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000
FXUS61 KRNK 220104
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
904 PM EDT Wed Jun 21 2017

.SYNOPSIS...
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Weak high pressure will remain over the region overnight into
Thursday. The remnants of Cindy will slide northeast from the
Gulf Coast states Thursday before getting caught up with an
approaching cold front from the west on Friday. The front along
with the remains of Cindy will push through the region Friday
night into early Saturday, before quickly exiting offshore
Saturday afternoon.
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&&

.NEAR TERM /THROUGH THURSDAY/...
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As of 855 PM EDT Wednesday...

Area remains in between deeper tropical moisture to the south
and a weak surface front to the north this evening. Latest
evening soundings also show some low level instability that
helped kick off earlier isolated showers beneath capped very dry
air aloft. Expect this along with loss of heating to limit
southward advance of upstream showers with the front across
parts of West Va attm. Also appears any showers to the south
with the weak front/tropical moisture wont push north until
later Thursday so keeping things mostly dry overnight. Also
given slower trends in latest short term guidance, delayed onset
of showers on Thursday over the southwest until midday or so.
Otherwise will call it mainly partly cloudy for intervals of
high/mid clouds overnight with some spotty fog around. Nudged up
lows a little in spots given higher dewpoints across the south/east
and projected influx of more low level moisture by morning.


Previous valid discussion as of 300 PM EDT Wednesday...

5h ridge will build over the southeast thru Thursday while upper
system in association with TS Cindy pushes into the TX/LA area.
Models are showing vort energy moving northeast along with moisture
by Thursday afternoon. At least some agreement to keep rain showers
likely over the southwest VA to NW NC mountains Thursday afternoon,
tapering to little to no chance around Lynchburg.

Tonight, should see partly cloudy skies, but more clouds will move
in from the southwest late along with low chance of showers.

The low level pattern does not favor a great deal of rain, and
limited threat of thunder, though pwats will surge to 1.0 to 1.5
inches late then 1.5 to 2.0 by the end of the day Thursday.

Highest rainfall amounts through Thursday afternoon will be around a
quarter of an inch in the NC mountains, so not expecting any
flooding concerns.

Dewpoints will rise and Thursday will feel more muggy than the past
couple of days. Lows tonight start that trend with readings in the
60s, then with more clouds Thursday, especially in the mountains,
temperatures should reach the 80s, with 70s over the Mountain Empire
to the NC High Country. May reach 90 in places like Dillwyn,
Keysville and Lynchburg.
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&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 300 PM EDT Wednesday...

The weather pattern across the region is expected to establish itself
during this time period to be one with plenty of potential for
rainfall, some on the heavy side.

Thursday night into Friday morning, the remnants of T.S Cindy are
expected to be moving north through the Lower Mississippi Valley.
Concurrently, a cold front will be approaching the region from the
northwest. The moisture fetch on the east side of the dissipating
tropical system will start to be advected into our region,
increasing the potential for showers across the region from
southwest to northeast during this time period.

By Friday afternoon, the cold front is expected to located just
north of the Ohio River, with the remnants of Cindy near Paducah,
KY. This will be the point that the moisture under the core of the
tropical system starts to ride eastward along the cold front, and
reach our region Friday night, with the focus of the best cover
across our southeast West Virginia counties.

By Saturday morning, the remnants of Cindy will be closer to the
Mason-Dixon line, and flow on the backside of the system will help
usher the cold front through our region, and precipitation chances
will be on the decrease during the course of the day.

For more information regarding the heavy precipitation concerns with
this event, please reference the HYDROLOGY section of this
discussion.

Winds associated with the remnants of Cindy are not anticipated to
be too strong across the region, but there will be enough of a
gradient remaining so that gusts across the higher elevations in the
25 to 40 mph range will not be uncommon on Friday into early Friday
evening.

Temperatures during this portion of the forecast will average a few
degrees above normal.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 130 PM EDT Wednesday...

