2 SIGNIFICANT EASTERN US LOWs TO IMPACT THE EAST COAST NOV 20–28.

Before I get into the forecast let me give you all a bit of news. The Geniuses at Facebook are once again screwing around with my Facebook page. They have done this several times over the past year and I am not exactly sure why. They have put a temporary hold on my identification even though I have gone through the Facebook identification process several times. FB says that they know what the problem is and they are working on it but I have no idea how long it is going to take. It is really very frustrating going through this when you have two potential early-season winter storms to deal with.

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The turn toward the substantially colder pattern for the last 10 days of November is now a high probability along with the potential for two significant East Coast early-season winter storms. The first one is primarily a rain event although there is the possibility that it could change over the snow in the mountains of the Appalachians as well as interior portions of New England and New York State. The second event is a much bigger winter threat because of the cold air that comes into the eastern CONUS behind the first event.

Currently there is a large blizzard raging across the Canadian prairies. This intense and powerful LOW pressure area is the triggering mechanism for the change. To begin with, this LOW will pass north of the Great Lakes on Thursday and Friday. This will drag a cold front through the Midwest, the Ohio Valley and into the East Coast. Ahead of the cold front SW winds will boost temperatures up into the 55–60 degrees in many areas in the Appalachian Mountains… and 65 to 74 degrees in the Piedmont areas east of the mountains in NC, VA, and MD as well as in the coastal areas.

The front will arrive on the East Coast Thursday night into Friday morning with rain. Behind the front, a seasonally called large Canadian HIGH pressure comes in and brings moderately good snowmaking conditions for the weekend on both Friday night and Saturday, and Saturday night into Sunday. By Sunday night, the HIGH pressure area will be moving off the east coast and winds will turn around to an easterly Direction.

That big Canadian LOW pressure area will track into Quebec Canada this weekend and cause the jet stream in eastern Canada to buckle or “amplify”. This will form a BLOCK in the jet stream in northeast Canada and Greenland , which is known in the weather business as the negative phase of the North American Oscillation (-NAO). The development of this strong block during the winter months is often — but not always- a strong signal that the pattern is going to turn colder and stormy in the eastern CONUS.

Then, a new powerful piece of energy coming in from the Gulf of Alaska will cut across the Canadian Prairies this weekend. This system however, will be forced to drop to the southeast because of the Blocking pattern developing in eastern Canada and Greenland (the — NAO). This block in Greenland will force this next trough in the jet stream to develop a special type of alignment or “tilt” known as a Negative Tilt. The combination of the negatively tilted Trough running from the Great Lakes to Virginia combined with the -NAO in eastern Canada / Greenland will cause a rapid intensification of the LOW pressure area diving out of the Great Lakes on Monday November 22nd.

The intensifying LOW pressure area in the Great Lakes will send its cold front eastward and heavy rain is expected to develop up and down the East Coast from NC to Maine on Monday afternoon and evening November 22nd. The LOW pressure area will jump to the MD coast as it reforms and rapidly undergoes massive intensification as it moves north into CT and northern New England on Tuesday November 23rd.

If the current model data is correct, and I strongly believe that it is since this scenario has very strong support from the GFS, Canadian, and European ensembles, the winds will become very strong across all of the Middle Atlantic and New England regions on Tuesday November 23, into Wednesday November 24. Wind gusts could reach over 50 or 60mph on the coast and in the mountain areas of the Middle Atlantic region which are also more exposed to high winds.

This massive storm is going to pull down an true polar air mass and the rain will change over to snow in the mountains of WA, southwest VA, western NC, and possibly in the Shenandoah Valley on Tuesday November 23rd.

Significant accumulating snow is POSSIBLE in much of mountains of western, central, and northern Pennsylvania as well as western NY State, and northern New England late on the 23rd into the 24th. — not in the coastal area of the Northeast US.

Winds will diminish significantly in the Middle Atlantic region on Wednesday afternoon November 24th and Thanksgiving across the entire eastern half of the country looks sunny for the most part and dry with seasonally cold temperatures and ideal for snowmaking given the fact that it’s November.

2ND EVENT

Meanwhile, while this big storm is hitting the East Coast, the jet stream on the West coast of North America is going to amplify — that is to say, expand northward from California into British Columbia and the Alaskan Panhandle. This will allow for steady flow of cold semi Arctic air coming out of western Canada into the Midwest and the East Coast for the last several days November going into December.

The combination of this big Ridge on the West coast of Canada and the blocking feature in Greenland (which remains in place until the first week of December), ensues that the pattern stays cold for the Eastern CONUS. But it also sets up the potential for something on Thanksgiving weekend. The various weather models are showing a strong piece of energy coming out of the southern jet stream on Thanksgiving night bringing rain to TX and OK, and snow to portions of KS and NEB as well as eastern COL.

If this was say December, January, February, or March, the overall pattern for Thanksgiving weekend would be screaming major East Coast snowstorm. Consider the following;

· There will be a large cold HIGH pressure area in place in Minnesota and the Great Lakes

· There will be significant southern stream Trough in TX with LOW pressure developing eastern TX or
near the Delta region

· There will be a strong Block in Greenland

· There will be large ocean LOW ( the 50/50 Low) in southeastern Canada.
The data shows the cold will be stronger than Normal for late November

If I had to commit one way or the other at this point for the second event I would favor an initial burst of snow even east of the mountains on Thanksgiving weekend which would probably go over to rain but it could stay all snow in the Central and Northern Appalachian Mountains with significant accumulations for the ski resorts.