Area Forecast Discussion
Issued by NWS Blacksburg, VA

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934
FXUS61 KRNK 180010
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
710 PM EST Sat Feb 17 2018

.SYNOPSIS...
High pressure along the Mid-Atlantic Coast will shift off the New
England coast this evening into tonight. Low pressure in Tennessee
will rotate eastward tonight into Sunday. High pressure will build
into our region Sunday. Warm front will move north through the
area late Sunday night and early Monday providing clouds and a
period of rain.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 700 PM EST Saturday...

Winter weather advisories remain in effect until Midnight tonight
for light wintry mix.

Precip continues to steadily push into the region and will cross
completely through by midnight. Stray upslope showers of mixed
type precip will continue along the western ridges into the
overnight before dissipating completely by sunrise. Adjusted
Pops to better illustrate the movement of the precip band, but
no notable change to the QPF. Temperature trend continues to
follow a very non-diurnal pattern until late in the evening as
clouds look to begin clearing out, particularly in areas east of
the mountains.

As of 300 PM EST Saturday...

High pressure to our north providing enough colder air to result in
wintry mixture of snow, sleet freezing rain and rain for our region.
The greatest amounts of accumulating snow and sleet will occur
along and north of Interstate 64. Wet snow accumulations of 2 to
4 inches, with localized amounts up to 5 inches, mainly higher
ridges of the Alleghanys of Greenbrier and Bath counties and
northward. The best chances for freezing rain will occur along
the spine of the Blue Ridge mountain. Ice accumulations of a
light glaze to up to two tenths expected along the Blue Ridge
especially between Peaks of Otter and Fancy Gap. Temperature
profiles will be the key to precipitation type this evening into
tonight associated with low pressure center. In the north,
colder air will allow for a mix of snow/sleet to remain around
longer. The accumulating snow/sleet will be focus on the higher
terrain, with less in the valleys and sleet will cut into totals
as well. If there is a dramatic increase in QPF or stronger
push of colder air may need to adjust headlines this evening
into tonight. May need to monitor Greenbrier and Bath for
potential upgrade depending on intensity. In the northwest,
snow showers kick in behind the departing surface low off the
coast with high pressure building into the Mid-MS Valley.

For temperatures this evening into tonight, utilized an non-diurnal
temperature curve and went with a blend of Namdng and isc continuity
to capture the fall of temperatures with CAD and the rise of warm
air pushing into the west outside of the wedge. For pops and weather
utilized the Forecast builder with an ensemble approach with top
down tool. In any case, light wintry mixture will transition to
clearing east of the mountains overnight, and snow showers tapering
off by dawn in the west. Also, there could be some freezing drizzle
along the western slopes per model forecast soundings showing little
if any moisture in the snow crystal growth temperature zone. Added
some fog and drizzle to isc grids. This may need to be expanded
in AREAL coverage. Low temperatures tonight will range from the
mid 20s in northwest Greenbrier county to the mid 30s in the
Piedmont.

High pressure to our west will build east across our region Sunday.
This high pressure area will shift low-level thermal gradient at
least briefly southward. Kept some morning stratus in the western
mountains Sunday morning, then lift or burn off the clouds by Sunday
afternoon. High temperatures on Sunday will vary from around 40
degrees in the northern Mountains to the upper 50s in the Piedmont.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 300 PM EST SATURDAY...

Warm front will move north through the area late Sunday night and
early Monday providing clouds and a period of rain...QPF of a
quarter /0.25/ or less.  There may be a brief period of p-type
issues around daybreak Monday with potential for freezing rain
across Greenbrier and Bath counties, but confidence low and coverage
limited per forecast early morning temperatures in the 32-36
degree range, and not yeilding enough values of 32 degrees or
less to generate icing. Attm it appears clouds/rain will
overspread our southern CWA shortly after midnight, and reach
our northern CWA just before daybreak Monday, followed by
partial clearing Monday afternoon as the warm front moves north
of the area.

Tuesday we will be well into the warm sector with unseasonably warm
temperatures returning to the Mid-Atlantic States. An anomalous
ridge of high pressure will become established just off the
southeast Atlantic Coast, this feature resulting in very mild
temperatures throughout the southeastern CONUS.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 300 PM EST Saturday...

Synoptic pattern features a strong subtropical ridge of high
pressure parked along the southeast Atlantic Coast with 590+ heights
at 500 mb. Relative to climatology, this is 2 to 2.5 standard
deviations above normal.

This set-up favors much above normal temperatures for the Southeast
States with the baroclinic zone forced to reside on the west side of
the Appalachians from East Texas to the Ohio Valley and into the
eastern Great Lakes. Repetitive rainfall is likely within this
corridor during the second half of the week with our forecast area
far enough east of the boundary to escape anything significant.
Toward the end of the week, models hint that a surface front will
impinge on the forecast area, but overall weather conditions for mid
week feature above normal warmth and only a chance for showers
pending any instability within the warm subtropical airmass.

Temperatures Wednesday are expected to be 20-30 degrees above normal
with highs in the 60s/70s and lows in the 40s. Models suggest
potential for a backdoor front to impinge from the north-northeast
Thursday, so somewhat cooler/wetter conditions are favored for
Thursday.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 700 PM EST Saturday...

Flying conditions will continue to be poor to start the forecast
period. MVFR to IFR conditions are being observed across the
region as a band of precip crosses through. DAN and LYH stay
warm enough that any precip should fall as a cold rain. Other
locations are and will be susceptible to a hodge podge of winter
weather for the next several hours. Conditions overnight will
begin to become VFR in the east and then begin spreading west.
Lower clouds will linger until around sunrise for BLF/LWB. Weak
high pressure building into the region Sunday will maintain VFR
conditions through the duration of the forecast period.


Extended Aviation Discussion...

VFR returns Sunday evening into Sunday night under weak high
pressure. A warm front lifts back north into the area on Monday
with another round of sub- VFR ceilings and visibilities with
rain, especially mountains. High pressure strengthens offshore
resulting in a return to overall VFR Tuesday ahead of the next
cold front well west of the Appalachians. Scattered MVFR showers
are expected Wednesday into Thursday.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Winter Weather Advisory until midnight EST tonight for VAZ011-
     014-016>020-022>024-032>035.
NC...None.
WV...Winter Weather Advisory until midnight EST tonight for WVZ043-
     044-507-508.

&&

$$
SYNOPSIS...KK/WP
NEAR TERM...JR/KK
SHORT TERM...PM
LONG TERM...PM
AVIATION...JR/KK



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