A Swing and a Miss – Massive Blizzard Slides Underneath Us

What a freaking storm!!!! Dulles (IAD) and Baltimore-Washington (BWI) both set all time records for the great blizzard of 2010. You know it’s a good storm when a reporter on Nightly News says the storm has been dubbed “snowpocalypse”.

With this storm a complete miss in Connecticut the question becomes what does the next storm do??? Most of our computer models are pointing to a compact but intense snowstorm on Wednesday. The 18z GFS, 12z Euro, 12z GGEM are all on board. Many of the ensembles are big hits for southern New England. Like the storm this weekend there will be a sharp cut off between minor amounts and significant accumulations. Additionally, this storm MAY track too far north which would increase the chance for rain or mixed precipitation.

There are a few reasons why I feel somewhat confident about this storm striking. For one, the upper level low that will ultimately spawn the storm is over Manitoba, Canada right now. This storm isn’t way out in the Pacific in a data sparse area so the models should have a decent handle on this (famous last words, right?). All the models which did a great job keeping the Friday-Saturday storm south of us thanks to a strong block north of New England show that block retreating in time for this storm to hit us. Many of the ensembles show a hit as well which leads to increased confidence.

You can see the 96 hour 18z GFS forecast on the left. There’s a very strong closed low at 500 mb (a few miles up in the atmosphere) over the Mid Atlantic. The very strong vorticity helps spawn a strong low off the coast (the water is warm and the difference between the cold over land/warmth over water leads to what’s called baroclinicity). When the closed low moves east toward the Ocean you get a vacuum that develops in the atmosphere and a storm develops as a response especially given the natural baroclinicity along the northeast coast. The storm doesn’t completely phase with southern stream energy (notice the vorticity east of Cape Cod at 96 hours) but it comes close. Bottom line is a short lived but likely intense snowstorm for someone in the northeast. Near blizzard conditions are possible in an area where this storm hits hard. Accumulations in the 5-10″ range or maybe even more are a good bet north of the low’s path.

The track of this closed low will be key. If it’s too far north we’ll dry slot and not get a whole lot. If it’s too far south (suppressed) we’ll miss out on the action as well. Right now I’d say the odds of getting >6″ of snow at about 30%.

Ryan

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