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January 17th-18th Winter Storm Discussion


BullCityWx

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I'm starting to think somewhere just north of Atlanta could get a nice surprise. It's going to snow under that deformation band and it could be heavy. Plus with this coming through at night adds a bonus. When I first saw the winter storm watch I balked but this situation for once has trended in our favor.

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Soundings look pretty lame for RDU. Most of the precip is over by the time temperatures get anywhere near freezing in the lower levels of the atmosphere. Even if it is snowing, it won't stick until the very end.

 

This is not the setup for a clasic big winter storm here. But the models are almost unanimous that we see a 3-6 hour period of moderate to heavy snow with surface temps at or just below freezing. The vertical velocities are impressive, so it will come down hard enough to accumulate. Pavements will likely hold out a while and then melt pretty quickly when the snow is over.

 

Think 1-3 and then be surprised and happy if we are in the top of that range.

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I'm starting to think somewhere just north of Atlanta could get a nice surprise. It's going to snow under that deformation band and it could be heavy. Plus with this coming through at night adds a bonus. When I first saw the winter storm watch I balked but this situation for once has trended in our favor.

I agree. It's amazing how fast things can change.

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This is a really big trend south. S VA is about to be left in the dust. Happy for you folks in GA/SC/NC though. I'm just happy to see something to be excited about this winter! Maybe you GSO/triangle people can share your deform band with me tomorrow. :whistle:

 

Good luck to everyone, I hope we all get buried! (Oh, and to make this post relevant to wx disco...well, it's dark and wet outside and I'm at 50 degrees!)

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I'm starting to think somewhere just north of Atlanta could get a nice surprise. It's going to snow under that deformation band and it could be heavy. Plus with this coming through at night adds a bonus. When I first saw the winter storm watch I balked but this situation for once has trended in our favor.

Agreed. Remarkable how much better the 0z NAM was for us compared to the 18z. Looked like a major improvement temperature-wise in the soundings. We'll see what the GFS says, but yes I could see somebody getting a solid 2" somwhere around here.

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‎*****MAJOR WINTER STORM TO IMPACT ALABAMA, GEORGIA, EAST TENNESSEE, NORTHERN SC, MOST OF NC AND SOUTHERN HALF VIRGINIA*******

Models trend colder, stronger, snowier, longer. A strong "bowling ball" type upper low, with cold air, longer duration than previously thought, and heavier axis of comma head snow, will aim at this region Thursday afternoon, night and early Friday. The upper low itself will provide snow and sleet through central and northern parts of Miss, Ala and Ga tomorrow but tomorrow night the precipitation EXPLODES quickly in most of western SC, central to west NC, eastern TN and southern VA. The atmosphere will cool off as all upper lows provide cold air and a crashing column when they're this strong. Rain will switch to snow and sleet suddenly then all snow, in all these areas. The heaviest snow looks to be as I have been pointing out for a while now, northern Georgia, eastern TN, and initially western NC and western, southwest Virginia, but spreading east across the Carolinas during the night. The way the axis sets up, the orientation of the "tilt" of the upper low, the most lift and dynamic cooling will occur much the same way March 2009 occurred..with all the Southern Apps receiving a 4 to 8 hour period of EXTREMELY heavy snow rates, which is much higher than the average Winter storm. Prepare now for power outages in east TN/ W NC/Central NC/sw VA/S VA, and scattered outages possible in northeast GA and Upstate SC. The storm will be short -lived, but very intense.

Trees will come down in some areas. Thundersnow will occur in some areas. Snow rates will be 2" per hour in some areas. Prepare now for suddenly changing weather beginning Thursday afternoon and reaching climax overnight Thursday night.-Robert, www.wxsouth.com

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Agreed. Remarkable how much better the 0z NAM was for us compared to the 18z. Looked like a major improvement temperature-wise in the soundings. We'll see what the GFS says, but yes I could see somebody getting a solid 2" somwhere around here.

