Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KRNK 271124
Area Forecast Discussion
National Weather Service Blacksburg VA
724 AM EDT Wed Jul 27 2016
A wavy front will be nearly stationary from the Mid Atlantic
region to the mid Mississippi Valley through the end of the week.
Weak impulses tracking along the front will combine with deep
moisture to produce periodic rounds of showers and thunderstorms. The
front will finally move well south of the area on Tuesday or
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --As of 720 AM EDT Wednesday...
Much of the mid and high level clouds have moves east out of the
forecast area this morning. Areas of fog have developed in
locations that had rain Tuesday afternoon and evening.
Thunderstorms were developing along the Kentucky/Tennessee border
at 5AM. Some of the short term models, including the HRRR and
HiResnmm and HiResarw, bring this precipitation into the southwest
county warning area before 7AM.
Models showed axis of lift and moisture from southern Indiana to
northern Virginia today. Expect showers and thunderstorms to develop
along this corridor this afternoon. Location and coverage of showers
and thunderstorms south of this axis is less well defined. Have
the highest probability of precipitation across the north today.
Will have enough sun this morning to push most locations back into
the 80s in the mountains and the 90s east of the Blue Ridge by
this afternoon. Guidance was too cool with maximum temperatures on
Tuesday so have gone closer to persistence.
Precipitable water values range from 1.8 inches in the western
county warning area to 2.0 inches in the extreme east. Storm
motion will be southeast about 20 knots. Areas that had heavy
rain on Tuesday will be more susceptible to flooding problems if
there are storms again in the same locations today.
-- End Changed Discussion --
.SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
As of 400 AM EDT Wednesday...
We are in for a continuation of unsettled weather as a shallow upper
trof becomes established over the eastern part of the country through
the weekend. This will allow a steady stream of short wave energy to
move into the region from the southwest, while the upper jet provides
diffluence to aid synoptic ascent. These factors will be combining with
warm/humid/unstable air along a diffuse old frontal boundary lingering
across the region. This all spells a good chance for showers and
thunderstorms for the latter portion of the week and into the weekend.
The variability among guidance solutions is still creating a good
degree of uncertainty in timing/location, but the general consensus is
for increasing shear to bring a severe threat to the area for Thursday
afternoon into Friday, with a possibility for an organized MCS. High
precipitable water values will also make excessive rainfall a threat,
so hydro issues are a concern during this period as well. There is
still much to be determined with this scenario so it warrants close
attention in later model runs. Coverage of showers/storms looks
considerable again for Saturday but with less shear and dynamic support
so a more limited severe threat.
Temperatures will continue to run a bit above normal with highs going
from the mid 90s to lower 90s east of the Blue Ridge, and generally
low/mid 80s to the west.
.LONG TERM /SUNDAY THROUGH TUESDAY/...
As of 130 PM EDT Tuesday...
Overall pattern situation favors storminess every day but especially
in the afternoon/evening. A frontal boundary situated from the Ohio
Valley over to the Central Plains will slowly shift southeast into
the Virginias and North Carolina over the weekend. Airmass will
remain unstable and moist. Some issue with how far this front makes
it as 5h ridge may be hard to break, but still looks like belt of
westerlies will shift at least into our northern forecast area over
Highs will be seasonal with lows slightly above normal through most
of the period. Highs will range from the lower to mid 80s mountains,
to upper 80s to around 90 east. Lows will be in the lower to mid 60s
mountains, to upper 60s to around 70 east.
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --As of 140 AM EDT Wednesday...
Locations that had rain Tuesday afternoon and evening have MVFR
to LIFR fog this morning.LIFR visibilities at KLWB will improve to
VFR by 14Z/10AM.
Threat for storms again this afternoon but for now will keep it
VCTS. 00Z models were showing the mountains as the preferred
location for storm development. Showers and thunderstorms will
also develop along a wavy stationary front from the mid
Mississippi Valley into the Mid Atlantic region. KLWB is close
enough to this axis to have thunderstorms this afternoon.
Extended aviation discussion...
The upper ridge will remain just south of the area and a residual
front nearby through Sunday. This should allow for periodic daily
convective coverage until the boundary either fades or sinks
farther south. Appears more widespread sub-VFR possible with
thunderstorms later Thursday with a stronger wave along the front
with perhaps some decrease in coverage by the weekend as this
feature passes. At least diurnal MVFR/IFR possible each
afternoon/evening through Sunday for now. Late night and early
morning fog will likely occur at the usual valley locations, and
those chances increase across the entire region if any rain occurs
during the afternoon or evening at any site.
-- End Changed Discussion --
Record high temperatures for Wednesday (7/27)
Roanoke.....103 in 1936
Lynchburg...103 in 1936
Danville....102 in 1952
Blacksburg...94 in 1993
Bluefield....89 in 1966
Record highs for July 28
Roanoke......104 in 1930
Lynchburg....103 in 1936
Danville.....102 in 1952
Blacksburg....95 in 1966
Bluefield.....90 in 2011