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Snow threats for the mountains.


Met1985

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TONIGHT THROUGH WEDNESDAY NIGHT...

.A STRENGTHENING LOW PRESSURE SYSTEM OVER THE UPPER MIDWEST THIS
MORNING WILL MOVE SOUTHEAST THROUGH THE OHIO VALLEY LATE TODAY AND
CROSS THE APPALACHIANS TONIGHT. AN ASSOCIATED COLD FRONT WILL
SWEEP THROUGH THE MOUNTAINS THIS EVENING...ALLOWING TEMPERATURES
TO RAPIDLY PLUMMET AFTER IT PASSES. ABUNDANT MOISTURE WRAPPING
SOUTHWARD DOWN THE APPALACHIAN MOUNTAIN CHAIN WILL INTERACT WITH
STRENGTHENING NORTHWEST WINDS AND THE VERY COLD AIR TO PRODUCE
RAPIDLY ACCUMULATING SNOWFALL OVER MUCH OF THE NORTH CAROLINA
MOUNTAINS TONIGHT INTO WEDNESDAY NIGHT. HEAVY SNOW ACCUMULATIONS
ARE EXPECTED IN THE TENNESSEE BORDER COUNTIES...AS WELL AS THE
HIGHER ELEVATIONS AWAY FROM THE BORDER. THE GUSTY NORTHWEST WINDS
WILL ALSO PRODUCE BLOWING AND DRIFTING SNOW AS WELL AS REDUCED
VISIBILITY AT TIMES. SOME DEEP SNOW DRIFTS WILL BE POSSIBLE NEAR
THE TENNESSEE LINE BY WEDNESDAY.
 

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AVERY-MADISON-YANCEY-MITCHELL-SWAIN-HAYWOOD-GRAHAM-
NORTHERN JACKSON-
INCLUDING THE CITIES OF...NEWLAND...SPRUCE PINE...BRYSON CITY...
WAYNESVILLE...SYLVA
402 AM EST TUE MAR 5 2013

...WINTER STORM WARNING IN EFFECT FROM 7 PM THIS EVENING TO 6 AM
EST THURSDAY...

THE NATIONAL WEATHER SERVICE IN GREENVILLE-SPARTANBURG HAS ISSUED
A WINTER STORM WARNING FOR HEAVY SNOW...WHICH IS IN EFFECT FROM 7
PM THIS EVENING TO 6 AM EST THURSDAY. THE WINTER STORM WATCH IS NO
LONGER IN EFFECT.

* LOCATIONS...THE TENNESSEE BORDER COUNTIES OF NORTH CAROLINA...
  FROM AVERY COUNTY SOUTH TO GRAHAM COUNTY...INCLUDING NORTHERN
  JACKSON COUNTY.

* HAZARDS...HEAVY SNOW ACCUMULATIONS. VERY WINDY CONDITIONS WILL
  PRODUCE BLOWING AND DRIFTING SNOW WITH REDUCED VISIBILITIES.

* TIMING...PRECIPITATION WILL CHANGE OVER FROM RAIN TO SNOW
  SHOWERS THIS EVENING BEHIND A PASSING COLD FRONT. MODERATE TO
  HEAVY SNOW SHOWERS WILL THEN DEVELOP ACROSS MOUNTAINS OVERNIGHT
  AND PERSIST THROUGH WEDNESDAY. THE SNOWFALL WILL SLOWLY PARE
  BACK TO THE IMMEDIATE TENNESSEE BORDER THROUGH WEDNESDAY NIGHT.
  THE WINDIEST CONDITIONS WILL BE LATE TONIGHT THROUGH EARLY
  WEDNESDAY AFTERNOON.

* ACCUMULATIONS...WIDESPREAD SNOW ACCUMULATIONS OF 4 TO 6 INCHES.
  LOWER VALLEYS IN THE SHADOW OF THE SMOKIES MAY SEE ONLY 2 TO 4
  INCHES. THE HIGHER RIDGES SHOULD SEE 6 TO 9 INCHES.

* IMPACTS...HEAVY SNOWFALL WILL RESULT IN SNOW COVERED
  ROADWAYS...BRIDGES...AND OVERPASSES. STRONG NORTHWEST WINDS WILL
  GENERATE BLOWING AND DRIFTING SNOW...WITH VISIBILITY REDUCED TO
  BETWEEN ONE QUARTER AND ONE HALF MILE IN SNOW SHOWERS AT TIMES.
  SCATTERED POWER OUTAGES WILL LIKELY RESULT.

* TEMPERATURES...MAINLY IN THE 20S...WITH SOME LOWER 30S
  WEDNESDAY.

