Thanksgiving weekend snow/ice threat

[Cyclonicjunkie]

IMO This is the real mccoy arctic front, not just our usual fall time frontal passage with a little cold/sn flurries on the back. The Cold air will really rush in, and most models now show the front to slow down and hang up somewhere in the south which will mean temps are going to plummit .

Temps will drop 30-40 degrees within hours of frontal passage. With an expected wave of LP to develop and move along the stalled boundary which means northern parts of the western and central SE will have a great chance of seeing snow/ice. I feel the elevated areas will do great and I really think this has the potential to lay a couple of inches down in some non elevated areas in TN. Models seem to be in unusually good agreement on this threat now, and I felt confident enough to start my first thread here at our new home.

[NCBlizzard]

Hope someone gets some snow but for us in western NC the cold air can never get over the apps fast enough.

[Tyler Penland]

I've been keepin my eye on this one too cyclonic. Whats the Euro saying about this? I dont know where to look at the Euro at so I normally just rely on y'all.

[Cyclonicjunkie]

I've been keepin my eye on this one too cyclonic. Whats the Euro saying about this? I dont know where to look at the Euro at so I normally just rely on y'all.

It looks alot like the gfs, but you have to pay to get the real goodies.

I like this site.

http://supercellweat...f.blogspot.com/

[CAD_Wedge_NC]

Hope someone gets some snow but for us in western NC the cold air can never get over the apps fast enough.

Agree..... This type of set-up usually favors areas to our west (west of the Apps) TN, Northern AL/GA.... Since the cold air is dense and shallow at first, it has to pool along the spine of the Apps until it gets enough steam to push over. By this time, the bulk of the precip has moved NE of us. Now with that being said, I have seen cases where the front will hang up along the coastal areas and set up an over-running event but this doesn't seem to be the case this time. However, we will need to keep an eye on the progression of the front as the models get closer to the event.

[Cheeznado]

You have to be careful with those Cool WX precip type maps- it is a past 3 hour precip field with the thickness being a snapshot, so it overdoes frozen behind cold fronts where it will probably just be dry by the time the cold air arrives. Not impressed for much if any frozen

with this setup.

[Cyclonicjunkie]

You have to be careful with those Cool WX precip type maps- it is a past 3 hour precip field with the thickness being a snapshot, so it overdoes frozen behind cold fronts where it will probably just be dry by the time the cold air arrives. Not impressed for much if any frozen

with this setup.

Yep, but thats not the case here. The artic air is undercutting the moist warmer air aloft creating ice/snow along and behind the front.

[SBUWX23]

Yep, but thats not the case here. The artic air is undercutting the moist warmer air aloft creating ice/snow along and behind the front.

Best way to assess this is too look at soundings.

[WeatherNC]

Best way to assess this is too look at soundings.

Ding, ding, ding, winner winner, chicken dinner... Best chance for seeing any frozen precip resides in the mountains, and looking at the 12z GFS sounding for Boone at 126 hrs, it is not even close for QPF, or favorable temps for SN. At 120hrs the column under 500mb is at-least saturated, but the layer below 700mb is >0C. At 132hrs, the entire column is below freezing, but even drier.

[WeatherNC]

Ding, ding, ding, winner winner, chicken dinner... Best chance for seeing any frozen precip resides in the mountains, and looking at the 12z GFS sounding for Boone at 126 hrs, it is not even close for QPF, or favorable temps for SN. At 120hrs the column under 500mb is at-least saturated, but the layer below 700mb is >0C. At 132hrs, the entire column is below freezing, but even drier.

Same holds true for the soundings I looked at in areas of E TN that have good elevation...

[Jon]

I've been keepin my eye on this one too cyclonic. Whats the Euro saying about this? I dont know where to look at the Euro at so I normally just rely on y'all.

http://raleighwx.ame...com/models.html

Allan Huffman's model page, on the right hand side where it says ECMWF...this is where I look.

[Lee]

Same holds true for the soundings I looked at in areas of E TN that have good elevation...

Those soundings have failed quite a few times before in these areas and @ much closer to an event time frame. Take for example the early November snowfall of 1-4 inches in the valley locations of East Tennessee. Soundings didn't suggest that then below 2500 ft.

Other factors , as you probably know, can affect the outcome pretty quickly.

[Cyclonicjunkie]

Same holds true for the soundings I looked at in areas of E TN that have good elevation...

at your soundings at mountainous locations.

[WeatherNC]

at your soundings at mountainous locations.

Not mine, these are from the 12z global off of twister data... I checked areas between Memphis and Nashville on I-40 and those looked close, but there is an evident warm nose working through, as well as rapid drying, and the warm nose usually grows stronger as an event nears if initially modeled correctly. Also, excellent job in adding constructive insight to the conversation that you started.

[Cheeznado]

Another thing to consider, we are talking about a 126 hour forecast here in a pattern where the models have been pretty bad in the medium range, so talking specifics in this case is somewhat problematic. In that vein, the 12Z Euro is not as gung-ho with the cold air as the GFS. I still think any frozen with this is likely to be minor anyway, with the best chance in central/western TN/KY.

