Area Forecast Discussion
Issued by NWS Blacksburg, VA

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833
FXUS61 KRNK 180157 AAA
AFDRNK

Area Forecast Discussion...UPDATED
National Weather Service Blacksburg VA
857 PM EST Wed Jan 17 2018

.SYNOPSIS...
Low pressure offshore will continue to move northeast and away
from the area overnight bringing any added snowfall to an end.
High pressure over the Central and Southern Plains will move
into the Gulf Coast region by late Thursday. Temperatures will
moderate over the weekend ahead of the next low pressure system
approaching the eastern United States on Monday.
&&

.NEAR TERM /THROUGH THURSDAY NIGHT/...
As of 854 PM EST Wednesday...

Light snow persists over the far southeast this evening associated
with complex surface low pressure offshore and the residual upper
low that remains about overhead. However starting to see the snow fade
as drier air works in from the north so will let the winter storm
warning expire at 9 pm with deeper moisture exiting per the latest
HRRR. This to be replaced by an advisory for black ice across the
remainder of our North Carolina counties and a SPS elsewhere for the
overnight. Expect subsidence to finally win out across the east with
skies clearing after midnight while lingering low clouds over the
northwest likely persist under northwest flow but should gradually fade
as well late as the column dries. Moisture appears too shallow
for much added snow other than flurries far northwest so
basically going dry with clearing overnight. However the
clearing over expansive snow cover will allow temperatures to
fall more than expected with some spots likely at or below zero
espcly valleys despite continued mixing. Appears winds will stay
up enough to even support expanding the wind chill advisory east
to include Roanoke and points along the eastern slopes where
thresholds are higher than the western zones. May be close to
wind chill warning criteria as well over the western higher
elevations but not enough coverage to upgrade at this point.
Otherwise bumped down lows a good category or two since already
near forecast lows in spots attm.


Previous discussion aS of 318 PM EST Wednesday...

Winter Weather Advisories were posted for Black Ice in western
North Carolina until noon on Thursday.

Winter Weather Warnings remain in effect for Eastern portions
of forecast area until 9 pm.

Wind Chills Advisories are in effect for the western mountains
into Thursday morning.

The upper trough will drift east across the region this evening and
off the coast later tonight into Thursday morning. The associated
surface front will track east into the Atlantic ocean. Good low
level moisture convergence and lift will continue bands of snow in
the east this afternoon into tonight. Snow will taper off this
evening into tonight from west to east. Used a blend of the HRRR,
Conshort and Nam for pops and weather this afternoon into tonight.
Low temperatures will range from the single digits in the mountains
to the mid teens in the Piedmont. Minimum temperatures tonight may
need to be lowered to account for the fresh snow cover. The
combination of winds and temperatures will produce low wind chills
values overnight into Thursday morning in the mountains. The melting
and freezing of snow will result in black ice across potion of
western North Carolina. The rest of the state of North Carolina may
need a black ice advisories also tonight into Thursday morning where
such advisories are issued.

The upper low will continue to travel east Thursday into
Thursday night. Very cold Arctic high pressure across the
Southern Plains will build east Thursday into Thursday night.
Winds will diminish fairly quickly during the day Thursday as
high pressure builds in from the southwest. With the warming at
850mb and near full sunshine, High temperatures will vary from
the mid 20s in Northwest Greenbrier county to the lower 40s
along the southern Blue Ridge.

Under mostly clear skies with a snow pack, Low temperatures Thursday
night will be cold with readings from the single digits in the
mountains to the lower 20s in the Piedmont.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
As of 318 PM EST Wednesday...

High pressure will travel east across the Southeast States Friday
into Friday night. This will result in a warming trend as flow
become southwest. 850mb temperatures will be in the 0C to +5C range.
With bright sunshine and west winds, high temperatures will
warm into the lower 409s in the west to the lower 50s in the
east. Low temperatures Friday night will generally be in the
lower 20s to near 30 degrees.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 235 PM EST Wednesday...

Little change this period with high pressure heading east late in
the weekend. An upper trough over the Gulf Coast states and return
flow may bring a few showers Sunday morning to the mountains of
WV/Far SW Va.

We stay warmer than normal ahead of a deep trough/closed low moving
across the central U.S. Monday which then sends a front across us
Tuesday with a threat of showers. Colder air behind it may bring a
few snow showers to the mountains of WV, but temps behind this
system are not as cold as the pattern we are in now.

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
As of 610 PM EST Wednesday...

Flying conditions will slowly improve from west to east this
evening as the final band of snow heads east across KLYH/KDAN
over the next couple of hours before exiting. In the wake of
this band, will see conditions quickly transition to VFR with
only scattered to broken strato-cu. Only exception will be
across the far western ridges where sub-VFR may linger around
KBLF and perhaps redevelop at KLWB this evening. KLYH,and KDAN
may again see visibility fall in MVFR or IFR until the band of
snow passes allowing visibilities to improve.

There may also be a brief period of upslope snow showers in
southeast West Virginia between 00Z/7PM and 06Z/1AM. Winds will
also be gusty in the mountains from the northwest with gusts of
20 to 30 knots. High pressure finally builds in late tonight.

High pressure will result in VFR conditions for all taf sites on
Thursday.


Extended Discussion...

Dry air will and high pressure will cover the region Thursday
afternoon through Sunday. VFR conditions are expected as well
as warming temperatures. Moisture will return to west Sunday
night into Monday with sub-VFR conditions possible ahead of
another cold front. VFR conditions should return on Tuesday.

&&

.EQUIPMENT...
As of 245 PM EST Wednesday...

NOAA Weather Radio, WXL60 (Roanoke Transmitter) which broadcasts at
162.475 MHz remains off the air. Telephone company will be working
on this and hope to have it back up by Thursday afternoon.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Wind Chill Advisory until 10 AM EST Thursday for VAZ007-
     009>020-022>024-032>035.
NC...Wind Chill Advisory until 10 AM EST Thursday for NCZ001-002-
     018.
     Winter Weather Advisory until noon EST Thursday for NCZ001>006-
     018>020.
WV...Wind Chill Advisory until 10 AM EST Thursday for WVZ042>044-
     507-508.

&&

$$
SYNOPSIS...AMS/JH/KK
NEAR TERM...JH/KK
SHORT TERM...KK/WP
LONG TERM...WP
AVIATION...AMS/JH/KK
EQUIPMENT...PM



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