Potential December 12th-13th threat

[MotoWeatherman]

the nam has a very cold pool and strong 5H feature wrapping around the main upper low late Sunday into Monday . There's almost no way for it "not" to snow in Ga with this, all models have had it to some degree, and usually a ULL tracking this way gets some wrap around there, so I'm still confident of snow showers in central Tn, northern third of Alabama and down to ATL in GA, but more will be around in the northeast part of Ala, and nw Ga, until it all tapers more for the Upslope regions. Who knows if theres enough to accumulate, I'd think 1" or even a few spots of 2" are very possible in N. Ga most likely the Nw section.

Both the NAM and the GFS have continued to show a nice shortwave rounding the base of the trough Monday at 12z across North GA. Actually strong enough to "kink" the trough just a bit as it rounds the base. Combine that with "ok" 700mb moisture and excellent 850mb moisture and I think that's a good recipe for snow showers. You can see that shortwave get injected down into the through as the northern PV starts to phase with the closed low. I just want to see flakes fly....which they should.

[oconeexman]

probably remaining north and west of 85, but a few flakes are possible, really anywhere east of the Apps with such strong winds, but not much at all. Just a novelty.

God I hate to ask this weenie question...don't want the label but do YOU think any chance of novelty flakes here in NW Oconee. Not seeing it on the models but I know they don't tell the whole story. GSP has had us getting some, take it away, and now back to getting some snow showers late sunday.

Again forgive me, said i'd never do it but this one is definitely not a normal system or I would have written it off already.

[FoothillsNC]

Both the NAM and the GFS have continued to show a nice shortwave rounding the base of the trough Monday at 12z across North GA. Actually strong enough to "kink" the trough just a bit as it rounds the base. Combine that with "ok" 700mb moisture and excellent 850mb moisture and I think that's a good recipe for snow showers. You can see that shortwave get injected down into the through as the northern PV starts to phase with the closed low. I just want to see flakes fly....which they should.

theres no doubt you'll see some good snowshowers from this on the wrap around. Are you going to make a call for Asheville or the mountains in NC? The gFS has about .50" liquid equivalent. Seems a little slower on arrival, like the nam was as well. Still a threshold /cusp event in the mountains of NC, could swing either way from totally wet snow to mix to plain cold rain and 33.

[FoothillsNC]

God I hate to ask this weenie question...don't want the label but do YOU think any chance of novelty flakes here in NW Oconee. Not seeing it on the models but I know they don't tell the whole story. GSP has had us getting some, take it away, and now back to getting some snow showers late sunday.

Again forgive me, said i'd never do it but this one is definitely not a normal system or I would have written it off already.

usually you don't see flakes pass over the mountains, right? But if theres an instance where it would happen, this would probably be it. Not much though, just a few flakes.

[BullCityWx]

Wow, incredibly close call for KMRN tomorrow:

