Deep South Cut-Off November 27-29 2011

[FoothillsNC]

I could keep on waiting for the runs to keep coming out but the trend is fully back to a cutoff. Besides, waiting until the last minute when all the models full agree isn't exactly fun forecasting (or forecasting at all?)...it's modeling. This may be further west than the Miss. River but for now I'm settling on around MEM or TN/MS border region, possibly beginning in central Arkansas. As the low cuts off it will continue to tighten and strengthen up, and actually grow colder at the core. However this is still not a really cold cutoff, and the further west it cuts off, probably the warmer it would be, the further east in the TN valley, the colder, thanks to having a longer connection with the northern stream before pinching off. This is going to be a very big deal. Its' not often we get 4 or 5 contours closed off this far south. The GFS seems to have had the right idea nearly a week ago, and pretty much all the ensembles and ops. have settled on a lower Miss or Tn. Valley strong cutoff that could pinwheel for acouple of days if not more.

The models are frequently too quick to move a cutoff (think Sept. Ohio Valley deep cutoff that sat a week). But for now, it appears we're in for a strong southerly fetch against a strong, very sharp trough that creates exceptionally good lift and a tap with the Gulf, so thunderstorms and severe is possible but I haven't seen too much of the severe parameters. Normally a cutoff in this location will funnel heavy but sort of narrow band that trains over the same areas, and that looks to be straight up through Alabama and western GA into Tenn. curving back into a developing axis of deformation. On the northwest side, precip may get an extra lift later on all th way to the Ohio River and southern Illinois.

The rain will probably come in atleast a couple good bands each producing a couple of inches for part of GA and Al, and the western Carolinas. Dynamics weaken further north but later on the storm could phase with another incoming trough, in which case the whole system would strengthen, and become a major snow maker for inland Northeast, but thats very far out.

As the cold air aloft begins to wrap on the west side, then rotate under the 850 low around MEM, rain may change to snow in central Ark, northern Miss even down to central Miss, nrn La and spread into western Alabama later on if the core of the lowest heights go toward the Tenn. River Valley and then southern Apps region. Time of day and precip rates will mean everything since we're dealing with marginal air and climo this time of year, but usually strong cutoffs of this caliber are capable of dyamic cooling down to the surface (even in daylight if heavy enough), but can vary tremendously from one city to the next. This could be a situation where at one point its snowing in Jackson Mississippi and raining in Nashville. And then snowing in Nashville but raining in Pittsburg. Depends on the location of the core and the wrap around moisture and precip rates.

Another major aspect will be the rain totals and rainfall rates. The models are pretty widespread and heavy through the Tenn Valley and probably not quite heavy enough in the Apps. If it cuts off too far west, that would reduce the totals for the southern facing Apps of northeast GA and western NC, but with the ensembles and most models showing the nature, location and orientation of the 3 to 5 contour cutoff, easily flooding type rains could be a problem esp. if it comes at rates like .50" an hour for 6 plus hours, which is very possible in one or more of the heavy bands that rotates through.

I think most have seen what strong cutoff lows are capable of, and keep in mind the models and soundings and such aren't gospel..these things do strange things all the time. And this particular one is one of the strongest I've seen modeled this far south. I'm sure there's been others but not lately, and not in the Deep South, and not at this time of year. Anything is possible and I'd bet the models have a trick up their sleeve yet, for example, possible phasing with another wave later next week if the system hangs around very long in the South. Or the system may end up further west, which would mean it won't be as cold core, so very little snow at all. This is my best call for now. I'm finishing this up and the 00zNAM is in. Nothing really to change my mind except to re-iterate, this is going to be a very big deal across the South. Lots of rain, hour to hour vast weather changes, and from city to city in the same state. If you like interesting weather, this should suit you on many levels. And for the snowlovers, as long as the models don't begin getting warmer with the cold intrusion, I think a surprise snow report will occur Sunday night , Monday or Monday night into Tuesday "somewhere". As always, have fun with this storm! Its' been a blast to follow all week long.

