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4th Annual Fall/Winter Thread for the Mountains/Foothills

Met1985

By Met1985,
in Southeastern States

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strongwxnc

strongwxnc

Posted
Posted

This will all depend of how the transfer and where the transfer occurs. Just down the road from you, I assume ip will cut totals for me. But GSP continues to lean more to the buck of the ip/frz to be I-85 area in SC into NC. Ian about 45 miles (crow miles) NW of I-85.

GSP has me between 9-17in. I'll gladly take it, would like to see all snow. I'm worried about sleet cutting my totals down, but its way better than frzr!

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HurricaneTracker

HurricaneTracker

Posted
Posted

A few morning thoughts after digesting the 00Z RGEM, Euro, and 06Z GFS and NAM. Focus is on Buncombe county because it looks like the French Broad Valley will be troublesome.

1. Model QPF looks far too low on the GFS. This is a system of Pacific origin and is tapping moisture from the Gulf and Atlantic during an El Niño winter. Euro has 1.6" of liquid...which seems better. May also be a tad low, but accounting for Gulf Coast convection...

2. The strength of the barrier jet on Friday is incredible! Absolutely slams wet and cold profiles into the spine of the Apps.

3. Onset looks to be just after midnight. P-type in AVL based on GFS soundings looks to start as freezing rain. Could be a few hours of this before the column cools and the wedge is diabatically generated. Even then, 850mb temps may not drop below 0°C fast enough for the French Broad Valley, while even surrounding ridges and elevated valleys will be cold enough for snow. This is worrisome. Unless 12Z shows us something different, it looks like a prolonged period of freezing rain in downtown AVL, with snow just 20 miles either side of town (no sleet. Not a single sounding I looked at showed or favored sleet). The full transition to snow in town could be as late as Friday afternoon. Unless the dynamic and diabatic cooling is enough to change it earlier - which is possible. That barrier jet, and it's cooling affects from rising motion along the spine, may be underestimated.

4. This is a long-lasting storm. The brunt of it will be 09Z Friday to 21Z Friday. Then we should have a lull as the upper level energy approaches. By early Saturday morning, we should have some backend snows as the low pulls away and then the northwest flow snow begins. Everything ends by 12Z Sunday.

5. Winds. Winds will howl on Saturday, many locations will see 20-35 mph winds. Impacts are too early to pin down as we really won't know how much ice or snow we will have built up by then. But I would prepare for power outages.

6. Given the above, I think it's prudent to scale back snow amounts for the French Broad Valley. Again, even within the same county, elevated valleys and ridges will do quite better.

So, here is my first forecast for AVL and surrounding mountains. I will update it as necessary if 12Z runs look colder and/or wetter.

AVL downtown: 0.25" of ice and 6-8" of snow.

AVL airport: 0.10" of ice and 8-10" of snow.

All other elevated valleys and ridges: 10-15" of snow, trace of ice at onset. Haywood, Madison, Yancy, Avery counties should be 10-15" as well.

Be safe!

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Hvward

Hvward

Posted
Posted

I see that they are going crazy in the Balsams with up to 20". There will be extreme upslope in the Southern Balsams with something like hurricane force winds at cloud level. (With such high winds, the upslope enhancement may carry further into Haywood/Jackson counties than it normally would with winds out of the South or SE.) Looking at point soundings..still too close to call on just how much of the precip will actually fall as snow or really just how much precip there will be. The latest NAM appears to be too low on QPF locally but I am still very pleased about the Northern Virginia grand slam!

Yeah Mike I am a tad concerned with mixing around the Asheville area, but I think that deformation band drops the boom on us for a good bit Saturday and produces thundersnow.

Glad to see they have upped your totals Met! I ment to put a red circle on my map close to your house in Haywood Co. but it slipped my mind lol. I don't think you have near the mixing issues that concern me in the valley. CAD source has been modeled to be pretty strong and I think this is a situation where the CAD gives us just enough cold air to keep most snow. Time to watch the radar and mesoanalysis like you said!

Guys take this one serious, I know all of you will be these winds will be no joke on the backside. Be prepared to lose power for a few days if not a week and also be prepared to sadly miss the panthers game. Good luck to everyone, I look forward to seeing pics and obs.

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strongwxnc

strongwxnc

Posted
Posted

Great thoughts HT. Your county, like most in WNC, has so many micro areas!

