Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 162204
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
504 PM EST Tue Jan 16 2018

.SYNOPSIS...
A cold front will move through the region overnight into Wednesday
morning bringing measurable snow and very cold temperatures to
the area. High pressure will build into the region through the
weekend, along with dry weather and milder temperatures. A
potent cold front will cross the area on Monday, bringing a line
of moderate to heavy rain showers, some with very gusty winds.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 500 PM EST Tuesday...

Added Yadkin County to the Advisory, otherwise headlines and
maps unchanged.

A positive tilted trough draped over Ohio Valley southwest to
the Ozark, will slowly push a cold front over the region tonight
into Wednesday morning. This front will also be slowed by a
series of reflections developing along the front, tracking to
the northeast. The upper level trough will move over the mid
Atlantic region Wednesday afternoon pushing the front and snow
off the coast. Associated with this front will be snow, wind,
and cold temperatures/wind chills.

As the front drifted over West Virginia and western Kentucky
today, snow amounts ranged from 2 to 5 inches. Slightly lesser
amounts (2-4 inches) are expected in our extreme western
counties (Tazewell VA to Greenbrier WV) this afternoon into
tonight. Accumulating snow will taper to flurries during the
early morning hours Wednesday, ending as early as sunrise.

As the front moves to the Blue Ridge this evening, jet dynamics
develop south and east of the area overnight. This will create
a precipitation minimum over counties along the Blue Ridge and
foothills, where less than an inch of snow is expected. Snow is
expected to taper to flurries around sunrise, ending by late
morning.

Waves tracking along the front after midnight will bring
accumulating snow to the piedmont counties of south-central
Virginia and northwest North Carolina. Snow should taper to
flurries by late morning, ending by early afternoon.
Accumulations will range from 1- 3 inches.

For this forecast package, there are no changes to any
headlines. Advisories in the west and east for snow remain in
place through Wednesday morning. Unless the forecast changes
overnight, a special weather statement will be issued for
counties bordering the Blue Ridge for possible minor travel
impacts.

A tight pressure gradient develops behind the front, but until
clouds can clear, most of the strongest winds will remain above
3000 ft. As the inversion lowers towards morning across the
mountains, winds will blow 15-25 MPH with gusts up to 35 MPH
through the day. These winds will likely blow snow on to treated
roadways. Wind coupled with very cold temperatures will also
send wind chills values below zero across the higher elevations
to the single digits in the mountain valleys Wednesday morning.

Light southwest winds and more sun than previously expected
allowed temperatures to warm into the upper 30s to lower 40s
across the mountains. Temperatures over the foothills and
piedmont counties warmed into the 40s. Despite the warmer
temperatures, snow accumulations should not change much as
temperatures will drop due to evaporative cooling this afternoon
and evening. Cold air will enter the mountains overnight with
temperatures dropping into the 10F-20F range. Cold air will
continue to surge in during the day tomorrow. Mountain
temperatures may only warm 5F with highs ranging from 15F to
25F. Cold air will make it east of the Blue Ridge while
temperatures will only drop into the 20s. Downsloping winds and
sun in the afternoon should allow temperatures to warm into the
upper 20s to lower 30s Wednesday. Areas with a 2-3 inch snow
pack will be cooler by 3F-5F.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 130 PM EST Tuesday...

At start of Wednesday night, the center of the upper level
low/trough partially responsible for Tuesday night and
Wednesday`s snowfall, will be directly overhead. As its shifts
east overnight, gusty northwest winds will help maintain some
upslope snow showers and flurries over portions of southeast
West Virginia. However, the trajectory will be a little bit more
north than true northwest, so the impacts of the upslope will
not be maximized. Regardless, much drier air is progged to
quickly enter the region thus minimizing what uplsope there will
be.

During the day Thursday, the prevailing flow will back to the
west and the overall synoptic pattern will be a near zonal flow
across the area. This pattern will continue through Friday will
gradually increasing heights/temps as a shortwave ridge starts
to build over the central potions of the nation.

Temperatures will trend milder during this portion of the
forecast with readings averaging some five degrees above normal
by Friday.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 1215 PM EST Tuesday...

Heading into the weekend, an upper level trough will begin to
deepen over the Four Corners region and eject into the Central
Plains states, all while upper level ridging builds over our
part of the country. Concurrently, the low level temperature
profile will gradually warm as southwest flow warm air advection
is forecast. Also, moisture will increase across our region,
especially the western sections. The result will be a period of
increasing temperatures, with limited chances of precipitation.
Only the far western sections of the area will have mention of
some isolated showers both Saturday and Sunday afternoon. High
temperatures by Sunday are forecast to range from the mid to
upper 50s across the mountains with upper 50s to around 60
across the Piedmont.

Sunday night through Monday night, the Central Plains trough is
expected to close off, and lift rapidly northeast into and
through the Great Lakes region, and then into southeast Canada.
Its associate surface cold front is progged to progress through
our region Monday afternoon and evening. Anticipate a well
defined line of showers to cross the area during this time
frame, along with the potential for some gusty winds based upon
an associated 40 to 50 kt jet crossing the area both pre- and
post- frontal passage. It may be a scenario very gusty showers
crossing the, with decent cold air advection in the wake of the
system. A mix or change over to snow is expected in the west
Monday night. By Tuesday, the system is expected to east of the
region, with low level winds backing rapidly during the course
of the day, thus shutting off any northwest flow upslope in the
west early in the morning.

Temperatures Monday into Tuesday will trend cooler, but still
average about five to ten degrees above normal for this time of
year.

&&

.AVIATION /22Z TUESDAY THROUGH SUNDAY/...
As of 1230 PM EST Tuesday...

A positive tilted trough draped over Ohio Valley southwest to
the Ozark, will slowly push a cold front over the region tonight
into Wednesday morning. This front will also be slowed by a
series of reflections developing along the front, tracking to
the northeast. The upper level trough will move over the Mid
Atlantic region Wednesday afternoon pushing the front and snow
off the coast.

Ceilings are starting to lower in the far west (BLF-LWB), but
remain VFR. Ceilings will lower to MVFR in the far west by mid
afternoon and continue to stay until early Wednesday morning.
Ceilings lower to MVFR towards the Blue Ridge (BCB/ROA) this
evening then recover to VFR by morning. Piedmont counties
(LYH/DAN) to lower to MVFR by sunrise and rebound to VFR by mid
afternoon Wednesday. Snow may also reduce visibilities during
periods of MVFR ceilings.

Pressure rises behind the front will bring winds of 15-25 kts
with gusts up to 35 kt along elevations above 3kft. As inversion
lowers and skies become mostly clear, these winds will mix to
the lower elevations through the day Wednesday. Moderate
turbulence is likely along the Blue Ridge.

Extended Discussion...

Dry air will restore conditions to VFR by Thursday under high
pressure. VFR conditions should persist into the weekend with
warming temperatures. Moisture will return to west Sunday night
into Monday.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Winter Weather Advisory until 10 AM EST Wednesday for VAZ007-
     009-010.
     Winter Weather Advisory until 3 PM EST Wednesday for VAZ034-
     035-043>047-058-059.
NC...Winter Weather Advisory until 3 PM EST Wednesday for
     NCZ004>006-020.
WV...Winter Weather Advisory until 10 AM EST Wednesday for
     WVZ042>044-507-508.

&&

$$
SYNOPSIS...DS
NEAR TERM...PM/RCS
SHORT TERM...DS
LONG TERM...DS
AVIATION...RCS



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