Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Remove Highlighting --
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FXUS61 KRNK 250111
Area Forecast Discussion
National Weather Service Blacksburg VA
911 PM EDT Wed Aug 24 2016
High pressure over the mid Atlantic shifts slowly east into
Thursday. The upper ridge will remain overhead through the end of
.NEAR TERM /THROUGH THURSDAY/...
-- Changed Discussion --As of 845 PM EDT Wednesday...
Soundings show a decent increase in pwats this evening although
showers have been limited by weak capping aloft under high pressure
including lack of forcing/instability. Models continue to show a
piece of mid level energy associated with ongoing convection to
the northwest approaching late as the flow turns more westerly.
This weak convergence setup may be able to aid a few showers over
the far west by daybreak, so leaving in some low pops toward
morning mainly northwest mountains. Otherwise expect quite a bit
of sheared high/mid clouds from Ohio Valley convection to spill
into western sections overnight, with some lower clouds possible
western ridges given weak upslope, and out east early on per residual
cumulus/strato-cu. This cloudiness may tend to limit fog while
keeping low temps up more in the mid 60s and perhaps staying around
70 in spots. Thus making small adjusts to limit fog some while
staying on the warmer side of latest mos outside the valleys.
Previous discussion as of 303 PM EDT Wednesday...
Building heights aloft to keep most showers and storms limited.
However, will be watching an area of convection in northern Indiana
this afternoon as models trend the flow more wnw to ese over time,
but in general keep threat further north late tonight. Still looks
as if some cloudiness will be around again late tonight as the wave
moves across the mid-Atlantic states. Thursday the center of the
upper high slides across the Southern Appalachians and Tennessee
Valley. Another weak upper impulse may scoot by early threatening the
mountains with a few showers in the morning then some break after
midday before possible isolated convection in the afternoon.
Difficult forecast in terms of cloud cover and sunshine. Expecting
more clouds than sun especially in the mountains and foothills.
Still with warming aloft, temps will be reach the 80s across the
entire CWA, and should close in on 90 toward Buckingham, VA to
-- End Changed Discussion --
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 400 AM EDT Wednesday...
An upper level ridge of high pressure is forecast to hold strong
over the Mid-Atlantic states into this upcoming weekend with 5H
heights hovering between 594-597 dm. As such, anticipate strong
subsidence, above normal temperatures, and little or no
precipitation threats. Certainly can`t rule out an isolated shower
or thunderstorm during the period, but warming aloft will limit
instability, and lack of dynamic forcing should keep the rain
threat to a minimum.
Summer heat and humidity will be the forecast highlight, 850mb
temps of +18C to +22C supporting daytime highs ranging from the
80s mountains to the lower to mid 90s across the piedmont.
Overnight lows will be warm and muggy too, dewpoints in the 60s
to lower 70s not allowing for much radiational cooling.
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 410 PM EDT Wednesday...
The main focus across the eastern half of the nation into early
next week will be the persistent upper level ridge, and a
developing tropical system which has the potential to impact parts
of Florida. Regardless of the tropics, our weather will be most
influenced early in the week by the persistent upper level ridge
of high pressure. This feature will ensure that heat and humidity
will be persist with daytime temperatures running at least 4 to 7
degrees above normal, and overnight lows a full 10 degrees above
normal. There will be a threat of diurnally driven showers and
thunderstorms, but this activity is expected to be mainly confined
to the mountains and lack any significant organization due to poor
.AVIATION /01Z THURSDAY THROUGH MONDAY/...
As of 650 PM EDT Wednesday...
Overall VFR conditions will prevail through most of the TAF valid
period as high pressure both surface and aloft drifts slowly east
across the region. However will likely see plenty of mid clouds
shift southeast into the region from convection in the Ohio
Valley overnight with some lower strato- cumulus possible
mountains late as the low level flow turns more westerly. This
could bring a period of MVFR cigs to locations from KBCB and
points west early Thursday. Otherwise the only other exception
will be patchy early morning fog, which so far has only really
been an issue at KLWB, but could occur at KBCB/KLYH as low level
airmass moistens back up. Any fog will be gone by mid morning
Deeper moisture will return from the west across the area Thursday
as the surface high shift east. A weak upper disturbance evolving from
upstream convection this evening should cross the mountains
Thursday morning and eastern sections Thursday afternoon while
weakening. This feature could bring some showers to the western
taf sites through midday Thursday with isolated redevelopment
possible mainly Blue Ridge west in the afternoon with heating.
Coverage still appears too low to include in any of the taf
sites espcly given uncertainty early in the day and spotty
coverage in the afternoon. Therefore keeping VFR under mainly
scattered-broken cumulus fields and without any shra/tsra mention
for now Thursday afternoon.
Expect any showers to quickly fade Thursday evening with mainly
VFR returning outside of patchy late night fog/stratus in the
Extended aviation discussion...
Storms will again be isolated and mainly confined to the mountains
on Friday as upper ridging strengthens, while a weak surface front
stalls to the north. Brief MVFR conditions could occur where any
convection does develop but appears mainly VFR given spotty nature
to any showers.
The front lingers in the area during the weekend keeping enough
moisture for diurnal mountain showers and storms when periods of
MVFR could occur.
Monday high pressure bubbles in but still a very humid airmass to
keep isolated mountain storms around in the afternoon, but mainly