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Jan 03

Weekend Winter Storm Threat For The Southeast, Mid-Atlantic.

Confidence continues to increase seemingly by the hour on the threat for a potentially significant winter storm for the Southeast and Mid-Atlantic regions of the United States this weekend. And sadly, that first sentence is about the only thing that we know with any certainty at this point, but that we study all of the data we have at our finger tips, the easier (haha, easier…) it will be to put the pieces together to form a solid forecast for such an event.

In order to gain a solid understanding of this winter storm, as it is the case with every winter storm threat, we need to look at what is occurring at mid-levels of the atmosphere and the energy that is coming down the pike as well as the overall pattern we are working with. Looking at precipitation forecasts at the surface do not paint the whole picture. We need to dig deeper…

A look at the surface according to the latest GFS rendering shows a formidable winter storm across the Southeast early Saturday morning… 

The driver behind the winter storm threat will be a piece of energy that is currently out in the Pacific Ocean. This is a BIG reason why model guidance is all over the charts with this storm threat going from a significant winter storm to the very next run showing next to nothing. Once this piece of energy comes on shore of the western US, we will have a much better understanding of the nature, timing and placement of this threat.

As noted, the piece of energy that will form this winter storm has not reached land yet. As of this evening, model output has it located off the Pacific NW coast (illustrated by the reds and yellows).

Once this piece of energy comes on land, it will dive south and east along the southern branch of a split flow setup. Split flow jet streams are the ideal setup for winter storms as the northern branch of the jetstream carries your dose of cold air while the southern branch carries the energy needed for the storm. If you can get the perfect setup where the cold air and the energy work in tandem, then you have a winter storm on your hands. I suspect this will be exactly the case with this threat.

By Friday afternoon then evening, notice where that piece of energy is located… over the Rockies and then over the Panhandle of Texas.

By Saturday morning, the piece of energy is now over the Southeast US as a developing winter storm. 

The European model illustrates a similar solution but is much more robust on the magnitude of the energy coming across southern jet stream. Essentially, the European model is calling for a much more vigorous winter event across the Southeast.

Let me break down the keys to the pattern setup for this winter storm threat.

  • The GFS and European models (at the 500 mb level) are showing winter mischief this weekend across the Southeast
  • The GFS is weaker with its rendering of energy, while the European model is more robust with its solution
  • A piece of energy in the northern branch of the jet stream (located in the Canadian Prairies) will determine the placement of the system as well as the timing. The stronger and slower the northern piece of energy is, the stronger a storm we are looking at across the Southeast. In addition, the stronger and slower the northern piece of energy in the Canadian Prairies is, the more time and room this storm threat will have to come up the East Coast. Something we NEED to watch closely.
  • On the contrary, the weaker and faster the northern piece of energy becomes, the weaker of a Southeast winter weather threat we are looking at and a lesser chance the storm skirts up the East Coast.

Which solution am I leaning toward? With complete certainty, I honestly am not sure yet. If I had to choose, I’d lean towards the European solution. I can see the piece of energy in the southern branch outrace the northern piece of energy and developing into a winter storm threat for the Southeast and up a good extend of the East Coast. Obviously, things can and likely will change between now and the weekend.

LOCATIONS: Given what we know and what continues to be watched, I will say that folks across northeast Texas, southeast Oklahoma, southern Arkansas, far northern Louisiana, northern Mississippi, northern Alabama, northern Georgia, interior South Carolina, parts of North Carolina and parts of Tennessee and Virginia should be monitoring this situation closely and be prepared for a winter storm threat. Now if the low tracks even a bit further north, then we’ll have to add locations like southeast Pennsylvania, the Delmarva, NYC and parts of southern New England to the mix as well. For now though, all these areas I’ve mentioned should keep this threat in mind moving forward.

Note that I did not talk about snowfall amounts. As the piece of energy needed for this winter storm is just now coming on land, models have been all over the boards with anticipated snowfall amounts, so quite frankly, they are useless. Also, please be mindful that the locations that could be impacted by this winter storm threat or some degree of winter mischief could change and locations can contract or expand. Those in the threat area, there is no reason to panic… just be prepared.

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