There are notable model differences during this portion of the
forecast. Guidance starts out similar Saturday night with a cold
front parked just to the southeast of the region. Lingering isolated
showers will be possible across southeastern sections of the area.

Where the models differ is the Sunday into Monday time period. Both
models offer solutions of a reinforcing cold front sweeping through
the area Monday, however, that concludes the similarities.  The GFS,
for the most part, offers very limited moisture associated with the
feature. Its European counterpart offers a wetter solutions. This
wetter solution is the result of this guidance bringing a shortwave
trough eastward the Tennessee Valley along the first cold front,
that interacts with the second cold front, producing a generous
coverage of showers across the area late Sunday night and through
the day on Monday. Our forecast during this time frame will
represent a blended solution that offers the potential of showers,
but not to the degree done so by the European solution.

On Tuesday, both the GFS and ECMWF hint at a shortwave trough
heading eastward through the Great Lakes region into New England.
Both keep the bulk of the energy and moisture north of our region.
Our forecast will reflect at best some isolated showers across
far northern sections of the forecast area.

High pressure and dry weather is forecast for Wednesday.

Temperatures during this portion of the forecast will start around
near normal and trend to slightly cooler than normal by Wednesday.

&&

.AVIATION /01Z THURSDAY THROUGH MONDAY/...
As of 730 PM EDT Wednesday...

VFR conditions will prevail tonight into Thursday. The only
except will be patchy fog late tonight into Thursday morning.
KLWB is the taf site with the best chance for fog. MVFR fog is
possible at KLYH and KBCB.

Mid and high clouds will increase overnight into Thursday ahead
of a front, and moisture from remnants of Cindy. Winds will
generally be southwest at 8kt or less.

High confidence in ceilings, visibilities and winds during the
taf period.

Extended Aviation Discussion...

Ceilings lower to MVFR Thursday evening into Friday with first
surge of showers advancing SW to NE. More sub-VFR conditions
through at least early Saturday with periods of moderate to
heavy rain. Less threat of showers Saturday evening into Sunday
so mainly VFR after Saturday morning, but fog Sunday morning is
possible. Scattered MVFR convection is possible Monday.

&&

.HYDROLOGY...
As of 320 PM EDT Wednesday...

The combination of the the remnants of T.S. Cindy crossing the area
in concert with the approach and arrival of a cold front may set the
stage for very heavy, flood producing, rain across parts of the area
Thursday night into early Saturday morning.

An analysis of the 00Z/8PM NAEFS Standardized Anomalies of
precipitable water around 1.75 to 2.00 inches across our region
during the Thursday night through Friday night time period, which
equates an anomaly of to +2 to +3 sigma across the area. Mean
integrated water vapor transport is forecast to have an anomaly
around +4 to +6 during this same time period. A review of the NAEFS
Probabilities place a 50 to 70 percent of extreme maximum of
precipitable water over southeast West Virginia mid-day Friday with
25 to 50 percent across a generous portion of the remainder of the
area.

The Day 3 Excessive Rainfall Outlook from the Weather Prediction
Center places a Marginal risk of flash flooding across our region,
with the slight chance on the western edge of our West Virginia
Counties.

WPC QPF numbers across our region during the Thursday through
Saturday morning time period has roughly 0.50 to 1.25 across the
Piedmont, with the highest amounts on the western parts of this
region. Across the mountains, 1.25 to 1.75 is the average. Higher
amounts near 2.00 inches are forecast across some of the higher
peaks across the Mountain Empire region of southwest Virginia into
the Northern Mountains of North Carolina. Western Greenbrier County,
West Virginia is forecast to have some of the greatest amounts
during this time period with totals around 2.50 inches possible.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.

&&

$$
SYNOPSIS...JH
NEAR TERM...JH/WP
SHORT TERM...DS
LONG TERM...DS
AVIATION...KK/WP
HYDROLOGY...DS