Verbatim the soundings I saw we're very close but not quite there. It wouldn't take much at all to tip it to snow and I'm talking a minute adjustment. I'm talking about cobb county a county or so north of us it looked like snow verbatim. It depends on where that band sets up but I feel atl and the north burbs are in the game.

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Agreed. Remarkable how much better the 0z NAM was for us compared to the 18z. Looked like a major improvement temperature-wise in the soundings. We'll see what the GFS says, but yes I could see somebody getting a solid 2" somwhere around here.

Like the new avatar. I am aware that the NAM snowfall map has 10:1 ratios but I also think that the NAM could be not recognizing the strong, dynamical cooling that should be occurring, especially under that deform band. Snow totals seem like they could be low in areas and I try to be a realists as opposed to wishcasting. Am I missing something here?

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I'm starting to think somewhere just north of Atlanta could get a nice surprise. It's going to snow under that deformation band and it could be heavy. Plus with this coming through at night adds a bonus.

 

I'm starting to think the same thing.  I'm also beginning to think that 1"-3" may be possible as far south as I-85 (in SC).  The warm tongue that looked to be appearing on the 18Z looks absent to me on the 00Z (however, according to the rules it must show itself at some point during the event).  Also, after a quick schooling by a firend, I realized that colder air has a better opportunity to be pulled in where that WT had been trying to pop (thanks homey) - I'm talking specifically about northern Spartanburg County:

 

USA_TMPHGTGRD_850mb_027.gif

 

Not a whole lot of obstacles for the cold air to get in:

 

USA_PCPPRSTMP_850mb_027.gif

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It does assume a 10:1 ratio.

I have a couple concerns regarding this setup, 1, I can't remember a time with a surface low track from Augusta to Myrtle Beach where NC saw an appreciable winter storm.  We do well with tracks along the Panhandle, HKY right along the coast, central and eastern parts an offshore track.  2nd is the warm punch between 875-925 that often happens when you see 850's surging to 6-9C and ingested into the system, while crashing on the backside.  Optimist:  I do not see impacts much north of I-64 in VA (call it a hunch), and the fact SE VA is showing a good signal makes me here in NE NC (kinda) feel ok, as we usually do well together.  The attendant cold pool aloft working in from the SW at about the same time the best lift comes overhead, coupled with a slow bleed of Arctic air from the north, coming down east of the Apps may be enough, but it is going to be close!  Noted a 468dm pv over Eastern Canada on the 12z EC @ 24hrs, can't remember the last time I saw one that low in the NH, usually in the 470-480 range this time of year, at best.

 

Strictly based on this, I can see room for it to become more suppressed.

post-382-0-46890100-1358392892_thumb.jpg

 

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Yes...you are missing the fact that the temperature profiles do not support 10:1 ratios...more like 4:1 or 5:1 ratios...so these "low" totals are correct...

Like the new avatar. I am aware that the NAM snowfall map has 10:1 ratios but I also think that the NAM could be not recognizing the strong, dynamical cooling that should be occurring, especially under that deform band. Snow totals seem like they could be low in areas and I try to be a realists as opposed to wishcasting. Am I missing something here?

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Yes...you are missing the fact that the temperature profiles do not support 10:1 ratios...more like 4:1 or 5:1 ratios...so these "low" totals are correct...

I understand your point and ratios certainly will be close to what you surmise. My point is the snow will fall for a longer period of time due to the switchover being quicker (therefore more snow less rain). My opinion only. 

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‎*****MAJOR WINTER STORM TO IMPACT ALABAMA, GEORGIA, EAST TENNESSEE, NORTHERN SC, MOST OF NC AND SOUTHERN HALF VIRGINIA*******

