Area Forecast Discussion
Issued by NWS Blacksburg, VA
FXUS61 KRNK 292007
Area Forecast Discussion
National Weather Service Blacksburg VA
407 PM EDT Mon Aug 29 2016
A weak frontal boundary to our north will slide southward tonight
into Tuesday. Tropical depression Eight off the Outer Banks of
North Carolina will move northwest tonight, then pivot north to
northeast Tuesday into Wednesday. A stronger cold front will
approach on wednesday and arrive on Thursday. Another tropical
system emerging from the Gulf of Mexico on Thursday is expected to
remain to our south and move offshore over the weekend.
.NEAR TERM /THROUGH TUESDAY/...
As of 300 PM EDT Monday...
Surface high pressure located over the Great Lakes and Ohio Valley
this afternoon will move east tonight into Tuesday. A weak frontal
boundary slides to the mid-Atlantic coast by Tuesday morning and
push southeast into Tuesday afternoon. Tropical depression eight
east of the Outer Banks will travel northwest until 8 am Tuesday,
then be pushed out into the Atlantic ocean by cold front Tuesday
afternoon into Wednesday. The combination of solar heating,
instability and low level convergence will generate isolated to
scattered showers and thunderstorms this afternoon into tonight. The
best chance will be across Southeast WV and far Southwest Virginia.
There is also a slight chance across the rest of the higher terrain
including portions of the New River Valley. Any slow moving
thunderstorm could produce locally heavy rains.
Any convection that develops will subside this evening into tonight.
Some models like the Hiresw-arw try to generate some showers tonight
in the northeast, but looked overdone. Light winds and low level
moisture will result in areas of low clouds and fog late tonight
into Tuesday morning. Low temperatures tonight will range from
around 60 degrees in the mountains to the upper 60s in the Piedmont.
A weak frontal boundary will drop southward on Tuesday and stall by
Wednesday. Several shortwave will rotate east across the region. The
presence of the front will help be the focus for isolated to
scattered showers and thunderstorms across the region. The Day two
convective outlook places our area in general thunderstorms. High
temperatures on Tuesday will range from the upper 70s in the
northwest mountains to around 90 degrees in the Piedmont.
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 345 PM EDT Monday...
There will certainly be quite a bit of interest in the tropics
this period with tropical lows along the Mid-Atlantic Coast and
eastern Gulf of Mexico. Both features are progged to steer clear
of our forecast area, but should be monitored never the less for
changes (Please refer to WWW.NHC.NOAA.GOV for the latest
For much of the central Appalachians and points north, the
weather will be influenced by a deepening upper level trough which
is forecast to amplify over the Great Lakes and New England by
Thursday. A series of surface fronts will come through the
forecast area, the first entering the area Tuesday night and
stalling Wednesday. This front will be weak, but still become the
focus for scattered afternoon and evening showers and
thunderstorms Wednesday. The second front will be much stronger,
this feature associated with the deepening upper level trough, and
will signal a more robust airmass change. Models bring this front
through the area during the day Thursday. Again, scattered showers
and thunderstorms will be present along this front, but once the front
passes Thursday night, both dewpoints and temperatures will take a
Temperatures for mid week will remain seasonably warm. Until
Thursdays frontal passage, dewpoints will remain elevated with
humid conditions persisting. Actual air temperatures will average
about five degrees above normal for Wednesday`s Tmax and close to
ten degrees above normal for the lows. Thursday will be the
transition day with temperatures returning to normal.
.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 400 PM EDT Monday...
Model consensus is for long wave trough in the eastern CONUS to
linger Friday and Saturday before upper ridging returns over the
Labor Day Weekend. At the surface, a 1030 mb surface high is
progged to pass across the Great Lakes and into New England,
wedging down the east side of the Appalachians. If the tropical
system in the eastern Gulf of Mexico tracks northeast into the
western Atlantic as forecast then this will result in a very dry
northeast wind Friday into Saturday between the building high from
the north and the departing tropical low to our southeast. At some
point (Sunday?) we should start to experience return flow on the
back side of the high, the building heights resulting in
With a dry airmass progged for Friday and Saturday, anticipate
good radiational cooling at night. This should allow for surface
temperatures to slip into the 50s for lows...and 70s to around 80
for highs. Sunday and Monday will feature warming temperatures
with lows closer to 60 and highs in the 80s.
.AVIATION /20Z MONDAY THROUGH SATURDAY/...
As of 124 PM EDT Monday...
Surface high pressure situated from the Ohio Valley into the Mid-
Atlantic will remain in place this afternoon into tonight. The
combination of heating and low level convergence will generate
isolated to scattered MVFR convection, mainly in the northwest
portion of forecast area. The taf site with the best chance for
convection is KLWB. Any convection that develops will tape off
quickly this evening into tonight. Light winds with low level
moisture will create areas of low clouds and fog tonight into
Tuesday morning. VLIFR conditions are possible at KLWB. While the
valley like KBCB may see MVFR fog.
Morning fog will burn off by 14z with VFR expected at all sites
Tuesday morning. Isolated diurnally driven MVFR convection will be
possible Tuesday afternoon. Coverage will be limited in duration and
area, thus holding off on mention at taf sites.
Medium confidence in ceilings,visibilities and winds during the taf
Extended aviation discussion...
Another front will move into the region Wednesday into Thursday with
a better chance for MVFR/IFR 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 county warning area.