Winter Storm in Georgia, December 8, 2017

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
650 AM EST Fri Dec 8 2017

.SYNOPSIS...
A moist frontal zone will linger just to our southeast through
tonight with light wintry precipitation for many areas north of
Interstate 85.  A cold upper level trof will then re-amplify over
the area later on Saturday and bring a shot of snow showers to the
North Carolina mountains. Cool temperatures will persist through
much of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 645 AM EST Friday: Seeing an elongated band of light precip
spreading across the NC mountains at daybreak with accumulation
beginning over the area S and W of AVL. This band of precip extends
back into central AL and ultimately down to the TX Gulf Coast,
so confidence is good that light snow will continue to accumulate
over the mtns through the better part of the morning and into the
afternoon. With temps being what they are across the mtns, the
precip should be mainly snow. Otherwise, precip still a bit patchy
over the rest of the fcst area, but liquid with a few sleet pellets
mixed in. Nothing seen yet to suggest any mid-course corrections.

A tricky forecast for the next 24 hours as we deal with the passage
of several weak short waves today bringing a large area of light
precip up from the SW, then the development of upper divergence
and mid-level frontogenesis tonight. As usual, there is plenty of
uncertainty with how the situation might unfold. The key will be the
boundary layer temperatures, or more specifically, the wet bulb temp
profile. Fcst soundings show the development of a nearly isothermal
layer near zero which defies thickness schemes and should allow wet
snow to fall toward the ground, ultimately melting in the relatively
warm boundary layer in most places outside the mtns. Needless to
say, precip probability ramps up to the categorical range from
the S/SW today and stays there well into the tonight period as all
manner of forcing acts on deep moisture. We are most confident in
the precip type over the mtns/adjacent foothills. Wet bulb temps
should be low enough to allow most (if not all) the precip to fall
as snow. This makes it more of a QPF problem, and the trend in the
guidance has been toward the wet. After considering the guidance
from WPC, an area on the Srn upslope zone and across the upper
Fr. Broad Valley should see a sustained period of snow continuing
through today and into tonight. We could see 4-6 inches of snow
in the area from Franklin and Clayton across the Balsams and Black
Mtns to the Escarpment above Old Fort, with some of the elevations
above 5k feet getting around 8 inches. That area was bumped up to a
Winter Storm Warning. The Advisory was extended across the northern
mountains where 2-4 inches could fall. Meanwhile...the cooler trend
in the guidance suggests the potential for precip to mix with or
change to snow extending out across the NW Piedmont later today,
with perhaps 2-3 inches possible mainly tonight.  An Advisory will
be issued beginning at Noon. The situation gets a little more tricky
over metro CLT. Think the SREF plume diagrams are overly optimistic
and do not take into account how warm the boundary layer is. Our
main problem is the lack of a source of cold and/or dry air. The
northern part of the area could see an inch or two, but probably
not until after nightfall. Uncertainty is greatest there, so the
consensus was to wait and see how the situation unfolds. The 06Z
sounding at FFC was a concern as it showed a stronger than expected
warm nose closer to 700 mb, meaning CLT would be more likely to
stay rain longer into the evening. We will let the day shift have
another look at trends in that area. As for the rest of northeast
GA and Upstate SC, they say rain changing to snow is a sucker's
bet. It looks like it will just stay too warm in the boundary
layer for the better part of the event for anything but rain,
though some small accum is possible in the I-85 corridor closer
to daybreak Saturday if the precip holds on long enough. The only
caveat for the I-85 corridor will be precip rate. If we can get
a high enough precip rate, the melting level could be depressed
lower to the ground and we could see some periods of wet snow. But,
even if that happened, it would NOT be likely to accumulate.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 330 AM Friday: Models have come in much slower in the exiting
of moisture on Saturday. Despite losing low-level forcing and CAA
ramping up, models spit out some light QPF across the eastern half
of the CWFA after 12z Saturday, due to the coastal low deepening. In
the upper levels, forcing will still be quite strong, as a northern
stream shortwave phases with a southern stream wave as it enters the
base of the longwave trough. So with some moisture to work with, a
comma head precip shield will likely linger over at least the I-77
corridor thru late morning. Forecast soundings support precip
staying mainly all snow. Additional snow accums should be light,
generally 0.5" or less. It will remain cloudy to mostly cloudy into
early aftn, which with the combination of decent CAA, result in
chilly max temps. I have lowered them using the latest consensus to
the 30s to mid 40s, about 10-15 deg below normal.

With the deep trough axis swinging thru the mountains Saturday
night, a quick shot of moisture will accompany modest low-level
northwest flow. So scattered to numerous snow showers are expected
along the TN border, mainly Saturday evening, tapering off by
daybreak or not long after. Saturday night looks like the coldest
night so far this season, as arctic air filters in from the
northwest. It will feel especially brisk in the mountains with gusty
NW winds. Lows will be about 10 degrees below normal.

