Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 200148

Area Forecast Discussion
National Weather Service Blacksburg VA
948 PM EDT Thu Jul 19 2018

High pressure will retreat off the northeast coast through
Friday as a complex area of low pressure approaches by the weekend.
This will result in increasing chances for rainfall into early next


As of 945 PM EDT Thursday...

Only minor adjustments this evening to forecast to reflect the
latest temperature, dew point, and wind observations and
expected trends into early Friday morning. Will still keep the
potential for isolated showers across the Northern Mountains of
North Carolina as moisture pools upslope in this region.

As of 640 PM EDT Thursday...

The biggest adjustment to the forecast for this evening will be
less aggressive POPs across the southwest portion of the area.
The nearest activity is farther southwest across the Smokies,
and is trending more easterly than northeasterly. This
adjustment downward will carry through the night and into at
least the first half of Friday.

Have made minor adjustments to hourly temperature, dew point,
wind/gusts, and sky cover to better match the latest
observations and expected trends through the evening hours.

As of 300 PM EDT Thursday...

Transition period develops in the near term as high pressure
over New England continues to slowly relinquish control over
the weather in our region. Upper level low is forecast to deepen
and then close off over the northern Mississippi Valley and
begin to drop southeast toward the Ohio Valley during this time
period. At the same time an inverted trough/low pressure will
be setting up along the southeast coastline with a rich feed of
tropical moisture lifting from Florida up along the coastline.
The heavy rainfall associated with this feature should remain
southeast of our CWA through Friday evening while moisture from
the northern system edges southeast toward our area. PoPs
should remain fairly low, generally under 30 through Friday
evening with the best chances in the southwest by late in the
day and possibly sneaking into far southeast as well. Will not
see the very cool temperatures of last night into tomorrow
morning with the slowly increasing clouds/humidity but still
pleasant enough for mid-July. Friday will see clouds on the
increase with near seasonable temperatures and only that slight
chance for rain by afternoon. Higher instability and significant
severe will remain west of the CWA across TN/KY during the day,
while the residual wedge and easterly flow maintains only a
general thunderstorm risk across our region through 00z Sat.


As of 300 PM EDT Thursday...

Unusual midsummer pattern shaping up through the weekend as a large
cutoff low develops over the upper midwest and slowly sinks south
through the Ohio/mid Mississippi valley with an established wedge east
of the Appalachians extending from high pressure off the New England

There appears to be good support for upstream convection developing
into a robust MCS Friday into Friday night, but anticipate it will dive
southward and follow the western edge of the wedge toward the best
instability. While the greatest impacts look to affect locations off to
our west and south, will have to see how close this system comes to
affecting southeast WV and other locations west of I77. Stabilizing
effects of the wedge will be waning as the wedge weakens and our flow
becomes southerly with good moisture transport. This will yield
increasing chances for showers and thunderstorms through the weekend.

Temperatures will be just on the cool side of seasonal normals with
highs generally in the mid 80s east of the Blue Ridge and in the upper
70s/around 80 to the west. Lows will generally be in the 60s.


As of 300 PM EDT Thursday...

As the stacked cutoff sinks south toward the Gulf coast and slowly
weakens, a large Bermuda high will push in from the east and place the
Appalachians and central mid Atlantic region under the proverbial ring
of fire with good chances for showers/thunderstorms each day. Deep
moisture transport will boost precipitable water values near 2 inches
by midweek especially east of the Blue Ridge. This will be setting the
stage for multiple periods of locally heavy rain and potentially some
hydro issues despite relatively dry antecedent conditions at some
locations. The potential for severe storms will depend in large part on
how much sun we see through abundant cloud cover to generate surface
based instability. Will be watching closely to see how this active
weather pattern develops over the next several days.

Temperatures will continue to be near to slightly below normal through
the middle of next week.


As of 740 PM EDT Thursday...

Mainly VFR conditions are expected through the current TAF
forecast cycle that ends at 00Z Saturday/8pm Friday. Some
patchy MVFR fog will be possible for a short time Friday morning
across the Piedmont. Also, isolated to scattered showers and
storms across the far western parts of the area on Friday
afternoon may be heavy enough to generate some brief MVFR
visibilities due to the heavy rain.

Winds will trend light and variable or calm overnight. An east
to southeast winds around 5 to 10 kts is forecast for Friday
with some gusts at higher elevations in the 15 to 20 kt range.

Confidence in the above portions of the forecast is high.

Extended Aviation...

Scattered showers and thunderstorms with sub-VFR conditions are
expected Saturday ahead of the next cold front. Scattered to
numerous showers and thunderstorms again on Sunday and Monday
with periods of sub-VFR mainly during the afternoon and evening




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