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1/28 - 1/30 Storm Thread II


burgertime

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Tomorrow is going to be a lot of fun or very disappointing for our area.  That gradient is tight.  Every model I've seen has put Wake right on that fine line.

 

It's going to be brutal!  I'm right on the Wake/Chatham line, so I'll probably be more in line w/ RDU obs.

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gfs is a devastating ice storm for chs, mainly frz rain, yikes. and precip lasts much longer than the nam and ends as a bout of snow for the coast, just imagine .50-.75" of ice with an inch or two of snow on top.  oy.

It's juicier than the 18z run for CHS, although the surface is coming in a bit warmer through 1am, before the temp drop comes (has the airport are 31F and areas to the south at or abv freezing).  If that actually occurs, could mitigate some ice accretion, but in my experience 2m temps aren't modeled all well.

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Big time Ice storm this run for ILM - MYR - CHS, more-so than 12z, >.75" in many spots along the coast, >.5" inland.  RGEM does a better job imo than the NAM identifying amounts, transition zones and dominant type, this should be taken seriously, scattered power outages would be a given.

 

attachicon.gifrgemzr.JPG

Living close to Charleston, that would be an absolute disaster for that area. Hope that doesn't come to pass.

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It's juicier than the 18z run for CHS, although the surface is coming in a bit warmer through 1am, before the temp drop comes (has the airport are 31F and areas to the south at or abv freezing).  If that actually occurs, could mitigate some ice accretion, but in my experience 2m temps aren't modeled all well.

what are your thoughts on 2m temps?  i just don't see it taking until midnight to get to 32.

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21z SREF numbers for ATL:
 Max: 12.11
 Mean: 3.32

 

 

I would watch for a dry air frontogenesis band to possibly develop somewhere near ATL in the late morning...if you want to see an example look at what occurred in Philadelphia during that Eagles/Lions game....they tend to form on the northern edge of a precip shield in these overrunning type events and are not usually caught except by maybe hi-res models...the RAP seems to show an indication of it and the 12Z SPC WRF had a subtle hint of it today as well...I think someone in Georgia near the north edge of the WSW will be surprised.

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It's juicier than the 18z run for CHS, although the surface is coming in a bit warmer through 1am, before the temp drop comes (has the airport are 31F and areas to the south at or abv freezing).  If that actually occurs, could mitigate some ice accretion, but in my experience 2m temps aren't modeled all well.

evaporational cooling usually takes its toll and most cases actual runs lower than model progs.   I would suspect with N and NNE winds at the SFC advecting cold, dry air in, this situation would be no different even if it isn't the "classical" CAD type event

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Funny that the 0z GFS upper air features looked better, but it didn't really translate. Still fixated on that big tongue of moisture left in the Gulf at 36 hours. I assume that is connected to the dissipating southern energy -- I think that's the energy Robert is banking on to get drawn up into the SE. It sure is close.

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what are your thoughts on 2m temps?  i just don't see it taking until midnight to get to 32.

I agree...over a majority of the area, outside of the beaches themselves, we should all be below freezing well before midnight.  I've been more trying to use the modeled 2m temps as a comparison run-to-run.  

 

The things that could save Charleston proper from a truly damaging ice event are the temps hovering around 32 a bit longer and also a quicker transition to sleet by the time temps drop into the 20's and your in the prime ice build-up zone.

 

If you have a min or two, this is a good read about the complexities of ice accretion: http://blogs.roanoke.com/weatherjournal/2013/12/complexities-of-ice-accretion/

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I would watch for a dry air frontogenesis band to possibly develop somewhere near ATL in the late morning...if you want to see an example look at what occurred in Philadelphia during that Eagles/Lions game....they tend to form on the northern edge of a precip shield in these overrunning type events and are not usually caught except by maybe hi-res models...the RAP seems to show an indication of it and the 12Z SPC WRF had a subtle hint of it today as well...I think someone in Georgia near the north edge of the WSW will be surprised.

 

 

Interesting. I've never heard of  'dry air frontogenesis banding' though I've heard of frontogenesis banding because that occurred for Atlanta in the Jan 2011 storm. Very heavy snowfall in a very thin band that moved north slowly. I'm on the northern edge of the current WSW so it may happen to me. :snowing:

 

This is what the band looked like....it was north of ATL by then.

post-13697-1294628457_thumb.png

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Agreed. Between you, pack backer, and me all could end up with great differences

 

Cold Rain looks good for 6", I think he is in SE Wake.   I am right on Hwy1/US64 in Apex, right on the 0.4"/0.5" gradient, 5 miles is going to make the difference between 3" and 6" possibly, if I get 4" that will be a victory.

