A deep arctic trough will dive into the central US over the weekend bringing bitter cold air into the eastern 2/3 of the US. As that trough pushes to the southeast, a wave of low pressure will develop along that boundary, over the Tennessee valley. That low pressure will intensify and ride NE along that arctic boundary… and should spread a swath of snow into the Hudson Valley Sunday afternoon and night.
Timing:
– 12pm to 4pm : Snow develops from SW to NE
– 12am to 4am : Snow tapers from SW to NE
Impacts:
– Temperatures turning bitter cold
– Snow accumulation on all surfaces
– Treacherous travel conditions Sunday PM & Monday AM
– Adjustments to the forecast expected on Saturday
Snow Accumulations:
– NW Catskills: 2 to 5 inches
– Majority of Hudson Valley: 4 to 6 inches (locally up to 8″)
– Extreme Lower Hudson Valley: 2 to 5″ (mixing possible)
Forecast Discussion:
A very tricky forecast for a fast moving system on Sunday afternoon and evening. A wave of low pressure will develop along the arctic boundary that will move through the Hudson Valley late on Saturday. That boundary will stall out a bit over the east coast on Sunday. That will allow time for a second wave of energy to intensify over the Tennessee valley, and begin to race northeast, along that frontal boundary. This will result in a band of snow to overspread many parts of the Mid Atlantic and Northeast.
NAM Futurecast Radar : Sunday 7am to Monday 7am
But there are still some questions… and some of those are BIG questions.
Where is the boundary?
The exact position of the boundary is crucial, because it will determine where the axis of heaviest snow is. The scenario above is the NAM model solution, and pushes the arctic boundary a bit further southeast. Thus, the low pressure is slightly further offshore, and takes the heaviest band of snow over the NY Metro area and portions of the lower Hudson Valley. If the GFS and Canadian model scenarios are correct, the storm is closer to the coast and generates a bit more precipitation… bringing heavier snow totals to the Hudson Valley and possibly changing NYC to rain for a time.
How much Precipitation is Available?
The difference in the data is STARK at this hour. There are basically two camps…
GFS & Canadian & HRRR models
vs.
European & NAM models
You can see the idea provided by the Euro and NAM model above. The wave is slightly more flat and further off shore. This results in a fast moving system with less precipitation available. Providing a light to moderate snow over the Hudson Valley. Our preliminary forecast is more in line with this idea at this time. However… the GFS, Canadian and HRRR models are all good resources as well… and they are much more Bullish on this storm.
HRRR Futurecast Radar : 5am to 7pm Sunday
The GFS model, Canadian model, and HRRR models all tilt the trough just a bit negative, resulting in a slightly stronger storm, that tracks closer to the coast. The deeper storm has more lift, and results in more moisture being available. When we factor in the arctic airmass… the end result is significantly higher snowfall totals being projected by these computer models. If this scenario is correct, we will need to increase our snowfall forecast by several inches.
We have decided to trust the European and NAM models at this time for a combination of reasons, but one is due to the speed with which the arctic boundary will race SE on Saturday into Sunday. We can see this storm being slightly further offshore than the GFS data suggest, and are being conservative for now… with the understanding that if the European and NAM model data shift toward the stronger, further NW idea… that we’ll be increasing our snowfall numbers for the final forecast Saturday evening.
We will be watching very closely… check back for updates on Saturday!