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Two more wintry events possible this week

An active mid and upper level atmospheric pattern continues to bring storm threats from the Central to Eastern United States this week. After a moderate snowfall event on Sunday Night into Monday, eyes will turn to two more potential winter weather events, both of very different nature, during the middle part of this upcoming work week. Both have the potential to bring snow, sleet, and ice accumulations to much of the forecast area.

The first threat will come Tuesday Night into early Wednesday Morning. A classic “southwest flow event”, as meteorologists often refer to it, will transpire throughout the Northeast United States. A low pressure system will be well to our north and west — over Canada — drawing in southerly winds and warmer air, but low level cold air over the Northeast will hold on long enough to allow for a period of snow.

Forecast models are in good agreement that precipitation will begin as snow late Tuesday throughout the area, with a few inches possible, before a transition to sleet, freezing rain, and eventually plain rain. But the accumulation of a few more inches of snow, plus ice on top of it, will create hazardous travel conditions. Precipitation should flip to rain before the morning commute on Wednesday — but roads will still be slick.

The highest snow and ice accumulations in this event will occur in the northern suburbs of New York City — from far Northeast New Jersey into Southeast New York and Connecticut. Here, a few inches of snow will be topped by a more prolonged period of sleet and freezing rain before the transition to rain occurs. The morning commute Wednesday will be a bit more slick in these areas.

NAM model showing warmer air working in the mid levels of the atmosphere on Tuesday Night into Wednesday, which will change precipitation from snow to rain.

NAM model showing warmer air working in the mid levels of the atmosphere on Tuesday Night into Wednesday, which will change precipitation from snow to rain.

As this storm pushes off to our north and east, it will drag a frontal boundary near the area by Thursday. This frontal boundary will become the focal point for the potential development of a winter storm on Thursday. As mid level atmospheric energy amplifies over the Central United States, it will shift eastward toward the Ohio Valley. The frontal boundary near our area will serve as a “highway” for the development of not only a low pressure system, but precipitation.

Models are in good agreement on an unusual expansion of precipitation to the west of a frontal boundary, in the cold sector, on Thursday. This precipitation expansion will spread from the Mid Atlantic to the Northeast States on Thursday. This will all be occurring as the atmospheric column is cooling behind a cold front. Rain and sleet will transition to snow, over time, as the precipitation expands and the front slides east.

The exact timing and placement of the frontal boundary will have massive impacts on the forecast. If forecast models are correct with their current depiction of the frontal boundary and the enhanced lift for precipitation on the west side of it, a moderate to significant snowfall would occur in parts of our forecast area on Thursday. But pinpointing the timing of the front, its location, and the transition from rain to sleet and snow is extremely difficult.

SREF model's mean snowfall for Thursday showing the potential for 5 or more inches in parts of the area.

SREF model’s mean snowfall for Thursday showing the potential for 5 or more inches in parts of the area.

And while confidence is building in the potential for moderate to significant snowfall, it remains quite low in regards to the exact area where that will occur. Post-frontal precipitation comes with very high “bust potential”. Forecast models, in general, will have trouble with the exact timing and placement of the front and the moisture that will be pooling along it. In addition, the models can struggle with the atmospheric profiles and the cooling that occurs to allow for precipitation to flip from rain to snow.

So, moving forward, the forecast is quite low confidence. We know that a few inches of snow are possible on the front end of the system on Tuesday into Wednesday, with an eventual changeover to sleet and rain. And we know that the potential exists, given the atmospheric setup, for several inches of snow on Thursday. Over the next few days, we’ll be working hard to iron out the intricate details of the setup.

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