December 27, 2000
The weather continues to be cold in the Delaware Valley, with current temperatures in the upper teens across the region. Skies will remain mostly cloudy overnight with the low around 16 degrees. Wednesday will be mostly cloudy through most of the day with the chance for a flurry as a system presses down from the north. Highs will be around freezing. Thursday will be partly sunny but continued cold with the high near 30. Then the real headache appears as we approach the weekend.
The current system which provided Arkansas and Texas with a nasty ice storm is forecast to move east along the Gulf of Mexico coastline through Friday. Meanwhile, a separate piece of energy will be heading down across the Great Plains out of NW Canada. As of last night, almost all the models were onto the fact that these two systems would phase (join forces) and give the East Coast it's first major storm since last January 25. Well, the models have slowly backed off of that idea, but for reasons we think may still imply an East Coast 'hit'.
Many times when a system like this is in cards up to 6 days out and guidance seems to have a good handle on the situation, the storm seems to 'get lost' within 48-72 hours. There are reasons for this. The piece of energy (shortwave) which may phase with the ejecting cutoff low out of Texas is still not on shore yet off the West Coast of Canada. The shortwave is sitting in the Gulf of Alaska where there is virtually no upper air data, a void if you will. Yesterday, it was over an area where data was able to be fed into the model guidance. Thus, agreement yesterday, slight disagreement today. This is not to say that that today's model guidance can just be rejected. It is very possible that the ejecting cutoff from the southwest gets too far ahead of the shortwave to phase and redevelop an East Coast storm. However, with data lacking where it is needed, questions arise as to timing and strength of the energy that will enter the coast in Western Canada later Wednesday. The 0Z Thursday (or 7PM tomorrow) runs of the models should give us a better handle of the developing situation.
Several ideas were thrown at us today by the models. First is that the cutoff low over West Texas ejects rather quickly as a sheared vortmax and gets ripped out into the Atlantic before the shortwave from the north has time to catch up to it, sparing much of the East Coast from any snow, save perhaps some areas south of DC. Another idea hinted at was that the cutoff ejects out into the Atlantic while the Northern shortwave closes off around Missouri saving much of the East Coast from any storminess 'early' in the weekend. However, the solution still winds up stormy, just a bit later in the weekend. As the closed low presses East from Missouri, it spawns a low pressure area off of NC and sends it northward. This system would not be as strong initially as if the two shortwaves were to phase, but still could provide some snow for our area into Sunday. Meanwhile, as the low pulls to the north, our friends in Eastern New England get clobbered with heavy snow. Finally, another solution has both pieces of energy fizzling out with little fanfare and sunny skies, but continued cold.
Well, lots to digest tonight as far as different solutions. Thought that guidance had a fairly good handle on things until around noon, but then diverged somewhat. As noted above, this scenario tends to happen quite a bit when key ingredients to a storm are located over a void when the models initialize. This is also reflected well in NCEP's Model Diagnostic Discussion this evening.
So decisions decisions. We are nearing 54 hours of a possible winter storm, and no clear solution at the moment. Will still hedge towards an east coast event over the weekend. Whether it is the first solution (phasing) or the second (closed low spawning a secondary low around Cape Hatteras)is still a bit premature to judge. If scenario 1 were to verify, would expect significant accumulations in our area Friday night into Saturday. If scenario 2 verifies, would still expect accumulations, possibly significant, but not as potentially large as if the systems phase. This would occur later in the weekend, possibly late Saturday night into Sunday. As mentioned, by Wednesday night, the important pieces of data we need will be fed into the guidance runs. This will likely clear things up as to how much, if anything, we get. Is there still a possibility that we get nothing . . . yes. But right now am hedging towards some storminess over the weekend. More later.
