Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Highlight Changed Discussion --
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FXUS61 KRNK 241144
Area Forecast Discussion
National Weather Service Blacksburg VA
744 AM EDT Wed Aug 24 2016
High pressure over the mid Atlantic slowly shifts east into
Thursday. The upper ridge will remain overhead through the end of
.NEAR TERM /THROUGH TONIGHT/...
As of 500 AM EDT Wednesday...
High pressure over the region will slowly move east today and
tonight. Mid and high clouds associated with a weak wave aloft will
spread east across the region this morning. This additional cloud
cover will limit fog development to pockets of where clouds thin
this morning. Any morning fog and low clouds will lift or mix out
quickly by mid morning. Moisture will increase this afternoon with
flow from the southwest at 8h. The combination of low level
convergence,solar heating and orographic lift may produce an isolated
shower or thunderstorm this afternoon across the western mountains.
The best chances will occur across the southwest mountains. High
temperatures this afternoon will range from the mid 70s in the
mountains to the mid 80s in the Piedmont. Decreased pops for the
tonight and added mention of patchy valley fog overnight under clear
to partly cloudy skies. Low temperatures will vary from the around
60 degrees in the west to the mid 60s in the east.
.SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
As of 400 AM EDT Wednesday...
The underlying theme through the period will be a strong subtropical
ridge anchored over the region. However, a weak front will drift
into the region Thursday and drift very slowly south into the
Carolinas over the weekend. Moisture and warmth will definitely be
on the increase under the upper high. With the front lingering
through the region, there will be some focus for increased
convection, although dynamics aloft are weak at the very best.
Convection that develops will be largely a result of differential
heating, but will tend to focus either near the frontal boundary
or across the mountains. For Thursday, this should be mainly west
of the Blue Ridge, with the focus drifting further south/southeast
with time into Friday and Saturday. Given the pattern and very
weak forcing, cannot support more than 20-30% pops at this time,
with areas east of the Blue Ridge overall seeing the least likely
chance for showers and thunderstorms. Thunderstorms should be non-
severe, quite spotty in nature, and limited in duration.
With respect to temperatures, 850mb temps will continue to hover
in the +15C range for Thursday, but jump into the +20C to +21C
range for the remainder of the period. This will result in surface
temps reaching the lower 90s again across the Piedmont and well
into the 80s west of the Blue Ridge Friday and Saturday. These
readings are well above normal.
.LONG TERM /SUNDAY THROUGH TUESDAY/...
As of 430 AM EDT Wednesday...
Will certainly need to keep an eye on the tropics as we head into
next week with the Atlantic Basin/Gulf becoming quite active as
several disturbances in the ITCZ drift west from African across
the tropical Atlantic and into the Caribbean and Gulf. Models are
at considerable odds with respect to tracks and intensity and with
yet no consistency from run-to-run, so have not introduced any
indication of tropical weather in this period at this time.
However, several models suggest that eventually one or more
tropical systems will drift into or develop in the western
Atlantic or the Gulf of Mexico. At any rate, it would appear that
if a tropical system were to impact the RNK CWA, it would be
beyond this period anyway.
For much of the period strong high pressure aloft is progged to
remain over the region. Another weak cold front will drift into
the region from the north late in the weekend, with the original
front washing out across the Carolinas. The proximity of the
fronts and strong insolation along with abundant low-level
moisture will continue to support widely scattered diurnal
convection, either focused near the frontal boundary or across the
mountains. Really no significant change in sensible weather during
this period with temperatures well above normal, especially low
temperatures. Expect minimum temperatures to average 10-15 degrees
above normal with maximum temperatures about 5-7 degrees above
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --As of 745 AM EDT Wednesday...
Mid and high clouds associated with a weak wave aloft will
spread east across the region today. VFR conditions will prevail
through most of the TAF valid period as high pressure drifts
slowly east across the region and high pressure aloft builds over
the area. The only exception will be patchy early morning fog,
which so far has only really been an issue at KLWB, currently at
0SM FG. This will dissipate by 14Z with VFR cigs and vsbys
expected through 06Z after that.
Surface high slips east to the Mid-Atlantic coast later today
with weak south to southwest 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 this 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 too isolated to mention near any western taf site.
Otherwise still appears cloud bases, after patchy early morning
fog/stratus, should remain VFR today with a possible period of
MVFR at KBLF/KLWB late afternoon.
Any showers should fade with loss of heating this evening given
lack of much support, making for mostly VFR again overnight
outside of late night fog/stratus in the valleys. Morning low
clouds and fog will lift by late Thursday morning. Fog could be a
little more widespread Thu morning, so have introduced for KLYH as
well as KBCB.
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...
Richer moisture will work its way north Thursday 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 prevail.
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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