Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 240114

Area Forecast Discussion
National Weather Service Blacksburg VA
914 PM EDT Tue Aug 23 2016

High pressure over the mid Atlantic shifts further east into
midweek allowing a return of more humid weather by the 2nd half of
the week. Outside of some mountain thunderstorms, it will be mainly
dry with the upper ridge overhead through Friday.


As of 900 PM EDT Tuesday...

Another quiet night with high pressure sliding across and dry air
aloft in place per evening soundings. However dewpoints have crept
up quite a bit since last night making for a bit more humid and
warmer overnight. In addition likely to have some mid/high clouds
crossing the region from the west through daybreak while spotty
strato-cu lingers in spots. Thus may tweak the west toward partly
cloudy overnight while keeping the east mainly clear under the
center of the surface ridge. With current temps running about 5-8
degrees warmer than this time last night, would expect lows to be
mostly in the 60s, similar to current dewpoints, with only the
valleys seeing a few 50s by daybreak pending spotty fog coverage.

Previous discussion as of 324 PM EDT Tuesday...

High pressure is situated over the mid Atlantic but mesoanalysis
loop suggesting that moisture is already back on the increase across
the Tennessee Valley into the Southern Appalachians. Still influence
of drier air aloft per WV will keep it dry over us tonight. Seems
the main issue will be if this current sc/cu field dissipates this
evening or stratifies as weak subsidence inversion sets up. Will
lean toward partly cloudy near and east of the Blue Ridge overnight
with mostly clear elsewhere. Fog will be limited to river valleys if
at all.

Wednesday shows increasing flow from the southwest at 8h with wedge
eroding. Models are starting to fire up some convection toward the
Southern Appalachians north into WV by the afternoon. Forecast
sounding showing some moisture but shallow so will only included
slight chance in the west tomorrow.

Warmer tonight than this morning but still cooler than several days
ago, and actually close to normal for Aug 24th. Lows will range from
around 60 in the mountains to lower to mid 60s east.

Should see more cumulus develop in the mountains Wednesday with
more sunshine east. Highs will be warmer ranging from the upper
70s to lower 80s mountains to mid 80s east.


As of 330 pm EDT Tuesday...

High pressure aloft  will start to center over our area Thursday
while main belt of westerlies stays across the upper midwest into
the Northeast. Showers and storms will be mainly orographically and
diurnally driven with coverage scattered in the mountains to little
or no coverage east. Friday looks even drier as the center of the
high is directly overhead capping much of the region. A few stray
showers or storms may fire across the ridges.

Temps and dewpoints begin returning to what we had a week ago with
highs Thursday in the lower to mid 80s mountains, to upper 80s
piedmont, running higher Friday from the mid to upper 80s mountains
to mid 90s piedmont.

Lows will return back into the mid 60s west to upper 60s to around
70 east.


As of 130 PM EDT Tuesday...

During this portion of the forecast, surface high pressure will
remain centered over the Carolinas. The prevailing synoptic flow
will trend zonal to slightly northwest. The location of the high
places southerly flow across the region, especially across western
sections. Also, a number of weak disturbances are forecast to
progress into or through the region within the northwest flow aloft.
The result will be a pattern that will favor daily chances of
showers and storms, especially across the western portions of the
area. Most of these will be isolated to scattered in coverage.
However, on days when the heating of the day coincides with the
passage of one of the weak shortwaves, a brief period of enhance
coverage is possible. The coverage will also have a greater
potential to progress east of the crest of the Blue Ridge.

Low temperatures will be around five to ten degrees above normal
during this time frame, with highs around 5 degree above normal.


As of 645 PM EDT Tuesday...

Cumulus field continuing to slowly fade this evening and should
dissipate to little more than scattered coverage after sunset.
However upstream axis of cloudiness associated with a weak wave
aloft and residual surface trough likely to arrive across the west
later tonight. This could bring another round of at least mid
clouds but appears given dry air that will remain VFR overnight as high
pressure drifts slowly east across the region. The only exception
likely to be early morning fog mainly at western TAF sites,
especially KLWB and possibly KBCB where MVFR/IFR will be possible
around daybreak pending late night clouds.

Surface high slips east to the Mid-Atlantic coast on Wednesday
with weak southerly flow helping moisture increase in advance of a
cold front well to the west. This should allow for a more
widespread bkn cumulus/strato-cumulus layer by Wednesday afternoon
with some lingering mid deck cigs above. Better low level moisture
may also lead to widely scattered showers across the far western
mountains but likely too isolated near any western taf site to
include mention at this point. Otherwise still appears bases,
after patchy early morning fog/stratus, should remain VFR on
Wednesday with a possible period of MVFR at KBLF/KLWB later

Any showers should fade with loss of heating Wednesday evening
given lack of much support, making for mostly VFR again overnight
outside of late night fog/stratus in the valleys.

Extended aviation discussion...

Thursday even more moisture will work its way north into western
parts of the area on the west side of a departing high pressure.
Isolated showers and storms will be possible across the
mountains, but for the most part, VFR conditions will still

On Friday, there is a greater chance of showers, and possibly
some storms, with the approach of our next cold front. Pockets of
MVFR conditions will again occur briefly under the stronger
showers or storms.

The front lingers in the area during the weekend keeping enough
moisture for diurnal mountain showers and storms when periods of
MVFR could occur.




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