Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KRNK 260225
Area Forecast Discussion
National Weather Service Blacksburg VA
1025 PM EDT Mon Jul 25 2016
Strong high pressure aloft will continue to result in hot and
humid weather early this week. A weak cold front approaching from
the north should bring increasing chances of showers and
thunderstorms over the mountains into tonight, and across the region
on Tuesday. This boundary looks to linger over the area through the
rest of the week with added showers and storms possible each day.
.NEAR TERM /THROUGH TUESDAY/...
AS of 1000 PM Monday...
Heat Advisory in effect from noon to 8 pm EDT Tuesday for South
Central Piedmont of Virginia.
Widely scattered thunderstorms have been mainly confined to areas
along and west of the Blue Ridge with forcing over the mountains
providing just enough lift to trigger storm activity. Can`t rule
out additional activity during the overnight, esp western slopes
of the Appalachian Divide (Mt Rogers vicinity) where light
westerly flow will continue to provide for weak low level
convergence during the overnight. Overall intensity however,
should wane per loss of daytime heating.
Upper ridge will slowly weaken or flatten tonight into Tuesday as
shortwave troughing passes to the north. Surface boundary sinks
southward to just north of the area late tonight into Tuesday with
the axis of higher pwats and weak lift strung out from the western
slopes to across the north. This may result in convection linger
especially across the north tonight. Otherwise, partly to mostly
cloudy and very muggy expected tonight. Low temperatures tonight
will range from the mid 60s in the mountains to the mid 70s in the
The frontal boundary will drop south across our region on Tuesday.
The combination of frontal ascent, orographic lift, and heating will
result in scattered showers and thunderstorms especially during the
afternoon. SPC in day two convection has portions of forecast area
in marginal risk for damaging winds with convective clusters. High
temperatures on Tuesday will range from the lower 80s in the
mountains to the mid 90s in the Piedmont. Heat indices will climb
as high as 105 degrees in the far east.
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 300 PM EDT Monday...
The upper level ridge will continue to sink south across the
southeastern US through Thursday. Lowering heights means
temperatures will be a little bit cooler each day. However,
temperatures will remain above normal until we can get a cold front
to pass over the region. Unfortunately, there is no frontal passages
expected this week. Afternoon temperatures will run around 5F warmer
than normal with 80s across the mountains and low to mid 90s east.
Dew points will also remain elevated ranging from the mid 60s to
lower 70s. Heat indices values will run 5F-8F warmer than the actual
Some heat relief will come in the form of showers and thunderstorms
each afternoon. Even though these storms may knock temperatures
down, they will increase dew points keeping conditions very
uncomfortable. The coverage of storms will increase each day and
start earlier and end later. With zonal flow aloft, storms will
start across the mountains by noon, then drift east over the
piedmont during the evening hours. Forcing both Wednesday and
Thursday is not ideal for widespread strong storms, however with
zonal flow aloft, any waves rounding the ridge could change that.
For now, we will continue to see a typical summer pattern with
scattered afternoon and evening pulse storms.
.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 215 PM EDT Monday...
The ridge of high pressure will drift off the southeast coast
Friday, allowing an upper level trough to move over the Ohio and
Tennessee Valleys Friday. Models develop a surface reflection along
a lee trough that will bring an increase chance for strong to
severe storms into the region. Models currently are placing the
stronger dynamics Friday north of DC, but with all the
instabilities, heat and moisture in the region, the chance for
widespread severe weather will increase for the area Friday and/or
Saturday. If we do not see widespread significant weather Friday,
then Saturday will be the day. The upper level trough over the Ohio
Valley strengthens Saturday and will push bulk of the energy east to
the coast on Sunday. The upper level trough remains to our west
Sunday and Monday, which keeps the chance for showers and
thunderstorms in the area.
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
As of 1000 PM EDT Monday...
Ridging aloft will remain in place through tonight, with
increasing low level convergence developing Tuesday over the
mountains ahead of a weak cold front to the northwest. Given
strong instability would expect greater coverage of storms Tuesday
afternoon compared to the widely scattered activity Monday.
Can`t rule out a stray storm overnight west of the Blue Ridge but
threat as a whole will wane until daytime heating results in
build-ups again Tuesday. Until then mainly VFR expected aside for
some river valley fog or shallow ground fog for areas which
received rain Monday. Any fog that does form will quickly disperse
Medium to high confidence in ceilings, visibilities and winds
during the taf period.
Extended aviation discussion...
The ridge will weaken through mid week as an initial cold front
sinks toward the area from the northwest. This should bring about
an increase in daily convective coverage Tuesday late afternoon
and evening into Friday with periodic MVFR/IFR possible depending
on exactly how far south the front makes it. 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.
Record high temperatures for Tuesday (7/26)
Roanoke.....101 in 1930
Lynchburg...104 in 1934
Danville.....99 in 2012
Blacksburg...94 in 1987
Bluefield....91 in 1993
VA...Heat Advisory from noon to 8 PM EDT Tuesday for VAZ046-047-058-