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The Big One - Forecast & Discussion


Wow

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Mhmm, but your RH is high which is bad when the warm nose comes through. I may be wrong though. 

 

One thing that is bothering me is that in the zone from Upstate SC to PA the temps and dew points are higher than either the NAM or GFS MOS numbers for 0z- both have dew points in the 24-26 degree range at 00Z, the current dew at KCLT is 30.

 

Those who got the snow, are higher. I just barely missed it today and my dewpoint is currently 25.

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 The 18Z GFS is an absolutely amazing run for ATL-AHN. I think it is the most bullish yet for IP/snow combined. Wow!

 

Yeah....coming closer to the 00z and 12z EURO runs too.  Glad KFFC is now forecasting 4-8" inches across Atlanta metro....with 6-10" around Lake Lanier and east/ ne from there.  I won't be surprised to see some 12"+ snowfall depths north and east of Atlanta.

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Those who got the snow, are higher. I just barely missed it today and my dewpoint is currently 25.

 

Chez's observation is a rather interesting development which none of the models had that I remember; the 1st event over-performed and saturated quite a bit of real estate which may play into the CAD situation.  One potential is this allows the lower levels to remain much closer to freezing instead of well below which could mitigate some of the devasting ICE predictions.  We'll have to keep a close eye on how this plays out or if it's a non-issue.  It does seem potentially important.

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I'm not sure what the NWS is calling for cause I haven't looked but I could see 12" of snow in northeast GA by tomorrow late afternoon where it stays cold enough plus banding/dynamic cooling and enhanced rates.

 

Also could see more snow in ATL metro than what is being called for.

 

Will be interesting to see just how much dynamics can cool the warm layer aloft .

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I'm not sure what the NWS is calling for cause I haven't looked but I could see 12" of snow in northeast GA by tomorrow late afternoon where it stays cold enough plus banding/dynamic cooling and enhanced rates.

 

Also could see more snow in ATL metro than what is being called for.

 

Will be interesting to see just how much dynamics can cool the warm layer aloft .

 

 

The HRRR seems to be catching onto something. It has continuously projected heavy snow in the early morning hours tomorrow. If it comes to fruition some areas are looking at over 6 inches of front end snow before the change to ZR. Add that with some back end snow and some areas could be looking at near a foot from Atlanta to Athens.

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Whoa! Here We Go! Significant Icing In MS/LA. >0.25"

mcd0086.gif
MESOSCALE DISCUSSION 0086
   NWS STORM PREDICTION CENTER NORMAN OK
   0630 PM CST TUE FEB 11 2014

   AREAS AFFECTED...PARTS OF CNTRL LA INTO SWRN THRU E CNTRL MS

   CONCERNING...FREEZING RAIN 

   VALID 120030Z - 120230Z

   SUMMARY...SIGNIFICANT ICING IN EXCESS OF 1/4 INCH APPEARS POSSIBLE
   ACROSS THE REGION BETWEEN NOW AND 02-04Z.

   DISCUSSION...WITHIN A LARGER AREA OF GENERAL ISENTROPIC ASCENT NOW
   DEVELOPING EASTWARD THROUGH THE LOWER MISSISSIPPI VALLEY...A BAND OF
   HEAVIER RAINFALL APPEARS TO BE IN THE PROCESS OF DEVELOPING ALONG AN
   AXIS FROM NEAR ALEXANDRIA LA THROUGH AREAS NEAR/SOUTH OF JACKSON
   MS...INTO THE MERIDIAN MS AREA.  THIS MAY BE IN RESPONSE TO
   LOWER/MID TROPOSPHERIC FRONTOGENETIC FORCING...IN THE PRESENCE OF
   SUFFICIENT INSTABILITY TO SUPPORT CONVECTION...INCLUDING WEAK
   THUNDERSTORM ACTIVITY. BETWEEN NOW AND 02-04Z...OCCASIONAL MODERATE
   TO HEAVY RAIN RATES YIELDING TOTALS IN EXCESS OF 1/4 INCH APPEAR
   PROBABLE.
  OF PRIMARY CONCERN IS THE SHALLOW SUB-FREEZING SURFACE
   BASED LAYER WHICH HAS ADVECTED AS FAR SOUTH AS THIS ZONE...WHICH
   COULD ALLOW FOR ACCUMULATING ICE ON VEGETATION AND OTHER EXPOSED
   OBJECTS AND SURFACES.  ALTHOUGH GROUND TEMPERATURES ARE RELATIVELY
   WARM... AND AIR TEMPERATURES ARE NOT EXPECTED TO FALL MUCH BELOW
   FREEZING...AMONG ROAD SURFACES...AT LEAST BRIDGES/OVERPASSES MAY BE
   IMPACTED.