 

UK, looks similar as rest of models, maybe wetter.  All models are showing around 12 hours for the duration of the snow.

post-2311-0-14653300-1390881631_thumb.pn

post-2311-0-24121300-1390881637.png

post-2311-0-59464900-1390881642.png

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The local maxima of snow in WNC is actually a very common feature with these types of setups (think back to Christmas Day 2010, which was a similar overrunning setup before the system bombed off the coast). What happens is that an inverted trough as 850 hPa sets up thanks to confluence that occurs due to the merger of both damming flow (northeasterlies) to the east of the Appalachians merging with northerly flow on the west side of the Appalachians. While the main confluence zone is associated with the frontogenetical forcing further to the south and east, the mountains essentially create another weaker frontogenetical zone which forces lift. Don't be surprised if somebody in TN or WNC ends up with a few inches from this secondary forcing zone. Unfortunately it also means somebody will be left out in the cold in between these two areas of forcing (likely the foothills where the combination of very dry air + little lift to overcome that dry air will be a death blow to their snowfall hopes) 

 

rad18.gif

 

t85w18.gif

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Kudos to Robert, if it plays out like he hinted to he may get an influx of subscribers. Good for him. Edit: sorry thought this was banter!

 

I haven't seen that complete model run of precip that Brad shows here. According to that run, the moisture from the actual system never makes it far enough NW to reach the 85 corridor in the upstate. The only moisture that may come our way would be what is left over from the NS after it comes through the mountains. In my experience and observation, down sloping virtually always chews that moisture up. No wonder all the models are showing the dry slot on the lee side from NGA through Upstate to NC. We may actually be lucky to see flurries in the immediate piedmont. 

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I don't know if anyone cares about the Hampton Roads area but we seem to be in the middle of the SE and MA regional threads. I'm going 7 in Newport News 9 in Hampton and 11 in VB. I do think that any bust will occur on the high side as the southern stream vort has trended east and the front has been slower to advance south than modeled. 

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Phil, you just showed and explained (much better) exactly what I was talking about. I too have seen this set up and it is very bad news for the piedmont. It literally results in an exclusive screw zone!

 

 

I was saying the same thing on another forum. I think someone in in the Piedmont Regions of GA, SC, and NC is going to get screwed. They will be too far north(GA) or east(NC/SC) of the main precip. band and too far south(GA) or west(NC/SC) for the overrunning band. Hopefully it does not happen.

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Probabilities

Site: KRDU WRF/NAM

(12z, 0Z)

QPF 0.00 inches

WndSp 13 knots WRF/NAM

(6z, 18Z)

QPF 0.00 inches

WndSp 8 knots GFS

QPF 0.10 inches

WndSp 7 knots

Heavy (less than 9:1) 0.152465 1.000000 0.012067

Average (9:1 to 15:1) 0.098403 0.000000 0.215968

Light (greater than 15:1) 0.749132 0.000000 0.771965

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what are your thoughts on 2m temps?  i just don't see it taking until midnight to get to 32.

 

This is going with my thinking related to the Arctic air that is coming in more slowly. Although the 0Z NAM was a little colder than the 18Z NAM and colder than the 0Z GFS, there is no doubt that the 0Z GFS is warmer by a few degrees vs. the 18Z GFS for CHS-SAV. As modeled, this could very well save SAV and parts of CHS from a really bad icestorm. But is it accurate? Who knows, but I feel it is plausible that it is warmer per the trends I've noted per nowcasting vs. models regarding the delay in the Arctic air.

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gfs has a zero reading at rdu thurs  morn

At first I thought you meant snowfall...

I'm getting nervous about the potential for a piedmont split, with banding in the foothills from the northern stream piece, and the big coastal low giving the coastal plain snow, and nothing in the middle. Thoughts?

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im starting to think ratios will be over 15:1 at rdu for this storm just looking at a combo of several differnt sites.

 

How about PGV seems there is some concern about ratios here I have seen several folks suggesting 13-15:1 but I dont see it what am I missing or is 10:1 a good bet around here

 

Edit: I am at work so I cant really pull up a lot of stuff but where did you get that from in your other post with the ratios etc

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