-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRNK 010514
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
114 AM EDT Sat Oct 1 2016

.SYNOPSIS...
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A strong upper level area of low pressure centered over Kentucky
will drift slowly to the north later tonight into Saturday. This
will finally allow drier air to the southwest to punch into the
region bringing an end to any ongoing showers by early Saturday.
Weak high pressure follows this system on Sunday with overall dry
weather into early next week.
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&&

.NEAR TERM /THROUGH TODAY/...
As of 1110 PM Friday...

Expect lingering showers over the Alleghany Highland toward
Lynchburg through early overnight, while a shower or two also
occurs in portions of Southeast WV where some deeper moisture
convergence resides, though drier air aloft is keeping things
mostly at bay.

For the overnight we will see some clearing over the southern half
of the forecast area roughly from Bluefield east to Danville,
while clouds stick around in the Alleghanys over to Lynchburg
corridor. Question again is fog formation and how widespread and
dense it will become. Think will see fog in patches across most of
the area where it clears but with some drier air it may vary at
times. Still think dense fog will be a factor around dawn in the
New River Valley, southern WV and portions of the VA/NC foothills
east toward Southside Virginia.

Another new weather issue will be rises along the main stem
rivers. Given that 2-5+ inches of rain fell in portions of the
Roanoke River basin, it looks like the river at Altavista and
Randolph will go into minor flood Saturday. It will be close
especially for Altavista, and right now the forecast takes it
about 1/2 foot above flood stage which mainly affects pasture and
low lying fields.

No other major changes to the forecast with lows ranging from the
upper 40s in the NC mountains to lower 60s across the Virginia
Piedmont.

Previous early evening discussion...

Flash flood watch expired at 6pm. Coverage and intensity of
showers has lessened today compared to earlier and yesterday.
High-res models, radar and meso-analysis continues to paint the
best shower threat from Greenbrier county WV southeast toward
Lynchburg and Buckingham, VA through mid evening, then shifts the
coverage further northeast overnight. Instability weakening to
just a small area over southside Virginia into the NC Triangle
area where SBCAPES at 23z were still in the 1000-2000 J/KG range.
Shear still high but drier air aloft is acting to hinder some
development. As we head into the overnight overall concern may
switch to fog especially in areas that clear out, as ground is
nearly saturated and airmass aloft is drying out. Could see
potential dense fog advisory for portions of the area from
southern WV into the New River Valley. Will monitor trends to see
if materializes.

Previous valid discussion from early this afternoon...

For the overnight and into the day Saturday, the upper low will
finally begin to lift north allowing drier air aloft to overspread
the entire region from southwest to northeast. This should result
in a continued decrease of shower coverage with time with the
entire forecast area clearing out for Saturday. With diminishing
cloud cover, temperatures should dip closer to the seasonal norm
with temperatures falling into the 40s for North Carolina
mountains and from the New River Valley west. Foothills should dip
into the 50s...and low 60s farther north and east where clouds
linger. For Saturday...temperatures expected to rebound into the
70s.

&&

.SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/...
As of 330 PM EDT Friday...

The closed low will continue to slowly migrate off to the northeast
through the period as it continues to fill and open up, dragging a well
occluded surface low with it. This will position our region essentially
in the dry slot under a neutral thermal advection regime with slight
warming aloft. This should yield essentially a dry forecast  through
the weekend. By Sunday night, high pressure pushing in form the upper
midwest will nudge a cold front to our western doorstep before it
stalls,  but the best forcing and instability will be shearing off to
our northwest and any chances for frontal precipitation will remain off
to our west.  The upper low will give way to ridging in the eastern US
through the early part of next week, allowing a large area of high
pressure to settle over New England and wedge down the east side of the
Appalachians. Moisture will be lacking and isentropic lift over the
wedge will not yet be appreciable do Monday looks to remain dry as well.

Expect temperatures to be seasonable with highs near 80 east of the
Blue Ridge and in the low/mid 70s west. Lows will range from well into
the 40s in the valleys west of the Ridge to the upper 50s east.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 330 PM EDT Friday...

The big variable mid to late week lies with the potential track of TS
Matthew as it is expected to turn north and move up the Atlantic coast.
The latest guidance indicates the tropical system will remain far
enough to our east to keep direct effects of this system out of our
region. However, the wedge will remain in place and the squeeze between
the wedge and the tropical system will create enough overrunning to
generate precipitation by late Tuesday/Tuesday night especially in the
east and continuing through the end of the period.

Temperatures in the wedge will remain cool and generally several
degrees below normal.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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As of 102 AM EDT Saturday...

Isolated showers/storms still lingering in spots across the east
and may stick around a few more hours along a KHSP-KLYH-KDAN
corridor. Otherwise the main concern heading into late tonight
will be fog and low clouds. Already seeing lower cigs at most
locations, and with drier air aloft working in from the south
combined with very moist ground and light winds, should see fog
develop as well. Think most sites will drop to MVFR/IFR or worse
by daybreak, which will vary between fog and/or low stratus.

Saturday, winds stay light but turn southwest. Fog and low clouds
will be slow to lift but overall should be VFR everywhere by
midday into early afternoon. Exodus of the upper low and
associated surface occlusion should lead to little more than
scattered-broken cumulus during the afternoon and without any
showers.

VFR to continue Saturday night with fog formation again likely
under clear skies and lights winds over moist ground conditions.
This mainly across the valley locations and less elsewhere.

Extended aviation discussion...

The deep upper level low will finally shift farther to the north
and away from the region on Sunday. The weather will trend back
into a dry pattern with mainly VFR conditions next week, aside for
river valley fog in the mountains resulting in brief period of
late night early morning LIFR conditions at some of the mountain
valley airports through Wednesday.
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&&

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

&&

$$
SYNOPSIS...JH/PM
NEAR TERM...PM/WP
SHORT TERM...MBS
LONG TERM...MBS
AVIATION...JH/PM/WP