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The Big One - Forecast & Discussion


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Here's one snapshot in time (at hour 57) of the snow depth off the 18Z GFS. That lee side minimum is troubling. I don't think it's realistic based off the most likely path of this storm, but I'd still not rather see that lull in precipitation amounts between the mountains and the rest of the piedmont show up on the modeling.

cj8lneK.gif

Somehow that shadow shows up everytime???

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Looking at the BUFKIT, for those nearer the coast, the NAM at 18z is showing 1.3" zr for FLO and .63" zr for MYR. ILM is showing .84" zr and FAY is showing 1.25" zr on top of a little over 2" of snow.

Definitely an outlier on what it's showing coastally.

18Z NAM is not doing RDU any favors either

post-3687-0-17073600-1392070447_thumb.pn

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Here's one snapshot in time (at hour 57) of the snow depth off the 18Z GFS.  That lee side minimum is troubling.  I don't think it's realistic based off the most likely path of this storm, but I'd still not rather see that lull in precipitation amounts between the mountains and the rest of the piedmont show up on the modeling.

 

cj8lneK.gif

I agree seeing that minimum always troubles me, but I haven't seen that trend on many maps except that one.  And its the 18Z GFS. The EURO has been incredibly consistent for totals hasn't changed the totals too drastically the past 2-3 days, I think we are in a good spot here in the lee..

 

EDIT- More snow falls past hr 57, in fact 3 inches or more across WNC

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He actually dropped totals from 4-8" in mtns to 4-5"...he's "not seeing high totals", his reasoning goes back to his argument for ratios...if ratios get close to 10:1 he's going to bust. He doesn't think so though because lots of sleet/ice in soundings still. All this is per his tweets btw. We'll see.

 

FWIW, I have analyzed the soundings at various mountain sites, including AVL, and I see nothing from either the NAM or the GFS to indicate a mixture of precip types.  The GFS is pretty cold aloft and has an all-snow sounding, while the NAM does too - and in fact goes isothermal for a bit during the height of the event (a classic heavy snow signal).  So I'm not sure what he sees in soundings, but from what I saw, it's all snow in the mountains.  That's the easy part.

 

The hard part is the ratios.  The last time we had a big snow like this was 2009-2010.  The ratios in that event, which featured a GoM low, were 8:1.  I see no reason to think otherwise for this event.  Even for today, the Asheville airport recorded .20" of liquid with 1.0" of snow.  A 5:1 ratio!

 

So with liquid amounts on the Euro and CMC spitting out amounts near 1.25" for mountain areas, this translates to 10-12" across the area.  I like the track of the Euro because it is more in line with climatology, which tends to favor a slightly more inland track than that of the GFS or NAM.  The CMC also has a more inland track.

 

Tonight's runs should be fascinating, since our key player finally made it onshore this afternoon into British Columbia, Canada.  It is my expectation that GFS gets juicier since dynamics are excellent, and the NAM gets a little more inland like the CMC/Euro blend.  We shall see!

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He actually dropped totals from 4-8" in mtns to 4-5"...he's "not seeing high totals", his reasoning goes back to his argument for ratios...if ratios get close to 10:1 he's going to bust. He doesn't think so though because lots of sleet/ice in soundings still. All this is per his tweets btw. We'll see.

 

GSP does not agree with him: 

 

ALTHOUGH THERE ARE SOME DIFFERENCES IN FCST SOUNDINGS AND PARTIAL

THICKNESS PATTERNS...THERE IS GOOD AGREEMENT ON THE DEVELOPMENT OF

WINTRY PRECIP. THE NAM IS COLDER THAN THE GFS...KEEPING ANY WARM

NOSE AND P-TYPE TRANSITION ZONE SOUTH OF THE CWFA. HAVE USED A MDL

BLEND FOR TEMPS WHICH MEANS PRECIP STARTS AS SNOW TUE NITE WITH SOME

FREEZING RAIN MIXING IN FROM ELBERT TO GREENWOOD AS A WARM NOSE

DEVELOPS. EVEN THE WARMER GFS KEEPS THE WARM NOSE RELATIVELY SUBDUED

ALONG THE I-85 CORRIDOR WITH MORE WARMING WORKING IN SOUTH OF I-85

ON WED. FOLLOWING THIS TREND MEANS STILL MAINLY SNOW ALONG AND NORTH

OF I-85...TRANSITIONING TO FREEZING RAIN SOUTH. THERE WILL LIKELY BE

SOME SLEET MIXING IN ALONG THE TRANSITION ZONE...BUT GIVEN THE WARM

NOSE PROFILE...DO NOT EXPECT THE SLEET TO BE MORE THAN TRANSITORY

WITH LITTLE SLEET ACCUMS.

 

As of right now it looks like CLT could flirt with big numbers.  Hopefully. 

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Here's my precipitation type map... I'm a little nervous about the southern side of the Freezing Rain area, but the rest looks good.