* WINDS...NORTHWEST 20 TO 30 MPH WITH GUSTS UP TO 50 MPH AT TIMES.

* VISIBILITY...AROUND ONE QUARTER MILE AT TIMES IN BLOWING AND
  DRIFTING SNOW.

 

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I don't get it, I haven't seen a model show over .3" for the mtns of NC. Where are they getting these totals??

 

Sounds like there will be some from synoptic & then a really strong NWFS. Here is part of GSP's afd from last night:

 

THE FORECAST IS ON TRACK WITH IMPROVING LOW LEVELUPGLIDE MOISTURE STEADILY INCREASING ACROSS THE FORECAST AREATHROUGH THE DAY...WITH INCREASING/EXPANDING POPS RESULTING. 850 MBWINDS WILL SLOWLY BACK AND STRENGTHEN BY LATE AFTERNOON IN THE WARMSECTOR ACROSS THE REGION...AND SFC BASED INSTABILITY WILL INCREASEENOUGH BY LATE DAY TO WARRANT A SCHC TO CHC TSTM MENTION OVER SRNSECTIONS...AND ALSO OVER THE WRN MTNS WITH IMPROVING LAPSE RATESALOFT. IN ADDITION...40 TO 50 KT OF LOW LEVEL SHEAR WILL WARRANT ANISOLD SEVERE THREAT MENTION TOWARD EVENING IN THE SRNPIEDMONT...WITH BL HELICITY VALUES AT OR ABOVE 500 M2/S2 CROSSINGTHE REGION TOWARD 00Z.THE STRONGEST 850 TO 500 MB DPVA SHOULD TRANSIT THE FORECAST AREAMAINLY 00Z TO 06Z AHEAD OF THE DEEP H5 LOW PRES CENTER MOVING FROMTHE LOWER OH VALLEY THROUGH THE SRN APPALACHIANS. THE ASSOCIATED SFCCOLD FRONT WILL MOVE QUICKLY THROUGH THE REGION CENTERED AROUND03Z...WITH PROFILES RAPIDLY BECOMING COLD ENOUGH TO SUPPORT SNOWOVER THE HIGHER TERRAIN...AND THEN THROUGHOUT THE LOWEST VALLEYSOVERNIGHT IN IMPROVING MOIST NW UPSLOPE FLOW. THE QUICK SHOT OF DEEPEVENING MOISTURE WILL MOVE EAST OF THE AREA...WITH PROMINENT MIDLEVEL DRYING ARRIVING ACROSS THE FOOTHILLS AND PIEDMONT FROM THE SWBY 06Z. HOWEVER...ADDITIONAL DEEPER MOISTURE WILL THEN WRAP SWDBEHIND THE PASSING CYCLONE TOWARD DAYBREAK WED TO ADD TO SNOWFALLTOTALS OVER THE WRN MTNS IN BLOSSOMING NW UPSLOPE FLOW IN THE VERYCOLD AIR. THE WINTER STORM WATCH WILL BE UPGRADED TO AWARNING...WITH AN ADVISORY TIER ADDED FOR BUNCOMBE AND MACON. INADDITION...EXPECT VERY WINDY CONDITIONS OVER THE MTNS WITH THE COLDADVECTION AND 50 KT OF 850 MB FLOW. WIND HAZARDS WILL BE WRAPPEDINTO THE WINTER STORM PRODUCTS...EXCEPT FOR A STANDALONE WINDADVISORY FOR MCDOWELL MTNS TO CALDWELL MTNS.

 

LLVL FLOW ACROSS THE TN BORDERCOUNTIES OF NC IS EXPECTED TO FAVOR WNW DIRECTION...A LITTLE WEST OFOPTIMAL NWFS GENERATION. HOWEVER...THE CLOSED LOW AND SFC LOW WILLTRACK EAST DURING THE DAY...RESULTING IN VEERING LLVL FLOW ACROSSTHE FORECAST AREA. WIND DIRECTION AND SPEEDS ACROSS THE SOUTHERNAPPALACHIAN REGION ARE FORECAST TO BECOME VERY FAVORABLE FOR NWFS BYMID DAY WEDNESDAY. FORECAST SOUNDINGS ACROSS NC MTNS AND EASTERN TNSITES INDICATE THAT THE LAYER OF SATURATED AIR SHOULD EXTEND FROMTHE BL TO H65 EARLY WEDNESDAY...GRADUALLY FADING TO A H9 TO H75 BYLATE AFTERNOON. BASED ON WIND TIMING...MOISTURE CONTENT...ANDTEMPERATURE PROFILES...CONDITIONS APPEAR VERY FAVORABLE FORACCUMULATING NWFS WEDNESDAY MORNING UNTIL THE EARLY AFTERNOON.DURING THIS TIME WINDOW...I WILL INDICATE HOURLY QPF AMOUNTS FROM0.03 INCHES ALONG THE TN LINE. SLR VALUES OF 12 TO 14 TO 1 WILLRESULT IN HOURLY SNOWFALL RATES FROM 0.25 TO 0.4 OF AN INCH ACROSSTHE FAVORED UPSLOPE AREAS. TOTAL DAYLIGHT SNOWFALL ACROSS THE MTNSON WEDNESDAY IS FORECAST TO RANGE FROM NEAR 4 INCHES ALONG THE SPINEOF THE APPALACHIANS TO 1 TO 3 INCHES ACROSS THE TN BORDER COUNTIES.
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I don't get it, I haven't seen a model show over .3" for the mtns of NC. Where are they getting these totals??

