December was cold, dry, and annoying. Everywhere in the country seemed to get snow — for god sakes the Florida panhandle got 4 inches — except the Mid-Atlantic. Then came the massive blizzard — 20 inches of snow, 60 mph wind gusts in the New York City Area. Typically these intense, sweeping storms lead to weather pattern changes. In this case– based on North Atlantic Osculation predictions — it seemed like we would get an extended thaw. We got the thaw, just not for an extended amount of time.
The NAO prediction continues to stay well below 0 (meaning entrenched cold weather), and is predicted to stay there through late January. With readings below 0 massive amounts of cold air are pushed down through the country, leading to all the cold temperatures. Also when the NAO is below 0 storms that form are colder in the upper atmosphere and will support snow where temperatures are near or below freezing. Based on this, and looking at the longterm GFS weather model, I expect a cold and snowy trend throughout the month in the NYC metro area, and east coast ski resorts! Speaking of snow…
As most know by now, a snow event is going to start Friday afternoon and continue through the night. It will not be a powerful blizzard, but I believe the City will get 6″ of snow from this storm. 2 factors could cause the city to get upwards of 10″:
Cold Air: Cold upper atmospheric conditions, combined with colder surface temperature help create higher snow ratios. Typical ratios for the east coast are 10 inches of snow for every inch of precipitation — a dense, wet snow. As more cold air is in place, the higher these ratios can go — the higher the ratio, the lighter the snow. With lighter snow, accumulations rise.
Norlun Trough: Think lake effect snow from the ocean. These small troughs cause a storm to sit and spin. The ocean will enhance the precipitation, due to the warmer water, and a band of strong snow showers will park over a location and produce heavier snow. Like lake effect snow, these bands are pretty thin — maybe 50 miles — and can have a drastic effect on snow amounts. I don’t know exactly where this banding will set up, but there is a decent chance it could be over the City and push up through the southern Catskill Mountains. I know I am going to Hunter on Saturday!
This won’t be the last of the storms either. Next week could produce a major storm!