Here is some wording out of the lastest GSP AFD:

 

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
651 AM EST THU JAN 21 2016

 

THE SURFACE HIGH BUILDING ACROSS

THE MID ATLANTIC REGION TONIGHT IS NOT ESPECIALLY STRONG AND DOES
NOT HAVE ESPECIALLY DRY AND/OR COLD AIR AT THE SURFACE. WHILE THE
CAD DEVELOPMENT IS HIGHER CONFIDENCE...HOW FAR THE BARRIER JET WILL
BE ABLE TO DRIVE THE SUB-FREEZING SHALLOW BOUNDARY LAYER AIR TO THE
SOUTH AGAINST THE INCREASING PRECIP COVERAGE IS THE KEY. CONFIDENCE
IN THE CHANGEOVER IS BEST OVER THE NRN MOUNTAINS/NRN FOOTHILLS/BLUE
RIDGE AND GOES DOWN FROM THERE...TO WHERE CONFIDENCE IS NOT
ESPECIALLY GREAT DOWN ON THE SRN FRINGE

A few morning thoughts after digesting the 00Z RGEM, Euro, and 06Z GFS and NAM. Focus is on Buncombe county because it looks like the French Broad Valley will be troublesome.

1. Model QPF looks far too low on the GFS. This is a system of Pacific origin and is tapping moisture from the Gulf and Atlantic during an El Niño winter. Euro has 1.6" of liquid...which seems better. May also be a tad low, but accounting for Gulf Coast convection...

2. The strength of the barrier jet on Friday is incredible! Absolutely slams wet and cold profiles into the spine of the Apps.

3. Onset looks to be just after midnight. P-type in AVL based on GFS soundings looks to start as freezing rain. Could be a few hours of this before the column cools and the wedge is diabatically generated. Even then, 850mb temps may not drop below 0°C fast enough for the French Broad Valley, while even surrounding ridges and elevated valleys will be cold enough for snow. This is worrisome. Unless 12Z shows us something different, it looks like a prolonged period of freezing rain in downtown AVL, with snow just 20 miles either side of town (no sleet. Not a single sounding I looked at showed or favored sleet). The full transition to snow in town could be as late as Friday afternoon. Unless the dynamic and diabatic cooling is enough to change it earlier - which is possible. That barrier jet, and it's cooling affects from rising motion along the spine, may be underestimated.

4. This is a long-lasting storm. The brunt of it will be 09Z Friday to 21Z Friday. Then we should have a lull as the upper level energy approaches. By early Saturday morning, we should have some backend snows as the low pulls away and then the northwest flow snow begins. Everything ends by 12Z Sunday.

5. Winds. Winds will howl on Saturday, many locations will see 20-35 mph winds. Impacts are too early to pin down as we really won't know how much ice or snow we will have built up by then. But I would prepare for power outages.

6. Given the above, I think it's prudent to scale back snow amounts for the French Broad Valley. Again, even within the same county, elevated valleys and ridges will do quite better.

So, here is my first forecast for AVL and surrounding mountains. I will update it as necessary if 12Z runs look colder and/or wetter.

AVL downtown: 0.25" of ice and 6-8" of snow.
AVL airport: 0.10" of ice and 8-10" of snow.
All other elevated valleys and ridges: 10-15" of snow, trace of ice at onset. Haywood, Madison, Yancy, Avery counties should be 10-15" as well.

Be safe!


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strongwxnc

strongwxnc

Posted
Posted

Banter I know but 610 Am the fan (which can be streamed online) has the Panthers game on Sunday. I assume this means they will be able to broadcast it online also.

 

Yeah Mike I am a tad concerned with mixing around the Asheville area, but I think that deformation band drops the boom on us for a good bit Saturday and produces thundersnow.


Glad to see they have upped your totals Met! I ment to put a red circle on my map close to your house in Haywood Co. but it slipped my mind lol. I don't think you have near the mixing issues that concern me in the valley. CAD source has been modeled to be pretty strong and I think this is a situation where the CAD gives us just enough cold air to keep most snow. Time to watch the radar and mesoanalysis like you said!


Guys take this one serious, I know all of you will be these winds will be no joke on the backside. Be prepared to lose power for a few days if not a week and also be prepared to sadly miss the panthers game. Good luck to everyone, I look forward to seeing pics and obs.