Sunday looks cold, but quiet with temps struggling to get into the
40s east of the mountains, despite mostly sunny skies. Melting snow
in the mountains and I-40 corridor may also limit max temps. Sunday
night will cold, but not quite as cold as Saturday night. Lows 6-8
degrees below normal.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 135 AM EST Thursday: the extended forecast begins 12Z Monday
with a dry northwest flow regime for our region under a broad upper
trof extending from the Rockies to the western Atlantic. At that
time, the next shortwave will be moving SE across the upper
Mississippi Valley.  The associated cold front arrives late Monday
night and is moving to the coast by late Tuesday morning. Northwest
flow snow begins along the NC and TN border areas early Tuesday with
trof axis crossing KY and height falls continuing for our area as
colder air drops down from Canada.  Forecast models in fairly good
agreement with axis of trof north to south over our area around 00Z
Wed.  GFS model ends NW FLow snow rather quickly after trof axis
passes while ECMWF continues snow into early Wed with lobes of
energy passing until about 12Z Wed.  Another cold front associated
with a quick moving shortwave will arrive on Thursday. Wednesday
should be the coldest day of the week with the deep trof passage
then a warm up of ten degrees on Thursday which will be just a few
degrees below normal. Monday would be the warmest day of the week
and even that day should have temps near or just below normal.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: Grim-looking aviation weather as flight
conditions are expected to deteriorate gradually this morning. Once
precip moves in from the south, we should see a steady progression
of the ceiling down through the MVFR category. The guidance
suggests that the ceiling will fall down to IFR around  15Z to
17Z and stay there, if it doesn't fall at least temporarily as a
precip band moves overhead, and right now I see no reason yet to
argue. Wind should come around to NE shortly and stay there for the
rest of the period. IFR ceiling will move/develop across most of
the area by late morning or early afternoon as the steadier precip
develops, and then will continue overnight probably falling down
into the low IFR category. The big concern later on in the fcst
will be the possibility of a mix/changeover to snow. The guidance
suggests that a mix could happen some time in the middle part of
the evening with a changeover late in the period, perhaps around
09Z. Elsewhere...suffice to say, as elevation increases, snow is
more likely, so KAVL should expect SN to be prevailing through
the entire period with a significant accum possible.

Outlook: Precip and associated restrictions will decrease during
the day Saturday, with dry conditions expected at all sites into
early next week. The possible exceptions would be KAVL/KHKY with
potential for northwest flow snow Saturday night.

Confidence Table...

            15-21Z        21-03Z        03-09Z        09-12Z
KCLT       High  81%     High  82%     Med   68%     Low   56%
KGSP       Med   70%     Med   75%     High  83%     Med   64%
KAVL       High  94%     High  85%     Med   70%     High  87%
KHKY       High 100%     High  83%     Med   66%     High 100%
KGMU       Med   76%     High  86%     High  85%     Med   63%
KAND       Med   76%     Med   65%     High  90%     Med   61%

The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Winter Storm Warning until 7 AM EST Saturday for GAZ010-017.
NC...Winter Weather Advisory until 7 AM EST Saturday for NCZ033-
     048>051-058-068-501>504-506-508-510.
     Winter Storm Warning until 7 AM EST Saturday for NCZ052-053-
     059-062>065-505-507-509.
     Winter Weather Advisory from noon today to 7 AM EST Saturday
     for NCZ035>037-056-057.
SC...Winter Weather Advisory until 7 AM EST Saturday for SCZ001>003.

&&

SYNOPSIS...DEO
NEAR TERM...PM
SHORT TERM...ARK
LONG TERM...DEO
AVIATION...PM

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
453 AM EST Fri Dec 8 2017

NCZ033-048>051-058-068-501>504-506-508-510-SCZ001>003-091000-
Avery-Madison-Yancey-Mitchell-Swain-Graham-Cleveland-
Caldwell Mountains-Greater Caldwell-Burke Mountains-Greater Burke-
Eastern McDowell-Greater Rutherford-Eastern Polk-Oconee Mountains-
Pickens Mountains-Greenville Mountains-
453 AM EST Fri Dec 8 2017

...WINTER WEATHER ADVISORY IN EFFECT UNTIL 7 AM EST SATURDAY...

This Hazardous Weather Outlook is for piedmont North Carolina,
western North Carolina and upstate South Carolina.

.DAY ONE...Today and Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Winter Weather Advisory.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

..Saturday...Winter weather likely. See the Winter Weather Advisory
for more information. Snow should taper off early Saturday morning.
..Sunday...No hazardous weather is expected at this time.
..Monday...No hazardous weather is expected at this time.
..Tuesday...No hazardous weather is expected at this time.
..Wednesday...No hazardous weather is expected at this time.
..Thursday...No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encourage to report snow and ice accumulations
to the National Weather Service.