[Ginx snewx]

I could keep on waiting for the runs to keep coming out but the trend is fully back to a cutoff. Besides, waiting until the last minute when all the models full agree isn't exactly fun forecasting (or forecasting at all?)...it's modeling. This may be further west than the Miss. River but for now I'm settling on around MEM or TN/MS border region, possibly beginning in central Arkansas. As the low cuts off it will continue to tighten and strengthen up, and actually grow colder at the core. However this is still not a really cold cutoff, and the further west it cuts off, probably the warmer it would be, the further east in the TN valley, the colder, thanks to having a longer connection with the northern stream before pinching off. This is going to be a very big deal. Its' not often we get 4 or 5 contours closed off this far south. The GFS seems to have had the right idea nearly a week ago, and pretty much all the ensembles and ops. have settled on a lower Miss or Tn. Valley strong cutoff that could pinwheel for acouple of days if not more.

The models are frequently too quick to move a cutoff (think Sept. Ohio Valley deep cutoff that sat a week). But for now, it appears we're in for a strong southerly fetch against a strong, very sharp trough that creates exceptionally good lift and a tap with the Gulf, so thunderstorms and severe is possible but I haven't seen too much of the severe parameters. Normally a cutoff in this location will funnel heavy but sort of narrow band that trains over the same areas, and that looks to be straight up through Alabama and western GA into Tenn. curving back into a developing axis of deformation. On the northwest side, precip may get an extra lift later on all th way to the Ohio River and southern Illinois.

The rain will probably come in atleast a couple good bands each producing a couple of inches for part of GA and Al, and the western Carolinas. Dynamics weaken further north but later on the storm could phase with another incoming trough, in which case the whole system would strengthen, and become a major snow maker for inland Northeast, but thats very far out.

As the cold air aloft begins to wrap on the west side, then rotate under the 850 low around MEM, rain may change to snow in central Ark, northern Miss even down to central Miss, nrn La and spread into western Alabama later on if the core of the lowest heights go toward the Tenn. River Valley and then southern Apps region. Time of day and precip rates will mean everything since we're dealing with marginal air and climo this time of year, but usually strong cutoffs of this caliber are capable of dyamic cooling down to the surface (even in daylight if heavy enough), but can vary tremendously from one city to the next. This could be a situation where at one point its snowing in Jackson Mississippi and raining in Nashville. And then snowing in Nashville but raining in Pittsburg. Depends on the location of the core and the wrap around moisture and precip rates.

Another major aspect will be the rain totals and rainfall rates. The models are pretty widespread and heavy through the Tenn Valley and probably not quite heavy enough in the Apps. If it cuts off too far west, that would reduce the totals for the southern facing Apps of northeast GA and western NC, but with the ensembles and most models showing the nature, location and orientation of the 3 to 5 contour cutoff, easily flooding type rains could be a problem esp. if it comes at rates like .50" an hour for 6 plus hours, which is very possible in one or more of the heavy bands that rotates through.

I think most have seen what strong cutoff lows are capable of, and keep in mind the models and soundings and such aren't gospel..these things do strange things all the time. And this particular one is one of the strongest I've seen modeled this far south. I'm sure there's been others but not lately, and not in the Deep South, and not at this time of year. Anything is possible and I'd bet the models have a trick up their sleeve yet, for example, possible phasing with another wave later next week if the system hangs around very long in the South. Or the system may end up further west, which would mean it won't be as cold core, so very little snow at all. This is my best call for now. I'm finishing this up and the 00zNAM is in. Nothing really to change my mind except to re-iterate, this is going to be a very big deal across the South. Lots of rain, hour to hour vast weather changes, and from city to city in the same state. If you like interesting weather, this should suit you on many levels. And for the snowlovers, as long as the models don't begin getting warmer with the cold intrusion, I think a surprise snow report will occur Sunday night , Monday or Monday night into Tuesday "somewhere". As always, have fun with this storm! Its' been a blast to follow all week long.

Fantastic post, good times for us geeks, not so good for forecasters.

[FoothillsNC]

Fantastic post, good times for us geeks, not so good for forecasters.

Thanks! You're right, its a headache to fx, still fun though!

[LithiaWx]

Well done sir, nice writeup. As a weather lover this is an exciting storm to watch unfold. I'll be anxiously awaiting it's arrival, whatever affects it might have on my location. Looks like rain and lots of it is certain, anything else would be icing on a extreme weather cake it seems.

