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Winter 2013-14 Pattern Discussion III


Marion_NC_WX

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I think the main takeaway with the Canadian is that the setup appears decent. The track will take awhile to narrow down and it very well may run inland and screw everyone outside the mountains, but at least there's some cold air to work with.

I'm going to hug last night's Canadian run, though. That would break GSO's record snowfall of 20.0" back in 1930. :D

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For the 2/13 storm, I think there were a few runs on the models that look like today's run. They kept showing the high not anchoring and being pushed out to sea.it also showed from time to time, a Great Lakes low, both of which did not happen , so we have hope and are trending in the right direction!

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Canadian is a crushing for the mtns.  500mb low closes off and moves right through that area.  12z Canadian handled the northern stream differently.  It dropped a shortwave from the PV into the Great Lakes, then held it there (it cutoff), allowing the sfc high to hang in longer.  It looks like an outlier evolution in that regard, but who knows...it's what we would want to see for sure.  The southern wave goes from positive tilt, to neutral, to negative, allowing the sfc low to track inland of the coast.  That's a monster of a wave in the southeast on the Canadian, with some northern stream shortwaves dropping into it...that's another element to watch for too, to inject more cold air aloft into the system

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 I'm very encouraged and am getting closer to the point that I think there will be a CAD based SE winter storm ~3/6-7 with lots of IP and ZR at a minimum. I'm not calling for it yet. but the chances in my mind are increasing. There have been too many model runs from various models to ignore this. And now the GFS looks like it is starting to see the light.

There isn't much doubt in my mind the 12z gfs is screaming major ice storm for north ga/a lot of sc and of course nc.  At hour 120, dewpoints are in the low to mid teens with temps in the upper 20s to lower 30s with precip knocking on the door. Wetbulb temps at 12z range from mid 20s in atlanta, low to mid 20s in northeast ga, low 20s in the upstate and possibly as low as the upper teens in nc. Yet somehow the gfs warms temps into the mid and upper 30s with rain falling by mid to late morning. That warming simply would not happen...especially so if the rain moves in just a couple of hours sooner.

 

But just taken at face value, the wedge is sufficiently deep, through 925mb, and sufficiently cold with freezing temps extending above 950mb. However the 925mb temps could be too warm as the gfs shows winds turning more to the northeast with time and you end up with a northeasterly flow from the surface all the way to 900mb by hour 138 to 144. That is something that tells me the wedge would not erode very fast. And to top it off, we have 850mb temps that are hardly very warm.

 

But if precip does in fact start shortly after sunrise, or before, watch out because there is no doubt we would stay subfreezing through a significant portion of the storm and the damage would have already been done by the time we get above freezing, if we do at all.

 

With such a strong high, and it's not very progressive as it's in damming position for quite a while, and the conditions of the boundary layer, the gfs would be quite something if it verified. I'm a little surprised to be quite honest the gfs isn't much colder. With Previous systems, one could argue that the models might not be too far off since evaporational cooling was not a big factor but with this one I think the gfs is way too warm and it's missing that initial cooling..which of course throws the entire temperature profile out the window if it is. 

 

This would be quite the ice storm if that much precip falls and it's hard to believe though we could have a major ice storm in early march. We are getting into the time of year though that sun angle does play a larger and larger role. So if conditions are only marginal and not nearly this cold/dry, it's something to consider that temps might in fact warm quicker than usual given the setup. But If conditions are so cold and dry initially and we get the timing right, it won't matter at all.  This system certainly has my attention.

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I think the main takeaway with the Canadian is that the setup appears decent. The track will take awhile to narrow down and it very well may run inland and screw everyone outside the mountains, but at least there's some cold air to work with.

I'm going to hug last night's Canadian run, though. That would break GSO's record snowfall of 20.0" back in 1930. :D

 

It definitely looks like there will be a coastal, I would love for a hybrid of the 0z/12z CMC to come to fruition, something big for western NC, N-SC/GA.  Be a fun way to end the winter.  I know probably leaves RDU out, but climo is a bXtch sometimes.

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If you take the Canadian literally, portions of the foothills and Piedmont of NC might chang over to snow on the back end with the deformation band.  Sort of March '93-esque, though that's probably a stretch.

