Thursday: Eyeing Potential Significant Winter Storm Sunday-Tuesday

 Good morning. Confidence is increasing in a signifigant winter storm to impact the Northeast Sunday afternoon into Tuesday. A lot of details still need to be worked out but I have enough information to start to make an initial forecast. We will need to see how this evolves next few days. This winter certainty has thrown a lot of curve balls at the last second with storms, so we need to watch for shifts.

Summary:

• A signifigant winter storm moves into the area on Sunday afternoon with light snow.

• All indications are the storm starts to really get going on Monday featuring heavy snow for all areas along the I-95 northwest

• Storm should wind down by Tuesday at some point (details still unclear)

• In terms of impacts, as a ROUGH INITIAL ESTIMATE:
• I would expect light snow for all areas from Balt/Wash north to spread into the area Sunday
• As the storm then starts to intensify off the coast Monday I would expect snow to change to rain for areas south of Philadelphia and CNJ, a mix of snow and ice along the I-95 corridor and all snow NW of I-95
• Storm should stay all heavy snow NW of I-95 with potential for signifigant accumulations up to a foot or more

• Despite the fact the storm will be long duration, the biggest impacts usually always hit within a 12 hour period. This period appears to be at some point on Monday

• Things could still drastically shift with this forecast as we are still days away

Since this storm is going to get a lot of hype in the media I decided to give a very rough sketch of what my initial thoughts are on impacts below. This map is very preliminary so take it with a grain of salt...

 So lets take a look at some details...

Ahead of this storm we have bitter cold air moving into the area this weekend. Below are temps Sat morning. Grey is sub zero..

Dense cold air is always an ingredient you want to see ahead of a major storm. You also want a pattern that can help some of this cold air stay locked in. We will have that pattern with high pressure to the north being blocked in by a low pressure system off of eastern Canada. In English this means cold air will continue to get funneled into the area ahead and during this storm for many areas...

This is due to the atmosphere blocking off or trapping the storm due to high pressure over Canada and a low pressure system over coordinates 50/50...

You do not have to understand everything I just said but the bottom line here is the pattern in the atmosphere you are seeing above is a classic look for a major winter storm. This is because energy moving thorough the country gets clogged up along the east coast because the jet stream is blocking it for just flying out to sea. This allows it to intensify over our area. 

Similar historical atmospheric setups have produced signifigant snows in the area of warm colors below...

By the way, this storm energy I am discussing is currently is blasting the mountains of the west with feet of snow...

Models project this energy moves across the country and becomes blocked off along the east coast seen below valid Saturday through Monday...

Remember the reasons why I said this is able to just bomb off once it hits are area as seen above. That is key.

So what could go wrong here? 

On one side, if the blocking in the atmosphere ends up being too strong then this storm can move more south. That woudl mean less snow over New England and more in the Mid-Atlantic.

On the other side, we could end up seeing some last min shifts north which would cause more mixing to areas even up to NNJ and Southern New England and interior New England gets all the snow

I will keep an eye on this next few days. 

Stay tuned. Daily updates will be coming.