[Gastonwxman]

As the saying goes: An upper level low is a forecaster's woe. Depressing but true fact indeed. This system is one of the most interesting I've seen in a long time. Lots of variety and excitement with this system, which will make for a fun experience as we watch this develop and see where it goes from here. What a way to close off the month; November ending with a bang.

[Met1985]

I could keep on waiting for the runs to keep coming out but the trend is fully back to a cutoff. Besides, waiting until the last minute when all the models full agree isn't exactly fun forecasting (or forecasting at all?)...it's modeling. This may be further west than the Miss. River but for now I'm settling on around MEM or TN/MS border region, possibly beginning in central Arkansas. As the low cuts off it will continue to tighten and strengthen up, and actually grow colder at the core. However this is still not a really cold cutoff, and the further west it cuts off, probably the warmer it would be, the further east in the TN valley, the colder, thanks to having a longer connection with the northern stream before pinching off. This is going to be a very big deal. Its' not often we get 4 or 5 contours closed off this far south. The GFS seems to have had the right idea nearly a week ago, and pretty much all the ensembles and ops. have settled on a lower Miss or Tn. Valley strong cutoff that could pinwheel for acouple of days if not more.

The models are frequently too quick to move a cutoff (think Sept. Ohio Valley deep cutoff that sat a week). But for now, it appears we're in for a strong southerly fetch against a strong, very sharp trough that creates exceptionally good lift and a tap with the Gulf, so thunderstorms and severe is possible but I haven't seen too much of the severe parameters. Normally a cutoff in this location will funnel heavy but sort of narrow band that trains over the same areas, and that looks to be straight up through Alabama and western GA into Tenn. curving back into a developing axis of deformation. On the northwest side, precip may get an extra lift later on all th way to the Ohio River and southern Illinois.

The rain will probably come in atleast a couple good bands each producing a couple of inches for part of GA and Al, and the western Carolinas. Dynamics weaken further north but later on the storm could phase with another incoming trough, in which case the whole system would strengthen, and become a major snow maker for inland Northeast, but thats very far out.

As the cold air aloft begins to wrap on the west side, then rotate under the 850 low around MEM, rain may change to snow in central Ark, northern Miss even down to central Miss, nrn La and spread into western Alabama later on if the core of the lowest heights go toward the Tenn. River Valley and then southern Apps region. Time of day and precip rates will mean everything since we're dealing with marginal air and climo this time of year, but usually strong cutoffs of this caliber are capable of dyamic cooling down to the surface (even in daylight if heavy enough), but can vary tremendously from one city to the next. This could be a situation where at one point its snowing in Jackson Mississippi and raining in Nashville. And then snowing in Nashville but raining in Pittsburg. Depends on the location of the core and the wrap around moisture and precip rates.

Another major aspect will be the rain totals and rainfall rates. The models are pretty widespread and heavy through the Tenn Valley and probably not quite heavy enough in the Apps. If it cuts off too far west, that would reduce the totals for the southern facing Apps of northeast GA and western NC, but with the ensembles and most models showing the nature, location and orientation of the 3 to 5 contour cutoff, easily flooding type rains could be a problem esp. if it comes at rates like .50" an hour for 6 plus hours, which is very possible in one or more of the heavy bands that rotates through.

I think most have seen what strong cutoff lows are capable of, and keep in mind the models and soundings and such aren't gospel..these things do strange things all the time. And this particular one is one of the strongest I've seen modeled this far south. I'm sure there's been others but not lately, and not in the Deep South, and not at this time of year. Anything is possible and I'd bet the models have a trick up their sleeve yet, for example, possible phasing with another wave later next week if the system hangs around very long in the South. Or the system may end up further west, which would mean it won't be as cold core, so very little snow at all. This is my best call for now. I'm finishing this up and the 00zNAM is in. Nothing really to change my mind except to re-iterate, this is going to be a very big deal across the South. Lots of rain, hour to hour vast weather changes, and from city to city in the same state. If you like interesting weather, this should suit you on many levels. And for the snowlovers, as long as the models don't begin getting warmer with the cold intrusion, I think a surprise snow report will occur Sunday night , Monday or Monday night into Tuesday "somewhere". As always, have fun with this storm! Its' been a blast to follow all week long.

Wow great post! Im new here my very first post . Sounds like it will be a fun week ahead!

