Monday: Arctic Air Arrives, Eyeing This Weekend for Storm Threat

Good morning. I think it is safe to say, winter is here! Snow is on the ground and cold air has taken hold. In fact, some true arctic air arrives for Tuesday and Wednesday where temps will plummet tonight and highs will struggle to break 20 in many locations. We then have a decent storm signal on the models for Sunday. Overall, this is a very active winter pattern next 7-14 days. Lets take a look...

Arctic air moves in tonight. Below are temperatures tomorrow morning. Anything is grey is subzero...

Things stay cold all week ahead of a storm threat this weekend, on Sunday.

The setup for this potential storm has a few variables that I am watching. For one we have very cold air for once on our side of the country. This is opposite of December. The image below shows this for end of this week...

In terms of storm development, the models have been hinting at a setup that can historically deliver. Below I highlight what I am watching in the upper atmosphere ahead of Sunday's storm threat...

The key to the image above is that you have support in the jet stream to allow storm energy (blue) to consolidate in the east and tap into cold air to the north. This is due to position of western ridge and the block I highlighted over Greenland. A block is high pressure that slows down jet stream.

Interesting enough we will have a big ocean storm on Thursday that will have a big impact on how that block sets up.

Taking at look at the surface level, there is a signature I really like to see showing up on models called a banana high.....

The reason I like to see this is the high pressure traps the storm underneath allowing it to move slowly and intensify while supplying cold air. Some of our classic storms have had this bananna high. The upper air pattern I showed before is producing this. You can see the blue low pressure developing in the Tenn valley under this high pressure signature. That is our storm threat.

From there is where all the uncertainty happens. We can say this far out that there is a decent chance low pressure develops somewhere but whether or not it intensifies rapidly or just slides offshore will not be known for several days.

Model spreads show potential scenarios of low pressure placement...

All those low centers are different projections. Below gives a general idea of where the model thinks there can be a snow threat Sunday...

This is an ensemble average and can change but it is best way to judge the potential threat area this far out. 

If we look to the historical analog forecast packages. Similar setups in history have shown a similar placement of snowfall..

Take all this with a grain of salt this far out. By Wednesday we can really start to dig into if this threat is to be taken seriously. This is far from locked in. 

Many surface models, which are a waste to look at this far out, have fluctuated from a miss out to sea to a big storm. They are not even worth showing. 

Stay tuned, much more to come.