Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 201209

Area Forecast Discussion
National Weather Service Blacksburg VA
709 AM EST Sat Jan 20 2018

High pressure aloft and at the surface will build over the
region into early Monday. Temperatures will continue to moderate
from the recent Arctic cold as this occurs. A strong system will
move from the Midwest into the Ohio Valley through Monday,
passing through our region Tuesday. Widespread showers and gusty
winds are expected to accompany this weather system, followed by
much colder temperatures and mountain snow showers into midweek.


As of 415 AM EST Saturday...

Quiet weather expected today and tonight with a continued
warming trend. Primarily a cloud and temperature forecast.
Remnant Arctic high that brought our most recent cold
temperatures was drifting slowly east off the southeast U.S.
coast. Return moisture was tracking from the Gulf through the
Midsouth and into the Ohio Valley, including adjacent West
Virginia, up the west side of the Alleghanys. Models generally
hold most of these clouds to our west, but could see some
creeping as far east as JFZ, BLF, and HLX at times. Eastern
sections should remain mostly clear again today. 850mb
temperatures average around +8C across the region today, warming
toward +10C by Monday.

Clouds may temper max temperatures in the west a bit, while
remnant snow cover from 1-4 inches eastern sections should hold
temperatures down a few degrees from what otherwise would be
expected. Leaned toward the cooler GFS/ECMWF for temperatures
and undercut eastern areas 2-3F degrees today and 1-2F degrees
for min temps Monday.

Otherwise, look for a nice day with high temperatures in the 40s
and 50s and lows tonight around freezing to near 40 with mainly
west to southwest winds 5-10 mph.


As of 300 AM EST Saturday...

The upper pattern will be in transition as a large closed low over the
midwest opens up and moves into New England early next week. So aside
from a slight chance of showers far west of the Blue Ridge for the
first part of Sunday, the Appalachians and central mid Atlantic region
will have fair but breezy conditions through the first part of Monday
with temperatures well above normal.

By Monday afternoon the chance for showers will be increasing in the
mountains later in the day as a strong cold front approaches from the
west. Guidance continues to advertise the front with a good deal of
dynamic support, being driven by low pressure moving through the Great
Lakes. The front is expected to be accompanied by widespread rainfall
though lapse rates are not impressive and surface based instability is
largely absent so chances for thunder look quite low. However, the low
level wind field amplifies considerably and there is very healthy shear
along the front so embedded convective elements may be able to mix down
strong wind gusts without thunderstorms. While the likelihood of this
is not great due to the lack of instability, the possibility can not be
dismissed due to the energetic nature of the system.

The front crosses the region Monday night with precipitation tapering
off to lingering upslope showers west of the Blue Ridge on Tuesday.
Winds behind the front will become quite gusty through Tuesday night
and a wind advisory may be necessary. Also, with colder air moving in
behind the front some wet snowflakes are possible at the higher
elevations west of the Ridge. The lingering upslope snow showers will
persist into Wednesday morning.


As of 200 PM EDT Friday...

Overall airmass behind the cold front is not that cold as it has a
Pacific origin, so not an arctic blast. Temperature start to rebound
late in the week as we dry out with surface high building in from the
TN Valley midweek, and off the VA coast by Friday.


As of 700 AM EST Saturday...

VFR conditions will prevail through the TAF valid period for
areas east of the Blue Ridge. In fact through much of the TAF
valid period these areas will be SKC, including KROA, KLYH, and
KDAN. Further west, low-level moisture was tracking from the
Gulf around the west side of the remnant Arctic high lingering
over the southeast states. Ceilings were mostly MVFR in these
areas, with KBCB still several hours east of the MVFR ceilings

Little change is expected through the day. The low clouds will
gradually spread further east from their current edge location
near the VA/WV border eastward toward the I-81 corridor by
evening. Ceilings will remain mostly in the 020-030 range
through the day, then drop into the 010-020 range after 00Z,
with the exception of higher terrain, such as KBLF, which will
see IFR-LIFR ceilings in the 003-005 range.,

Visibilities are expected to be mostly VFR through the TAF valid
period. However, if the ceilings drops below 005 at KBLF, MVFR
visibilities in fog/mist will be possible.

Winds will be WSW-WNW through the TAF valid period at speeds of
7-12kts with low end gusts 20-25kts, mainly along and west of
the Blue Ridge. Winds will diminish to less than 10kts after

With strong winds aloft on the west side of the high, some LLWS
will be present, especially this morning until the air becomes
better mixed and the strong winds come down closer to the
surface as noted in the paragraph above.

Medium confidence in ceilings through the TAF valid period.
Medium to high confidence in visibilities through the TAF valid
Medium to high confidence in wind speed/direction through the
TAF valid period.

Extended Discussion...

Low clouds may linger much of the weekend west of the Blue Ridge
with associated MVFR ceilings. Mostly VFR conditions are
expected across the Piedmont.

Sub-VFR conditions will start to return to the entire area
Sunday night into and through Tuesday night as a cold front and
its associated precipitation moves through the region. Strong
convective showers are expected with this weather system,
including a potential QLCS and isolated thunderstorms.

Very gusty northwest winds return to the area Tuesday night
into Wednesday on the backside of the departing system.
Lingering sub-VFR conditions possible across SE WV thanks to
strong upslope flow and residual low level moisture.


As of 325 PM EST Friday...

NOAA Weather Radio, WXL60 (Roanoke Transmitter) which
broadcasts at 162.475 MHz remains off the air. The phone company
reported that the circuit line had been cut and will take until
Monday January 22nd to fix it.




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