Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 111756

Area Forecast Discussion
National Weather Service Blacksburg VA
1256 PM EST Mon Dec 11 2017

High pressure will bring a brief period of fair weather to the
Appalachians and central mid Atlantic region to start the
work week. However, low pressure moving through the Great Lakes
region will push another surge of very cold air into the region
on Tuesday with blustery conditions and snow showers in the


As of 1256 PM EST Monday...Overall forecast holding up well,
and have made no significant changes to the forecast attm.

Previous discussion issued at 245 AM follows...

Not too much change from previous forecast for this period with
upslope cloudiness expected to erode by dawn or shortly thereafter.
Today will likely be the warmest day this week with temperatures
rising into the 40s, maybe close to 50 in the southeast CWA.

Clouds increase tonight ahead of shortwave/clipper front seen on
water vapor this morning over the northern Plains. Most model
solutions show light precip arriving by dawn in the far west along
the front, with main sfc low and better lift staying north over the
Ohio Valley. With clouds tonight will see low temperatures close to
normal with upper 20s to lower 30s.


As of 255 AM EST Monday...

Looking at strong cold air advection behind front Tuesday with
temperatures starting out steady or slightly warming in the west in
the lower to mid 30s, with mid 40s east, then temperatures should
crash into the 20s by late afternoon. There will be a burst of winds
behind this front with gusts to advisory levels likely in the higher
terrain of the Blue Ridge and Alleghanys, but coverage at the moment
is borderline in terms of issuing headlines. Since its 3rd period
will let next shift re-evaluate it. Will mention in the HWO.

Will see snow shower machine kick in shortly thereafter in the
mountains with best upslope and upper support occurring late Tue
afternoon into late Tue night. Could see 4-6 inches on the western
slopes of Greenbrier by Wed morning with 1-3 inches to southern WV
near Bluefield, and possibly the NC/TN border mountains into Mt
Rogers, with a dusting as far east as the Alleghanys to New River

As this trough deepens should another period of stronger wind
Tuesday night and Wednesday. In addition, temperatures falling into
the lower teens in the mountains, combined with wind speeds should
send wind chills below zero in the mountains, and single digits to
around zero in the foothills/piedmont Wednesday morning.

Will see axis of trough accelerate east Wednesday with snow showers
ending early. Still cold with highs in the 20s west to lower to mid
30s east.

By Wed night, next clipper enters the TN valley with increasing
clouds with maybe a few snow showers reaching the mountains by dawn.
With flow turning more west and some warm advection ahead of clipper
lows should will be in the mid teens to around 20 west, to lower 20s
east, with potential for some rise in temperature late.


As of 340 PM EST Sunday...

Upper air pattern is forecast to remain amplified with a cold
upper level trough over eastern North America through Friday.
Embedded short waves passing through the general flow pattern
will result in clouds and potential for mountain snow showers
and flurries. Temperatures will favor the colder side of normal
until Friday...trending back closer to normal for the weekend
as the upper flow becomes more zonal.


As of 1256 PM EST Monday...

VFR through at least 06z, though ceilings will steadily lower
from west to east, especially into the evening/overnight hrs.
Winds southwest 4-8 kts.

We`ll then expect deterioration in flight categories as
approaching Alberta Clipper and shot of modified Arctic air
introduces periods of MVFR to LIFR snow showers, along with
gusty northwest winds. These conditions are more likely west of
Roanoke along the southern Blue Ridge in NC up into
southeastern West Virginia. May see a period of short-duration
snow squalls associated with the Arctic frontal passage between
11-14z at Bluefield, Lewisburg and perhaps Blacksburg. Ceilings
expected to drop to sub-VFR levels by early morning along and
west of the Blue Ridge. VFR conditions expected away from the
mountains, with gusty post-frontal northwest winds developing.
Sustained winds between 10-15 kts with gusts up to 30 kts,
highest at Roanoke.

Extended Discussion...

A continuation of MVFR to IFR snow showers are expected west of
the Blue Ridge through Tuesday night. Weak high pressure builds
in Wednesday followed by another weaker clipper Thursday that
passes to our north.

Into Friday, potential for a stronger clipper system to re-
energize off the Atlantic coast, inducing a period of sub-VFR
with light to moderate snow.

Conditions then trend VFR for Saturday.




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