Arctic blast, weekend storm?

I don't have much time, being in between finals at the moment.

Anyway, we are looking a major arctic blast hitting the northern tier of the nation this week. A cold front sliced through the region this morning with little in the way of precipitation, however the story is what comes in behind it. Strong surface high pressure has dropped into the central Plains and will be drifting eastward through Thursday. Northwest winds will be ushering in the airmass over the northern Plains and Canada, where high temperatures stuggle just to get above zero! This airmass will modify as it reached New England, but we can still expect highs only in the teens and low 20's Wednesday through Saturday.

What's the cause of this sudden regime shift? In the last few days a mammoth block developed over the polar region, completely displacing the polar vortex south into Canada. Right now, you can see the intensity of this block as measured by the Arctic Oscillation (AO) which is currently at -3.8SD (almost off the CPC charts!).

What can we get out of this other than cold air? It's still uncertain. The potential for a storm this upcoming weekend continues to look interesting. The shortwave associated with today's frontal passage is an extention of the polar vortex, and will be closing off over New Brunswick. The evolution of this new low will be crucial to our weather this weekend.

Energy riding up and over the ridge out west will dive into the central Plains by Friday. Surface low pressure will develop in the Gulf of Mexico associated with a weak upper level shortwave and a preexisting baroclinic zone. Beyond this point, a lot of disagreement exists in the model guidance. The new Euro agrees to some extent with the GGEM and shows the central Plains shortwave picking up the surface low and intensifying it just off the east coast. The American models are less enthusiastic.

There is a lot of uncertainty, but the potential does exist for a significant to major snow storm for the northeast this weekend. A lot can change in the next 5 days, in either direction.