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Feb 16th/17th/18th Winter Wx


burgertime

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The UKIE looks like 8"+ of presumably all-snow with more to come post-hr 72. :)

Looks like RDU is mostly-snow, but probably goes over to ZR/IP by hr 72. 2m temps are very cold. Looks like at least mid-20s or maybe below for us.

The track and position of the low is critical for p types!the Jan 88 storm transitioned to freezing rain and sleet for the last hour or two and that gave us 1/4 crust on top of 16 inches of snow, temps in mid teens
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Which vendor are you using, James?

 

Just Meteocentre.  They have a meteogram for RDU, so you can kind of extrapolate from that.

 

http://meteocentre.com/models/get_mgram.php?stn=Raleigh&mod=ukmet&run=12&var=std〈=en&map=us

 

Unfortunately, they do not have one for Charlotte or Greensboro.  They do have one for Atlanta, however.

 

Actually, looks like the 850 mb panes are now out.  Looks like RDU and CLT are IP/ZR at this point with GSO probably just changing over to IP.  SN still in the foothills and N of GSO.

 

qqcoeu.gif

 

850s are cold enough for the whole state at hr 60, so just about everyone probably gets good snows before the changeover.

 

http://img.meteocentre.com/models/ukmet_amer_12/TT_GZ_UU_VV_060_0850.gif

 

2m temps are cold.

 

http://meteocentre.com/models/explorateur.php?lang=en&map=na&run=12&mod=ukmet&stn=TT2m&comp=1&run2=-99&mod2=cmc_anal&stn2=TT2m&hh2=060&fixhh=1&stn2_type=anal&mode=latest&yyyy=latest&mm=latest&dd=latest&hh=072

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The likely too warm GFS even has near 32 in Marietta. Also, from my own experiences in the 4 major ZR's of the 2000's as well as looking back at older storms in newspapers/NWS records, ice can accrete quite well at 31 and even close to 32 as per the 3/1971 and 1/1973 ATL ZR's. Tony even confirmed this from his personal account of 73. Now roadwise, very little ice would likely occur at 31+ outside of raised roads.

 Whether or not freezing rain accumulates at marginal temps is related to rates, time of day,  how deep/warm the mid levels are and how deep and cold the low level cold is. In this case, based on those above  factors, i believe even temps at 31 and 32 there will be significant ice accumulations where ever freezing rain happens. The canadian really hits north ga hard now with temps falling into the 28 to 31 range with upwards of 1 to 1.25 liquid. Some of that will fall as sleet and snow in many areas but there will be a stripe of pretty bad icing

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Boom. Crushed by hr 72! The UKMET still largely looks consistent! (WNC from GSO-west has some precip on the hr 60 pane, too... and I'd guess there's a little more precip after this, as well).

This looks the most reasonable between NAM and GFS right now. UKMET also has second best verification scores at 72 hours, right behind the Euro. GFS not faring well and it is not handling the Baja low correctly.

Consistency of UKMET solution cannot be ignored. GFS continues to be all over the map. Even NAM honing in more consistently now. IMHO, throw out the GFS. Use a blend of NAM, Euro ensembles, and UKMET. Actual track and QPF will likely fall within their mean.

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New 12z CMC has ZR for some of the NW ATL burbs for about 15 hours straight per the precip type map.

Yeah it even has upwards of 1.50 liquid just west/southwest of atlanta so there is at least potential  for more than 1.25 liquid falling. Atlanta might end up getting some of the worst icing since areas to the north and east are likely to see more snow or at least sleet. Nega will still have their share of it though for sure.

 

gem_mslp_pcpn_frzn_seus_11.pngI_nw_g1_EST_2015021412_062.png

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GEFS about the same as the Op might be a little lighter on QPF.

 

Indeed.  Maybe less crazy, amped warm members this run?  It's also quite a bit cooler.  Looks like the 0.5"+ QPF line makes it well past Blacksburg and 0.75"+ makes it to GSO with 1"+ QPF around RDU/CLT.  At 06z, the 1"+ QPF line made it to GSO.  Mean snowfall is roughly the same (noise).

 

This looks the most reasonable between NAM and GFS right now. UKMET also has second best verification scores at 72 hours, right behind the Euro. GFS not faring well and it is not handling the Baja low correctly.

Consistency of UKMET solution cannot be ignored. GFS continues to be all over the map. Even NAM honing in more consistently now. IMHO, throw out the GFS. Use a blend of NAM, Euro ensembles, and UKMET. Actual track and QPF will likely fall within their mean.

 

Sounds good.  I'd take the UKMET or a blend. :)

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New 12z CMC has ZR for some of the NW ATL burbs for about 15 hours straight per the precip type map.

Some of the CMC's 15 hours of precip on the N side of ATL is IP fwiw. Some areas on the N could even be mainly IP per the CMC like was the case in some N areas in 2/2014. It gives Marietta mainly ZR.

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Some of the CMC's 15 hours of precip on the N side of ATL is IP fwiw. Some areas on the N could even be mainly IP per the CMC like was the case in some N areas in 2/2014. It gives Marietta mainly ZR.

 

The CMC also tends to be warm in the BL so that speaks volumes, the 18Z RGEM will go out through 00Z Monday evening on ptypes so that'll be interesting

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Some of the CMC's 15 hours of precip on the N side of ATL is IP fwiw. Some areas on the N could even be mainly IP per the CMC like was the case in some N areas in 2/2014. It gives Marietta mainly ZR.

 

Ground temps will be cold, where the ZR sets up I think it will accrue well, even with marginal temps.   Lows in the lower 20's Sunday night for most of N/GA

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The CMC also tends to be warm in the BL so that speaks volumes, the 18Z RGEM will go out through 00Z Monday evening on ptypes so that'll be interesting

Good point. Especially considering that this is coming so closely behind the peak of a solidly cold airmass without warming winds for the short interval between, I do think that below 32 and probably a lot of high 20's would be likely in this setup.

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Whether or not freezing rain accumulates at marginal temps is related to rates, time of day, how deep/warm the mid levels are and how deep and cold the low level cold is. In this case, based on those above factors, i believe even temps at 31 and 32 there will be significant ice accumulations where ever freezing rain happens. The canadian really hits north ga hard now with temps falling into the 28 to 31 range with upwards of 1 to 1.25 liquid. Some of that will fall as sleet and snow in many areas but there will be a stripe of pretty bad icing

Good points. I've never seen ZR not accrete well at 31 even in daytime outside of when heavier rains have brought down too warm drops.

Edit: Also, I think wind may be a factor though not in this case. I noticed in one of the big ATL ZR's that too high of a wind may have tended to keep it from accreting as well on the trees even with as cold as 29-39, possibly due to more of it blowing off? Maybe more on ground?

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The 12z NAVGEM is a big-time snowstorm for much of NC.  This area is pushing 10", at least.  Fairly cold, too, even for RDU and CLT who don't mix much, it seems.

 

The NAVGEM has also generally been consistent.

 

I don't know where the best site is to look at the NAVGEM, Does it throw much QPF over the VA border? Similar to the UKMET?

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I don't know where the best site is to look at the NAVGEM, Does it throw much QPF over the VA border? Similar to the UKMET?

 

Less up your way, but still decent enough precip.  Probably 3-6".  Ratios would be good up there, I'd think.

 

https://www.fnmoc.navy.mil/wxmap_cgi/cgi-bin/wxmap_all.cgi?type=prod&area=nvg_namer∏=prp&dtg=2015021412&set=All

 

I know it's almost silly to even bring up the NAVGEM at this point, but it has been fairly consistent, so it's perhaps worth a look.

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