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NWS Area Weather Forecast Discussion
County Warning Area [CWA]: RNK
Regional NWS Weather Office: Blacksburg, VA

000
FXUS61 KRNK 221757
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
157 PM EDT Thu Jun 22 2017

.SYNOPSIS...
High pressure will remain over the southeast United States
today as Tropical storm Cindy tracks north through the  lower
Mississippi Valley. The tropical system will cross the Tennessee
Valley tonight ahead of an approaching cold front. This front passes
through the Mid Atlantic region on Saturday, followed by high
pressure for the beginning of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 945 AM EDT Thursday...No significant changes needed with
this update; essentially just modified the start time of
steadier rain associated with leading edge of warm front, using
a blend of the slower finer-resolution guidance. Regional radar
shows rain shield generally along and south of I-40 in NC and
TN. Precip shield is making slow northeastward inroads due to
dry air as sampled by 12z RNK/GSO RAOBs. Should see
progressively lowering/thickening clouds, but steadier rain
should really hold off until about 1 PM across Smyth, Wythe,
Tazewell Counties in VA and Ashe and Watauga Counties in
northwest NC.

Highs today should be warmest in the central VA Piedmont as
these areas will stay mostly clear to partly cloudy the longest
(in the mid 80s), contrasting with temps into the lower/mid 70s
at most west/southwest of I-77.

Previous near-term discussion issued at 245 AM follows...

Staring out with a relatively dry air mass across southwest
Virginia, southeast West Virginia, and northwest North Carolina this
morning. Moisture increases quickly today and tonight with surface
dew points rising into the mid 60s to lower 70s and precipitable
water values reaching 1.5 to 2.0 inches by this evening.

Models similar in arrival time of precipitation. Wide band of
showers across northern Mississippi to northern Georgia will
continue to move northeast and reach the Virginia-North Carolina
border between 15Z/11AM and 18Z/2PM. Will be after 00Z/8PM before
the bulk of the showers advance past Roanoke and Lynchburg. Not much
support for thunderstorms. Highest convective available potential
energy and lowest Lifted Index values will be across the piedmont
of southern Virginia and northern North Carolina.

Clouds will hold back heating today. Will stay close to warmer
guidance for lows tonight based on the expected dew points.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
As of 330 AM EDT Thursday...

Remnants of Tropical Storm Cindy will bring rain into the area in
two parts Thursday night into Friday morning and Friday night into
Saturday morning.

The main circulation with TS Cindy will move ashore along the SE TX
and SW LA this morning. Out ahead of the main circulation are
tropical short waves tracking across MS/AL. These short waves will
move across the Tennessee Valley today, over the area tonight, then
to the Mid Atlantic coast by Friday afternoon. In the wake of these
waves will be a very humid air mass with dew points in the mid 60s
to lower 70s. Under destructive sunshine Friday, clouds are expected
to develop breaks in the afternoon which could lead to a few pop-up
showers in the afternoon. For the most part, this sunshine will help
temperatures climb into the lower 80s across the mountains to the
upper 80s in the piedmont.

A cold front will pickup the remnants of Cindy and track her across
the Tennessee Valley Friday afternoon and over the forecast area
Friday night into Saturday morning. The interaction of a cold front
and tropical storms remnants will bring a period of heavy rain into
the region. With a tropical air mass in place (precipitable water
values approaching 2.0 inches) and strong dynamics, heavy rain is
likely for the area, especially north of hwy 460. If storms are
efficient enough, flooding is a strong possibility. However, this
event will come across the area during non-diurnal hours and moving
at a fairly fast pace. If models are correct, heavy rain potential
will only last for 2 to 4 hours. Rainfall amounts across the
mountains will range from three quarters south of hwy 460 to an inch
and a half north. Amounts east of the Blue Ridge will range from a
third of an inch south to three quarters of an inch north of hwy
460. The chance for severe weather is also possibly with
damaging wind being the primary threat.

As remnants of Cindy exit by Saturday afternoon, temperatures will
rebound into the upper 70s to lower 80s west of the Blue Ridge to
the upper 80s east. Dew points will drop into the 60s, which should
make the day feel somewhat better. Subsidence in the wake of the
storms will bring some breezy/gusty conditions to the area Saturday
afternoon.

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.

Front will be east of us Sunday but wave of low pressure moving
northeast along it through the eastern Carolinas may send more
clouds into the southern CWA with a slight threat of
showers/sprinkles.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
As of 125 PM EDT Thursday...

Fairly quiet wx this period with cooler temperatures as 5h trough
digs across the eastern U.S. A few shortwaves in the Monday-Tuesday
time frame may fuel a few showers, but overall it looks dry.

Toward Thursday the upper trough exits to the east with shortwave
ridging building across the Appalachians. Highs and lows Monday-
Wednesday should run 5 to 10 degrees below normal, then edge close
to normal by Thursday.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
As of 157 PM EDT Thursday...

Initial VFR conditions first couple hours of the TAF period, but
with gradually deteriorating conditions after 00z with
approaching warm frontal showers. Ceilings steadily lower to
MVFR from southwest to northeast. Better confidence on lower
ceilings west and a little lower confidence on lower ceilings
for Lynchburg and Danville. Visbys in rain generally VFR-MVFR.
In addition, increasing low-level winds of up to 40 kts may
produce periods of low-level wind shear after 04z, with the best
chance at Roanoke, Lewisburg, Bluefield and Blacksburg.
Southwest/south winds should be in the 4 to 6 kt range through
overnight.

Warm front should clear the forecast area early Friday morning,
with related rain showers lifting into northern VA. Slow
improvement to BKN/OVC VFR ceilings expected by mid-morning.
Could see an isolated shower or thunderstorm develop toward the
end of the TAF period, though coverage and timing is of low
confidence. Any thunderstorm that does develop has potential to
produce gusty winds and heavy downpours. Winds will continue to
be gusty along the ridges, leading to localized periods of
turbulence in and around these.

Extended Aviation Discussion...

Coverage of showers and thunderstorms continue to increase later
Friday afternoon but particularly into Friday night. Sub-VFR
conditions should be the rule during this period with showers
and thunderstorms, which may be heavy at times. A few stronger
storms could produce gusty winds. West to east clearing
anticipated through mid-day Saturday with VFR conditions and
a wind shift to northwest. VFR conditions appear to continue
until Monday afternoon with possible VFR/MVFR conditions
northwestern terminals Monday night/Tuesday associated with a
upper-level disturbance.


&&

.HYDROLOGY...
As of 720 AM EDT Thursday...

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
Friday night into early Saturday morning.

Forecast precipitable water values are around 1.75 to 2.00
inches across our region Friday and Friday night, which equates
an anomaly of to +2 to +3 standard deviations above normal
across the area. This type of airmass will result in efficient
rainfall production and very heavy rainfall rates.

The Day 2 Excessive Rainfall Outlook from the Weather
Prediction Center places a Marginal risk of flash flooding
across southeast West Virginia and much of southwest Virginia
and northwest North Carolina, with the Slight Risk on the
western edge of southeast West Virginia.

The highest rainfall amounts will be over the mountains where 1
to 2 inches of rain area possible. Localized three inch amounts
are not unreasonable for parts of southeast West Virginia.

&&

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

&&

$$
SYNOPSIS...AMS
NEAR TERM...AL
SHORT TERM...RCS
LONG TERM...WP
AVIATION...AL/AMS
HYDROLOGY...DS

Forecast Discussion from: NOAA-NWS Script developed by: El Dorado Weather