Date: 18 hour AVN valid 6Z SUN 12 DEC 10
Station: KMRN
Latitude:   35.82
Longitude: -81.61
-------------------------------------------------------------------------------
LEV PRES  HGHT  TEMP  DEWP  RH  DD   WETB DIR SPD THETA THE-V THE-W THE-E   W
    mb     m     C     C    %   C     C  deg knt   K     K     K     K    g/kg
-------------------------------------------------------------------------------
 0 1000    86                                                                 
 1  950   500                                                                 
SFC  949   511  -2.1  -3.7  88  1.7  -2.7 148   2 275.2 275.7 273.2 283.6  3.06
 3  900   934   1.0   0.0  93  1.0   0.6 167  13 282.6 283.3 278.9 294.5  4.25
 4  850  1393   0.5  -1.1  89  1.6  -0.2 176  24 286.7 287.4 280.7 298.5  4.16
 5  800  1881   1.4  -3.3  71  4.7  -0.7 189  33 292.6 293.3 282.8 303.6  3.74
 6  750  2400   0.8  -1.3  86  2.1  -0.2 204  37 297.5 298.3 285.8 311.3  4.65
 7  700  2953  -1.8  -4.8  80  3.0  -3.1 211  40 300.5 301.2 286.1 312.1  3.82
 8  650  3539  -4.8  -7.9  79  3.0  -6.1 218  43 303.5 304.1 286.6 313.6  3.25
 9  600  4165  -8.6 -10.3  87  1.7  -9.2 225  43 306.2 306.7 287.2 315.3  2.91
10  550  4834 -12.7 -13.8  91  1.1 -13.0 228  44 309.0 309.5 287.6 316.7  2.39
11  500  5555 -17.7 -18.5  94  0.8 -18.0 231  47 311.4 311.8 287.8 317.2  1.78
12  450  6334 -23.5 -24.4  92  0.9 -23.7 231  52 313.7 313.9 288.0 317.7  1.18
13  400  7184 -30.4 -31.2  93  0.8 -30.5 232  55 315.5 315.6 288.1 317.9  0.71
14  350  8117 -38.8 -39.3  95  0.5 -38.9 240  59 316.4 316.5 288.0 317.7  0.36
15  300  9152 -48.6 -48.7  99  0.1 -48.6 245  78 316.9 316.9 287.9 317.5  0.15
16  250 10324 -57.8 -58.0  97  0.2 -57.8 240  93 320.1 320.1 288.9 320.4  0.06
17  200 11720 -59.7 -63.3  63  3.6 -59.8 242  92 338.2 338.2 293.9 338.3  0.04
18  150 13522 -57.4 -70.9  16 13.5 -57.6 248  74 371.2 371.2 300.8 371.3  0.02
19  100 16073 -60.6 -79.9   6 19.3 -60.9 246  54 410.7 410.7 306.6 410.7  0.01
TRP                                             0                              
WND                                             0      

[code]Date: 24 hour AVN valid 12Z SUN 12 DEC 10
Station: KMRN
Latitude:   35.82
Longitude: -81.61
-------------------------------------------------------------------------------
LEV PRES  HGHT  TEMP  DEWP  RH  DD   WETB DIR SPD THETA THE-V THE-W THE-E   W
    mb     m     C     C    %   C     C  deg knt   K     K     K     K    g/kg
-------------------------------------------------------------------------------
 0 1000    17                                                                 
 1  950   432                                                                 
SFC  941   511   1.5   1.2  98  0.3   1.4 144   4 279.5 280.2 277.5 291.7  4.43
 3  900   866   0.6   0.2  97  0.5   0.4 180  15 282.2 282.9 278.7 294.2  4.30
 4  850  1326   0.7  -0.1  95  0.8   0.4 202  29 286.9 287.7 281.2 299.6  4.48
 5  800  1813  -0.1  -1.3  91  1.2  -0.6 220  37 291.1 291.8 282.8 303.7  4.34
 6  750  2328  -2.7  -3.7  93  1.0  -3.1 227  42 293.6 294.3 283.4 305.0  3.87
 7  700  2872  -5.1  -5.8  95  0.7  -5.4 225  52 296.8 297.5 284.4 307.4  3.54
 8  650  3453  -6.7  -7.0  98  0.3  -6.8 219  66 301.3 302.0 286.0 311.9  3.47
 9  600  4076  -9.3  -9.5  98  0.3  -9.4 213  66 305.4 306.0 287.1 315.0  3.09
10  550  4744 -13.3 -13.5  98  0.3 -13.3 205  63 308.3 308.8 287.5 316.2  2.45
11  500  5465 -17.1 -17.5  97  0.4 -17.2 202  73 312.2 312.5 288.3 318.5  1.94
12  450  6247 -22.1 -22.5  97  0.4 -22.2 208  80 315.4 315.7 288.8 320.1  1.39
13  400  7100 -29.7 -30.0  97  0.3 -29.8 210  89 316.3 316.5 288.5 319.1  0.79
14  350  8034 -38.7 -39.1  96  0.4 -38.7 212  90 316.5 316.6 288.1 317.9  0.37
15  300  9071 -47.4 -47.6  99  0.1 -47.4 219 105 318.5 318.5 288.5 319.1  0.17
16  250 10253 -54.4 -54.6  98  0.1 -54.5 222 129 325.1 325.1 290.4 325.5  0.09
17  200 11664 -59.4 -61.9  72  2.5 -59.5 235 113 338.7 338.7 294.0 338.9  0.05
18  150 13480 -55.2 -71.6  11 16.5 -55.5 241  82 375.0 375.0 301.4 375.1  0.02
19  100 16053 -58.9 -80.4   5 21.5 -59.2 238  56 413.9 413.9 307.0 414.0  0.01
TRP                                             0                              
WND                                             0                              

[isohume]

KGSP did not handle last weekend and the following days well at all.  I am hoping they are back to their best on this one.

