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Wednesday, December 30, 2009

Expected storm track shifts east but....

not that far east. Far enough perhaps so that a repeat performance of 1969 or 2001 will be a bit tough. Far enough so that the threat of sleet has all but vanished if there was any to begin with. Close enough still so that much of northern New England, especially those sitting in areas with the "oragraphic advantage" should do very well over a span of several days.

The weather map on early New Years day (Friday) should consist of a gradually weakening clipper system over the eastern Great Lakes and a strengthening storm in the Virginia tidewater. Snow from the clipper should begin falling early New Years day. Accumulations will be on the light side because the snowfall intensity will be on the light side but it may be enough to fluff up the trails a bit. As we go through time, the coastal system will bomb and swallow all the remaining energy from the clipper. Models are still at odds regarding exactly where this coastal storm tracks and our forecast still remains uncertain as a result. The last three runs of the European ECMWF have taken our coastal system farther east and are not as dramatic with this westward retrogression on Saturday and Sunday. Such a solution would still mean snow for both Saturday and Sunday (Jan 2 and Jan 3) but accumulations would be on the lighter side and snowfall totals for the weekend will be in the 8-14 inch range by Monday morning. Snowfall rates would also stay on the lighter side in such a scenario and waist deep powder at first tracks time between Saturday to Monday would be a stretch. The American GFS model continues to show a very dramatic amplification with this system. The deepening is shown to be so fierce that the westward "retrogression" mentioned above would be the result. This scenario would put us directly in the thrust of the moist conveyor of this powerful storm and would do so for multiple days. Accumulations would be on the order of 30 inches by late Monday with epic powder Saturday, Sunday and Monday.

Having faced this fork in the road many times in the short history of the SCWB I have typically found faith in the European model since it has proven to catch a trend or shift prior to the American Model. This instance would be no different except that in doing so I would be disrespecting the potency of systems coming out of the southern branch and up the east coast. Most of these systems this year have been stronger and tracked farther northwest relative to the consensus of models. I will therefore cautiously predict 1-2 feet over a 4 days period and at the same time purchase the "huge margin of error" insurance policy.

There is always concern with any system with strong winds closing lifts. This has typically been a bit out of the SWCB domain since I would hate to wrongly steer people away or toward MRG as a result of a wind forecast. Wind and wind holds are always a risk and winds will be gusty through the weekend since this is an intense storm with a tight pressure gradient. I will say that in my 10 years skiing regularly at MRG, the wind holds on the single have resulted from strong easterly winds at the summit. Winds will be strong throughout the weekend but they will not be blowing from the east and will instead be much closer to north. Does this save the MRG single from wind holds ? No guarantees, but for those that requested the information, there you have it.

Garden variety cold will grip the Green Mountain chain through next week but when the dust, fluff and powder finally settle from the New Years storm the storm track will be suppressed well to our south and our snow will be the result of clipper systems and terrain enhancement. Blocking remains in the jet stream but there should be a gradual shift from a cold pattern energized by the NAO to a cold pattern supported by a positive PNA. This in the need could send bitter chill into New England sometime after January 8th.

I will try and provide updates as often as a I can but tomorrow is a holiday and my presence is needed at work so an update might not come until late New Years day or early New Years day.

1 comment:

Mark said...

Thanks Josh. The American model makes much more sense to me:)