TZUTC: 0000   
   MSGID: 167517.weather@1:2320/105 2da2480c   
   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 110840   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   340 AM EST Thu Dec 11 2025   
      
   Valid 12Z Thu Dec 11 2025 - 12Z Sun Dec 14 2025   
      
      
   ...Montana...   
   Days 1-2...   
      
   A swath of heavy snowfall is likely tonight into Friday across   
   much of central and eastern MT. A strong cold front will drop   
   south today in response to a building mid level ridge off the West   
   Coast. While considerably weaker than prior days, IVT is still   
   forecast over the 97th percentile over MT, with PWs around the 90th   
   percentile. This moisture will override the cold front and result   
   in a swath of significant snowfall. The latest WPC probabilities   
   indicate a high chance (greater than 80%) of >4" of snow over much   
   of central and eastern MT, with portions of the area likely to   
   exceed 8". This is expected to be more of a prolonged moderate   
   snowfall with the event picking up in intensity later tonight and   
   ending late Friday night...although periods of more intense   
   snowfall rates are likely.   
      
   ...Great Lakes into Northeast...   
   Days 1-3...   
      
   Cold advection within cyclonic flow around the storm system   
   exiting the Northeast will result in several lake effect snow bands   
   today. The most prominent bands will be over the Chautauqua Ridge   
   and off of Lake Ontario towards Syracuse. WPC probabilities give   
   both of these areas a greater than 70% chance of an additional 4"+   
   of snow today into tonight.   
      
   On Friday a weak area of low pressure will bring an initial batch   
   of light WAA snow to the Great lakes, followed by CAA lake effect   
   snow in its wake. WPC probabilities of exceeding 6" of snow with   
   this event are over 50% across the lakeshore of the U.P. of   
   Michigan, northwest lower MI, and the favored areas downwind of   
   Lake Erie and Ontario. While some areas may locally exceed 8", this   
   is not expected to be a high end lake effect event given the   
   relatively short duration of the most favorable ingredients.   
      
      
   ...Dakotas, Midwest, Ohio Valley, & Central Appalachians...   
   Days 1-2...   
      
   Northwest flow will support a clipper system moving from the   
   Northern PLains into the OH Valley today into Friday morning   
   resulting in a swath of light to moderate snowfall amounts.   
   Initially we should see a swath of freezing rain this morning from   
   portions of south central ND into central SD just north of the   
   shallow cold front, with the latest WPC forecast supporting some   
   ice accumulations of around or even a bit higher than 0.10".   
   However as the system quickly moves east today the main   
   precipitation type will be snow, with perhaps just a bit of a mix   
   and/or rain on the far southern extent of the precipitation shield.   
      
   Even at this short lead time there remains some uncertainty with   
   the exact axis of highest snowfall with this system. The 00z high   
   res models remain north of the global guidance, but they did trend   
   south compared to their 12z runs. The latest WPC preference takes   
   a consensus approach, resulting in a swath a bit south of the 00z   
   HREF mean, and a tad north of the global model consensus. The quick   
   movement of this system will limit snowfall magnitudes, although   
   the latest WPC probabilities depict a swath of a 30-50% chance of   
   >4" of snow from portions of central IL into south central IN and   
   towards the KY border. These probabilities could be a bit low, with   
   these quick hitting clipper systems often verifying with a narrow   
   band of higher amounts, and a good amount of this snow falling   
   overnight helping with accumulations. Thus would expect to see a   
   swath of 4-5" with this system, with a few totals over 5" possible.   
      
   The system will begin to weaken as it moves into the Mid-Atlantic,   
   and thus not expecting much in the way of snow to make it east of   
   the Appalachians. Even with the weakening nature of the system,   
   upslope flow will still support accumulating snow over the favored   
   terrain of WV into southwest VA, with >4" snow probabilities   
   peaking in the 30-50% range over southeast WV Friday.   
      
      
   ...Corn Belt, Midwest, Ohio Valley and Mid-Atlantic...   
   Day 3...   
      
   Another quick moving system will eject into the Northern Plains   
   Friday night into Saturday, quickly moving across the OH Valley on   
   Saturday and into the Mid-Atlantic Saturday night into Sunday   
   morning. This will be a quick moving system which will limit   
   snowfall magnitudes, however widespread minor impacts can be   
   expected, with WPC probabilities already indicating a 60-80%   
   chance of >2" of snow from SD into OH. The probabilities of >4"   
   drop into the 10-40% range...indicating that totals of this   
   magnitude are currently unlikely to be widespread, but may very   
   well occur in localized swaths along the track.   
      
   As this system approaches the Appalachians the mid level trough   
   begins to dig and take on more of a neutral tilt. This will   
   increase mid and upper level southerly flow and begin the process   
   of coastal low development. Most likely this trough will remain   
   too progressive and take on a negative tilt too late to bring a   
   significant snowfall risk to the Mi-Atanltic and Northeast.   
   However, it is becoming increasingly likely that we see enough   
   increase in forcing to see an expansion of some accumulating snow   
   into the Mid-Atlantic Saturday night.   
      
   This expected evolution will support a more prolonged period of   
   accumulating snowfall into portions of WV and southwest PA, where   
   probabilities of >4" of snow have increased into the 50-80% range,   
   with >6" probabilities even over 40%. By later Saturday night model   
   guidance is trending towards a more favorable solution for a quick   
   shot of snow even into coastal areas of the Mid-Atlantic. In fact   
   the 00z deterministic GFS/CMC/ECMWF/AIFS would all bring some   
   accumulation of snow into the DC to NYC corridor. From an ensemble   
   perspective, the WSSI-P shows a 50-60% chance of minor impacts   
   from DC to NYC and a 10-20% chance of Moderate impacts. This   
   generally seems like a 1-3" event, but the latest guidance does   
   support the potential for a narrow axis of 3-5" somewhere over the   
   eastern Mid-Atlantic. This is a lower probability outcome and   
   likely the ceiling for this event given the quick storm motion, but   
   the risk is supported by the aforementioned low WSSI-P moderate   
   probabilities and some low >4"+ WPC probabilities. These quick   
   northwest flow systems are tricky to pin down with much lead time,   
   so future adjustments to the forecast are likely.   
      
   Chenard   
      
      
   $$   
      
   = = =   
   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