Why Monday’s storm will disappoint NYC snow lovers

Much has been made over the past few days about a potential winter weather event in New York City on Monday morning. Vindication, they’ve called it. After the Blizzard of 2015 barely skirted our area and brought historic snowfall to New England, this Monday’s event was seen by snow lovers as the makeup-call to our blown chance last week. But, we say, not so fast. Despite what forecast models have hinted at over the past few days, there are meteorological elements to this storm system which not only argue against significant snowfall in New York City — but in fact, argue for a few inches of snow followed by sleet and then plain rain. A snow lovers nightmare.

For those who aren’t enamored by snowfall in New York, this article will serve as a bit of detail and an opportunity for understanding some atmospheric processes which are going to be occurring on Sunday Night into Monday Morning. There is a method to the madness of meteorologists, despite what the public opinion may have been on Tuesday morning when most woke up to much less snow than they anticipated.

As a storm system drives toward the Ohio Valley on Sunday, significant preicpitation will begin to expand east-northeast from the Ohio Valley into the Mid Atlantic and eventually the Northeast States. There’s no question about it, this precipitation will start as snow in New York City. As you may have already noticed, it’s cold out there. A Canadian airmass with its roots near the pole settled into the area on Saturday, and it’s just now finally beginning to be pushed northward and moderate a bit. So the moisture coming toward the area on Sunday evening will be overrunning that airmass — and falling as snow.

As the low pressure system drives northeastward, owing to a strong and potent mid level disturbance, it will move toward Western Pennsylvania. And this, my friends, is where problems begin for any snow lovers south of the NJ/NY State Border. As the cyclone matures, low pressure centers close off at multiple levels. This means we’ll have a closed low at the surface in Western Pennsylvania, a closed low at 925mb, and a closed low at 850mb. The NAM model shows this 850mb low very well. We took the liberty of highlighting the wind direction in yellow.

NAM model showing warm air flooding northward in the mid levels of the atmosphere as the 850mb low is tracking well to our northwest.

NAM model showing warm air flooding northward in the mid levels of the atmosphere as the 850mb low is tracking well to our northwest.

With an 850mb low (and other mid level lows) in Western Pennsylvania, southerly winds will develop at those levels. This spells trouble, because as mid level temperatures warm above freezing, any snowflake that can form will fall and melt on its way down through the atmospheric column. If the surface temperature can remain below freezing, that melted snowflake can either fall as sleet or freezing rain — but definitely not snow. This is where model forecast soundings come into play. They help us get a visualization of the atmospheric column.

The NAM model depicts the scenario very well. After a few hours of snow, the atmospheric column warms in the mid and low levels in New York City and surrounding areas. As a snowflake forms, it will fall through this atmospheric column and melt. The depth of the warm air (in this case, temperatures 1 or 2 degrees above freezing) argues that not only will snowflakes melt, they will fall as rain in New York City. Note how the surface temperatures are above zero as well, so the threat for freezing rain would be mitigated.

Atmospheric sounding from the NAM model in New York City for Monday Morning.

Atmospheric sounding from the NAM model in New York City for Monday Morning.

Forecast models indicate a period of time, as this mid level warming pushes north, where sleet or freezing rain could fall. But near the coast and in the city, the surface will warm up after an hour or so — meaning precipitation will be falling as rain. In the suburbs, wintry mixed precipitation could be prolonged, creating icing problems. Farther north across the Hudson Valley and Connecticut, this mid level warming will take longer to occur.

Given the discussed mid level warming, and the depth of the warm layer in the atmospheric column, our confidence is very high that less than 6 inches of snow will fall in New York City. In fact, given receent warming trends among forecast models, our confidence is highest in snow totals being closer to 3-6″ in the NYC Metro Area from Sunday Night into Monday morning before a changeover. In the suburbs, a different story will likely evolve and wintry precipitation could be prolonged.

For more information on the storm as it approaches, stay tuned to our social media and hang tight for the latest articles and snowfall total forecasts.