Models trend colder, stronger, snowier, longer. A strong "bowling ball" type upper low, with cold air, longer duration than previously thought, and heavier axis of comma head snow, will aim at this region Thursday afternoon, night and early Friday. The upper low itself will provide snow and sleet through central and northern parts of Miss, Ala and Ga tomorrow but tomorrow night the precipitation EXPLODES quickly in most of western SC, central to west NC, eastern TN and southern VA. The atmosphere will cool off as all upper lows provide cold air and a crashing column when they're this strong. Rain will switch to snow and sleet suddenly then all snow, in all these areas. The heaviest snow looks to be as I have been pointing out for a while now, northern Georgia, eastern TN, and initially western NC and western, southwest Virginia, but spreading east across the Carolinas during the night. The way the axis sets up, the orientation of the "tilt" of the upper low, the most lift and dynamic cooling will occur much the same way March 2009 occurred..with all the Southern Apps receiving a 4 to 8 hour period of EXTREMELY heavy snow rates, which is much higher than the average Winter storm. Prepare now for power outages in east TN/ W NC/Central NC/sw VA/S VA, and scattered outages possible in northeast GA and Upstate SC. The storm will be short -lived, but very intense.

Trees will come down in some areas. Thundersnow will occur in some areas. Snow rates will be 2" per hour in some areas. Prepare now for suddenly changing weather beginning Thursday afternoon and reaching climax overnight Thursday night.-Robert, www.wxsouth.com

 

Well, someone is being bullish.

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OK...but you didn't say that in your post...you quoted strong dynamical cooling as a reason why these totals seemed low to you.

I understand your point and ratios certainly will be close to what you surmise. My point is the snow will fall for a longer period of time due to the switchover being quicker. My opinion only. 

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I have a couple concerns regarding this setup, 1, I can't remember a time with a surface low track from Augusta to Myrtle Beach where NC saw an appreciable winter storm.  We do well with tracks along the Panhandle, HKY right along the coast, central and eastern parts an offshore track.  2nd is the warm punch between 875-925 that often happens when you see 850's surging to 6-9C and ingested into the system, while crashing on the backside.  Optimist:  I do not see impacts much north of I-64 in VA (call it a hunch), and the fact SE VA is showing a good signal makes me here in NE NC (kinda) feel ok, as we usually do well together.  The attendant cold pool aloft working in from the SW at about the same time the best lift comes overhead, coupled with a slow bleed of Arctic air from the north, coming down east of the Apps may be enough, but it is going to be close!  Noted a 468dm pv over Eastern Canada on the 12z EC @ 24hrs, can't remember the last time I saw one that low in the NH, usually in the 470-480 range this time of year, at best.

Great analysis and thanks for adding this. It is an odd trajectory. Do you think it is model error or is it just an unusual setup?

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Like the new avatar. I am aware that the NAM snowfall map has 10:1 ratios but I also think that the NAM could be not recognizing the strong, dynamical cooling that should be occurring, especially under that deform band. Snow totals seem like they could be low in areas and I try to be a realists as opposed to wishcasting. Am I missing something here?

No I think you are right about it potentially missing some of the dynamic cooling. As Marietta said the soundings are very close for us, and probably snowy for you.

 

If in fact the NAM is not recognizing the dynamic cooling, then that very well could put the Northern ATL burbs into the snowy goods. Just my opinion though.

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A Winter Storm Warning is up for Central Mississippi with 2-4" expected over much of the area.

 

http://forecast.weather.gov/hazards/?wfo=jan&lat=32.6462&lon=-90.0848&pil=JANWSWJAN&iss=1358391000&etn=0001&maptype=text

That is good news. Typically we do better than Central MS in the Atlanta metro area. Higher in elevation plus a little further north.

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00z Canadian RGEM is farther north with the snow changeover, more like I-40 north in central NC.  

 

From my experience, the NAM has a tendency to be a little too cool, and the GFS a little too warm.  Not sure what to say about the Canadian, though some have said it tends to be a little warm....I would be leary of how far south the NAM has the changeover to snow.

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That is good news. Typically we do better than Central MS in the Atlanta metro area. Higher in elevation plus a little further north.

 

The key for ATL will be if the low can stay closed off longer...the high res NAM sim radar shows that at 21Z an excellent deformation band is sitting west ready to barrel through but it crumbles a bit crossing N GA as the low opens, if that low opens slower that band could swing across.

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