 

The dark blue colors are the mainly snow areas that could see 6-12" with lower totals in NE Alabama and NW GA (closer to 3-6" of all snow). The light blue is where it's going to be a snow/sleet mix that could accumulate to 3-6" combined. The freezing rain is going to be bad, especially in the areas I have highlighted in pink. We could see as much as .75", maybe 1" in isolated spots, of ice; most, however, see closer to 0.5". The green is rain, obviously, but I'm unsure about how far southwest the freezing line goes, hence why the pink is "feathered" or blurred more than the other colors.

 

post-1807-0-07273200-1392070782_thumb.pn

 

Let the critiques rip! LOL!

 

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18z NAM Cobb output shows a worst case scenario for RDU.  Over an inch of liquid equivalent freezing rain on top of an inch of snow/sleet topped off with a couple inches of snow.  

that honestly would be a worst case scenario and one that would keep me from chasing this storm back home. that would be identical to the 96 icestorm in hickory. that was actually a few weeks after the blizzard and it's the most memorable storm of my life.

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I saw a quick comment from snowstorm?? asking about the backend snow. The map posted above is the main precip for most of the event. Locally, I'm certainly watching the chance for backend snow showers. However, I'm unsure how much it'll accumulate, especially on grassy areas considering all the rain we are going to pick up. That's why I don't really show it on the map above...

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I know a lot of you have asked about Andy Wood, and Mods - please move this to banter if it qualifies - but he posted his general idea on FB a while ago regarding this storm. Thought it was pretty spot on:

 

"Off work and can get back to following this storm. New developments overnight and today pointing to a more consolidated system and better forcing leading to more of an impact for more people. Bottom Line: An absolute whiteout of a snowstorm is pegged to impact the states of GA (northern), TN(mainly eastern TN, although some middle TN), SC (northern/Upstate) and NC (all you lucky people) on Wednesday. At it's height, South Carolina better get ready for a good bit of snow and central Georgia needs to prepare for a major freezing rain accumulations! In particular, the Upstate of SC couldn't ask for a more favorable setup for snow. A: two pieces of energy linking up and acquiring a favorable tilt southwest of the area... B: an intensifying surface low running from Mobile to Charleston or maybe just inland of that... C: a gob of moisture incoming... D: as the upper forcing intensifies on Wednesday morning, a snow band forms during the day and proceeds to STAND STILL... the band of snow only slightly pivots and absolutely lays the hammer down on Upstate SC and Western NC. Get prepared for a beautiful sight on Wednesday. I'm drawing up a new snow map, because my older one was based around a much weaker storm in the upper and lower levels."

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what is he looking at to come up with that map? More snow in Greensboro than the mtns? The euro and its ensembles continue to paint 10-12 for the mtns. Not sure how he has a map like that.

Two things to be mindful of with Brad P. regarding his current snowfall forecast. #1 - He's continually stated throughout his SM updates that if his forecast were to bust it would do so on the high end (simply meaning that more snow would fall than what he has forecasted). #2 - He's good, tells it how it is, he never let's the 'weather weenie' in him effect his decisions and his forecasts verify. Trust me... if he's confident that his totals are too low he'll adjust them accordingly...

 

If you're not following him I highly recommend doing so. Just my .02

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fwiw the last few rap models have the snow/sleet/rain transition zone with the first wave going right over atlanta or in the northern atlanta suburbs. The soundings are so close near the metro area  I don't think anyone will know until it happens. Not sure if I have ever seen such a deep layer all at the same temperature.

 

 The soundings below is centered near the northern perimeter. Only thing really going against it is the near surface temps. But if snow reaches the ground, these temps are most likely too warm. rap is pretty bullish on precip totals and radar implies more than this afterwards

RAP Text Sounding | 14 UTC Tue 11 Feb 2014 | Latitude: 33.9458 | Longitude: -84.5504
PRES	HGHT	TEMP	DWPT	RELH	MIXR	DRCT	SKNT	TWTB	TVRT	THTA	THTE	THTV
987.7	317	2.1	1.8	98	4.4	49	5	2.0	2.8	276.2	288.5	277.0
975.0	410	1.0	0.8	99	4.2	58	10	0.9	1.7	276.1	287.7	276.8
950.0	618	-0.0	-0.0	100	4.0	81	18	-0.0	0.6	277.2	288.4	277.8
925.0	831	-0.5	-0.7	99	4.0	97	20	-0.6	0.1	278.8	289.9	279.4
900.0	1050	-0.5	-0.5	100	4.1	108	16	-0.5	0.2	280.9	292.6	281.6
875.0	1276	-0.8	-0.8	100	4.1	120	8	-0.8	-0.1	283.0	294.8	283.7
850.0	1507	-0.9	-0.9	100	4.2	163	2	-0.9	-0.2	285.2	297.4	285.9
825.0	1746	-0.6	-0.8	99	4.4	274	4	-0.7	0.1	287.9	300.7	288.6
800.0	1992	-0.5	-0.8	98	4.5	282	8	-0.6	0.2	290.6	303.8	291.3
775.0	2246	-0.9	-1.3	97	4.5	283	14	-1.1	-0.2	292.8	306.1	293.6
750.0	2507	-1.9	-2.2	98	4.4	282	17	-2.0	-1.2	294.5	307.5	295.2
725.0	2777	-3.0	-3.4	97	4.1	279	20	-3.2	-2.4	296.1	308.5	296.8
700.0	3054	-4.3	-4.8	96	3.8	276	22	-4.5	-3.7	297.7	309.4	298.4
675.0	3340	-5.5	-6.1	96	3.6	272	25	-5.8	-4.9	299.4	310.5	300.1 

\RAP_255_2014021021_F18_PCPIN_18_HR.png

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Here's my precipitation type map... I'm a little nervous about the southern side of the Freezing Rain area, but the rest looks good.

