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Monday, December 8, 2014

Variety pack of weather set to hit MRG with mid-week nor'easter

Almost game time with this storm though it's only beginning to take shape as of Tuesday afternoon.  It is a rather unique merging, almost collision of two garden variety weather systems. One, well off the Mid Atlantic coast that will migrate northwestward toward the coast, and another passing rather innocently through the Great Lakes. The two will phase in magnificent fashion Tuesday morning and the fireworks show ensues. Rain and snow will light up the radar screen by Tuesday afternoon and snow should spread into MRG by the middle of the afternoon. Cold arctic air snuck its way into New England Sunday night and will continue a tenuous grip on the region through the onset of precipitation tomorrow. It should get quite fun for a time with huge snowfall rates Tuesday evening into early Tuesday night allowing accumulations to get as high as a foot and very quickly.


The track of this quite powerful nor'easter is expected to proceed to southern New England before becoming nearly stationary. Warm air will thus get sucked around the top side of the storm in counter-clockwise fashion. I expect we will see a lull in the precipitation as this happens, often referred to as a dry slot. Once precipitation does re-commence during the day Wednesday, it is unlikely to be snow.  There are some interesting temperature profiles being shown by some of the shorter range computer models and they run counter to some of my thoughts from the last post. During the day Wednesday, a layer of above freezing temperatures is expected to cover northern Vermont between 6,000 and 10,000 feet. Below that, readings struggle to reach the freezing mark. One would look at this storm and quickly conclude that it is not an "overrunning-style" event but temperature profiles show that type of structure. So instead of a elevation sensitive rain/snow day on Wednesday, it looks more like sleet/freezing rain/rain type of day. Any powder that falls Tuesday evening is going to get a very quick glaze or get mashed up by the sleet.


After a period of the non-snow type stuff Wednesday, temperatures in the lower troposphere should cool enough to support snow, particularly at the high elevations. The storm is expected to occlude by this point and although this eliminates the chance for extremely heavy precipitation. Elevation sensitive snow should be able to persist through Thursday into Friday. I am still hoping that the storm just gets a small second wind while repositioning itself near the coast Thursday. This could allow a period of at least moderate snow Thursday or Thursday night. Whatever does fall Thursday into Friday will be wet at low elevations and only powdery near the summits and accumulations will range from a relatively low few inches in the valley's to upwards of an additional foot near the summits. Because of the sleet/freezing rain/rain situation Wednesday, I highly doubt we will ever have 2 feet on the ground at the end of the storm. We are more likely to get a good 6-12 inch thump Tuesday night which will get compressed Wednesday with another layer of 6-12 inches between Wednesday night and Friday. Classic New England !


I've seen some maps suggesting a widespread 1-2 foot storm for Vermont. This might work for the Adirondacks but I think this is too aggressive for all of Vermont. Don't think we will score those results unless you above 2000 feet but fortunately most of Mad River is.


We still are going to have to contend with a nasty string of mild days beginning late this weekend. The Pacific is not friendly right now with the positive EPO (Equatorial Pacific Oscillation) creating the dreaded evil empire. We will have an active southern branch of the jet next week into the Winter Solstice but with very limited cold air. Expect several above freezing days next week and a day with some plain rain. Unfortunately, the pattern could linger until just before the Christmas holiday.

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