=20   
   reside in the more remote areas above 5,000ft. Snow levels rise=20   
   from 4000 to 5000ft over the WA Cascades Wednesday through=20   
   Thursday. By Friday, snow levels approach 6,000ft by Friday in   
   western WA. WPC probabilities for >4" is high (>70%) around Stevens   
   Pass, but lighter accumulations around Snoqualmie are anticipated   
   at this moment given the higher snow levels.   
      
   ...Northern & Central Plains...   
   Days 2-3...   
      
   A weak Pacific shortwave trough tracking NW-SE will ride along a   
   nearby 850mb front to support periods of snow from the northern   
   High Plains on south in the the central High Plains. Snow is not   
   expected to be overly heavy, although the Black Hills through   
   orographic lifting may be able to see snowfall amounts surpass 6".   
   This is supported in WPC probabilities which show moderate-to-high   
   chances (50-70%) for >4" of snow in the Black Hills, and low   
   chances (10-30%) in their peaks for >8". Elsewhere, from eastern MT   
   on south and east through the Missouri River Valley, most snowfall   
   accumulations are likely to range between 1-3". Some hazardous   
   travel is possible, especially where roads temperatures are at or   
   below freezing in wake of the recent extreme cold.   
      
      
   ...Southern Appalachians & Mid-Atlantic...   
   Days 3-3.5...   
      
   ...Confidence In Impactful Snowfall Increasing For the Southern=20   
   Appalachians and Southern Mid-Atlantic...   
      
   To say there remains a large amount of model spread in the   
   potential winter storm beyond Day 3 would be an understatement. In   
   the past 24 hours, ensemble guidance have flipped camps to where   
   the GEFS are the snowier members, CMCE are more in the middle, and   
   the EC-EPS are trending less snowy. It is worth noting that AI=20   
   ensemble membership are not as snowy as the GEFS, but show a little   
   more snow than the EC-EPS, making this an interesting test in how=20   
   the AI ensemble membership performs.=20   
      
   Regarding the setup-- WPC Cluster Analysis shows this potential=20   
   winter storm comes down to several factors: 1) strength of the=20   
   emerging Great Lakes shortwave trough. 2) speed of the shortwave=20   
   trough. 3) tilt/amplitude of the shortwave trough as it tracks=20   
   east. 4) Confluence strength near Nova Scotia. They all work=20   
   together in an intricate dance that makes for difficulties in=20   
   modeling. A stronger/slower shortwave can buy time for confluence=20   
   over New England and Nova Scotia to weaken, giving the shortwave=20   
   more time to amplify, and allow for closer storm tracks to the=20   
   coast that bring heavy snow as far west as the I-95 corridor (some=20   
   GEFS members and some CMCE members). Where the shortwave is=20   
   stronger but progressive, heavier snowfall occurs but largely=20   
   closer to the coast and as far west as the NC Piedmont (CMCE=20   
   members, UK ensembles, split EC/GEFS members). If the shortwave=20   
   trough is more progressive and cannot separate itself from the=20   
   larger TPV to the east there is less amplification, it results in=20   
   a flatter and more positively/tilted shortwave trough, and thus the storm   
   remains largely out at sea (EPS, EC-AIFS ensembles, some GEFS/CMCE   
   members). It is worth noting that, while the EC-AIFS has largely=20   
   performed well inside of 5 days much of the winter season, the EC-=20   
   AIFS and ECMWF did suppress the track of the most recent winter=20   
   storm too much ~4-5 days out before correcting northward inside of=20   
   72 hours out.   
      
   This setup is highly timing dependent; from the primary shortwave   
   trough currently east of Hudson Bay, to the interaction/spacing of   
   the 500mb cyclonic gyres in southeast Canada and south of Iceland   
   that promote the confluence ahead of the potential storm, to the=20   
   incoming Pacific shortwaves that track into western Canada and   
   adjust the strength/position of the western North America ridge.=20   
   There remain a host of embedded shortwaves that will work together=20   
   to create a complex storm evolution off the East Coast. Whatever=20   
   the current model solutions show beyond 72 hours out is unlikely to   
   be the final product. Expect additional model changes in the=20   
   coming days. If there is one thing that has increased in confidence   
   in the past 24 hours, it is the opportunity for coastal flooding=20   
   and beach erosion along the Mid-Atlantic coast. Please refer to our   
   "What We know, What We Don't Know" social media post for=20   
   additional information.   
      
   The one thing they do agree on is this upper trough tracks through   
   the OH Valley Friday afternoon with sufficient PVA and 850-500mb=20   
   mean layer moisture to support snow from central KY to the southern   
   Appalachians through Friday evening. WPC probabilities do   
   show increasing chances for at least minor accumulations >2" over   
   KY and northeast TN, while there are low-chances (10-30%) for   
   snowfall totals >4" through early Saturday morning in the TN/NC   
   Smokeys and Blue Ridge of NC. Residents and those traveling to the   
   Carolinas on north up the East Coast will want to continue=20   
   following the forecasts from WPC and your local NWS WFO for the=20   
   latest regarding this potential winter storm.=20   
      
      
   The probability for significant icing is less than 10 percent.   
      
      
   Mullinax   
      
      
      
      
      
   ...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!54SB-pOI55Au96P5L94fHwqMmZ5LkWpzYAasipw8QCoDB=   
   HpKat7rnUR9CGCuvaNDYBiVEtFlpNZAFxNTxzAKGVc0XKY$=20   
      
      
      
   $$   
      
   =3D =3D =3D   
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