What was wrong with it? 

[Carvers Gap]

The NWS folks in E TN have a tough call to make. The NAM shows virtually nothing in terms of snowfall in the northern TN Valley. The 12z GFS shows decent accumulation in the northern TN Valley.

[BullCityWx]

If I'm looking at this sounding, where's my snow growth layer?:

Date: 42 hour AVN valid 6Z MON 13 DEC 10
Station: 35.31,-81.23
Latitude:   35.31
Longitude: -81.23
-------------------------------------------------------------------------------
LEV PRES  HGHT  TEMP  DEWP  RH  DD   WETB DIR SPD THETA THE-V THE-W THE-E   W
    mb     m     C     C    %   C     C  deg knt   K     K     K     K    g/kg
-------------------------------------------------------------------------------
 0 1000   -13                                                                 
SFC  967   254  -4.1  -6.0  86  2.0  -4.7 233  13 271.7 272.1 270.3 278.6  2.52
 2  950   393  -4.4  -7.2  81  2.7  -5.4 240  23 272.7 273.1 270.6 279.1  2.34
 3  900   819  -5.3 -10.0  69  4.7  -6.7 269  26 276.1 276.4 272.1 281.7  1.98
 4  850  1265  -8.0 -11.4  76  3.4  -9.0 290  37 277.8 278.1 273.0 283.1  1.88
 5  800  1734 -10.0 -13.9  74  3.8 -11.1 296  37 280.4 280.7 274.1 285.2  1.63
 6  750  2229 -13.1 -16.6  75  3.4 -14.0 296  34 282.3 282.6 274.8 286.4  1.40
 7  700  2750 -17.5 -18.9  88  1.4 -17.8 294  34 283.2 283.4 275.0 286.8  1.23
 8  650  3302 -19.7 -20.9  90  1.2 -19.9 281  30 286.7 286.9 276.7 290.1  1.12
 9  600  3895 -21.3 -23.9  80  2.5 -21.8 268  32 291.4 291.6 278.7 294.3  0.93
10  550  4531 -25.5 -28.3  77  2.8 -25.9 261  38 293.8 293.9 279.5 295.9  0.67
11  500  5215 -30.8 -34.0  73  3.2 -31.2 259  44 295.5 295.5 280.0 296.9  0.43
12  450  5954 -36.4 -40.5  66  4.1 -36.7 259  49 297.4 297.5 280.6 298.3  0.25
13  400  6761 -40.8 -47.5  48  6.7 -41.1 257  53 301.9 302.0 282.4 302.4  0.13
14  350  7666 -42.4 -54.8  24 12.5 -42.9 257  55 311.6 311.6 286.0 311.8  0.06
15  300  8709 -41.1 -61.3   9 20.2 -41.8 251  44 327.5 327.5 291.0 327.6  0.03
16  250  9940 -44.0 -63.1  10 19.2 -44.6 240  45 340.7 340.7 294.5 340.8  0.03
17  200 11427 -47.1 -67.0   9 19.8 -47.7 238  47 358.2 358.2 298.4 358.3  0.02
18  150 13315 -49.6 -76.0   3 26.4 -50.3 247  51 384.5 384.5 303.0 384.6  0.01
19  100 15951 -53.7 -82.5   2 28.8 -54.3 238  41 424.0 424.0 308.2 424.0  0.00
TRP                                             0                              
WND                                             0                             

[MotoWeatherman]

theres no doubt you'll see some good snowshowers from this on the wrap around. Are you going to make a call for Asheville or the mountains in NC? The gFS has about .50" liquid equivalent. Seems a little slower on arrival, like the nam was as well. Still a threshold /cusp event in the mountains of NC, could swing either way from totally wet snow to mix to plain cold rain and 33.

That's a very tough call with the front but I do think AVL and the rest of the NC mountains get some frontal snow. Inch or two in AVL with more in the high country. Now with the flow snow I would not be surprised if the high country gets another foot as the moisture is much deeper although the duration should be shorter.