[Cold Rain]

Good disco, Robert. Looks like the Triangle misses out on everything.

This is a remarkable system, and it will be very fascinating to watch it play out. Anyone who sees snow, take some pix!

[Cold Rain]

Wow great post! Im new here my very first post . Sounds like it will be a fun week ahead!

Welcome aboard!

[Met1985]

Welcome aboard!

Thanks i love the weather. I decided to join so i can learn more and participate in a cool Wx board like this one. Im looking forward to to talking with everyone and learning a lot more from the people on here.

[ams30721us]

That is a VERY detailed and informative post Robert. I am impressed at the effort you put in on this one and as usual. Puts my paragraphs to shame! haha Very good work my friend!

[tnweathernut]

This may be a case where there are two distinct, yet localized areas of snow accumulation, one where the low pinches off and deepens, then another where the second vorticity dives in and re-energizes things further east/northeast, with an area of rain in between two areas of snow.

This one will be a headache. I am glad I am not a met.

[Met1985]

This may be a case where there are two distinct, yet localized areas of snow accumulation, one where the low pinches off and deepens, then another where the second vorticity dives in and re-energizes things further east/northeast, with an area of rain in between two areas of snow.

This one will be a headache. I am glad I am not a met.

Ya this storm is going to be very interesting to track. There will be a lot of rain and someone may get hit with a swath of heavy wet snow.

[strongwxnc]

Sweet work bro! Here's to some rain for us lee side folks!!

Welcome to amwx Met1985!!!

[BIG FROSTY]

Great write up Robert, Now you need to shift that snow just a tad east of the mountains!

[NEGa]

Nice analysis and graphics! Looking forward to sme interesting wx again for a change.

[Frederick Weather]

Great wright up Robert. Thanks for the info.

[Lee]

This may be a case where there are two distinct, yet localized areas of snow accumulation, one where the low pinches off and deepens, then another where the second vorticity dives in and re-energizes things further east/northeast, with an area of rain in between two areas of snow.

This one will be a headache. I am glad I am not a met.

The way Robert depicts it's path is the way we want it up here in the upper east Tn, Sw VA area, if you want a decent amount of snow from it. Let's hope his projection comes to fruition

[jrips27]

Fantastic post, Robert! I would need this baby to push a tad further south to get in on the backside snow.

[FoothillsNC]

Fantastic post, Robert! I would need this baby to push a tad further south to get in on the backside snow.

well its certainly possible. This is just my best guess but it could end up sagging further south than on my graphic. Or more north. Its hard to say yet. One thing though, the further south the cutoff becomes, the slower it would be, meaning a whole lot more rain than I have, or any of the models have. This is an evolving situation. If anything, I'm leaning slower and slower with it, and I'm not doing up the rain enough, generally speaking.

[sctvman]

Charleston needs a lot of that rain. We've only had about 1/2 inch of rain the entire month of November, but it looks like it will be farther north.

[FoothillsNC]

Charleston needs a lot of that rain. We've only had about 1/2 inch of rain the entire month of November, but it looks like it will be farther north.

I hope you get a good amount with this one, but like so many of these systems its favoring well inland for the Southeast and esp. around the TENN valley. The track seems to be toward the Apps. The latest GFS is very impressive with the cutoff, and almost identical to where it was putting it for days before it became progressive.

Now it wouldn't surprise me to see the models moving it out too quickly. A large 5 contour cutoff well removed from the flow could linger a while. This looks super-wet for the Tenn valley and the southern Apps. I wouldn't be suprised to see some usual wet spots in ne Ga and NC border regions get up to 8" of rain before its over. The 850 flow is perfect for some of the big stationary bands.

[tnweathernut]

I know a call map for snow amounts would be premature, but one showing where significant snow is possible would be fun to look at. Any takers??

Great write up Robert, your time and abilities are appreciated.

[FoothillsNC]

I know a call map for snow amounts would be premature, but one showing where significant snow is possible would be fun to look at. Any takers??

