Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Remove Highlighting --
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FXUS61 KRNK 152327
Area Forecast Discussion
National Weather Service Blacksburg VA
627 PM EST Wed Feb 15 2017
A cold front will continue to progress from the Blue Ridge
eastward into eastern Virginia and North Carolina early tonight,
with high pressure building in behind the front. Gusty
northwest winds are expected for areas from the Blue Ridge
westward tonight into Thursday, with the strongest winds
expected along the southern end of the Blue Ridge into the North
Carolina mountains. A period of brief upslope snow showers are
also possible in the favored upslope areas in southeastern West
Virginia. The shot of cooler air is brief and temperatures again
begin to rebound on Friday ahead of the next storm system for
the latter part of the weekend.
.NEAR TERM /THROUGH THURSDAY/...
As of 313 PM EST Tuesday...Cold front extending along the Blue
Ridge continues to advance eastward this afternoon. Its main
notable affect is a sharp drying in surface dewpoints and a wind
shift to northwest. 500 mb cyclonic gyre associate with phased
northern and southern streams remains in place across most of
the Northeast, mid-Atlantic into the central Appalachians.
For Tonight: As high pressure ridge is building into the
region, an increase in northwesterly wind gusts already evident
mainly for areas along/west of the Blue Ridge. These wind gusts
should only continue to increase as the evening progresses.
Compared to prior post frontal wind events, 6-hourly pressure
rises are not particularly strong (around 4-5 mb), low-level
inversion heights are fairly high and 850 mb winds are only in
the 45 kt neighborhood off the 12z GFS. After collaboration with
surrounding offices and with winds already having started to
increase, opted to issue a Special Weather Statement for sub-
Advisory winds for locales along and west of the Blue Ridge
through 15z. General expectation is for wind gusts to 45 mph -
and may at times approach Advisory criteria - for the southern
Blue Ridge tier of counties (Watauga/Ashe/Alleghany NC up
through Roanoke VA), with peak gusts to 40 mph for the rest of
the area. The peak winds should occur roughly at two points: one
later tonight accompanying the strongest pressure rise, and
again into the mid-morning due to mixing. Increasing low-level
moisture plunging southward from the Great Lakes as seen on
visible imagery should allow for variable cloud cover and
chances for snow showers primarily for western Greenbrier
County. However the best moisture still is further to the north,
and so I`ve shown forecast snow amounts to be an inch or less.
While conditions for the Virginia/North Carolina foothills and
Piedmont areas are locally milder in the upper 20s, it stands to
be rather chilly tonight along/west of the Blue Ridge where
lows are projected to drop into the upper teens to mid 20s.
Given that winds will be higher in these western areas, wind
chills in the upper single digits to low teens are anticipated
by early morning.
For Thursday: High pressure remains in control with 1000-500 mb
thermal trough overhead. Pertaining to winds, since low-level
wind fields trend lower as we progress into the afternoon, wind
gust magnitudes should begin to lower in turn during late
morning into the afternoon hours. However it still will be
rather blustery due to mixing. Guidance suggests that we`ll
still have some leftover upslope cloudiness but that snow
showers do begin to taper off by mid-morning. Temperatures west
of the Blue Ridge/NC mtns are expected to be very slow to rise
(highs only mid/upper 30s to near 40), with downsloping aiding
to push highs into the mid/upper 40s along and east of the Blue
Ridge into the Piedmont.
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 313 PM EST Wednesday...
In a progressive split flow regime, we will transition from
being under the influence of a northern stream trof to a
southern stream ridge as we head into the weekend. This will
bring warmer temperatures and generally quiet weather through
Surface high pressure will slide off to our east Thursday night
and push a warm front through the region as a nice pulse of
short wave energy swings through aloft. While there is a good
amount of associated moisture and isentropic lift, it looks like
any flurries Thursday night into Friday morning will remain off
to our north. Ridging aloft will support a weak high pressure
at the surface with dry weather through most of Saturday.
However, the ridge axis will move east of the region later on
Saturday and allow an approaching upper trof with a weak surface
low reflection off the coast to bring a chance of showers back
to the forecast for late Saturday into Saturday night.
Temperatures will trend from above normal to much above normal
as highs on Saturday reach the mid to upper 60s east of the Blue
Ridge, with mid 50s to around 60 degrees more common to the
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 313 PM EST Wednesday...
We will continue to reside in the southern stream of a progressive
split flow regime through the first part of next week with temperatures
well above normal. Lingering effects from a departing upper trof will
keep a chance of rain showers west of the Blue Ridge through Sunday.
Ridging aloft and high pressure at the surface will then bring dry
weather into Tuesday. However, the ridge will start to flatten and may
allow a low moving through the Great Lakes region to push a front into
the region with a few showers possible mainly across the Alleghany
Highlands into southeast West Virginia. Guidance solutions then start
to diverge for midweek in handling development of a southern stream
closed low along the Gulf coast and potential for wedge pushing down
with a backdoor front on Wednesday. Believe a blended approach is the
best course of action and will indicate a slight chance/chance for
showers to cover the situation Wednesday.
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --As of 627 PM EST Wednesday...
VFR conditions will prevail this evening into tonight, SCT to BKN
MVFR clouds will move into the western mountains after 02z Thursday.
Overnight, moisture from the Great Lakes will be forced upslope and
result in MVFR Ceilings. The two taf with the potential of MVFR
ceilings will be KBLF and KLWB. MVFR clouds in the west will
continue until around mid-day Thursday. Gusty northwest winds will
continue tonight into Thursday afternoon, gusting the strongest at
BLF and ROA (potential of 30-32 kts). Given the strong wind field,
pilots show watch for turbulence in/around the ridgetops due to
mountain waves Thursday.
Extended Aviation Discussion...
Ceilings begin to improve to VFR all terminals late Thursday
afternoon. While winds will continue to be rather gusty,
anticipate a diminishing trend to northwesterly sustained wind
and gusts during the overnight hours on Thursday.
Generally VFR overnight into early Friday, perhaps briefly
falling to an MVFR ceiling at BLF and LWB as a shortwave trough
rotates southeastward. Next potential for sub-VFR conditions
is not until later Saturday as a disturbance moves in from the
Deep South producing showers. Lower ceilings may linger into
Sunday across BLF and LWB, but becomes VFR Sunday night through
Monday. Drier weather will prevail Monday night into Tuesday.
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