January Winter Threat Jan 6th - 8th

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DDD

GON Winter Weatherman
Well, I hope you guys and gals have enjoyed the chase. Today the chase ends and the reality begins. I have changed my thinking a little given short range modeling. Just like the global models, the short range models are all over the place, so you have to take a blend of those and what is happening and make an educated guess.

So let's get right into it.

I cannot stress this enough. There is going to be a serious line between ALL SNOW, Snow and sleet mixed together, ALL SLEET, Freezing Rain and Sleet, All Freezing Rain and Rain. Got all that? LOL

I have made a last call map. I think the I-85 corridor is going to be sort of the fall line. 50 miles north or 50 miles south of I-85 is going to be where the heartbreak (if you want snow) and the magic will happen.

I could see a scenario (just an example) where Buford is shoveling 5" of snow and Dacula only has 2". There is not one MET or anyone that I know that can tell you where that line will be. Complete guess work.

There is a warm layer of air that keeps making the mixing issues a problem. If that warm layer is stronger, this will have a hard time being much of anything, however if that warm layer is not as strong as some models have, it will be more snow.

Also, it's worth noting that some modeling thinks we will have trouble switching over to much of anything at all. So much uncertainty.

So here we go:

A: What falls here will be all snow. Temps and atmosphere layers will be plenty cold. Problem here is lack of precip. I think when it's all said and done, this area may end up with 1-2" of snow.

B: Going West to North East the snow will go from light to heavier as you move into the foothills of the Appalachians and into the mountains. The farther North and East you go in this area the higher the totals. This area should be 1-5" going from that West to to NE direction.

C: This area is going to be the Fail / Win zone. There is just no other way to put it. This area stands the best chances at scoring a large amount of snow and a large amount of rain. Just no way to sugar coat it. This area could also become one heck of a sleet storm if the warm air aloft does not bend. This area has the potential to be 1-6" of snow, 3" of sleet, .10" of freezing rain and all of the above. It simply is going to be the battle ground. The silver lining of this area is that whoever is on the snow side of this area is going to be the envy of snow lovers in the state of GA.

D: This area has become concerning for sleet / freezing rain only due to thermal issues. This area needs to be more concerned about ice and freezing rain than snow totals.



UPDATE: Just as I am typing this, 12Z short range modeling and GFS continue to inch up the warm layer and warm nose Northward. NE GA mountains would have almost a foot of snow and that area won't have mixing issues. This will rob many, including the Metro Atlanta area of heavier snow totals. Not saying it will happen, I am just telling you how it looks. If the trend continues NW, Atlanta will be out of the game.

Anyone have a cliff I can jump off of?
 

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Thread starter #22

DDD

GON Winter Weatherman
Here is my post storm analysis.

All anyone wants to know from this storm is why did it not snow a lot and in my backyard. Yes some people got snow, the NE GA mountains got snow and weather people everywhere scratched their heads.

To try and keep it as simple as possible I have used some of the screen shots I saved of this storm and tried to explain it a little.

The reason temperatures on the East side of the state never got below freezing at the surface or even 5,000 feet up in the air is because of a warm air coming from the south and a "warm nose" in the 900mb and 850mb layers of the atmosphere.

The earliest I could find it modeled on the model pictures I saved was Tuesday / Wednesday. However, it was minor in my mind and would become "overtaken" by the super cold air coming from the North West. You can see it outlined below.

I, like many other weather geeks and METS alike, thought it would be regulated to the East side of the state around Athens maybe as far north as Hartwell and would eventually cave to the cold air.

That was wrong.

That warm nose was strong at the lower levels of the atmosphere all the way up to 5000 feet. That was why it was all rain (except for certain areas outlined below) and not freezing rain. I wish I had kept screenshots of the radar last night but it lines up nicely with what the GFS was cranking out as early as Thursday January 5th in the Precip Type maps. I outlined it with a black line to highlight it. If you watched any news last night or looked at radar, this is roughly how it looked and stayed for 6-10 hours before the back end of the storm arrived. The cold air just could not push the warm air out of the way.

There was significant freezing rain on the south side of Atlanta up to in and around the Dunwoody / outer perimeter of 285. The reason this happened is, the cold air was able to penetrate the warm nose close to the surface (2mm temp region) in this area and "lock in" below the warm air above. This shallow layer of cold air at the surface was what allowed the rain to fall into it and cause freezing rain. The "locking in" process basically happens like a cooler. Once the ice starts forming, it basically acts like an ice pack in the bottom of a cooler and the rain from above just adds to the thickness of the ice formation.

In the end, it is my opinion that those on the East side of the state should be happy they did not get in on the ICE that the south side got in on. It really could have been a large area of freezing rain and being in the dark without power is not fun.

The warm nose over performed and models did not pick up on the level of warmth at the surface and the first 5000 feet of the atmosphere. The METS in Atlanta could not have known how that would over perform until it was happening. I had said many times that the "line" could vary by 50 miles but it was more than 50 miles. Also, the cold air did not win out and shove the warm air East as had been modeled. It just hit a brick wall. My hat is off to the NWS in Birmingham, NWS in Atlanta, METS like James Spann in Alabama and all of our local METS in Atlanta. There was nothing that could have prepared anyone for that strength of that warm nose or the freezing rain area that set up where it did on the south side.

The last model picture shows how at 850mb / 5000 feet above the surface the battle lines were drawn. This was the difference in Snow and Rain for the most part.

Very last picture was the totals from the NWS that they put out this afternoon. Lines up pretty well with the 850mb temp profile.

Congrats to those of you up in Canton, Dawsonville and other areas that got what they wanted! :cool:

One last thing I want to address. There was some serious misinformation going around on Facebook and social media early in the week about this storm. If you have a love for weather that you "geek out" on, when putting it on Social Media, Facebook especially, know that when you post something it has the chance of going viral. If you are going to make statements like "Blizzard" or a certain model is showing a "Blizzard" you need to be able to back those statements up with data. When you make outrageous claims you need to know that this day in age those are going to be scrutinized by pros. Those same pros will have to spend unnecessary time undoing and correcting the general public from your misinformation. I personally take exception to it because I get lumped into the "weather geek" population and people like that make me look bad and I don't like it. The storm will make us look bad enough, don't help with your ignorance. Also, before you share something, do a little research and consider the source of who is spouting crazy talk. When you "share" something you are becoming part of the problem as you are spreading the infection.

Winter is not over.
 

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