Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 210120

Area Forecast Discussion
National Weather Service Blacksburg VA
920 PM EDT Tue Jun 20 2017

Variable cloudiness for tonight as a stalled front lifts
northeast across southeastern Virginia. Weak high pressure
remains in control on Wednesday. Weather turns increasingly more
unsettled into Friday and Saturday with several periods of rain
and embedded thunderstorms.


As of 920 PM EDT Tuesday...

Added a few showers in the west early tonight as highlighted on
HRRR and HiResW-ARW-east, and continue light pops across
southern portions of forecast area as frontal boundary lifts
northward overnight into Wednesday morning. Modified cloud cover
to capture sharp cloud gradient on satellite image. Made some
minor adjustments in low temperatures to allow for cooler
readings in the north with less cloud cover. Have a good night!

As of 710 PM EDT Tuesday...

Made some minor adjustments in temperatures for this evening
utilizing surface obs with their trends and shaped towards
glamp tonight. Slowed the drop of temperatures in the south
with additional cloud cover. Trimmed back northern edge of light
pops for the overnight.

As of 325 PM EDT Tuesday...

Overall a pleasant afternoon across the central Appalachians and
into the Piedmont, along with a much-needed dry repreive from
several prior days of wet weather conditions. Broad trough exists at
500 mb across the Great Lakes region, with upper-level moisture/high
clouds stemming from circulation associated with what is now
Tropical Storm Cindy in the central Gulf streaming northeastward.
Weak surface ridge in place across the northern two-thirds of the
forecast area, with a stalled frontal zone which trails across
eastern VA into the central VA Piedmont and into Upstate SC.

For Tonight: Generally quiet conditions tonight. Toward mid-
evening, will watch a a mid-level shortwave trough embedded in
the broad Great Lakes trough lift some of the deeper moisture
associated with the stalled front back northeastward. The net
effect this will have, though, is for an increase in clouds
across the southeastern tier of counties in VA and in the
Piedmont counties in NC. There may even be a isolated light
shower from these but the prospect of that is not high. Honestly
waffled between whether or not to call it a sprinkle or light
shower, so definitely not significant. Patchy river fog will
again be possible outside of the cloud shield and particularly
in the New River and Greenbrier Valleys into the lower Tennessee
Valley. Lows should be pretty similar to last night, in the mid
50s to near 60 east of the Blue Ridge and some 5-7 degrees
warmer east of the Blue Ridge into the Piedmont.

For Wednesday and Wednesday Night: Any light showers associated with
the frontal wave dissipates by mid-morning, along with any river
valley fog. Deeper west to northwest flow develops during the day,
with mostly sunny to partly cloudy skies (mainly fair weather
cloudiness with high clouds interspersed) from mid-morning through
early evening. While most of the evening hours are dry, will be
returning into a warm, moist advection pattern especially late in
the night. Look for mostly clear skies to start, but with an
increase in mid-level clouds late across the far southwest mountains
of VA and the High Country of NC. Overall, looking for highs
Wednesday in the upper 70s to mid/upper 80s (warmest northeast),
with light west to southwest winds. Lows should be a few degrees
warmer than tonight in the upper 50s to middle 60s, tending to occur
a few hrs before sunrise with the increase in warm advection.


As of 324 PM EDT Tuesday...

Transition to tropical/muggy airmass commences this period as upper
ridge of 588 to 590 DM builds across the southeast U.S. while what
is now Tropical Storm Cindy heads into the LA/TX area.

Westerlies aloft will stay north of us, from the northern Plains to
the mid-Atlantic Thursday. Should see less of a threat Thursday of
storm coverage, as models seem to confine activity more over the
Southern Appalachians west and southwest to the Gulf Coast. With
convergence in the low level winds and increase in moisture will
still see a few showers/storms fire up in the afternoon. Best threat
likes over the NC mountains/foothills into the Mountain Empire of
Southwest VA. At the moment flooding threat looks marginal.

Thursday night into Friday night, Cindy is expect to shift northward
into Arkansas. A deeper northern stream shortwave will move across
Ontario/Hudson bay digging a trough over the midwest, and causing
heights to fall over our area. Models indicate a few pieces of
energy moving east ahead of Cindy with potential for heavier rains
shifting from KY/TN east/northeast to the Central Appalachians.
Precipitable water values will be increasing to 1.5 to 2.0 inches
and right now, rainfall Friday will be heavy at times, but still
some question on where greatest corridor of rain will fall, with 12z
GFS/ECM very close in having northern KY into Ohio, northern WV as
the area to get the higher amounts. Given some uncertainty should
still be a limited threat of localized flooding from downpours. As
far as svr threat, thinking is with more clouds/tropical like
soundings, the storms should stay sub-severe.

Lows this period will be warm, about 5-8 degrees above normal
ranging from the lower to mid 60s mountains, to around 70 to lower
70s east of the Blue Ridge.

Thursday appears a little less cloudy in the east, so will see
temperatures reach the mid 80s, possibly near 90 east of Danville,
while the mountains get into the mid 70s to around 80.

Friday should be a few degrees cooler with more clouds/rain around,
but still noticeably muggy in the 70s mountains, to lower to mid 80s


As of 148 PM EDT Tuesday...

Still looking muggy and showery this weekend, especially Saturday as
remnants of now Tropical Storm Cindy get pooled in along a cold
front moving in from the northwest. Model solutions favor Cindy
weakening/eroding but some have it staying situated back over the
mid MS Valley behind the front into Saturday then getting kicked
east ahead of digging northern stream trough.

So in terms of precip chances, Saturday looks like a good soaker,
Sunday is iffy as but still chance is there with frontal boundary in
the vicinity. Northern stream front moves across Monday morning so,
overall Monday/Tuesday look drier and a little cooler.

Temperatures this weekend will be seasonal but muggy, with highs in
the mid to upper 70s west to lower to mid 80s east.

Still early on flooding concerns with 12z GFS a little lower on QPF
into Sunday keeping higher amounts west of the Appalachians. Will
ease off some on the HWO wording, but localized flooding will remain
the main concern.


As of 719 PM EDT Tuesday...

VFR conditions will continue at the taf sites this evening into
tonight. In general, some SCT CU expected with some high level
clouds especially in southern portions.

Tonight into Wednesday morning, the frontal boundary`s
northeast advance may push MVFR clouds, SCT020 to BKN020 into
KDAN. There may even be an isolated unrestricted shower or
sprinkle. With such a high clouds base, have low confidence
in precipitation. However, the NAM and HRRR still support
an isolated showers across the extreme southeast portion of
the forecast area. Radiation fog is possible with higher
confidence of MVFR/temporary IFR visibilities at KLWB and
KBCB. Potential is there at KLYH as well but a little less
confident there as it will depend on extent of cloudiness. Held
on to some light fog after 09z for Lynchburg. Winds should
trend light and variable tonight.

Should trend VFR again Wednesday, though like today, greater
low to mid-level cloud cover further southeast. Winds again
become west to southwest 4-8 kts.

Extended Aviation Discussion...

Generally VFR Wednesday late afternoon through Thursday
afternoon. Low-confidence prospect for radiation fog Wednesday
evening into Wednesday night.

More active aviation forecast period Thursday evening into the
weekend. Lowering, sub-VFR conditions anticipated Thursday
evening into Friday with first surge of showers advancing SW to
NE. Potential for low-level wind shear western terminals.
Continuation of sub-VFR conditions Friday evening into Saturday with
moderate to at-times heavy rain. Confidence is low on timing of
rain. The unsettled weather continues Sunday into Monday with
sub-VFR condition possible with convection.




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