[Cyclonicjunkie]

Not mine, these are from the 12z global off of twister data... I checked areas between Memphis and Nashville on I-40 and those looked close, but there is an evident warm nose working through, as well as rapid drying, and the warm nose usually grows stronger as an event nears if initially modeled correctly. Also, excellent job in adding constructive insight to the conversation that you started.

Either way they're usually junk at elevated areas.

No biggie, but its important to realize the limits of a sounding. The sounding is a single image of the atmosphere, taken at one time in one location. This will be a factor depending on the larger-scale weather patterns and in any case will be less accurate in mountainous regions. The upper air patterns can change during the day due to passing boundaries and smaller upper air features. For example, wx patterns near mountains can alter the air aloft over nearby valleys. A temperature change aloft of only a few degrees also can make a large difference.

That said the sounding analysis is still an excellent tool for air plane pilots.

[WeatherNC]

Another thing to consider, we are talking about a 126 hour forecast here in a pattern where the models have been pretty bad in the medium range, so talking specifics in this case is somewhat problematic. In that vein, the 12Z Euro is not as gung-ho with the cold air as the GFS. I still think any frozen with this is likely to be minor anyway, with the best chance in central/western TN/KY.

Agree, and even that scenario would place more weight on a GFS solution, but given the lack of run-to-run continuity, particularly in the EC, a very low confidence forecast going forward. Never a fan though of frozen precip associated with a front. 9 times out of 10 the cold air chases the precip, and we all know how that goes...

[Lee]

Another thing to consider, we are talking about a 126 hour forecast here in a pattern where the models have been pretty bad in the medium range, so talking specifics in this case is somewhat problematic. In that vein, the 12Z Euro is not as gung-ho with the cold air as the GFS. I still think any frozen with this is likely to be minor anyway, with the best chance in central/western TN/KY.

Agree with the fact it is still so far out and the models waffling so much; way too early to be arguing over it. Soundings do suggest further west in Tn/Ky based on current guidance. Maybe those folks get to see their first flakes, eastern sections already have (Nov. 5-6) .

[WeatherNC]

No biggie, but its important to realize the limits of a sounding. The sounding is a single image of the atmosphere, taken at one time in one location. This will be a factor depending on the larger-scale weather patterns and in any case will be less accurate in mountainous regions. The upper air patterns can change during the day due to passing boundaries and smaller upper air features. For example, wx patterns near mountains can alter the air aloft over nearby valleys. A temperature change aloft of only a few degrees also can make a large difference. That said the sounding analysis is still an excellent tool for air plane pilots.

Not sure I understand where you are coming from on this. Soundings are that, a snapshot of the column's profile at said time based on what a model shows. They show saturation as well as temps for the layer above and that imo is an excellent tool, especially in the short term in determining QPF type. That coupled with thickness data from the american model's makes me wax the sled if a "go" within the magic 48hr window. For you to imply that soundings are only a good tool to airline pilots is not only inaccurate, but also harmful to the new members who are just beginning their understanding of the weather. I am not discounting topographic influences, but if you look at the sounding for Boone that I posted, you can clearly see the elevation taken into account. The dynamic models, at least how I understand them, take topography into account. Still a long ways out in a pattern that poses major fits in modeling. Strong Nina coupled with what may be a near record -NAO, we have seen the perturbations over the past week and look for them to continue going into Dec. Lots of potential here, no question, and a big winter storm can pop pretty quick. But I would look at the overall pattern, instead of what one model shows as far as QPF-type is concerned, which is less accurate than sounding data.

[Cyclonicjunkie]

Not sure I understand where you are coming from on this.

The sounding analysis is limited by how well it represents the greater area. The sounding balloon rises at about 1,000 fpm, so it takes about 30 minutes to reach 30,000 feet, during which time it has drifted west, or south, or north, or east, with the winds aloft from the launch point, and even more so in mountainous terrain. So to get an Ideal sounding you have to have ideal conditions which you rarely ever have in the mountains.

For you to imply that soundings are only a good tool to airline pilots is not only inaccurate, but also harmful to the new members who are just beginning their understanding of the weather.

I didnt imply that, I said they are a great tool for airplane pilots. I appologize if it sounded like thats the only thing they should be used for. They can be a great forecast tool if used along with other data.

I m not discounting topographic influences, but if you look at the sounding for Boone that I posted, you can clearly see the elevation taken into account. The dynamic models, at least how I understand them, take topography into account.

The sounding analysis is limited by how well it represents the greater area. The sounding balloon rises at about 1,000 fpm, so it takes about 30 minutes to reach 30,000 feet, during which time it has drifted west, or south, or north, or east, with the winds aloft from the launch point, and even more so in mountainous terrain. So to get an Ideal sounding you have to have ideal conditions which you rarely ever have in the mountains.

But I would look at the overall pattern, instead of what one model shows as far as QPF-type is concerned, which is less accurate than sounding data.