I have not seen the 12z GFS soundings yet so I going off what I saw with 0z and 6z runs.

[nchighcountrywx]

Considering GSP hasn't issued any watches or warnings, not even so much as an advisory, this must be a nonevent. I'll tell my grandmother to go ahead and travel 35 miles to Asheville Monday morning for her doctors appointment. Looking forward to maybe something down the road.

KGSP did not handle last weekend and the following days well at all. I am hoping that was just a hickup and they are back to their best on this one.

However, so far, I'm with Joe. The new criteria is seems to be failing them. Maybe they should just slice each county vertically on elevation break around 3800 - 4000 feet.

What a blessing Dr.Ray Russell is with Rays Weather for the NC High Country. The third option would be for KGSP just to contract out the Mountain FWAs to Ray. Then it would be job done and done well!

[phil882]

06z NAM run came in colder for western NC. Right now Asheville's wetbulb is 27, Boone's is 24. I know they're going to rise today, but theres always been shown a cold pocket aloft , as well as surface, remaining there. Still think the prefrontal precip somewhere in there will be mostly snow, several quick inches.

Yea the 06z nam was a snow run for KAVL. BUFKIT had heavy snow with an isothermal sounding at 11z on the 06z run. The 12z nam run is warmer by about 1 degree C which is just enough to have mainly rain for the synoptic portion of this event. Its only about a 5,000ft layer warm nose. I don't know how far snowfall can fall before it melts into rain, but I imagine a 5,000 foot layer of 33-34 degree temperatures is not that deep.

[isohume]

KGSP did not handle last weekend and the following days well at all.  I am hoping that was just a hickup and they are back to their best on this one.

What was wrong with it? 

[phil882]

What was wrong with it?

Well I think some people were surprised that some of the favored NWFS areas picked up 10+" of fresh powder from the last extended event after the clipper. Granted this took place over a long time interval, so the extended WWA you guys had out for the northern mountains was a good call. I don't know if there were any cases where there were greater than 5" snowfall reports within a 24 hour period... and I get the feeling you might know a lot better than I with all the coop reports coming in from the mountains.

[NavarreDon]

Well KGSP has issued a WWA from 11:00PM tonight thru 7:00AM tomm. above 3500 ft. For the boarder counties plus Buncombe. Would paste or link but I am at work.

[isohume]

Well I think some people were surprised that some of the favored NWFS areas picked up 10+" of fresh powder from the last extended event after the clipper. Granted this took place over a long time interval, so the extended WWA you guys had out for the northern mountains was a good call. I don't know if there were any cases where there were greater than 5" snowfall reports within a 24 hour period... and I get the feeling you might know a lot better than I with all the coop reports coming in from the mountains.

Yeah a few locations above 3500' did reach warning level criteria, but not until the last 12 hrs of the event and by then it was too late to upgrade the advisory. But across all other zones the advisory had the amounts well in hand. We missed 3 events out of 10 issued for. Not excellent....but not horrible either. One of the main things we missed was not accounting for the arctic air affecting the higher elevations and producing 40:1 SLRs near the end of the event.        

[Itunis]

Fox 5 has a pretty reasonable forecast...flurries with a dusting north of Canton/Gainesville and light accum for higher elevations.

[phil882]

Well KGSP has issued a WWA from 11:00PM tonight thru 7:00AM tomm. above 3500 ft. For the boarder counties plus Buncombe. Would paste or link but I am at work.

Yep like the advisory is just for the frontal passage tonight...

Winter Weather Advisory

[NavarreDon]

Yeah a few locations above 3500' did reach warning level criteria, but not until the last 12 hrs of the event and by then it was too late to upgrade the advisory. But across all other zones the advisory had the amounts well in hand. We missed 3 events out of 10 issued for. Not excellent....but not horrible either. One of the main things we missed was not accounting for the arctic air affecting the higher elevations and producing 40:1 SLRs near the end of the event.