 

Also, the initial band of heavy WAA precip features 850s of 0-1C in areas like GSO, INT, Gastonia, etc., so it's not that far away from a massive front-end dump of snow.  Of course, 850s shoot up into the 4-6C range as the coastal comes inland, but still.  Still, it's more than 1" of liquid falling with 850s in the 0-1C range, so that's close.

 

I wouldn't even be mad if we do snow-to-rain since it's not like whatever (if anything) falls is going to last long without any arctic air in the aftermath of the storm, plus the harsh March sun angle.

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The 12z NAVGEM has a nice, cold setup. FWIW (not much)...

nav_pr6_slp_t850_east_25.png

Dam, that is a massive , cold high! There is no way that just casually slides out to sea. At 1041 , it's a good bit stronger than the 2/13 high, by about 6 or 7 MB, iirc? All are picking up on the high and strength , position is the only question now!
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There isn't much doubt in my mind the 12z gfs is screaming major ice storm for north ga/a lot of sc and of course nc.  At hour 120, dewpoints are in the low to mid teens with temps in the upper 20s to lower 30s with precip knocking on the door. Wetbulb temps at 12z range from mid 20s in atlanta, low to mid 20s in northeast ga, low 20s in the upstate and possibly as low as the upper teens in nc. Yet somehow the gfs warms temps into the mid and upper 30s with rain falling by mid to late morning. That warming simply would not happen...especially so if the rain moves in just a couple of hours sooner.

 

But just taken at face value, the wedge is sufficiently deep, through 925mb, and sufficiently cold with freezing temps extending above 950mb. However the 925mb temps could be too warm as the gfs shows winds turning more to the northeast with time and you end up with a northeasterly flow from the surface all the way to 900mb by hour 138 to 144. That is something that tells me the wedge would not erode very fast. And to top it off, we have 850mb temps that are hardly very warm.

 

But if precip does in fact start shortly after sunrise, or before, watch out because there is no doubt we would stay subfreezing through a significant portion of the storm and the damage would have already been done by the time we get above freezing, if we do at all.

 

With such a strong high, and it's not very progressive as it's in damming position for quite a while, and the conditions of the boundary layer, the gfs would be quite something if it verified. I'm a little surprised to be quite honest the gfs isn't much colder. With Previous systems, one could argue that the models might not be too far off since evaporational cooling was not a big factor but with this one I think the gfs is way too warm and it's missing that initial cooling..which of course throws the entire temperature profile out the window if it is. 

 

This would be quite the ice storm if that much precip falls and it's hard to believe though we could have a major ice storm in early march. We are getting into the time of year though that sun angle does play a larger and larger role. So if conditions are only marginal and not nearly this cold/dry, it's something to consider that temps might in fact warm quicker than usual given the setup. But If conditions are so cold and dry initially and we get the timing right, it won't matter at all.  This system certainly has my attention.

 

 The 12Z GFS per MeteoStar is only 3-5 degrees away from a major, 24 hour long (1.25-1.50" qpf) ZR for the ATL-AHN corridor 3/6-7! The GFS has definitely finally woken up. This would be the first major March ZR for at least ATL since the 3/25/1971 big one. Even as it stands now, the 12Z GFS starts KATL out at 33 with rain while AHN gets as cold as 35 with rain. As you suggested, with those teen TD's being suggested to precede it, it is likely too warm even here. But even ignoring some warm bias, the trend is the important thing right now. I expect later GFS runs to trend even colder.

 

 Edit: 12Z Euro coming in colder with the NE high. Watch out later! Trends are colder and more threatening to say the least.

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Folks,

 Based on hour 108, I'm guessing the 12Z Euro will show a doozie of a ZR/IP storm 3/6-7.

 

 

Yeah, I'm out to hr 96 and it's considerably colder in both the midwest and the east coast.  Very interesting.

 

Come on, DYNAMIC DUO, don't let us down!

 

I'm hoping that we get locked in to run after run getting a little colder and more favorable once the models get a handle on how cold this airmass is going to be.

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through 144 hours it has precip into north ga with 0c 850s down through the upstate. CAD is showing up at 850mb..very strong signal of an impressive cad event.

 

at 150, it's sleet or freezing rain north ga with snow in the upstate. temps into the upper 20s across north ga by 150 with 32 degree temps down to atlanta. around 0.50 liquid so far in north ga and 0.25 to 0.50 across the upstate. none yet in nc.

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