These are two things that we need to be concerned about for tomorrow's snow event. In a brief synopsis this is what we will see happening Thursday night through Friday evening. An Alberta Clipper will be moving into the region overnight Thursday. At the same time, a coastal system will be phasing over the Atlantic, too far east to impact our weather directly. As this coastal low develops and gains strength, it will merge with the Alberta Clipper. When this happens, a trough, known as a Norlun trough, will form. A Norlun trough acts in a similar way as a Lake Effect snow band in that it can dump a surprisingly large amount of snow in a brief period of time. Where this trough sets up will determine who will get significant snowfall totals.
So, the question you may be asking yourself is, What is an Alberta Clipper? and What is a Norlun trough?
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| Typical Path of an Alberta Clipper |
An Alberta Clipper is defined as a fast moving low pressure system that moves southeast out of the Canadian Province of Alberta (southwest Canada) through the Plains, Midwest, and Great Lakes region usually during the winter. This low pressure area is usually accompanied by light snow, strong winds, and colder temperatures. We usually do not see large snow falls with Alberta Clippers as they are typically to dry to sustain intense snow bands plus they move through too swiftly.
A Norlun trough is a trough that acts very similar to a Lake Effect snow band in that it can dump snow at a rate of 2"-6" per hour in a narrow band where just a few miles away would receive little if any snow at all. Norlun troughs aren't as common as Lake Effect snow but when they do form they could be found over the New England region. They are a rather recent discovery when research was conducted after two storms surprised many areas in New England. The first storm occurred in March of 1992 when portions of Maine recieved 1-2 feet of snow after a clipper system moved through and a trough developed and stalled over the region. The second storm was in Feb 1993 when Cape Cod received 30 inches of snow after forecasts were calling for only 3 inches! Two scientists, Steve Nogueira and Weir Lundsted conducted research on these events and came to the conclusion that a unique stalled trough was to blame for these surprise events. As a result of their joint discovery, the trough was named after them and became the Norlun trough.
Ok, now enough with the meteorology lesson. Let's get down to the forecast, shall we? Light snow should develop west to east early Friday morning. As the clipper system begins to merge with the coastal low, the Norlun trough will develop. Where this trough develops is vital to the forecast for this snow event. As was mentioned earlier, the trough is a very narrow band of persistent and intense snowfall. My belief is that this trough will develop and remain over the lower Hudson valley and western Connecticut. Those areas could see snow totals as high as 6"-8". For northeast NJ, we are currently in a Winter Storm Advisory and should see only snow totals of 2"-4" before this is all said and done. I wouldn't be concerned with impassable roads and buried cars like we saw with last weeks blizzard. That storm dumped 3"-6" per hour over several hours. This snow event will give us 2"-4" of snow over a period of 12-18 hours.
As always, if anything changes, I will post any updates. In the meantime, let's hope this Norlun trough keeps it's intense snow bands and 6"-9" of snow over the lower Hudson Valley and away from northeast NJ.
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