[00Z Euro model surface forecast map for early Thursday evening; map courtesy of College of DuPage Meteorology]
A major east coast storm will not only greatly impact the Mid-Atlantic region from Wednesday night through Thursday night, but it will be a major news making event from the Deep South to New England during the next 72 hours or so with massive icing in some areas and 1-2 feet of snow in others. While there are still some disagreements amongst the many computer forecast models and some important details that still need to be ironed out regarding the unfolding event, it is increasingly clear that a powerful storm will track from near Norfolk, VA late Wednesday to just off the New Jersey coastline by late Thursday and then to near Cape Cod, MA by early Friday. There is likely to be a widespread path of heavy snow of a foot or more extending from the western Carolina mountains to northern New England by the time all is said and done and a major ice storm will occur in many locations just to the south and east of the heavy snow band from the Deep South to the Northeast US.
Snow is likely to begin in the DC metro region during the early evening hours on Wednesday and then near or after midnight across Philly and NYC. The Wednesday evening rush hour appears to be safe from the upcoming storm, but all bets are off for Thursday and even early Friday. The storm will be in full throttle for both rush hours on Thursday in the Mid-Atlantic region and Friday morning may still be quite problematic given the fact that the “wrap-around” snow in the “cold conveyor belt” region of the storm (northwest flank) can last right into Thursday night. In fact, the “wrap-around” snow looks quite impressive on the back side of the storm late Thursday. There still is the question as to how much mixing of sleet and/or freezing rain will occur during this storm with the greatest chances of mixing from I-95 to points south and east. The northern and western suburbs of the big cities may stay as primarily snow, but even in those areas a changeover to sleet and/or freezing rain can occur on Thursday. It is possible that the storm results in the scenario of “snow changes to a mixture and then changes back to snow” and, by the way, "thundersnow" is also in the pciture for this storm. Preliminary snowfall estimates are 8-14 inches in and around the DC, Philly and NYC metro regions with the higher amounts in that range occurring in the northern and western suburbs and the lower amounts to the south and east.
As far as the computer forecast models are concerned, the GFS (NOAA) model has indeed come farther to the north and west with the pending coastal storm and it has strengthened it as well compared to its earlier runs, but the European computer forecast model is still the most impressive in terms of storm strength and precipitation amounts. Last night’s 00Z Euro model run depicted a powerful storm just off the Mid-Atlantic coastline as of early Thursday evening. The Euro model has been quite consistent and experience says that when the Euro is locked into one solution - as it has been in recent days - then it is best to go with it. [Surface map from 00Z Euro model run showing powerful storm off the Mid-Atlantic coastline as of early Thursday evening; map courtesy College of DuPage Meteorology].
Finally, let me point out that there will be a couple of smaller events this weekend that could bring a little more snow to the Mid-Atlantic region.