I am kinda new here but, would assume you are with NWS-GSP (If not Sorry). I am sure you get asked this a ton but, any thought to splitting Buncombe county like Jackson. There seems to be such a wide range of conditions here. In last event close to Weaverville I got 3+ inches while South of town got a dusting. Sorry to be a bother. Don

[FoothillsNC]

My rough call. Likely this will come down to nowcasting for western NC mountains after midnight, as its a close call. Theres big bust potential in the mountains and maybe even western Foothills during the pre-dawn Sunday morning event, as either option could occur: precip arrives mainly as snow, and pick up 2 to 5" by early Morning, or the bulk is rain or mix, only ending as snow toward dawn. Eventually the changeover will arrive while some good precip rates are still occuring, before the wrap around and upslope, which still looks impressive. For the areas west of the Apps and south toward northern ATL burbs, some snow showers should easily make it that far south during Sunday afternoon and overnight, with a few spots picking up dustings north of town. More duration snow showers along the NC/GA border counties for possible 1" accumulations , scattered among the dustings that occur.

Upslope potential is high with this, good duration of 36 hours should be easily achievable with high ratios, so I have no doubt parts of Avery and Watauga will get atleast 12" , with 6" -12" also fairly common in the southwest Smokies along the TN/NC border. Several bands of streamers with white out and blizzard conditions at times in the high country.

[BullCityWx]

Speaking of the foothills robert, did you notice the soundings I posted for KMRN? It's razor thin close.

[NEGa]

My rough call. Likely this will come down to nowcasting for western NC mountains after midnight, as its a close call. Theres big bust potential in the mountains and maybe even western Foothills during the pre-dawn Sunday morning event, as either option could occur: precip arrives mainly as snow, and pick up 2 to 5" by early Morning, or the bulk is rain or mix, only ending as snow toward dawn. Eventually the changeover will arrive while some good precip rates are still occuring, before the wrap around and upslope, which still looks impressive. For the areas west of the Apps and south toward northern ATL burbs, some snow showers should easily make it that far south during Sunday afternoon and overnight, with a few spots picking up dustings north of town. More duration snow showers along the NC/GA border counties for possible 1" accumulations , scattered among the dustings that occur.

Upslope potential is high with this, good duration of 36 hours should be easily achievable with high ratios, so I have no doubt parts of Avery and Watauga will get atleast 12" , with 6" -12" also fairly common in the southwest Smokies along the TN/NC border. Several bands of streamers with white out and blizzard conditions at times in the high country.

good map - and nice that we actually have wx on tap that warrants a map of course now my updated forecast has removed ALL mention of snow, including flurries anyone have any tranquilizers for us ga peeps? lol

considering my past experience with this set up, i would be ecstatic to see flakes or a dusting at this point

[isohume]

I am kinda new here but, would assume you are with NWS-GSP (If not Sorry). I am sure you get asked this a ton but, any thought to splitting Buncombe countie like Jackson. There seems to be such a wide range of conditions here. In last event close to Weaverville I got 3+ inches while South of town got a dusting. Sorry to be a bother. Don

No, that's a good question and we get it all the time. It is something we want to do and we are working on. There are political reasons (NOAA, NC, and Buncombe Co.) why that just doesn't happen...but it's in the works. It's always tricky trying to talk up the sn amounts across nrn Buncombe without mentioning warning criteria explicitly and it really needs two zone groups.      

[nchighcountrywx]

What was wrong with it?

Joe bundled it all up in a superb real life example here:

":That might be a good idea Bill. Something they also need to remember is that even though the valleys might not get the foot of snow, you have to traverse areas that do. Take a good friend of mine that lives just a couple of miles from me. He lives down on the Toe river at about 2800 feet and rarely gets much flow snow and is always much warmer that me. But, to get to Burnsville (our only town in the county) he'll cross three ridges that are 4k+. So even high elevation snow affects all of us no matter where you live here. "

He was referring to the comment I made on: "Maybe KGSP should just slice each county vertically on elevation break around 3800 - 4000 feet"

Specifically for this past event, there were quite a few times where the roads were at the impassable level in many areas and when all was said and done, we all know the accumulation was much more than forecasts would have led to one to expect and the blowing was a major issue too.

As Powerstroke reminds us, the proof is often in what is available to plow:

December 07 2010:

Overall, KGSP has a tremendous understanding of our NC Mountain events and it is recognized it places a considerably heavier workload into their grids and their final output product than what the vast majority of the forecast offices across the country deal with.

