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Another Wintry Mess to Impact the Mid-Atlantic/Northeast this Week. 2/18


The general theme for this winter has been for storms to start as snow before dumping every besides the kitchen sink on the region then quickly departing ushering in warmer temperatures. That will continue this Wednesday as most of the region will be hit with a mix of snow, ice sleet before everyone eventually changes to rain.

Synopsis:

A low pressure is expected to cut across the mid west into the Great Lakes Tuesday into Wednesday and deliver multiple precipitation types to the region. A well placed high pressure is going to be drilling cold air south while the low pressure is going to be moving north and warming or atmosphere. How fast this warming takes place and how fast the high pressure moves out is going to determine who gets snow, ice, or plain rain. Below I attached my general overview of the storm system.



There is a large area of a mixed bag of precipitation, most of the mix area will at least start out as some snow before going to ice and rain. The high pressure is dragging cold air down while the low pressure continues to move northward and supply warm air from the Gulf of Mexico. This is why there will be such an icing problem for the eastern third of the nation. Snow will be the main precipitation type from northern Texas up north through the Canadian border through most of Michigan, northern New York and all of northern New England. This will be a prodominantly rain event for the south.

Some models have been hinting at a strong 700-850mb frontogenesis band that will create heavy snow for at least southern portions of the region. In this band there will be high lifting in the atmosphere creating good snow growth and high snow rates as the snow falls to the ground. We can visualize it on the NAM here.


As you can see the band of snow begins to die out and lifting ceases as it moves north. This is why I believe areas like Washington d.c./Baltimore/Atlantic City may do well with this system as the band has a greater chance of reaching those areas, keeping them snow for longer. New York City is right on the edge of a light-moderate snowfall before some ice and those details will be worked out over the next day. If I had to put a call on New York City I would likely say the band will die quicker and mid-level warming will take over before much if any snow is able to fall because that has been the obvious trend this year.


With this system, as we have seen in the past with similar setups this year, there is a high icing threat for a good chunk of the region further south and away from the coast. With the high pressure pushing cold air down and southward and the low pressure flooding the atmosphere with warmer air this is a prime setup for icing. Below I attached a map that I created detailing where the highest threat for icing is.


I believe at least some icing will be evident throughout the region from the central Mid-Atlantic up through southern Vermont and New Hampshire. This area will generally see some but not much freezing rain. Then again all ice is dangerous no matter how much. The area with a bit higher risk I have from the mid altitudes of the Appalachian mountains up just west of Washington D.C. into all of central/eastern Pennsylvania as well as portions of the Hudson valley and northwestern New Jersey. The highest chance for dangerous ice accumulation will be in the higher elevations of the Appalachian mountains into the central third of Pennsylvania. Those areas will experience the most effects from the high pressure and are likely to hold cold air and frozen precipitation longer than the rest of the northeast.


I also created a snowfall forecast without specific number ranges. I do this just to highlight specifically what areas are generally likely to see the highest snow totals. Tomorrow will feature a more specific map with numbers zoomed into our region.


I expect the whole region to have at least light snowfall accumulations of under 3" The only exception to that will be Cape Cod which may only see a few flakes before transferring to all rain. My 3"+ area stretches from the northern half of Massachusetts and New York and including the rest of northern New England. Further south I have the 3" line just north of Washington D.C. extending southwest and northeast into eastern Pennsylvania up to the Pennsylvania New York border. The heaviest accumulations for snowfall will be the upper elevations of the Appalachian mountains in West Virginia into central Pennsylvania. The next heaviest axis of snow starts at the northern half of New Hampshire extending through Maine.

The map, at first glance, appears a bit wonky with a gap of snowfall in the middle. The reason there is a gap is because southern areas will experience heavy snow and higher accumulations due to intense lifting in the upper atmosphere. This lifting starts to die off around New York Cities latitude and since there is a high pressure that is departing places north of New York City will not be able to hold in enough cold air to thump snow before going to sleet and rain. North of the Connecticut/Massachusetts border there will likely be enough cold air in place to see a pickup of higher totals again that we did not see from New York City to Boston.

#Snow #ice #sleet #rain