 

Because the models don't ever handle NW flow snow events very well.  To a degree, the NAM, only because of its higher resolution, captures some of it.  The GFS captures essentially none of it.

 

This is one of those times where local rules and knowledge completely outweigh the models.

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Upslope enhancement should do the trick along with high ratios. I think Beech should get 6-12 out of this deal.

Because the models don't ever handle NW flow snow events very well. To a degree, the NAM, only because of its higher resolution, captures some of it. The GFS captures essentially none of it.

This is one of those times where local rules and knowledge completely outweigh the models.

I figured a lot would come from NWFS but what gets me is they are calling for 4-7" of HEAVY WET snow...shouldn't it be dry and powdery with the NWFS?

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Because the models don't ever handle NW flow snow events very well.  To a degree, the NAM, only because of its higher resolution, captures some of it.  The GFS captures essentially none of it.

 

This is one of those times where local rules and knowledge completely outweigh the models.

 

Very true...Yesterday was the first time I know of that GSP mentioned Buladean along with Beech Mountain...Buladean is a small community in extreme northern Mitchell county that has been an upslope magnet for years...entire community is @ 3000' and on up

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Upslope enhancement should do the trick along with high ratios.  I think Beech should get 6-12 out of this deal.

Ya Moto I think this will be great for the higher elevations.

 

Because the models don't ever handle NW flow snow events very well.  To a degree, the NAM, only because of its higher resolution, captures some of it.  The GFS captures essentially none of it.

 

This is one of those times where local rules and knowledge completely outweigh the models.

Did not now that. No wonder every time I looked at the models for NWFE the totals were just not there.

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Very true...Yesterday was the first time I know of that GSP mentioned Buladean along with Beech Mountain...Buladean is a small community in extreme northern Mitchell county that has been an upslope magnet for years...entire community is @ 3000' and on up

Yep very true also here for Haywood county. You get into those higher up really close to the boarder like Fines Creek, Crabtree, Panther Creek, and into Hot springs, Max patch you get some unreal snow totals.

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Another thing about NWFS is the main thing I pay attention to (besides the obvious cold 850's) is the surface wind direction and the duration of the 850mb 90%+ RH.  The longer the 90%+ RH hangs around the more snow regardless of what the model QPF is.  Once the 850 90+% RH is gone then the NWFS pretty much is over at that point.

 

Also, as Franklin just posted a map, if you can get 700mb moisture to go with it then that just makes it all the better.

 

Just my 2 cents...

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Another thing about NWFS is the main thing I pay attention to (besides the obvious cold 850's) is the surface wind direction and the duration of the 850mb 90%+ RH.  The longer the 90%+ RH hangs around the more snow regardless of what the model QPF is.  Once the 850 90+% RH is gone then the NWFS pretty much is over at that point.

 

Also, as Franklin just posted a map, if you can get 700mb moisture to go with it then that just makes it all the better.

 

Just my 2 cents...

I think you nailed it with that statement. Ive seen it play out much the same.

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Another big part of the storm will be the strong northwest flow snow event (NWFS) in the Southern Appalachians. Eastern TN and western NC mountains will get slammed with the best setup for upslope snows this Winter, strong winds, plenty of moisture at the 850 level and very cold (-10 !) coming in Wednesday, so look for strong instability, steep lapse rates and vicious snow squalls if you're travelling I-81, I-26, I-40 through the southern Apps tomorrow. The snow will continue until Thursday morning. Snow showers easily making it down into the northern GA counties of Fannin, Union, Towns, Rabun. Some mountain peaks will get over a Foot of snow in TN, NC. Asheville NC has the best shot at finally seeing some flakes this Winter--now that it is March.

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