Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KRNK 122348
Area Forecast Discussion
National Weather Service Blacksburg VA
648 PM EST Thu Jan 12 2017
A cold front will approach the region from the west late
tonight into early Friday, then stall across northern North
Carolina Saturday before returning north as a warm front late
Saturday night. This front will then oscillate north and south
across the region into early next week keeping an unsettled and
wet weather pattern in place.
.NEAR TERM /THROUGH FRIDAY/...
-- Changed Discussion --As of 640 PM EST Thursday...
A slow moving cold front continues to make headway towards the
forecast region through the Ohio Valley. We are still
anticipating arrival in the western sections of the area around
or a little before midnight. The associated showers are not
expected to make much progress eastward into the forecast area.
The eastern extent is expected to be near a Alleghany, VA to
Radford, Va to Boone, NC line by daybreak Friday. Have adjusted
hourly temperatures, dew points and winds to reflect the latest
observations and expected trends through the evening.
As of 230 PM EST Thursday...
A quasi-stationary cold front over the Ohio Valley will track
to the southeast through the period. This front is expected to
move and stall across southeastern West Virginia Friday morning.
Farther north, this front is expected to move east of the
Appalachian Mountains then slides south across the central
Virginia Piedmont in the afternoon, possibly into northern North
Carolina by the evening. With the front mostly staying out of
the forecast area for the next 24 hours, we will continue to see
warmer than normal temperatures. tonight and tomorrow.
Overnight temperatures will run 3F to 8F warmer than normal with
readings in the mid 40s to lower 50s. Friday`s highs will vary
from the upper 40s to lower 50s near the front in southeastern
West Virginia to the mid to upper 60s across Southside Virginia.
These temperatures are 15F to 20F warmer than normal.
Precipitation chances will be limited to the vicinity of the
frontal boundary with a few stray showers coming across the
mountains in westerly flow. The best chances for showers will be
along western slopes of southeastern West Virginia tonight
through early Friday morning and southwestern Virginia Friday
morning to early afternoon. No rain is expect to fall east of
the Blue Ridge. Since the region is expecting warmer than normal
temperatures through the period, all precipitation will fall as
Breezy conditions this afternoon are in response to a wave of
low pressure tracking along the front in the Ohio Valley. These
winds will decrease starting this evening evening as this wave
tracks northeast into New England this evening.
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.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As OF 243 PM EST Thursday...
Lift increases over the top of the wedge Friday night. This
brings an increasing chance for precipitation, and as the cold
wedge continues to build some freezing rain and possibly sleet
is expected to develop from the mountains of SE WV north of I-64
east to the Blue Ridge north of Roanoke. Still looks like a low
qpf event, so no more than advisory impact will occur and
mainly on the east/northeast sides of slopes into valleys. Will
continue to highlight in the HWO. Will see cold air slowly erode
Saturday with all places seeing plain rain, though higher
percentage will be west of the Blue Ridge. Another weak wave
moves across the southern Appalachians Saturday night with weak
wedge, so rainfall still around for the west with less chance
east. Another strong high will wedge in for Sunday and Sunday
night. At this time it looks like just a chance of rain for
everyone but temperatures trends will be monitored closely.
.LONG TERM /MONDAY THROUGH THURSDAY/...
As OF 220 PM EST Thursday...
Wavy front across the area Monday morning lifts north into New
York Tuesday as strong upper low moving across the central U.S.
amplifies ridge downstream. Will see less threat of showers
Monday but still looks cloudier, though some sunshine should
peek out. Warm air will stick around into midweek with models
slowing the front moving into the CWA until late Thursday into
Friday. Decided to keep pops low Tuesday with mainly dry in the
foothills/piedmont then chance pops start Wednesday with better
threat Thursday. Highs running about 10- 20 degrees above normal
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
As of 555 PM EST Thursday...
Deeper moisture now slowly returning to the far western
locations just ahead of a weak cold front that should pivot
southeast into the area later tonight. Expect some of this
cloudiness to make for a return to MVFR cigs at KBLF/KLWB this
evening and perhaps KBCB/KROA before midnight. Narrow band of
showers along the front should also work into the southeast West
Va sites as well prior to midnight but likely light with mainly
VFR to high end MVFR restrictions possible. Still appears that
strong westerly flow aloft will allow for less deeper moisture
to push across the mountains so maintaining VFR cigs further
east at KLYH/KDAN overnight for now. However latest ensembles
including the HREF show some fog development in the east where
clouds will be less and winds lighter. This primarily around
KDAN but cant totally rule out at KLYH late tonight into early
Friday as the front arrives. Otherwise keeping in some LLWS
mention in spots where winds look to be lighter this evening
given the strong jet aloft.
Cold front pushes well to the south during Friday with strong
high pressure slowly building in from the north. This may allow
for some drying and improvement in conditions to take place
espcly along the KLWB-KLYH corridor in the morning before
moisture starts to return later in the day. Otherwise most
recent guidance suggesting that most will stay locked into MVFR
cigs for much of the day with potential pockets of fog around if
clouds lock in sooner so something to watch. This looks moreso
around KBLF given upslope flow where could bounce around in IFR
at times, while KDAN may stay VFR before lowering to MVFR later
in the afternoon. Do expect cigs to once again lower to more
widespread sub-VFR by Friday evening with some spotty
showers/rain possible near KBLF.
Medium confidence in cigs throughout the TAF valid period.
Medium to low confidence in vsbys throughout the TAF valid
period. Medium to high confidence in wind dir/spd throughout the
TAF valid period.
Extended Aviation Discussion...
Low level moisture will then arc back north Friday night into
Saturday, maintaining the threat for additional sub- VFR in low
cigs/fog, along with light rain and/or drizzle, including
possible patchy freezing rain across the northern Blue Ridge.
Unsettled weather will continue into Sunday with some slow
improvement in conditions as high pressure weakens to the north
leaving the residual weak front near the area. However given
uncertainty appears mainly MVFR to prevail under passing showers
as the boundary likely oscillates across parts of the region.
Southerly flow aloft will develop Monday ahead of a frontal
system in the Central Plains with continued MVFR as the low
level wedge redevelops while helping keep low clouds in place.
Appears enough warm advection just ahead of the front at this
time to help return much of the area to mainly VFR Tuesday with
perhaps spots across the northwest clinging to sub-VFR a while