TZUTC: 0000   
   MSGID: 168509.weather@1:2320/105 2dcd1075   
   PID: Synchronet 3.21a-Linux master/123f2d28a Jul 12 2025 GCC 12.2.0   
   TID: SBBSecho 3.28-Linux master/123f2d28a Jul 12 2025 GCC 12.2.0   
   BBSID: CAPCITY2   
   CHRS: ASCII 1   
   FORMAT: flowed   
   FOUS11 KWBC 121909   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   209 PM EST Mon Jan 12 2026   
      
   Valid 00Z Tue Jan 13 2026 - 00Z Fri Jan 16 2026   
      
      
   ...Great Lakes...   
   Days 1-3...   
      
   Slowly amplifying flow across the east will result in periods of   
   light synoptic snow, and more impressive lake effect snow (LES)   
   through the period.   
      
   Tonight, a surface trough will track rapidly eastward across the   
   eastern Great Lakes and into New England while weakening. Although   
   this feature is progressive and of modest intensity, the enhanced   
   south-westerly flow in its wake will help spawn LES, especially   
   downwind of Lakes Erie and Ontario through Tuesday morning. Slowly   
   rising heights within shortwave ridging Tuesday morning will bring   
   a quick end to this LES, but at least briefly heavy snow rates of   
   1"/hr (10-20% chance) will produce significant accumulations,   
   especially in the Tug Hill Plateau where WPC probabilities are   
   moderate (50-70%) for at least 4" of snow.   
      
   Thereafter, a series of fast-moving shortwave troughs will track   
   southeast downstream of an amplifying ridge across the western   
   CONUS. This will lead to a gradually deepening trough in the east,   
   with increasing cold advection within impressive cyclonic flow. The   
   first of these shortwaves will track across MI and into northern   
   New England late D1 into D2, pushing a surface low along the   
   US/Canada border through Wednesday. Some modest WAA will spread   
   light synoptically forced snow from WI into MI, but with only   
   modest accumulations.   
      
   More impressively, this low will drag an arctic cold front   
   southward behind it, aided by a secondary impulse which will track   
   towards the Gulf Coast helping to deepen the longwave trough with a   
   closed low over the Great Lakes. While there has been a lot of   
   uncertainty and latitudinal changes with this evolution the past   
   few model runs, impressive CAA behind this front will result in   
   impressive LES, especially in the north-wind lake effect belts   
   across the U.P., northern L.P., and south of Lake Michigan, with   
   additional LES likely into northeast Ohio and the Chautauqua Ridge   
   during D3. WPC probabilities for more than 4" of snow D2 reach   
   50-70% for parts of the U.P., and then expand to southeast of Lakes   
   Erie and Ontario D3, with the most significant snowfall likely in a   
   single band southeast of Lake Michigan (with possible Lake Superior   
   connection) across northern IN where 8+ inches of snow is possible   
   (30-50% chance).   
      
      
   ...Central Appalachians through the Northeast...   
   Day 3...   
      
   Amplification of the mid-level pattern through Thursday will result   
   in an anomalous trough digging across the eastern CONUS, reflected   
   by NAEFS 500-700mb heights falling below the 0.5 percentile across   
   portions of the Mid-South and Southeast before 00Z Friday. While   
   this trough is impressive, there has been considerable variability   
   over the past several model cycles both in terms of the intensity   
   and placement of the core of this trough, most notably with the   
   position of the closed low likely to develop Thursday morning.   
      
   This closed low will manifest from a deepening shortwave tracking   
   almost due south out of Manitoba, while secondary energy rotates   
   towards the Gulf Coast. Together, these will amplify the trough as   
   noted above, with the lead shortwave closing off and forcing a   
   slightly negative tilt by the end of the forecast period. At the   
   same time, a powerful jet streak will arc increasingly poleward   
   over the Atlantic (downstream of this trough axis) to provide   
   intense left-exit diffluence overlapping the impressive mid-level   
   height falls and divergence. While this should support a deepening   
   surface low pressure, guidance has systematically backed off on the   
   intensity and southern latitude of this low, with any secondary low   
   development occurring too far east to bring heavy   
   snowfall/precipitation to the east coast despite the lead low   
   moving across northern New England.   
      
   The cluster analysis (00z/11 cycle) indicates that the GEFS is   
   likely underdispersive into D4 as 77% of its members make up one   
   cluster, which is also the most amplified and slowest due to   
   extremely different ridging intensity over northern Ontario. While   
   this solution can't be ruled out entirely, the trend in the GFS   
   heights combined with the more broad solution envelope of the other   
   ensembles indicates the more likely scenario is for a low pressure   
   moving through New England Thursday, with modest warm air aloft   
   (TROWAL) pivoting behind this low coincident with weak deformation   
   atop an inverted trough supporting heavier snow generally from   
   Lake Erie through northern New England. This robust ascent may   
   overlap effectively with a deepening DGZ as well, with the cold   
   column supporting fluffy SLR that can accumulate rapidly. While   
   confidence remains lower than usual at this time range, current WPC   
   probabilities are moderate to high (50-90%) for at least 4" of   
   snow in the vicinity of Lake Ontario and northeast into the St.   
   Lawrence Valley and parts of the Adirondacks.   
      
   Farther southwest, there is higher confidence in brief but   
   impressive upslope snow behind the arctic front on Thursday.   
   Forecast soundings indicate a deepening PBL with theta-e lapse   
   rates around 0C/km, coincident with impressive ascent into the DGZ   
   and then lifting into the terrain, especially from the Laurel   
   Highlands south into the Southern Appalachians. Initially some of   
   this precipitation may be rain, but will quickly dynamically cool   
   (and thermally cool behind the front) leading to periods of heavy   
   snowfall beginning early Thursday and persisting through much of   
   D3. WPC probabilities have dropped a bit as QPF trends have been   
   more to the north, but still indicate a 30-50% chance for at least   
   4" of snow across the higher terrain of WV, with high probabilities   
   (>70% or more) for 2+ inches along most of the Appalachians from SW   
   NC through the Laurel Highlands of PA.   
      
      
   Weiss   
      
      
   $$   
      
   = = =   
   To unsubscribe from WX-STORM and you already have a login, go to   
   https://lists.illinois.edu and use the "Unsubscribe" link.  Otherwise email   
   Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.   
      
   --- SBBSecho 3.28-Linux   
    * Origin: Capitol City Online (1:2320/105)   
   SEEN-BY: 19/10 104/119 105/81 106/201 114/10 120/302 128/187 129/14   
   SEEN-BY: 153/757 7715 154/10 30 50 110 700 218/700 840 220/10 20 30   
   SEEN-BY: 220/70 90 221/1 6 360 226/17 18 30 44 50 227/114 229/110   
   SEEN-BY: 229/134 206 300 307 317 400 426 428 470 664 700 705 266/512   
   SEEN-BY: 267/800 291/111 301/1 320/219 322/757 335/364 341/66 342/200   
   SEEN-BY: 396/45 460/58 633/280 712/848 770/1 100 340 350 772/210 220   
   SEEN-BY: 772/230 902/26 2320/0 105 304 3634/12 5020/400 5075/35   
   PATH: 2320/105 154/10 221/6 218/840 770/1 633/280 229/426