Area Forecast Discussion
Issued by NWS Blacksburg, VA

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274
FXUS61 KRNK 200020
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
720 PM EST Sun Nov 19 2017

.SYNOPSIS...
Clouds and periods of snow showers will continue tonight in the
western flanks of the Appalachians in WV, with winds becoming
lighter as the evening progresses. High pressure settles into the
region on Monday into Tuesday with dry conditions and moderating
temperatures. A disturbance passing to our south wiLL lead to
increased clouds and light showers Tuesday night. The
Thanksgiving holiday looks dry with temperatures slightly below
normal.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 715 PM EST Sunday...

No significant changes to make at this time. Temperatures appear
to be on track as clouds linger across the Alleghanys, which
will gradually erode from the east over the next 4-6 hours,
leaving mostly clear conditions in place by morning. Winds have
fallen to 10 mph or less in most areas, but won`t decrease a
whole lot more overnight. Reduced threat for snow in western
Greenbrier down into the chance category from this point
forward. Otherwise, no significant changes.


As of 235 PM EST Sunday...

Post-frontal northwesterly flow regime in place across the
Appalachians, Blue Ridge and into the Piedmont this afternoon.
Breezy northwest winds are common everywhere this afternoon, with
gusts to 35 mph. The western slopes of the Appalachians in WV/VA are
the most plagued by upslope-forced stratus with periods of snow
showers. Temperatures in the cloudiest locations have been hovering
within a few degrees of the freezing mark. Much milder conditions
present across the Piedmont with temps having warmed into the 50s.
Broad cyclonic flow aloft with a secondary 500 mb vort max moving
into the Ohio Valley.

Aforementioned shortwave/vort max will progress across the forecast
area roughly through mid-evening, the 12z GFS closer to early
evening. This will serve to enhance ongoing area of intermittent
snow showers, reflected in higher-resolution CAM output from about
Bluefield northward to Quinwood/northwest Greenbrier County until
about midnight. There may be some lingering flurries after midnight,
though additional accumulations totaling up to 1.5". Further south
into the NW NC mountains, would expect only a few flurries early
this evening before air mass becomes too dry to support any
additional snow. In addition, moderately strong pressure rises
occuring early this evening should allow for a slight increase in
wind speeds and gusts, though forecast wind gusts should be sub-
Advisory levels maxing out at 40-45 mph at elevation. Winds should
begin to ease off areawide looking into the after-midnight hours.
Lows tonight are somewhat complicated, with the coolest areas in the
far west contending with clouds and winds and clearest/mildest areas
in the Piedmont also taking a deeper period of time this evening for
winds to abate. Will have cold advection throughout the night,
though temperatures may cool more slowly given the lingering winds.
Kept lows in the Piedmont to values just below freezing; with values
in the 20s from the Blue Ridge to the western slopes.

Much quieter weather expected for Monday with large high pressure
centering itself across the region. Will have a rather chilly start
with wind chills from the Blue Ridge west in the middle teens to
near 20. Looking at wall to wall sunshine which should help to push
temperatures from the lower 40s to the mid 50s. Temperature
advection trends neutral to weak warm advection late in the day, so
the shot of cold air is pretty short. Winds trend light through most
of the day, with a light west/southwest component developing late.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 245 PM EST Sunday...

Shortwave ridging will slowly weaken Monday night/Tuesday as surface
high pressure slides offshore in advance of both northern/southern
stream shortwaves within the split flow regime. These features still
remain just out of phase with only a couple solutions pulling enough
moisture north for showers Tuesday night as the southern surface low
passes off the Carolinas. Since the latest ensembles show a few
showers both across the east, and also northwest with the northern
piece of energy will keep in some low pops in spots Tuesday night.
High pressure following these systems to bring drier weather
including a quick punch of cooler air on brief gusty winds Wednesday
before the gradient diminishes by Wednesday night. Highs 50s to near
60 Tuesday before cooling back to 40s mountains and 50s east
Wednesday per cool advection. Lows mostly 20s/30s except mainly 30s
Tuesday night.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 200 PM EST Sunday...

Overall upper troffiness to prevail through the period with
reinforcing energy arriving next week that looks to carve out
an even deeper 500 mb cold pool. Will see low pressure develop
offshore the Carolinas later on Thanksgiving within split upper
flow early on but appears too far offshore for any showers at
this point. Otherwise should see mainly dry weather under weak
high pressure and overall below seasonal temps until a strong
cold front arrives Saturday. This front will again be followed
by colder temperatures next Sunday similar to this weekend.
Appears a few western rain showers possible ahead of the front
Saturday night, followed by western snow showers early Sunday,
but little more than low pops for now.

&&

.AVIATION /01Z MONDAY THROUGH FRIDAY/...
As of 645 PM EST Sunday...

Mainly MVFR conditions west of the Blue Ridge to VFR conditions
east of the Blue Ridge tonight, becoming VFR all areas by
daybreak Monday.

In the wake of the strong cold front that moved through the area
yesterday, a large area of surface high pressure will slide
across the southern states through Tuesday. This will keep a dry
westerly flow in place across our region through the TAF valid
period.

MVFR level or low end VFR upslope clouds (025-040 ceilings)
across the Alleghanys will gradually diminish overnight,
especially after midnight and all TAF sites should be VFR by or
shortly after daybreak, if not sooner. The Piedmont areas,
including ROA, LYH, and DAN, are expected to be VFR through the
TAF valid period. No restrictions to visibility are expected
through the period.

West to northwest winds will continue overnight, with speeds
continuing to diminish as the surface high slides east across
the Midsouth and into the Southeast U.S. Sustained winds of 8-12
kts with gusts of to around 20 kts can be anticipated through
the next few hours, but winds speeds are expected to be 10 kts
or less all areas by 06Z. Aviation interests should also be
aware of the wave clouds seen in satellite imagery and the
likelihood of associated turbulence especially just downstream
of the Alleghany front across southwest and west central VA.
Winds will continue to diminish during the day Monday as the
surface high draws closer to the area. Speeds will be mostly
10kts or less with the direction trending more toward the west
or west-southwest.

Medium to high confidence in ceilings through 14Z, then high
confidence in VFR ceilings all TAF sites through the TAF valid
period.
High confidence in VFR visibilities throughout the TAF valid
period.
Medium to high confidence in wind speed and direction throughout
the TAF valid period.

Extended Discussion...

Mainly VFR conditions are expected Monday night into Friday.
Exceptions would be some lower cigs with a front/trough Tue
night-Wed in the mountains, and again Thanksgiving. With the
flow aloft mainly northwest, no appreciable amounts of moisture
or expected through the Thanksgiving week.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.

&&

$$
SYNOPSIS...AL
NEAR TERM...AL/RAB
SHORT TERM...JH
LONG TERM...JH
AVIATION...AL/RAB



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