Great write up Robert, your time and abilities are appreciated.

thanks to everybody on the compliments. I know I wouldn't do a snowmap on a cutoff, this time of year especially. Its going to vary a lot from one county to the next under those bands. This cold air isn't too cold only -3 or -4 at 850 I'd like to see it colder but some areas will get some good snow falling, the question is how hard it falls and whether day or night. I think some spots will get a quick 6" of snow, maybe even more but not in huge regions. It would be the type that clumps to trees and power lines too, so that could do a number for whoever gets hit with that kind of snowrates. This is one powerhouse cutoff .

[WilkesboroDude]

Very nice write up.

That is a whole lot of rain for me. Still hoping for a flake near the North Wilkesboro area. I also wonder if all this water will freeze over by Tuesday morning?

[dsaur]

Thanks, as always, Robert. I'm looking forward to a rain parade if it sets up right One of my top weather experiences was Alberto, so anytime I'm looking at training heavy rains I'm up for it. There is just something about having things come together to make it rain so hard you can hardly breathe. And hour after hour of it...just fascinating to watch and listen to. Not as good as sleet, but getting there T

[weatherman566]

Did anyone read the HPC's discussion? Very interesting....and they seem to like the European and NAM solutions...

STRONG LOW-LEVEL COLD ADVECTION BENEATH THE DEVELOPING H5 LOW ANDDECENT MID-LEVEL SHEAR ACROSS THE NORTH AND NORTHEAST QUADRANT OFTHE H5 CIRCULATION CONTAINING M20C COLD POOL WILL PERIODICALLYBECOME ENTRAINED WITH GULF MOISTURE ALONG/AHEAD OF THE DEEP COLDFRONT. ISENTROPIC ANALYSIS...BETWEEN 305K AND 320KSURFACES...SUGGEST DYNAMICAL LIFT...INCREASING INSTABILITY ANDPOSSIBLE CONVECTIVE ACTIVITY SUPPORTING BRIEF PERIODS OF RAIN/SNOWMIX AND SNOW/SLEET SHOWERS ACROSS PORTIONS OF THESOUTHEAST...INITIALLY ALONG THE COLD FRONT IN EASTERNOKLAHOMA...WESTERN ARKANSAS AND SOUTHERN MISSOURI...BEFORESHIFTING EAST SOUTHEASTWARD INTO NORTHEAST LOUISIANA...NORTHERNMISSISSIPPI...WESTERN TENNESSEE AND NORTHWEST ALABAMA. MUCH IF NOTALL THE ELEVATED RAIN BANDS MOVING NORTHWARD INTO THE COLD POOLALOFT WILL BE ENHANCED BY THE STRONG DYNAMICAL PROCESSES/LIFT.BASED ON THE ECMWF/UKMET/CANADIAN/GFS...SFC TO H5 MASSFIELDS...THERMO-DYNAMIC PROFILES SUGGEST THE BETTER PROSPECTS FORACCUMULATING SNOWFALL TO BE ACROSS NORTHEAST MISSISSIPPI...SOUTHWESTERN TENNESSEE...AND NORTHWEST ALABAMA...FOLLOWING THE LOWTRACK AND COLD FRONT. POSSIBLE SNOWFALL ACCUMULATIONS SHIFTEASTWARD INTO THE SOUTHERN APPALACHIANS...INCLUDING NORTHERNGEORGIA AND SOUTHWEST NORTH CAROLINA ON MONDAY WITH BROAD WRAPAROUND DEFORMATION PRECIPITATION AND BANDING EXPANDING NORTH ANDWEST ACROSS PORTIONS OF THE COLD SECTOR...ENCOMPASSING A LARGEPORTION OF THE SOUTHEAST...INCLUDING THE LOWERMISSISSIPPI/TENNESSEE VALLEYS.

Where's the popcorn??

[NavarreDon]

Just the norm for you Robert! Another great write up for Mets all the way to weenies. Really like the graphics. Thanks for taking the time to post it. No matter what happens it is fun to track a system like this.

[ncjoaquin]

Just the norm for you Robert! Another great write up for Mets all the way to weenies. Really like the graphics. Thanks for taking the time to post it. No matter what happens it is fun to track a system like this.

I can't add to this from Don.

[NavarreDon]

I can't add to this from Don.

Thanks J! Heres to a third snowy winter in a row for Aville. It's gonna seem kinda strange without Phil though.

[DaculaWeather]

I don't get out much... just found this topic!

Thanks for the great write up Robert!!!