   ..KERR.. 02/12/2014


   ATTN...WFO...JAN...LIX...LCH...SHV...

   LAT...LON   31329303 32079170 32738954 32848872 31878904 31299077
               30899219 31089276 31329303 

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These frontogenetically enhanced initial snow bands are nothing to slouch at... a similar band preceded the main event in December 2009 and dropped a quick 2-4" across NC mountains and points eastward. 

 

Here's a brief excerpt from the Raleigh NWS

 

http://www4.ncsu.edu/~nwsfo/storage/cases/20091218/

 

At the beginning of the event across central North Carolina, a narrow band of precipitation moved north into North Carolina from South Carolina just after 12 UTC on 12/18. This narrow band advanced north, reaching Raleigh and Greensboro just after 17 UTC with most of the precipitation falling as light snow. The precipitation lasted from 30 to 60 minutes and then diminished. This area of precipitation appeared to be associated with an axis of frontogenesis at mid/upper levels as noted in the SPC analysis at 16 UTC 18 UTC, and 20 UTC.

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The few Bufkit's I have looked at around triad area and north show 16:1 to 9:1 ratios 

 

That leads me to ask, what kind of ratios are we realistically looking at with this one?  5:1? 8:1? 10:1?  Higher?  I'm not good with ratios at all.  I'd have to think lowish ratios early on, at least, and maybe higher as the storm pulls to the north, 850s crash, and the deformation band keeps hammering.

 

I know 5:1 is pretty exceptionally low, but Asheville had ratios somewhere around there in March '93, IIRC, so I guess it's possible.

 

----

 

On another topic, soil temperatures should really be no issue for most areas.  It appears that many areas are in the upper 30s, so that's plenty low enough for significant accumulations.  The last couple days have been cold with limited sun, so that's helped a lot.  I don't think soil temperatures would matter too much either way with precipitation rates like we should see, but every little bit helps.

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These frontogenetically enhanced initial snow bands are nothing to slouch at... a similar band preceded the main event in December 2009 and dropped a quick 2-4" across NC mountains and points eastward. 

 

Here's a brief excerpt from the Raleigh NWS

 

http://www4.ncsu.edu/~nwsfo/storage/cases/20091218/

 

At the beginning of the event across central North Carolina, a narrow band of precipitation moved north into North Carolina from South Carolina just after 12 UTC on 12/18. This narrow band advanced north, reaching Raleigh and Greensboro just after 17 UTC with most of the precipitation falling as light snow. The precipitation lasted from 30 to 60 minutes and then diminished. This area of precipitation appeared to be associated with an axis of frontogenesis at mid/upper levels as noted in the SPC analysis at 16 UTC 18 UTC, and 20 UTC.

 

 

Thanks Phil, would love to get your thoughts on the path of the low. Kind of a debate going on in banter about how the RGEM is sending the low so far west and inland. Do you think this is legit? 

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These frontogenetically enhanced initial snow bands are nothing to slouch at... a similar band preceded the main event in December 2009 and dropped a quick 2-4" across NC mountains and points eastward. 

 

Here's a brief excerpt from the Raleigh NWS

 

http://www4.ncsu.edu/~nwsfo/storage/cases/20091218/

 

At the beginning of the event across central North Carolina, a narrow band of precipitation moved north into North Carolina from South Carolina just after 12 UTC on 12/18. This narrow band advanced north, reaching Raleigh and Greensboro just after 17 UTC with most of the precipitation falling as light snow. The precipitation lasted from 30 to 60 minutes and then diminished. This area of precipitation appeared to be associated with an axis of frontogenesis at mid/upper levels as noted in the SPC analysis at 16 UTC 18 UTC, and 20 UTC.

 

 

I'm assuming this is what the HRRR might be projecting for Atlanta east to Athens tomorrow morning. It drops a narrow East-West band of heavy heavy snow.

