Overview Not too sure what the bigger story is as far as the weather is concerned…the two brutal Arctic air outbreaks headed our way or the snowstorm coming to the Mid-Atlantic region Thursday night and early Friday. The Arctic outbreaks are a couple of the coldest air masses in recent memory – perhaps the coldest in 20 years - and they will invade the Upper Midwest, Great Lakes, Ohio Valley, and Northeast during the next week or so. The snowstorm will likely generate blizzard conditions late tomorrow night and early Friday from New Jersey northeastward across the New York City metro region to eastern New England – perhaps even as far back inland as eastern Pennsylvania - with heavy and blowing snow, strong winds, plunging temperatures and poor visibilities.
Now for the details… The ingredients that are on the playing field do indeed have the potential to generate a major snowstorm in the Northeast US. These include the following: (1) an active sub-tropical jet (2) vigorous energy in the upper atmosphere dropping southeastward from western Canada (3) an associated strong upper-level jet streak (4) an upper level low over southeastern Canada that will force that vigorous energy towards the east coast and (5) strong high pressure situated to the north that will be anchoring an impressively cold Arctic air mass.
It appears that initially there will be multiple low pressure centers in the eastern US on Thursday and then one of these will consolidate near the Mid-Atlantic coastline as the upper level trough approaches the eastern seaboard. While there can be some snow and/or rain at times during the day on Thursday, the real action is likely to occur Thursday night into Friday when the precipitation becomes all snow. Snow will fall heavily at times tomorrow night with increasing winds and plunging temperatures. Indeed, an unusual aspect of this storm will be the major Arctic intrusion that occurs while it is still snowing. The result of this is that the normal “snow-to-rain” ratio of 10-to-1 will likely climb to as high as 15-to-1. This will translate into higher snowfall accumulation amounts - of the light and fluffy variety - given the expected total precipitation values.
Preliminary snowfall accumulation estimates are as follows: coating to 3” from the DC metro region across to the Delmarva Peninsula, 4-8 inches in southeastern Pennsylvania and southern New Jersey, and 6-10 inches across northern New Jersey and the NYC metro region - still subject to upward revisions. Temperatures by early Friday will plunge to the single digits in some I-95 corridor locations north and east of the PA/MD border with much lower wind chills and temperatures will not budge much at all during the rest of the day as the core of this first major Arctic outbreak moves into the Mid-Atlantic region. Friday will likely be a "snow day" for many with numerous schools and businesses closed down for the day; especially, from SE PA north and east. The next brutal Arctic air mass arrives by around Tuesday of next week and it could be even colder than this first shot.