Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Highlight Changed Discussion --
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FXUS61 KRNK 281141
Area Forecast Discussion
National Weather Service Blacksburg VA
741 AM EDT Sun Aug 28 2016
High pressure at the surface and aloft will remain over the region
today. A weak cold front will begin to approach from the north
Monday, then stall near the North Carolina border awaiting another
front that will arrive from the north Thursday as high pressure
.NEAR TERM /THROUGH TONIGHT/...
As of 400 AM EDT Sunday...
High pressure along the northern Mid-Atlantic coast has pushed a
backdoor cold front toward the Alleghany front and northwest
North Carolina Blue Ridge. The air mass across central and
northern Virginia was drier and mostly void of low clouds/fog as a
result. The location of the backdoor frontal boundary will be
further west today as compared to Saturday. Thus, expecting any
afternoon showers/storms to be confined to areas mainly west of
the RNK CWA, but a few could develop or creep into the western
periphery of the CWA, especially where the wedge normally tends
to be weaker, say west of the I-77 corridor. Will maintain low
pops in those areas, otherwise looking at a precipitation free day
for the vast majority of the CWA along with mostly sunny skies.
Any convection in the western areas will dissipate quickly with
the loss of daytime heating.
Temperatures will be slightly cooler today as 850mb temps fall
back closer to +20C and the drier/slightly cooler air mass
spreads southwest into the region from the northern Mid-Atlantic.
The drop in dewpoints/RH values will likely be more noticeable
than any temperature drop as the sun will still feel quite
warm/hot this afternoon at any rate temperatures will still
average about 8-10 degrees above normal.
Overnight, a weak tropical low off the NC coast will drift
northwest toward the coast and this will likely result in
increasing RH values after midnight along with mid/high clouds
into the Piedmont. To the north, a weak front will be nearing the
PA/WV/MD border. Expect partly cloudy skies most areas with
increased likelihood of patchy fog development as the wedge
weakens and moisture begins to encroach from the southeast.
.SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/...
As of 145 AM EDT Sunday...
A persistent upper ridge will continue to rest across the Ohio River
Valley eastward into northern Virginia through Monday. This will
help maintain a prevailing easterly flow into and through the region
that will bring with some Atlantic moisture. Trajectories will have
their origin initially across New England before skirting the far
western Atlantic then coming onshore once again. Look for the
development of isolated to scattered afternoon showers and a few
thunderstorms across western portions of the area. Here the impacts
of any capping inversion will be least and orographical impacts and
differential heating will lead to convection development. Any
activity is anticipated to wane through the Monday evening hours.
More of the same is expected on Tuesday. However, even a greater
fetch of moisture off the Atlantic is anticipated. This will allow
for a increased coverage of showers and storms as compared to 24
hours prior. The far southeast portion of the area may be hard
pressed however to experience any convection. Convection will again
wane through the evening hours, with some isolated coverage in the
west into the early morning hours of Wednesday.
Wednesday into Wednesday night, a cold front is progged to move
southeast into, through and out of the area. Look for a trend of
increasing showers and storms during the day Wednesday, with
lingering showers across the eastern portion of the area during the
evening and overnight hours.
Temperatures during this portion of the forecast will trend slightly
cooler each day. However, readings will still be above average for
this time of the year. Highs will average around five degrees above
average with the lows close to ten degrees above average.
.LONG TERM /THURSDAY THROUGH SATURDAY/...
As of 400 AM EDT Sunday...
General model consensus for the second half of the week is for
the upper ridge to give way to some weak upper level troughing
over the eastern CONUS, progressive flow across the northern tier
states gradually whittling away at the eastern ridge. This should
allow for another front to come through from the northwest during
the period, although model uncertainty is high with respect to
timing per unresolved solutions ongoing in the tropics. As such
will keep the forecast pretty close to persistence with respect to
precip probabilities, but shave a degree or two off the
temperature per potential for drier air to infiltrate from the
north later in the week, temperature trending closer to normal.
.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --As of 735 AM EDT Sunday...
Mostly VFR conditions expected through the TAF valid period. A
back door front will stall in the far western part of the CWA near
the VA/TN/WV border during the period as another weak front
approaches from the north Monday. Deeper moisture will be pushed
mostly west of the CWA today by the developing drier east-northeast
flow across the area from the weak surface high pressure off the
northern Mid-Atlantic coast. Meanwhile, a strong ridge aloft will
prevail over the region, centered across the Delmarva during the
period. BKN low clouds mainly west of the Blue Ridge this morning
could linger til around 15Z, then should dissipate. However, some
low end VFR cigs could linger across southwest WV and far
southwestVA, mainly west of I-77 into the early afternoon.
Cannot completely rule out isolated shra/tsra western periphery of
the CWA, including KBLF during the late afternoon, but feel that
push of drier air should limit the threat to areas further west of
the RNK CWA. Confidence to include in the KBLF TAF is too low at
this point. Overnight and Monday morning, other than cirrus clouds
spreading in from the southeast associated with a tropical
disturbance off the SC/NC coast, cigs will be VFR. Fog development
early Monday is in question as feel enough northeast-east wind
will remain in place combined with the slightly drier air to
preclude such. However, as always, KLWB and KBCB will be in
question. Included a MVFR condition for KLWB, which could end up
being none or the usual 1/4SM FG. Winds will be NE- ESE through
the period at speeds of 5-8kts. Cannot completely rule out some
low end gusts across the Piedmont from late morning through mid-
afternoon, but have not advertised such at this time.
Medium to high confidence in cigs and vsbys through the TAF valid
Medium to high confidence in wind speed/direction through the TAF
Extended aviation discussion...
A weak west-east oriented front will drift south through the
forecast area Mon. Isolated diurnally driven convection will be
possible along the front toward the I-64 corridor Mon, then
toward the NC/SC border by Tue. Coverage will be limited in
duration and area on all days and have minimal impact on the TAF
sites. Another front will move into the region Wed into Thu with a
better chance for showers/thunderstorms, followed by cooler and
drier air for Friday. Most of the period looks VFR at this point,
outside of the usual late night/early morning fog/low clouds. At
this time, it does not appear that any tropical systems will
impact the CWA.
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