Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 202340

Area Forecast Discussion
National Weather Service Blacksburg VA
740 PM EDT Wed Sep 20 2017

A weak short wave will move southeast across our region this
evening, then high pressure follows for tonight through Saturday. A
cold front will approach the Mid Atlantic region the middle of next


As of 700 PM EDT Wednesday...

Showers and storms will continue to decrease in coverage across
the area with the loss of heating. Upper level support will not
be zero, so still anticipate some isolated showers lingering a
couple of hours after sunset. No major changes were made to the
ongoing forecast. Tweaked hourly temperature, dew point, sky
cover, and wind grids based upon the latest observations and
expected trends heading into the early overnight hours.

As of 300 PM EDT Wednesday...

The upper level pattern continues with ridging dominating the East
and troffing in the West. A shortwave trough with several lobes of
vorticity will travel southeast tonight into Thursday. Scattered
showers and thunderstorms have developed this afternoon in the deep
moisture convergence and surface LIs around minus 3. However,
convection should remain shallow as it will be fighting the
northwest wind especially out east. HRRR, HiResW-ARW-east, RUC, NAM
and GFS showed convection traveling eastward this afternoon into
this evening, then storms taper off on most solutions by 06z. In
general, scattered showers and thunderstorms will diminish this
evening into tonight with the loss of solar heating.

The combinations of light winds and low level moisture will result
in patches of fog late tonight into early Thursday morning. Low
temperatures tonight will range from the upper 40s in the colder
mountains valleys to the mid 60s in the Piedmont.

Differential heating, surface convergence and orographic lift
Thursday along the Appalachians may produce isolated to scattered
showers and thunderstorms. Convective depth will remain rather
shallow given dry mid-level air in place and surface-based CAPES
at/below 1000 J/kg. Any showers or thunderstorms should follow a
diurnal trend and dissipate with sunset. High temperatures Thursday
will vary from around 70 degrees in the mountains to the mid 80s in
the Piedmont.


As of 310 PM EDT Wednesday...

Will stay rather quiet in our area this period, with showers/few
thunderstorms Thursday evening waning fairly quickly once sunset
occurs. Will see a weak convergent area set up over the southern
Appalachians Friday which should lead to isolated coverage of
showers or storms then drying out Friday night, with potential for a
stray shower into Saturday, though better upper support stays south
of our area, while upper ridge builds across the Ohio Valley into WV.

Temperatures to stay above normal by several degrees, but not seeing
any records threatened.


As of 310 PM EDT Wednesday...

We will remain in an amplified pattern across the country with two
storms in the western Atlantic to watch. Will see Jose weaken into a
post-tropical system in the short term and continue to weaken this
period. Will see Hurricane Maria head north to off the NC coast,
with question remaining on how close and if it Maria comes ashore.
Model ensembles and consensus from NHC keep it east of the mainland.

Meanwhile, the central U.S. will be active with deep upper trough
and slow moving front. Will see this translate to upper ridge across
our area but expect potential for some clouds and possible showers
to flirt with our piedmont counties Tuesday per leftovers of Jose
interacting with coastal front/trough. However, threat of any
appreciable rain looks low for the next 7 days and even beyond the
front washes out as it moves into the eastern U.S. by Thu-Fri next

Temps remain above normal during this time frame with lows in the
upper 50s to around 60 west, to lower to mid 60s east. Highs ranging
from the mid 70s to around 80 west, to lower to mid 80s east, with
some upper 80s not out of the question, especially if Maria stays
strong and we get on the western subsidence side of the system
without any mid/high clouds Tuesday.


As of 730 PM EDT Wednesday...

VFR conditions prevail across the region. This will change has
we progress through the overnight hours with IFR/MVFR fog
anticipated, with also the development of area of IFR/MVFR
stratus across the mountains. Any sub-VFR conditions are
expected to improve to VFR around 13Z-14Z/9AM-10AM Thursday.
Winds will be light and variable or calm.

Extended Aviation Discussion...

Overall persistence forecast to prevail for the rest of the
week, but with a lower probability of precipitation than
Wednesday. Strengthening high pressure remaining in place
between exiting Jose offshore and a weak cold front approaching
from the west. This should maintain good flying weather outside
of isolated diurnal showers and thunderstorms . Dry weather is
expected Friday through Monday. Isolated showers may be possible
on Tuesday.




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