Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 211338
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
938 AM EDT Mon Aug 21 2017

.SYNOPSIS...
High pressure across the mid-Atlantic will gradually take up a
position off the coast, allowing winds to turn southerly and
bring a return of deeper moisture to the region along with a
chance for showers and thunderstorms mainly along and west of
the Blue Ridge. A cold front will approach the area by the
middle of the week, bringing a better chance for showers and
storms to the Appalachians and central mid Atlantic region.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 930 AM EDT Monday...

Flat ridging in quasi-zonal flow aloft will combine with a
surface high taking up position as Bermuda high off the coast to
keep warm and humid conditions across the region as we start
the work week. While the warm and moist conditions will help
generate surface based instability, BufKit soundings show some
capping warmth aloft that will suppress convection. Expect
orographic forcing along and west of the Blue Ridge will give
enough support to updrafts for a chance of showers and
thunderstorms mainly from the Ridge westward this afternoon into
this evening. Diurnal heating will start to drive convective
cloud development by late morning, but coverage at least through
the start of the eclipse should allow for some viewing with
clouds decreasing heading off to the southeast across Southside
VA and the piedmont. Note that the presence of clouds will still
not make for safe eclipse viewing without the proper certified
eye protection.

Convection will dwindle with loss of heating this evening,
yielding dry conditions for Monday night with the possibility
for more valley fog toward daybreak Tuesday.

Highs today will generally be in the lower 90s east of the Ridge
with 80s to the west. Lows will be around 70 east to generally
the middle 60s west.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/...
As of 330 AM EDT Monday...

On Tuesday, high pressure drifts further east into the Atlantic.
Return southwesterly flow on the back side of this high will bring
more heat and humidity into the region. Upslope flow along the Blue
Ridge and a lee trough over the piedmont may produce a few storms
across the mountains Tuesday afternoon, especially in favored areas
on the southern and eastern slopes. Increase mixing ahead of an
approaching cold front may be a deterrent to limit convection
activity to scattered coverage pre-frontal passage. Any afternoon
storms should fade during the evening, with best forcing delayed
until after midnight. The cold front progress in from the Ohio
Valley after midnight and before dawn, with decaying convection
already ongoing. Best chances of seeing a strong storm will be early
Wednesday morning as the front moves in from the west, and late
Wednesday evening as convection reforms on the lee side of the
Appalachians. With the passage so far removed from proper heating,
will likely keep even thunder at a minimum, except during these time
periods. Muggy conditions are expected through Tuesday evening, with
highs in the 80s west of the Blue Ridge and low 90s east. A bit
cooler on Wednesday mainly due to showers/cloud deck.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
As of 330 AM EDT Monday...

A bit of uncertainty remains on how far and fast the front will
progress from our area. Guidance seems to be settling on a bit
slower progression, but also kicks POPs/QPF out of the region for
good by early Thursday morning. Behind the front, cooler and drier
conditions settle in for most, with temperatures in the middle 70s
(West) and lower 80s (East) into next weekend, where a wedge-like
pattern takes shape.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
As of 745 AM EDT Monday...

Surface observation indicate patchy fog across the mountains
this morning, mainly in the river valleys. However, bands of mid
level clouds continue to pass across the area, limiting
radiational cooling and resulting in up and down visibilities.
At any rate, with another day of strong heating, fog will burn
off quickly after 9 AM, resulting in widespread VFR conditions.



Flat ridging in quasi zonal flow aloft will combine with a
Bermuda high at the surface to keep warm and humid conditions
across the region this TAF period. While the warm and moist
conditions will help generate surface based instability, BufKit
soundings show some capping warmth aloft that will suppress
convection. Expect orographic forcing along and west of the Blue
Ridge will give enough support to updrafts for a chance of
showers and isolated thunderstorms mainly from the Ridge
westward this afternoon into this evening. Will go with VFR
conditions at all sites. Any convection will dwindle with loss
of heating this evening, yielding dry conditions for Monday
night with the possibility for more valley fog toward daybreak
Tuesday. Winds will be light through the period.

Extended Aviation Discussion...

Moisture will continue to increase on Tuesday as high pressure
moves farther offshore ahead of another cold front that will
arrive from the northwest around midweek. This will again lead
to more afternoon clouds and isolated convection mountains
Tuesday afternoon but overall VFR at this point. Better
potential for sub- VFR will come Wednesday when more widespread
showers and storms arrive with the next cold front. Flying
conditions should slowly improve behind the passing cold front
on Thursday although sub-VFR cigs may linger across
southern/western sections a while longer.

&&

.EQUIPMENT...
As of 930 AM EDT Monday...

KFCX doppler radar is expected to be back in operations as early
as Wednesday evening (Aug 23rd). Technicians have replaced the
bull gear and are reassembling the radar today and tomorrow
with calibration worked on Wednesday.

&&

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

&&

$$
SYNOPSIS...MBS
NEAR TERM...MBS/RCS
SHORT TERM...JM
LONG TERM...RCS
AVIATION...MBS/NF
EQUIPMENT...RCS



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