Thursday, December 21, 2017

Potential Christmas Day Winter Storm

There are some indications that the Northeast could see accumulating snow on Christmas Day.

Source: CoD
We begin by showing the 12z GFS model forecast for precipitation type and intensity, valid at 09z (4am Eastern Time) on December 25th. Note the presence of a storm system offshore of the Northeast, with the rain/snow line far enough offshore so that coastal areas look to receive primarily snow from this system, taking the GFS verbatim. The primary exception in this frame is the strips of land jutting out from New England, which look to at least begin this event with rain.

Source: CoD
Three hours later, at 7am local time, the storm system has intensified and is now bringing heavier snow to the same areas. It appears as if Connecticut, Rhode Island and Massachusetts look to receive the heaviest snow at this point in time, with accumulating snow also aiming for portions of New Jersey, New York and Vermont into New Hampshire. Again, extreme coastal areas near Massachusetts look to be receiving rain at this point in time.

Source: CoD
Our last frame brings us to 10am eastern time, and we see that the storm system has not only intensified further but brought the rain/snow line far enough east to transition the coastal regions of Massachusetts to all snow - and heavy snow, at that. By this time, as the storm system begins to move east, the heaviest snow looks to impact Massachusetts, Connecticut, Rhode Island and the Maine/New Hampshire/Vermont region, broadly. While accumulations in these coastal regions will likely be cut due to the earlier rainfall, a white Christmas does look to be in store for a good portion of the Northeast.

Source: Instant Weather Maps
48-hour accumulated snowfall by late afternoon on Christmas Day pinpoints accumulations nearing 6" for Connecticut and Massachusetts, with a broad 3-6" accumulation forecast for New York, Vermont and New Hampshire. Lake effect snowfall will likely tack on several more inches in western New York both during and after this storm system.

To Summarize:

- A potential winter storm looks to impact portions of the Northeast on Christmas Day.
- Accumulations of 3-6" are most likely at this time, with CT/MA/RI among the most impacted areas.
- Heaviest snowfall should begin falling in the aforementioned states in the early morning hours, and continue through the late afternoon.
- Prepare for significant delays, if you plan on traveling for the holiday.