Perhaps one day, the Grandfather Mountain Summit could be designated an official automated observation site. The new heated sonic anemometer is a superb addition to the instrument pack on GFM Summit. I did once suggest to KGSP if Grandfather Mountain Summit could be considered for an official observation site. Response was 'no one lives up there at those levels in N.C.'. Well, then why is Mount Washington an official network NWS observation site in New Hampshire? A heck of a lot more NC High Country residents are affected by conditions not too far off from the Grandfather Mountain Summit as compared to New Hampshire residents who have weather similar to the Mount Washington Summit. Also, the GFM Summit is a pretty darn good indicator of what's going on up there at the 850mb level!

[rosie]

good map - and nice that we actually have wx on tap that warrants a map of course now my updated forecast has removed ALL mention of snow, including flurries anyone have any tranquilizers for us ga peeps? lol

considering my past experience with this set up, i would be ecstatic to see flakes or a dusting at this point

Hope it changes for ya, at least hopefully a short drive to get you some snow.

[NEGa]

Hope it changes for ya, at least hopefully a short drive to get you some snow.

me too - although i'd rather see flakes with nothing forecasted than have it in the forecast and see nothing and yes, i am already planning to drive tomorrow for snow since i am not going to need to go that far since it should be within one county from mby. thankgoodness its on the weekend

good luck up your way - hopefully all of n ga at lesat sees some flakes.

[isohume]

He was referring to the comment I made on: "Maybe KGSP should just slice each county vertically on elevation break around 3800 - 4000 feet"

We do issue high elevation warnings (above 3500') and this last event would have been a good candidate for one across the nrn mtns for sure.    

[Local Yokel Wx]

Perhaps one day, the Grandfather Mountain Summit could be designated an official automated observation site. The new heated sonic anemometer is a superb addition to the instrument pack on GFM Summit. I did once suggest to KGSP if Grandfather Mountain Summit could be considered for an official observation site. Response was 'no one lives up there at those levels in N.C.'. Well, then why is Mount Washington an official network NWS observation site in New Hampshire? A heck of a lot more NC High Country residents are affected by conditions not too far off from the Grandfather Mountain Summit as compared to New Hampshire residents who have weather similar to the Mount Washington Summit. Also, the GFM Summit is a pretty darn good indicator of what's going on up there at the 850mb level!

Great question. We know why, but its one of those questions that makes GFM seem not worthy when we all know its extreme and worth being official. Great Write up.

[NavarreDon]

No, that's a good question and we get it all the time. It is something we want to do and we are working on. There are political reasons (NOAA, NC, and Buncombe Co.) why that just doesn't happen...but it's in the works. It's always tricky trying to talk up the sn amounts across nrn Buncombe without mentioning warning criteria explicitly and it really needs two zone groups.

Thanks for your response. Sounds like we have something to look foward to. I have heard that GSP is one of the hardest offices to forecast in because of all the microclimates in the mnts. would you agree with this?

[phil882]

Yeah a few locations above 3500' did reach warning level criteria, but not until the last 12 hrs of the event and by then it was too late to upgrade the advisory. But across all other zones the advisory had the amounts well in hand. We missed 3 events out of 10 issued for. Not excellent....but not horrible either. One of the main things we missed was not accounting for the arctic air affecting the higher elevations and producing 40:1 SLRs near the end of the event.

Not bad! I know your likely not at work right now but do you think we might be getting anything similar SLR wise with this event? I think Dr. Perry and Dr. Miller are gonna be launching weather balloons from both Poga Mountain and Warren Wilson College so it will be nice to have the added soundings to help out with this event. It seems that the valleys generally do better in regards to snowfall with these colder NWFS events.

[FoothillsNC]

Speaking of the foothills robert, did you notice the soundings I posted for KMRN? It's razor thin close.

sure is.

good map - and nice that we actually have wx on tap that warrants a map of course now my updated forecast has removed ALL mention of snow, including flurries anyone have any tranquilizers for us ga peeps? lol

considering my past experience with this set up, i would be ecstatic to see flakes or a dusting at this point

GFS is very cold for you too, at the surface. As usual its a close call between 32 and 33 for your area, but something other than rain is possible around your neck of the woods.

850 6Z Sun:

2M temps 12z Sun: