Brett Anderson

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Eastern Storm and a Pattern Change

November 06, 2012; 9:25 AM

Tuesday morning update..... we made adjustments with the wind and snow map below as the storm will not be quite as intense and will be tracking a little more to the east. I will have a full update later today...

Moderate strength nor'easter for Wednesday and Thursday

A potent upper-level trough currently diving southeastward into the lower Mississippi Valley this evening will round the bend and turn northeastward along the Southeast U.S. coast by Tuesday evening.

At the same time, a second trough will be diving into the Midwest U.S. and will eventually merge (phase) with the coastal trough, leading to an intensifying storm off the Eastern Seaboard Tuesday night through Wednesday night.

As is always the case, where and when these two troughs phase is crucial to the forecast. The earlier they phase, the more likely that this storm will form quicker and track closer to the coast. A later phase will lead to a slower intensification initially and a farther east track off the East coast.

The main computer models actually came into better agreement this afternoon as the ECMWF model, which has been the strongest and farthest west trended weaker and more east, while the GFS model solution, which was weaker and farther east to begin with ended up stronger and slightly farther west.

Basically, this looks like a rain and wind storm for the Northeast U.S. coast and up into Nova Scotia/PEI Wednesday afternoon through Thursday. The storm actually peaks in intensity off the Middle Atlantic coast then weakens as it turns northeastward Thursday. I am concerned about strong northeast winds Wednesday evening from the New Jersey coast up through Long Island.

There will also be a relatively narrow band of accumulating snow with this particular storm. We drew up this initial snow forecast map for the storm before the eastward shift of the ECMWF model, but we will leave it for now since I have seen the ECMWF briefly go away from a consistent idea only to go back to it on a later run.

This does not look like a major snow event for Canada as the storm will be weakening and drier air will be getting wrapped into the circulation Thursday which will cut down on snowfall rates. However, I can certainly see some accumulation over southeastern Quebec with higher amounts to the southeast in the mountains.

I am sure this map will go through a few more adjustments between now and Wednesday so stay tuned.

As I predicted yesterday, the snow map has changed.....

For Montreal and Quebec City, the western edge of the snow will not be too far away and thus much of the event will be light, wet snow.

Major pattern change by the end of the week

The weather pattern across North America will almost do a complete flip by the end of this weekend as the cold drills into the West with interior snow, while a warming trend takes place in the East.

The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com

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Brett Anderson
Brett Anderson covers both short-term and long-term weather and storm forecasts for Canada in this blog for AccuWeather.com.