GAZ010-017-NCZ052-053-059-062>065-505-507-509-091000-
Rabun-Habersham-Haywood-Buncombe-Northern Jackson-Macon-
Southern Jackson-Transylvania-Henderson-McDowell Mountains-
Rutherford Mountains-Polk Mountains-
453 AM EST Fri Dec 8 2017

...WINTER STORM WARNING IN EFFECT UNTIL 7 AM EST SATURDAY...

This Hazardous Weather Outlook is for northeast Georgia and western
North Carolina.

.DAY ONE...Today and Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Winter Storm Warning.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

..Saturday...Winter weather likely. See the Winter Storm Warning for
more information. Snow should taper off early Saturday morning.
..Sunday...No hazardous weather is expected at this time.
..Monday...No hazardous weather is expected at this time.
..Tuesday...No hazardous weather is expected at this time.
..Wednesday...No hazardous weather is expected at this time.
..Thursday...No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encourage to report snow and ice accumulations
to the National Weather Service.

NCZ035>037-056-057-091000-
Alexander-Iredell-Davie-Catawba-Rowan-
453 AM EST Fri Dec 8 2017

...WINTER WEATHER ADVISORY IN EFFECT FROM NOON TODAY TO 7 AM EST
SATURDAY...

This Hazardous Weather Outlook is for piedmont North Carolina.

.DAY ONE...Today and Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Winter Weather Advisory.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

..Saturday...Winter weather likely. See the Winter Weather Advisory
for more information. Snow should taper off early Saturday morning.
..Sunday...No hazardous weather is expected at this time.
..Monday...No hazardous weather is expected at this time.
..Tuesday...No hazardous weather is expected at this time.
..Wednesday...No hazardous weather is expected at this time.
..Thursday...No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encourage to report snow and ice accumulations
to the National Weather Service.

GAZ018-026-028-NCZ069>072-082-SCZ004>010-012>014-091000-
Stephens-Franklin-Hart-Lincoln-Gaston-Mecklenburg-Cabarrus-Union-
Greater Oconee-Greater Pickens-Greater Greenville-Spartanburg-
Cherokee-York-Anderson-Laurens-Chester-
453 AM EST Fri Dec 8 2017

This Hazardous Weather Outlook is for northeast Georgia, piedmont
North Carolina and upstate South Carolina.

.DAY ONE...Today and Tonight.

Winter weather possible. Rain may change over to snow
late this afternoon through tonight. Light snow accumulation of up
to an inch is possible north and west of I-85 tonight.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

..Saturday...No hazardous weather is expected at this time.
..Sunday...No hazardous weather is expected at this time.
..Monday...No hazardous weather is expected at this time.
..Tuesday...No hazardous weather is expected at this time.
..Wednesday...No hazardous weather is expected at this time.
..Thursday...No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encourage to report snow and ice accumulations
to the National Weather Service.

GAZ029-SCZ011-019-091000-
Elbert-Abbeville-Greenwood-
453 AM EST Fri Dec 8 2017

This Hazardous Weather Outlook is for northeast Georgia and upstate
South Carolina.

.DAY ONE...Today and Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

..Saturday...No hazardous weather is expected at this time.
..Sunday...No hazardous weather is expected at this time.
..Monday...No hazardous weather is expected at this time.
..Tuesday...No hazardous weather is expected at this time.
..Wednesday...No hazardous weather is expected at this time.
..Thursday...No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

ARK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
835 AM EST FRI DEC 8 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0834 AM     SNOW             MORGANTON               35.74N 81.70W
12/08/2017  E1.0 INCH        BURKE              NC   PUBLIC

&&

KRENTZ

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
838 AM EST FRI DEC 8 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0837 AM     SNOW             VALDESE                 35.75N 81.56W
12/08/2017  E0.5 INCH        BURKE              NC   PUBLIC

&&

KRENTZ

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
856 AM EST FRI DEC 8 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0848 AM     SNOW             CANDLER                 35.54N 82.69W
12/08/2017  M2.0 INCH        BUNCOMBE           NC   AMATEUR RADIO

&&

KRENTZ

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
859 AM EST FRI DEC 08 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0859 AM     SNOW             CANDLER                 35.54N  82.69W
12/08/2017  M2.0 INCH        BUNCOMBE           NC   AMATEUR RADIO

&&

WIMBERLEY

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
957 AM EST FRI DEC 08 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0956 AM     SNOW             5 W ROSMAN              35.14N  82.91W
12/08/2017  M2.0 INCH        TRANSYLVANIA       NC   TRAINED SPOTTER

&&

SBK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1000 AM EST FRI DEC 08 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0958 AM     SNOW             6 NW CLAYTON            34.94N  83.48W
12/08/2017  M2.0 INCH        RABUN              GA   TRAINED SPOTTER

&&

SBK