Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 111430

Area Forecast Discussion
National Weather Service Blacksburg VA
930 AM 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 929 AM EST Monday...No significant alterations needed to
the going forecast; only minor change made was to increase warm
advection cloudiness into the mid-late afternoon hours in the
Greenbrier Valley and into the southern Shenandoah ahead of
Alberta Clipper system. Eastern extent of these clouds extends
into eastern Ohio and will continue to advance eastward as the
day progresses. Did increase high temperatures by a degree or
two as well. Many areas today should see sunny to mostly sunny
skies, and will help to erode the light snowpack seen in visible
imagery from the weekend`s snowstorm.

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 615 AM EST Monday...

Lower clouds eroding west of LWB at 11z, and expect VFR
conditions at all sites for the rest of the day. Some mid level
warm advection and moisture will bring mid and high clouds to
the Mid Atlantic region in the afternoon. Winds will also
diminish during the afternoon.

Late in the TAF period...ceilings will begin to lower as a
stronger short wave approaches out of the Ohio Valley. Expect
ceilings at KLWB and KBLF to remain VFR until after 06Z with
medium confidence, with some high end MVFR reaching BLF by the
end of this TAF period.

Extended Discussion...

The more prominent clipper moves in Tuesday with the passage of
a cold front and gusty winds behind it. MVFR to IFR snow showers
are expected west of the Blue Ridge Tuesday and Tuesday night.
Weak high pressure builds in Wednesday followed by another
weaker clipper Thursday. Overall mainly VFR during the Wed-Fri
time frame.




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