Area Forecast Discussion
Issued by NWS Blacksburg, VA

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641
FXUS61 KRNK 091501
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
1001 AM EST Sat Dec 9 2017

.SYNOPSIS...
Upper disturbance moves from the Mid Mississippi Valley overhead
today bringing another round or two of snow to the area. This
system lifts northeast this afternoon, then another
disturbance/clipper rotates into the area tonight with windy
conditions and mountain snow showers. Weak high pressure builds
in briefly Monday before clipper arrives Tuesday.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 1000 AM EST Saturday...

No changes to advisory or warning this morning. Light snow
continues to fall in deformation zone fueled by upper divergence
associated with brisk upper jet. Expect this band to slowly
migrate eastward through the region today and produce another 1
to 3 inches of accumulation before everything winds down to
lingering flurries by mid/late afternoon.

Previous discussion...

Upper flow per WV loop showing deeper moisture/convection off
the NC coast with some drying moving across the NC
piedmont/foothills. This also depicted well on radar. Northern
stream shortwave digging across the midwest looks to finally try
to phase with the southern shortwave over the mid-MS Valley
tonight over Virginia, but by then the main sfc low will be off
the coast of New England. However, the southern stream shortwave
and jet dynamics will interact with the coastal system allowing
for 1-2 more bands of snow to fill back in over the forecast
area by today with most high-res models favoring this taking
place between 7am-4pm which is when our winter weather headlines
expire. Should see another 1 to 3 inches, with higher amounts
along/near the Blue Ridge, with potential for 1-3 inches into
the I-81 corridor. No changes to the headlines at this time.

Temperatures today should be held down again by precip/clouds so not
showing much rise from this mornings readings and undercutting MOS
by a couple-4 degrees, with highs in the upper 20s higher ridges to
lower to mid 30s elsewhere.

Should see snow tapering off in the west early this afternoon and in
the piedmont by dark. The northern stream shortwave will dig across
the southern Appalachians tonight with bringing a good shot of
upslope snow showers along with windy conditions as it passes. Local
wind study suggests near advisory level wind gusts likely in
the higher mountains of NC into Mt Rogers VA. However, showing
little coverage so at the moment no wind headlines will be
hoisted, but could see it happening after we get past this early
snow event.

Snowfall from the upper wave and clipper will mainly be in the 1-2
inch range on the higher ridges of NC/SW VA and SE WV with isolated
3-4 inches possible in western Greenbrier. Per collaboration with
WFO RLX and GSP will not put an advisory out for this with this
morning package.

This shortwave pushes east fast so looking at snow showers ending in
the far west by dawn-10am Sunday. However, cold air remains.
Tonight`s lows will range from the upper teens to around 20 west, to
lower to mid 20s east.

Sunday will stay 10-15 degrees cooler than normal with highs in the
lower 30s west, to upper 30s east.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 300 AM EST Saturday...

Changes were not made to this period due to busy near term
weather.

Previous valid discussion from Friday afternoon...

Flurries may linger into the mountains thru Monday. Somewhat
blustery conditions look to continue through the first part of
next week as the wind field remains energized by numerous short
waves zipping through fast upper level flow.

Temperatures will remain well below normal into the first part
of next week. Many locations will see departures of 10 to 15
degrees below seasonal norms.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 100 PM EST Friday...

Amplified upper pattern featuring a western ridge and eastern
trof will persist through next week, though some deamplification
looks to occur toward the end of the week. The main storm track
will keep areas of low pressure moving from the Great Lakes
into New England with trailing cold fronts pushing reinforcing
shots of cold air into the Appalachians with occasional bouts of
snow showers west of the Blue Ridge. The fast moving pattern
will also keep a good amount of energy in the low level wind
field with blustery conditions through the period.

With little change to the cold pattern in place, expect
temperatures to remain well below normal through the upcoming
week.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
As of 615 AM EST Saturday...

Cigs/vsbys will drop to IFR at times in snowfall this morning as
upper level disturbance and associated jet stream across.
Appears lower vsbys will occur at BCB/ROA around 12-15z, in the
DAN/LYH in the 14-18z time frame with improvements in cigs/vsbys
this afternoon. BLF/LWB could have a minor window of lower
cigs/vsbys but should increase to VFR by 17z.

Upstream clipper arrives this evening and will bring snow
showers/flurries to BLF/LWB overnight with gusty winds as far
east as Roanoke. Cigs should stay VFR, except BLF/LWB which
expecting MVFR after 05-07z.

Extended Discussion...

Strong northwest winds will continue into early Sunday.

VFR conditions then return Sunday evening through Monday. Next
chance for sub-VFR conditions is with a clipper system Tuesday,
particularly in the western mountains. These sub-VFR could
linger into Wednesday as northwest flow continues.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Winter Weather Advisory until 4 PM EST this afternoon for
     VAZ009-012>014-022>024.
     Winter Storm Warning until 4 PM EST this afternoon for
     VAZ015>017-032>035-043>047-058-059.
NC...Winter Storm Warning until 4 PM EST this afternoon for
     NCZ001>006-018>020.
WV...None.

&&

$$
SYNOPSIS...WP
NEAR TERM...MBS/WP
SHORT TERM...MBS/WP
LONG TERM...MBS
AVIATION...AMS/NF/WP



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