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NavarreDon

NavarreDon

Posted
Posted

Morning guys, got rain off & on all night so the gulf is open for business. Plenty of moisture to work with. Still feel pretty likely this is going to be a great storm for most of you. As someone who has walked in your shoes before I'm sure the pre storm hesitation abounds. This is still a great op for a big snow so hold on tight. Some great posts overnight & this am. As 85 noted the long range models are for just that. I'm interested in seeing how the HRRR does but, it's really go time now. As always their will be winners & losers but at least you have something to track. Good luck to all!

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BlueRidgeFolklore

BlueRidgeFolklore

Posted
Posted

6. Given the above, I think it's prudent to scale back snow amounts for the French Broad Valley. Again, even within the same county, elevated valleys and ridges will do quite better.

So, here is my first forecast for AVL and surrounding mountains. I will update it as necessary if 12Z runs look colder and/or wetter.

AVL downtown: 0.25" of ice and 6-8" of snow.

AVL airport: 0.10" of ice and 8-10" of snow.

All other elevated valleys and ridges: 10-15" of snow, trace of ice at onset. Haywood, Madison, Yancy, Avery counties should be 10-15" as well.

Be safe!

Sent from my iPad using Tapatalk

 

Awesome stuff HT but I feel inclined to ask. Given that both KAVL and downtown AVL reside in the French Broad River Valley, is there any significant reasoning as to why you believe the airport south of town will receive more in the way of accumulation?

 

My mother lives on Forge Mountain in Mills River, not far from the airport, and I am guessing she would be included in your 'even within the same county, elevated valleys and ridges will do quite better' synopsis, I was just quiet intrigued as to what you knew.

 

Thanks!

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NavarreDon

NavarreDon

Posted
Posted

Here's a facebook post from Robert (Foothills Weather) that should put a lot of you at ease. I know most of the vets follow him but if your new & don't you really should!

 

Good morning. Final day on preparations for what is going to be a BLOCKBUSTER Winter storm from TN, KY, WV, VA , both Carolinas, northern GA right up through NJ, MD and very near New York City.
Both GFS and European model pulled ever so slightly Southward again on all the main features, so this appears to be a very unique system, rather than a traditional Nor'easter that just rockets up the Coast.
Blocking confluent stream in the far Northeast US will keep on forcing the main low in the South to cut more east than north. This has been fooling a lot of forecasters, as each time the models "think" the low will pull into Tennessee, they recognize the strength of the Northern Stream and the storm down south is forced to redevelop and cut more eastward, across Georgia into South Carolina late Friday night.
Growing signs of that deformation backside snow band to get northern Alabama, northern Georgia overnight, where I have more snow than all models, and the Western Carolinas where sleet goes back to snow, and it will snow much of the day Saturday in the Piedmont of NC, while a blizzard rages all of Virginia, except the immediate coast.
One of the biggest concerns besides heavy snow totals and winds, will be the major icestorm in a narrow band of the Upstate , northern Midlands of SC and northeast Georgia, to the 85 corridor in part of NC. Somewhere won't have solid sleet, but mostly freezing rain, and lots of it, with massive power loss in the counties that get that icestorm.

Stay safe!

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NavarreDon

NavarreDon

Posted
Posted

Thought some of the more advanced (weather wise) posters might find this a good read. This is the AFD from MOB which is my office. Our severe risk was very limited thru last night but apparently has increased a good bit with the upcoming event. I not sure what to make of it for you guys.

 