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That leads me to ask, what kind of ratios are we realistically looking at with this one?  5:1? 8:1? 10:1?  Higher?  I'm not good with ratios at all.  I'd have to think lowish ratios early on, at least, and maybe higher as the storm pulls to the north, 850s crash, and the deformation band keeps hammering.

 

I know 5:1 is pretty exceptionally low, but Asheville had ratios somewhere around there in March '93, IIRC, so I guess it's possible.

Looks like most of the storm is in the 12:1. of course who knows if this is right? 1 inch equals 1 foot. 

 

example: 1.70 QPF  @ 12:1 is 20.4 inches  1.5QPF@ 16:1 is 24.5  

Just mult. QPF X Ratio leave out the 1 on ratio

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Robert is very, very enthusiastic. Looking @ mesoscale details....

 

will be updating my snow map for northern third of Ala, MS most of southern and eastern TN, bigtime. #snow RAP coming in strong #alwx #tnwx

 

already see 850 temps will be too warm on GFS over N. AL, n. GA, southern TN. More snow there.

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Could a met (or anyone) speak on the possibility of 40+ MPH wind gusts in the CLT-GSO corridor tomorrow night?  The last few Euro runs have shown 40-50 MPH wind gusts during the height of the storm, which is both exciting and concerning.  Is this realistic?  That's borderline blizzard conditions and they'll be power outages galore...

 

 

Looks like most of the storm is in the 12:1. of course who knows if this is right? 1 inch equals 1 foot. 

 

example: 1.70 QPF  @ 12:1 is 20.4 inches  1.5QPF@ 16:1 is 24.5  

Just mult. QPF X Ratio leave out the 1 on ratio

 

How accurate is bufkit usually with snowfall ratios?

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Thanks Phil, would love to get your thoughts on the path of the low. Kind of a debate going on in banter about how the RGEM is sending the low so far west and inland. Do you think this is legit? 

 

Charlotte is right on the edge, but I do think you guys change over to sleet/freezing rain for a significant period of time. The RGEM is in good agreement with the ECMWF and both have CLT going over to sleet/freezing rain from 00z to 12z on Thursday. Probably going to see quite a bit of snow (4-6") before the changeover though.

 

 

I'm assuming this is what the HRRR might be projecting for Atlanta east to Athens tomorrow morning. It drops a narrow East-West band of heavy heavy snow.

 

Yes... you can actually see the band developing nicely on radar... HRRR seems to be doing a good job projecting the expansion of this band. Its not surprising that its also setting up right along the boundary where most of the folks got snow today, so this initial band might be a good thump of snow for folks 10-20 miles south of places that got the most snow today. 

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That leads me to ask, what kind of ratios are we realistically looking at with this one?  5:1? 8:1? 10:1?  Higher?  I'm not good with ratios at all.  I'd have to think lowish ratios early on, at least, and maybe higher as the storm pulls to the north, 850s crash, and the deformation band keeps hammering.

 

I know 5:1 is pretty exceptionally low, but Asheville had ratios somewhere around there in March '93, IIRC, so I guess it's possible.

 

----

 

On another topic, soil temperatures should really be no issue for most areas.  It appears that many areas are in the upper 30s, so that's plenty low enough for significant accumulations.  The last couple days have been cold with limited sun, so that's helped a lot.  I don't think soil temperatures would matter too much either way with precipitation rates like we should see, but every little bit helps.

 

 

Bufkit from the 18z gfs has GSO getting 8:1 ratios as an average during the snow.

 

Can anyone tell us about the EPS ensemble mean track or the members?  I know that it's a little late in the game to be using the ensembles but I wondered if the mean track was east of the op.  Thanks!

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Charlotte is right on the edge, but I do think you guys change over to sleet/freezing rain for a significant period of time. The RGEM is in good agreement with the ECMWF and both have CLT going over to sleet/freezing rain from 00z to 12z on Thursday. Probably going to see quite a bit of snow (4-6") before the changeover though.

 

 

 

Yes... you can actually see the band developing nicely on radar... HRRR seems to be doing a good job projecting the expansion of this band. Its not surprising that its also setting up right along the boundary where most of the folks got snow today, so this initial band might be a good thump of snow for folks 10-20 miles south of places that got the most snow today. 

 

 

Exciting stuff. HRRR centers the band right on me. It showing 6-8 inches(10 inch isolated) in a matter of a few hours. Insane.

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