Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 251952
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
352 PM EDT Mon Jul 25 2016

.SYNOPSIS...
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 352 PM Monday...

Heat advisory remains in effect until 8 pm this evening for
South Central Piedmont of Virginia.

Heat Advisory in effect from noon to 8 pm EDT Tuesday for South
Central Piedmont of Virginia.

Isolated storms are developing over the mountains this afternoon
in the unstable air. These storms have been weakening as they
move east into the Piedmont. An isolated pulse severe
thunderstorm may be possible across the north closer to frontal
boundary this afternoon into this evening.

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
Piedmont.

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
temperature.

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 /20Z MONDAY THROUGH SATURDAY/...
As of 148 PM EDT Monday...

SCT to BKN MVFR clouds this afternoon with isolated to widely
scattered IFR conditions near thunderstorms. Ridging aloft will
remain in place this afternoon into tonight, with a bit better
low level convergence developing over the mountains ahead of a
weak cold front to the northwest. Given strong instability would
expect somewhat better tsra coverage mainly west of the Blue Ridge
this afternoon, with perhaps some of this shifting slowly east by
late in the day. Still overall coverage appears scattered to
widely scattered but more clustering potential mountains given
slow movement.

Will keep VCTS at most western sites including KBLF/KBCB and
KLWB this afternoon into tonight. Added the mention vcsh for KROA
with nearby convection.

Despite loss of heating the approach of an upstream cold front and
leftover instability/outflow may keep at least isolated convection
going this evening into tonight. The best chance for any storms
will occur across the north and west. Otherwise should return to
VFR outside of any leftover tsra this evening prior to patchy fog
formation again late.

Ridge is slowly breaking down Tuesday with scattered MVFR/IFR showers
and thunderstorms possible mainly during the afternoon and
evening hours.

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.

&&

.CLIMATE...
Record high temperatures for Monday (7/25)

Roanoke.....100 in 1934
Lynchburg...102 in 1934
Danville....102 in 2010
Blacksburg...92 in 1987
Bluefield....90 in 1987

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Heat Advisory until 8 PM EDT this evening for VAZ046-047-058-
     059.
     Heat Advisory from noon to 8 PM EDT Tuesday for VAZ046-047-058-
     059.
NC...None.
WV...None.

&&

$$
SYNOPSIS...RCS
NEAR TERM...KK
SHORT TERM...RCS
LONG TERM...RCS
AVIATION...JH/KK
CLIMATE...JH



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