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The Big One - Forecast & Discussion


Wow

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Can't it just be right once? lol I was just badly not wanting anything to trend to the RGEM. 

 

Oh it definitely wasn't just the RGEM... the ECMWF has been showing this for now 48 hours. Of course since most people only focused on the GFS and NAM these concerns were ignored until all the guidance trended the ECMWF's way. When the ECMWF and ECMWF ensembles agree with little spread... its pretty much game over even if the rest of the guidance is out to lunch (as was the NAM and GFS yesterday). 

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Just checked WeatherBell's higher resolution maps... That's all-snow for GSO and just NW of CLT based on 850s. Definitely colder than past NAM runs.  I guess there could be a little mixing around hr 24 in GSO if it gets a little warmer between the 3-hr panels, but I'm not positive and it would be short-lived.

 

Oh, yeah, it's very close, but the farthest the 850 mb 0C isotherm gets is southern Guilford County at hr 24, so southern High Point and Archdale, etc. would change over for a little bit, maybe.

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Oh it definitely wasn't just the RGEM... the ECMWF has been showing this for now 48 hours. Of course since most people only focused on the GFS and NAM these concerned were ignored until all the guidance trended the ECMWF's way. When the ECMWF and ECMWF ensembles agree with little spread... its pretty much game over even if the rest of the guidance is out to lunch (as was the NAM and GFS yesterday).

So, stay with me here but I have a theory:

Could extreme omega+heavy rates=defeated warm nose?

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You can see early on in the NAM the trough wasn't as sharp, curious to see what other models show early on.

 

0z (12 hr)  - http://www.tropicaltidbits.com/analysis/models/namconus/2014021200/namconus_z500_vort_us_5.png

 

18z (18hr) - http://www.tropicaltidbits.com/analysis/models/namconus/2014021118/namconus_z500_vort_us_7.png

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Evening FFC AFD update:

.UPDATE...
LOW PRESSURE HAS BEGUN TO DEEPEN ACROSS THE NORTHERN GULF THIS
EVENING. LATEST OBSERVATIONS SHOW THAT WINDS HAVE BEGUN TO
STRENGTHEN AND THE WEDGE HAS BEGUN TO SURGE SW CLOSER TO THE CWFA.

STARTING TO GET A PEEK AT THE 00Z MODELS COMING IN. THE NEW NAM IS
SHOWING VERY STRONG UPPER DIVERGENCE OVERNIGHT AND EARLY WEDNESDAY
MORNING. THE NAM DID INITIALIZE THE STRONG UPPER DIVERGENCE OVER
SW MS AND NE LA FAIRLY WELL...VERY CLOSE TO THE AREAS THAT ARE
REPORTING THUNDER. THE DIVERGENCE IS RIGHT IN THE COUPLED JET
STRUCTURE...SO DO EXPECT A RAPID INCREASE IN PRECIPITATION AFTER
06Z TONIGHT.

THE FORECAST LOOKS ON TRACK...AND DO NOT ANTICIPATED MAKING ANY
CHANGES. ALSO...NO CHANGES TO THE WINTER HEADLINES AT THIS TIME.

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Oh it definitely wasn't just the RGEM... the ECMWF has been showing this for now 48 hours. Of course since most people only focused on the GFS and NAM these concerned were ignored until all the guidance trended the ECMWF's way. When the ECMWF and ECMWF ensembles agree with little spread... its pretty much game over even if the rest of the guidance is out to lunch (as was the NAM and GFS yesterday). 

 

Phil - so you think the Euro/RGEM inland track is the way to go as opposed to a coastal hugger?

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QPF is much less prolific on the 00z NAM for the snowy areas.  The 1" QPF contour doesn't seem to make it into the all-snow areas.except in the southern foothills and mountains.  It's mostly 0.8-.0.9" in the foothills and places like Winston-Salem.  Will that be the story of the 00z models or is it a blip?

 

EDIT: Never mind, looks like GSO and INT might make 1" QPF with the deformation band late.

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The sounding isn't terrible at KCLT.

I have not looked at charlotte lately and I'm actually pretty shocked really. I didn't expect it to look this warm. There is very tight gradient between all snow and freezing rain around charlotte. Just to the south and east of charlotte it looks like freezing rain with a very deep  warm nose. Not saying i buy it and admittedly I haven't followed the charlotte area as closely but it's a bit surprising. North and west of town look fine..the city seems to be the dividing line.

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QPF is much less prolific on the 00z NAM.  The 1" QPF contour doesn't seem to make it into the all-snow areas.except in the southern foothills and mountains.  It's mostly 0.8-.0.9" in the foothills and places like Winston-Salem.  Will that be the story of the 00z models or is it a blip?

The whole system seems substantially weaker on the NAM.  It has the 2 low look for a long time and doesn't complete the transfer until the main low is around Hatteras and still much weaker than most of the other models.

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Lemme ask yall something, how in the hell can the clown maps on wxbell site, I know they take account all precip types, show so much accum around here, but the precip maps when scrolling through time barely have any "pink" (ZR) shown for my county until its about over.  So, what gives?