 

The dark blue colors are the mainly snow areas that could see 6-12" with lower totals in NE Alabama and NW GA (closer to 3-6" of all snow). The light blue is where it's going to be a snow/sleet mix that could accumulate to 3-6" combined. The freezing rain is going to be bad, especially in the areas I have highlighted in pink. We could see as much as .75", maybe 1" in isolated spots, of ice; most, however, see closer to 0.5". The green is rain, obviously, but I'm unsure about how far southwest the freezing line goes, hence why the pink is "feathered" or blurred more than the other colors.

 

attachicon.gifFEB 12-13 Winter Precip Chances.png

 

Let the critiques rip! LOL!

Good looking map!!

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I know a lot of you have asked about Andy Wood, and Mods - please move this to banter if it qualifies - but he posted his general idea on FB a while ago regarding this storm. Thought it was pretty spot on:

 

"Off work and can get back to following this storm. New developments overnight and today pointing to a more consolidated system and better forcing leading to more of an impact for more people. Bottom Line: An absolute whiteout of a snowstorm is pegged to impact the states of GA (northern), TN(mainly eastern TN, although some middle TN), SC (northern/Upstate) and NC (all you lucky people) on Wednesday. At it's height, South Carolina better get ready for a good bit of snow and central Georgia needs to prepare for a major freezing rain accumulations! In particular, the Upstate of SC couldn't ask for a more favorable setup for snow. A: two pieces of energy linking up and acquiring a favorable tilt southwest of the area... B: an intensifying surface low running from Mobile to Charleston or maybe just inland of that... C: a gob of moisture incoming... D: as the upper forcing intensifies on Wednesday morning, a snow band forms during the day and proceeds to STAND STILL... the band of snow only slightly pivots and absolutely lays the hammer down on Upstate SC and Western NC. Get prepared for a beautiful sight on Wednesday. I'm drawing up a new snow map, because my older one was based around a much weaker storm in the upper and lower levels."

Do you mind linking his facebook page. I have been trying to find him since he left Fox Carolina. and can not find it. This may get deleted and sorry but I am new and it will not let me PM. thanks

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Here's one snapshot in time (at hour 57) of the snow depth off the 18Z GFS.  That lee side minimum is troubling.  I don't think it's realistic based off the most likely path of this storm, but I'd still not rather see that lull in precipitation amounts between the mountains and the rest of the piedmont show up on the modeling.

 

cj8lneK.gif

No way that happens! That has the look of a clipper system that skips the foothills and redevelops to the east in the piedmont. Plus angle of the precip. is in perfect shape to enhance the snowfall amounts.

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fwiw the last few rap models have the snow/sleet/rain transition zone with the first wave going right over atlanta or in the northern atlanta suburbs. The soundings are so close near the metro area  I don't think anyone will know until it happens. Not sure if I have ever seen such a deep layer all at the same temperature.

 

 The soundings below is centered near the northern perimeter. Only thing really going against it is the near surface temps. But if snow reaches the ground, these temps are most likely too warm. rap is pretty bullish on precip totals and radar implies more than this afterwards

I'm already at 40 after a high of 44. It's too cloudy to radiate down but I'm sure once the sun drops we will settle close to freezing. I want just enough to justify not going to work tomorrow.
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The best write up from FFC in my opinion all winter. Breaks everything down in excellent detail based on their best meteorological opinions.:

 

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE PEACHTREE CITY GA

338 PM EST MON FEB 10 2014

...MAJOR WINTER STORM EXPECTED THROUGH THURSDAY MORNING...

.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...

 

 

Jason gets the credit on this. We all look good when he's on the job.  Some good briefings today too. The 10am call had 250+ and went on for quite a while with all the questions. 

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One thing that has to be considered for the eastern escarpment of the Blue Ridge is the impact of orographical uplift with this system. With precip streaming in from the south or south east it puts the east slopes of the Blue Ridge in perfect position to enhance uplift. Much of the same principle of NWFS.

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One thing that has to be considered for the eastern escarpment of the Blue Ridge is the impact of orographical uplift with this system. With precip streaming in from the south or south east it puts the east slopes of the Blue Ridge in perfect position to enhance uplift. Much of the same principle of NWFS.

 

That's a great point and should enhance totals even more in the foothills. 

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One thing that has to be considered for the eastern escarpment of the Blue Ridge is the impact of orographical uplift with this system. With precip streaming in from the south or south east it puts the east slopes of the Blue Ridge in perfect position to enhance uplift. Much of the same principle of NWFS.

100% agree, many models don't have high enough resolution to pick that up, someone just to the east of the blue ridge is in for a crushing I believe.

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