A COMPLICATED FORECAST INDEED FOR OUR AREA TODAY AND TONIGHT...BUT
THE POTENTIAL FOR SEVERE THUNDERSTORMS LOOKS TO BE INCREASING
ESPECIALLY AS WE HEAD INTO THIS EVENING AND LATE TONIGHT. SHORT
RANGE GLOBAL MODELS ARE IN GOOD AGREEMENT WITH TAKING THE UPPER
TROUGH PINCHING OFF IN THE VICINITY OF THE TX PANHANDLE EARLY THIS
MORNING EASTWARD TOWARD THE ARKLATEX REGION BY THIS EVENING...BEFORE
DEEPENING THIS FEATURE INTO AN UPPER LEVEL LOW ACROSS THE VICINITY
OF NORTHERN LA AND CENTRAL/NORTHERN MS BY TONIGHT. THE ASSOCIATED
AREA OF SURFACE LOW PRESSURE OVER SOUTH CENTRAL TX EARLY THIS
MORNING WILL MEANWHILE LIFT EASTWARD ACROSS LA BY THIS AFTERNOON...
THEN NORTHEASTWARD INTO NORTHERN PORTIONS OF MS TONIGHT. AN
ATTENDANT COLD FRONT WILL ADVANCE EASTWARD ACROSS THE MISSISSIPPI
VALLEY REGION THIS AFTERNOON AND TOWARD THE CENTRAL GULF COAST
REGION THIS EVENING INTO LATE TONIGHT. THE EXPECTED TRACK OF THE
SURFACE LOW WILL PLACE OUR FORECAST AREA IN THE WARM SECTOR AHEAD OF
THE ASSOCIATED APPROACHING COLD FRONT TONIGHT. SURFACE DEWPOINTS ARE
FORECAST TO INCREASE TO THE UPPER 50S TO AROUND 60 F ACROSS MOST IF
NOT ALL OF OUR REGION THIS AFTERNOON INTO THIS EVENING. DEEP LAYER
FORCING WILL CONTINUE TO SPREAD FROM THE MISSISSIPPI VALLEY TO THE
CENTRAL GULF COAST REGION THIS AFTERNOON THROUGH TONIGHT AS THE
UPPER TROUGH EJECTS INTO MS.

IN TERMS OF EXPECTED WEATHER...SHOWERS AND PERHAPS A FEW
THUNDERSTORMS WILL CONTINUE TO INCREASE IN COVERAGE TODAY. THE HRRR
AND THE NAM/ECMWF ARE SIGNALING THE BEST COVERAGE ACROSS SW/S
CENTRAL AL AND THE NW FL PANHANDLE THIS MORNING...WITH ADDITIONAL
ROUNDS OF CONVECTION DEVELOPING ACROSS MUCH OF THE REMAINDER OF THE
REGION THIS AFTERNOON. DEEP LAYER SHEAR WILL BE QUITE STRONG [APPX
60 KTS IN THE 0-6 KM LAYER] TODAY...AND THE LATEST RAP MODEL SHOWS
THE 850 MB JET INCREASING TO 30-40 KNOTS BY LATE THIS AFTERNOON.
THERE MAY ALSO BE SOME INSTABILITY TO WORK WITH THIS AFTERNOON...
PARTICULARLY OVER OUR INTERIOR WHERE AROUND 500 J/KG OF MLCAPE MAY
BE REALIZED. ISOLATED SEVERE STORMS WITH DISCRETE SUPERCELLULAR
STRUCTURES MAY DEVELOP AS EARLY AS THIS AFTERNOON OVER INTERIOR
AREAS. HOWEVER...A MORE ELEVATED SEVERE THREAT MAY MATERIALIZE THIS
EVENING INTO LATE TONIGHT AS THE DEEPENING SURFACE LOW LIFTS FROM LA
INTO NORTHERN MS/AL...AND THE ASSOCIATED COLD FRONT MOVES EASTWARD.
DISCRETE SUPERCELLS MAY CONTINUE TO DEVELOP AND MOVE ACROSS THE
REGION THIS EVENING BEFORE AN ORGANIZING QLCS OR BROKEN LINE OF
STORMS FORM ALONG THE ADVANCING FRONT LATE THIS EVENING AND
OVERNIGHT...WHICH IS SUPPORTED BY THE LATEST WRF-NMM. DAMAGING WIND
GUSTS OVER 60 MPH AND A FEW TORNADOES WILL BE POSSIBLE GIVEN THE
STRONG LOW LEVEL JET/DEEP LAYER SHEAR...IN ADDITION TO POTENTIAL FOR
SOME LARGE HAIL. THE SEVERE THREAT SHOULD MOSTLY BE ENDING WEST OF I-
65 BY AROUND MIDNIGHT...AND ACROSS EASTERN PORTIONS OF OUR AREA BY
AROUND 4 AM OR SO AS THE FRONT AND ASSOCIATED LINE OF STORMS MOVES
THROUGH THE REGION. EXPECT TEMPERATURES TO DROP WITH INCREASING W
WINDS FOLLOWING FRONTAL PASSAGE LATE TONIGHT INTO EARLY FRIDAY
MORNING. BRIEF LOCALLY HEAVY RAINFALL WILL BE POSSIBLE WITH STORMS
THROUGH TONIGHT WHICH COULD LEAD TO LOCALIZED MINOR FLOODING...BUT
THE OVERALL FLASH FLOODING RISK LOOKS QUITE LIMITED. /21