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Just checked WeatherBell's higher resolution maps... That's all-snow for GSO and just NW of CLT based on 850s. Definitely colder than past NAM runs. 

 

Can't really say that about it colder. But it is another NAM sounding indicating all snow here too. That one skew T had me worried but but just a thick layer 0 to -1. Highest was 900mb @ 0.2

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QPF is much less prolific on the 00z NAM for the snowy areas.  The 1" QPF contour doesn't seem to make it into the all-snow areas.except in the southern foothills and mountains.  It's mostly 0.8-.0.9" in the foothills and places like Winston-Salem.  Will that be the story of the 00z models or is it a blip?

 

EDIT: Never mind, looks like GSO and INT might make 1" QPF with the deformation band late.

 

You follow the steady and superior Euro and Euro Ensemble which pretty much show the same thing run, after run, after run

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Prior to this event, does anyone know the last time they did aircraft recon in the Gulf for an ETC?

i dont remember the exact time, but saw a post that it was done late afternoon/early evening and the data was supposed to be incorporated into to 0z runs

 

edited to add: i know the models are still going back and forth but if history holds true this time, it would not surprise me at all to have some sleet (or even zr) mixing in through ne ga and the upstate.  there are times it is all snow, but alot also have mixing at some point. just happy to see radar lighting up with round 2 (and the biggie) still on tap for most of us

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Well it may be garbage but Hi-Res NAM has sleet for everyone west of CLT except for the mountains after an initial burst of snow. Then it switches back to snow for everyone even CLT based on p-types. Kind of flips and flops for CLT after that. 

 

Ew, yeah, the Hi-Res looks warmer than the regular NAM.  Of course, we're talking about GSO getting to +1C and CLT to +2C at 850 at one point, so it's not torching.  Looks like maybe 3-6 hours of sleet depending on where you are.

 

Toss it.  :weenie:

 

Surface temperatures look pretty cold on the 12-km regular NAM.

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The NAM looks a little better for the RDU area. Surface temps continue to stay below freezing during the main precip event. The Twister site actually pushes the 6" inch snow line farther east of Raleigh; of course the is probably a lot of ice mix.

Only to hour 36. looking at the simulated radar it looks like RDU gets into the deformation band later on.

http://www.twisterdata.com/index.php?prog=forecast&model=NAM&grid=221&model_yyyy=2014&model_mm=02&model_dd=12&model_init_hh=00&fhour=36&parameter=SNOWIN&level=SURFACE&unit=none&maximize=n&mode=singlemap&sounding=n&output=image&view=large&archive=false

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The NAM looks a little better for the RDU area. Surface temps continue to stay below freezing during the main precip event. The Twister site actually pushes the 6" inch snow line farther east of Raleigh; of course the is probably a lot of ice mix.Only to hour 36. looking at the simulated radar it looks like RDU gets into the deformation band later on.http://www.twisterdata.com/index.php?prog=forecast&model=NAM&grid=221&model_yyyy=2014&model_mm=02&model_dd=12&model_init_hh=00&fhour=36&parameter=SNOWIN&level=SURFACE&unit=none&maximize=n&mode=singlemap&sounding=n&output=image&view=large&archive=false

Read at another board it still had RDU with 4 to 8 inches of snow but also a lot of ice. That would be great as long as we got that much snow and the power stayed on, and a tree doesn't fall on my house.

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So, stay with me here but I have a theory:

Could extreme omega+heavy rates=defeated warm nose?

 

Only in cases where WAA isn't that substancial. Remember that in order to get precipitation in the first place, you have to get lift induced by WAA. So when you get heavy rates, you also get WAA on the frontside of the system. Where dynamical cooling really has the best impact is on the backside of the 850 hPa, which is the deformation induced snowfall where the temperature advection is neutral or even CAA in the low-levels and most of the WAA is far enough aloft that its already in a subfreezing layer.

 

Phil - so you think the Euro/RGEM inland track is the way to go as opposed to a coastal hugger?

 

Yes... its really been the ECMWF that has lead the way with this. The RGEM only came on board on the 12z cycle. The ECMWF had this 48 hours ago.

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The NAM switches the upstate over to sleet with the arrival of the dry slot.  I think basically all of the first initial heavy precip will be snow. Then we will have a lull of sorts where the whatever is falling will be sleet, and then potentially switch back to snow if we get good rates with any sort of deformation axis.  

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Read at another board it still had RDU with 4 to 8 inches of snow but also a lot of ice. That would be great as long as we got that much snow and the power stayed on, and a tree doesn't fall on my house.

Man this is going to be some storm. Temp at my house has already dropped to 25.2 so I don't think we'll have any surface temp issues. I'm holding out hope that we stay sleet longer and don't get any freezing rain over a quarter of an inch.
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Heavy rates will help limit ice accretion.  If you're 30 and it is pouring, much will run off before freezing.  Now if you have the same amount of qpf spread over twice as much time, it would likely be (much) worse.  Not to say it won't be bad, but the heavy rates do improve the chances of keeping your power on.

TW

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