I have taken into account several models when I started this thread (which are in very good agreement with each other regarding this threat). Not to mention the pattern.

Now I started this thread with the central and western SE in mind.

Temps will drop 30-40 degrees within hours of frontal passage. With an expected wave of LP to develop and move along the stalled boundary which means northern parts of the western and central SE will have a great chance of seeing snow/ice.

I realize the majority of posters here are from NC, but there are other areas in the SE.

[CAD_Wedge_NC]

The sounding analysis is limited by how well it represents the greater area. The sounding balloon rises at about 1,000 fpm, so it takes about 30 minutes to reach 30,000 feet, during which time it has drifted west, or south, or north, or east, with the winds aloft from the launch point, and even more so in mountainous terrain. So to get an Ideal sounding you have to have ideal conditions which you rarely ever have in the mountains.

I didnt imply that, I said they are a great tool for airplane pilots. I appologize if it sounded like thats the only thing they should be used for. They can be a great forecast tool if used along with other data.

I have taken into account several models when I started this thread (which are in very good agreement with each other regarding this threat). Not to mention the pattern.

Now I started this thread with the central and western SE in mind.

I realize the majority of posters here are from NC, but there are other areas in the SE.

I don't know how the weather acts in East TN, but here in NC we pay very close attention to the soundings data. It is an extremely valuable tool that will tell you whether you will have rain, ice, or snow. If you don't evaluate the soundings, your forecast will bust 90% of the time here. There are some good links that will teach you how to use this data....here's an example of one that I use frequently to determine p-type in close calls.

http://www4.ncsu.edu/~nwsfo/storage/trend/

[WeatherNC]

I don't know how the weather acts in East TN, but here in NC we pay very close attention to the soundings data. It is an extremely valuable tool that will tell you whether you will have rain, ice, or snow. If you don't evaluate the soundings, your forecast will bust 90% of the time here. There are some good links that will teach you how to use this data....here's an example of one that I use frequently to determine p-type in close calls.

http://www4.ncsu.edu/~nwsfo/storage/trend/

Excellent post CAD, one of those graphics, which I have seen you post elsewhere, I continue to reference every winter as an invaluable tool...

[Carvers Gap]

It has been a very, very long time since cold air has "caught" the precipiation shield in front of it in NE TN and then resulted in significant snow/ice. Could it happen? Yes. Is it likely? No. I think the first three weeks of December are our best chances for snow/ice this winter. I think the cold will have to be in place first - per the usual. That SE ridge is not playing around this year. It's takin' names as we speak. By January, the La Nina pattern could very well take hold and wreak havoc on any chance of a cold winter. Anyway, I'd suggest listening to those folks on this board. They have the best discussion on the net for weather in our region.

[Cyclonicjunkie]

Nashville starting to like the idea of some frozen.

AREA FORECAST DISCUSSION...UPDATED

NATIONAL WEATHER SERVICE NASHVILLE TN

539 PM CST SUN NOV 21 2010

LOOKS LIKE A WARM FRONT WILL PUSH NORTHEASTWARD ACROSS MIDDLE

TENNESSEE ON WEDNESDAY AS A DEVELOPING LOW CENTER MOVES FROM THE

CENTRAL PLAINS INTO THE UPPER MIDWEST. GFS SHOWS DRAMATIC

FRONTOGENESIS JUST TO OUR WEST, RIGHT AHEAD OF THE 850 MB TROUGH,

WITH MORE PRECIPITATION THURSDAY AND THURSDAY NIGHT.

IT NOW APPEARS THAT THANKSGIVING DAY WILL STILL BE MILD, WITH THE

COLD AIR NOT INFILTRATING THE MID STATE UNTIL THURSDAY NIGHT. AS

SUCH, BELIEVE A RAIN/SNOW MIXTURE IS POSSIBLE ACROSS THE NORTHWEST

HALF OF MIDDLE TENNESSEE LATE THURSDAY NIGHT.

[oconeexman]

Well good luck Tenn. it won't happen in SC or most of NC or Ga...guaranteed!

On the other hand the word "epic" was thrown around a bit the other day and this to me would be epic for early December

[Weather Czar]

Soundings have worked for me in my area. By the way I get soundi gs from the euro now so that should come in handy this winter. Also I live in the mtns and I am not reall expecting anything other that a few flurries or light snow showers.

[oconeexman]

Almost comical but noteworthy

[Carvers Gap]

Off topic..What is this "warn status" junk showing up below my profile pic? Can it be removed?

[oconeexman]

Soundings have worked for me in my area. By the way I get soundi gs from the euro now so that should come in handy this winter. Also I live in the mtns and I am not reall expecting anything other that a few flurries or light snow showers.

Lookout is a soundings expert, would like to see him and Cylonic go at it!

[Cyclonicjunkie]

Lookout is a soundings expert, would like to see him and Cylonic go at it!

lolz..... Soundings are a good forecast tool, dont get me wrong. I just have a problem with them in elevated areas. Im sticking with my guns here, if this thread busts I will be the first one to admit it.