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Met1985

Met1985

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If the columns cool quick enough, Transylvania, southern Jackson, southern Haywood and western Henderson counties, will get smoked! The models have been on to a very high QPF in that region for a while now.

namconus_asnow_seus_21.png

Yeah this is a high risk storm if things trend in the right direction. All the mountains and I believe most of the foothills are in for one wild ride. This is a high impact storm as most have outlined this morning. Also Don very interesting. The gulf could see some narly storms down there.
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HurricaneTracker

HurricaneTracker

Posted
Posted

Awesome stuff HT but I feel inclined to ask. Given that both KAVL and downtown AVL reside in the French Broad River Valley, is there any significant reasoning as to why you believe the airport south of town will receive more in the way of accumulation?

 

My mother lives on Forge Mountain in Mills River, not far from the airport, and I am guessing she would be included in your 'even within the same county, elevated valleys and ridges will do quite better' synopsis, I was just quiet intrigued as to what you knew.

 

Thanks!

 

Airport is closer to the escarpment and tends to benefit more from upslope-induced cooling.  Plus models are showing more liquid further south in the county, so that's my two main reasons.

 

I live in a valley at 2,600', surrounded by 3,200' peaks.  That's what I call "elevated valleys", since FBV is at 2100'.  Basically anyone above 2500' should do well.

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HurricaneTracker

HurricaneTracker

Posted
Posted

12z NAM looks a bit colder for WNC with a more sustained wedge. Switches to snow pretty quickly after the onset, but will have to examine temp profiles to confirm. Anyone got 700mb temps?.. I am at work.

 

700mb temps at 06Z are -8.  By 12Z Friday, they are -2 and pretty much stay there the rest of the day.  850 is at or below zero after 09Z Friday throughout the rest of the event.

 

EDIT: this is starting to look like a classic "wet paste" snow with temperatures nearly isothermal between 0 and -5 through 700 mb.  Dendritic growth layer grows with each hour as well, maximizing on Saturday as the deform band comes through.

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franklin NCwx

franklin NCwx

Posted
Posted

700mb temps at 06Z are -8. By 12Z Friday, they are -2 and pretty much stay there the rest of the day. 850 is at or below zero after 09Z Friday throughout the rest of the event.

EDIT: this is starting to look like a classic "wet paste" snow with temperatures nearly isothermal between 0 and -5 through 700 mb. Dendritic growth layer grows with each hour as well, maximizing on Saturday as the deform band comes through.

I live at 2500' just east of franklin. It looks like the warmer models want to drive wedge to Wayah bald standing Indian line near the macon clay county line. That's where the AT comes thru my county.
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NavarreDon

NavarreDon

Posted
Posted

Awesome job HT, I know the folks are happy to have you posting. I agree about the sleet while i wouldn't completely rule some sleet out it seems very unlikely that there would be that much. No matter how you slice it that's a full throttle winter picture below!

 

prec.png

 

 

Just a note on the sleet.  I totally disagree with that idea.  Soundings (even from the new NAM) absolutely DO NOT support any sleet at all.  If it is snowing hard enough and fast enough, which it should be, we should stay all snow after the initial burst of freezing rain late tonight.

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Hvward

Hvward

Posted
Posted

700mb temps at 06Z are -8. By 12Z Friday, they are -2 and pretty much stay there the rest of the day. 850 is at or below zero after 09Z Friday throughout the rest of the event.

EDIT: this is starting to look like a classic "wet paste" snow with temperatures nearly isothermal between 0 and -5 through 700 mb. Dendritic growth layer grows with each hour as well, maximizing on Saturday as the deform band comes through.

Thanks HT that is exactly what we want to see. I was think the same thing that if rates were high enough, that would keep us all snow. With a saturated dendritic growth zone and 850mb temps below zero, I think we stay snow throughout most of it. I will be interested to look at the omega overlay later tonight when I get a chance.

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BlueRidgeFolklore

BlueRidgeFolklore

Posted
Posted

Airport is closer to the escarpment and tends to benefit more from upslope-induced cooling.  Plus models are showing more liquid further south in the county, so that's my two main reasons.

 

I live in a valley at 2,600', surrounded by 3,200' peaks.  That's what I call "elevated valleys", since FBV is at 2100'.  Basically anyone above 2500' should do well.

 

Thank you very much for the info. The escarpment would explain why in many of these events, and in general period, I have seen readings where Hendersonville is a degree or 2 cooler than downtown AVL.

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