What a diffence a week makes! At the end of last week, many were talking about the potential for a major winter storm that could possibly impact the I-95 corridor from VA to New England. This would include plenty of snow and wind, yielding all the ear-marks of a classic and powerful nor'easter. And why not? The global patterns were ripe for a storm with a strong Greenland block, typically the calling card for big blizzards in the Northeast. However, that solution shifted over the weekend, as the pieces of upper level energy over Canada started teaming up or phasing earlier as they dropped into the US, with one piece of energy sucked back into the Arctic. This led to a 600 mile shift northwest from an East Coast low pressure to a Great Lakes cutter. As you can see below:
Comparison of last week's forecast guidance versus this week's forecast guidanace. Maps courtesy Tropical Tidbits.
This is a huge reason why we as meteorologists use caution with predictions too far into the future. It's not that we are withholding information, it's that we know solutions will change many times before settling on a conclusion. In this instance, we knew big storm would develop based on the overall pattern (and it still will form), the question mark was the track and phasing.
Now let's talk about the upcoming storm impacts since the track is more certain. All eyes will be on a strong low pressure system which will dive out of the Rockies and strengthen over the Plains and into the Ohio Valley on Thursday. This will bring a large swath of snowfall from Missouri through Michigan, with many seeing plowable amounts and some places topping a foot around the Great Lakes (we're looking at you Michigan!). Meanwhile on the East Coast and into the Northeast, mainly rain will fall Thursday into Friday with the Appalachians from western VA into PA and from the Adirondacks to White Mountains seeing some decent snow. For the major cities of the East Coast, however, we're talking about a wind driven rain and even a squall line along the cold front on Friday. With gusts of 40 - 50+ mph and 1 - 3" of rainfall, some downed trees and power outages are certainly possible. Behind the front, temperatures will plummet well below freezing in the matter of a few hours. In some cases, we are looking at a 30 degree crash in temperatures!
Surface temperatures from the European model around 1 PM Friday. Courtesy Pivotal Weather.
Needless to say, any areas of runoff and ponding from the rainfall will freeze very quickly after the front passes. A flash freeze is possible, but we are thinking rain would have to change to a bit of snow for that to happen. This change to some wet snow behind the front is still in play, but it would likely be brief and mostly in northeast PA into Upstate NY. So keep you guard up Friday and prepare those salters!
Around the entire system, travel delays are expected Thursday into Friday as winds will be very strong, likely delaying flights for the holidays at many airports in the northeast quarter of the country. Behind the storm, an sprawling high pressure system will dive into the Plains states, dropping temperatures below zero from Montana southeast into parts of the Ohio Valley (see image at the top of the blog, courtesy Tropical Tidbits). In fact, some places likely dip to 20 to 30 below zero Fri and Sat morning in the Northern Plains! Meanwhile, temperatures will even crash into the 20s from Texas along the Gulf Coast to Florida. The cold will continue to grip the eastern half of the country through the holiday weekend, but things will gradually quiet down weather wise, with the exception of lake effect snow in the typical snowbelts and some snow pushing across the northern Rockies.