Premium: Friday AM snow potential hazards analysis

Forecast models have trended farther northwest — and stronger — with a low pressure system, which is forecast to develop on a frontal boundary off the East Coast from late Thursday into Friday. This is the same frontal boundary which is crossing the area this evening, and its eventual positioning offshore will have significant impacts on the forecast evolution.

Models suggest that as the frontal boundary moves offshore, a secondary area of energy in the mid levels of the atmosphere approaches the area. This energy provides enough lift for precipitation, with sufficient moisture, and snow will re-develop to the west of the offshore front. A favorably positioned 250mb jet streak could enhance precipitation on the northwest side, bringing light snow to the New Jersey, New York City, Long Island, and Southeast Connecticut on Friday morning.

What are the uncertainties moving forward?

Forecast models remain inconsistent with the eventual positioning of the frontal boundary offshore from late Thursday into Friday. This will have a large impact on exactly where the shield of precipitation sets up. For example, the Euro remains farther northwest — bringing a few inches of snow to NYC and points east — while the GFS is almost completely offshore.

Additionally, while thermal profiles support snow aloft and in the mid levels, surface temperatures remain somewhat warm on all models. This suggests that even though light snow is falling, accumulations may be somewhat limited until temperatures fall, which is forecast to occur during precipitation.

Mesoscale models should help us discern between solutions over the next 12 hours or so, giving us the ability to gain confidence in the forecast.

NAM model showing snow grazing the coast on Friday morning.

NAM model showing snow grazing the coast on Friday morning.

What are the expected hazards and accumulations?

Currently, we favor a forecast that leans slightly toward a farther offshore track, but also gives some room for a northwest movement. This generally suggests up to 1″ of snowfall along the NJ Coast and on Long Island, with less accumulation farther west toward New York City (while snow may fall, we aren’t expecting much accumulation there at this time).

The snowfall may impact travel during the morning commute on Friday in these areas, especially in the noted areas from the NJ Coast to Long Island. Regardless of your location, leave extra time for travel and be sure to do so carefully as roads may be slick, slippery, and icy.

We have included a preliminary accumulation map below. This will change over the next 12 hours or so as confidence increases in the exact track and intensity of the storm.

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