1/16/12 Still no snow...and why

By now,  you may be wondering, where is the snow? Or why hasn't it snowed, or better yet, why is is so warm? The answers are complicated, of course but the main reasoning is the way that the upper atmosphere is working and has been working since the fall. 

The jet stream, which helps control the flow of weather in the middle latitudes has primarily been in a zonal flow, pretty much along the US/Canada border. 

This winters overall weather pattern. The Northern Jet Stream is locking in all the cold air to the north in Canada and not allowing it to dig into the US. The Southern Jet Stream, which usually contains a lot of moisture from the Pacific Ocean is staying south and bringing more storms to Texas and the deep south. It is also not merging with the northern Jet stream to create any snow storms for the north east!

 
The flow of air that we eventually receive here in New England is air that has been warmed by the Pacific ocean and any true arctic air has a difficult time coming down and mixing in with it. When it does, it is usually short lived, since the upper flow of air wants to keep everything locked up.

In a typical (normal) winter pattern, the northern Jet Stream will rise into Canada, tap into the cold arctic air, then dive into the Great Lakes and the Northeast to create a cold winter. As for snow storms, the southern Jet stream will also be tapped into by the northern Jet and when they meet, usually storm will form with great moisture and when mixed with moisture and cold air, a snow storm is the end result.

 

 So for this week, there are no major storms on the horizon. 

A few weak systems will work their way in on Tuesday and Thursday, but likely be in the form of rain, with a little snow mixed in.

The map below shows the cold air locked in Canada with warmer air mainly over the US.

This weather map for this coming Friday, shows how the coldest air in purples, reds are located in Canada and along the US border, where blue and green are typically mild for January.