Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 141355
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
955 AM EDT Mon Aug 14 2017

.SYNOPSIS...
An upper level disturbance through the area today. A frontal
boundary will stay south of us into Tuesday, the shift away and
dissipate into Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 950 AM EDT Monday...

Precipitation across the area is still anticipated to be on the
increase as the day progresses. An upper level disturbance is
progressing eastward through KY/TN, just north of the stalled
frontal boundary to our south. This system will arrive across
our area this afternoon into the evening hours. Coverage is
expected to be greatest in the west with precipitation chances
in the likely category for at least the western half of the area
by mid-afternoon. Showers more scattered in coverage are
expected in the east. Thunderstorms will also be possible this
afternoon across mainly southern and western sections of the
region. Temperatures will experience limited increase through
the day thanks to plenty of cloud cover and cooling rains.

As of 245 AM EDT Monday...

Convection continues to linger over the NC foothills/western
piedmont earl this morning due in part to increased southeast flow
into the mountains leading to convergence, and increased theta-e
ridging. High-res models showing this area moving slowly east
northeast toward southside VA through dawn, while keeping some
lingering back over the same area. Some reports have come in of 2-6
inches of rain in the foothills. Given how this will move out, will
stick with flood advisories for now, with no flood watches
anticipated.

For today, thinking is models may be underdone somewhat into the
rainfall expansion, and feel that the Blue Ridge, from Roanoke
south, and west to the WV will have a decent shot of rain showers
and some thunder through the day. This will be aided by southeast
flow into the mountains, combined with an upper vort moving out of
TN into the Blue Ridge by 18z, then east of the area by this
evening, as well as lift over the stalled frontal boundary in the
Carolinas.

There is another wave at 5h progged to move out of the TN
Valley and cross the southern Appalachians this evening, which will
keep a decent rain chance over our southern counties from the VA/NC
border south through at least midnight. Once this wave passes,
appears just some lingering showers through dawn Tuesday.

Similar to previous forecast, kept high temp below mos, as think
skies stay bkn/ovc most of the day, with a east-southeast wind.

Highs will be mainly in the 70s across the area, but could surpass
80 over the Mountain Empire outside the wedge and possibly southeast
of Danville and Yadkinville.

Not much change in the airmass tonight, so lows still in the mid 60s
to lower 70s.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 245 AM EDT Monday...

What ever is left of the wedge will erode through the day Tuesday as
a weak upper level trough tracks over the south-central Appalachains.
This trough will take advantage of afternoon heat (highs in the 80s)
and abundant moisture (dew points in the mid 60s to low 70s) to
produce afternoon showers and thunderstorms. Low level convergence
is best along the VA/NC border south, therefore have the highest
PoPs. A few storms could become strong or severe in this area
however, our primarily concern is flooding from heavy downpours and
slow moving storms in a PWAT environment of nearly 2 inches.
Climatology does not favor widespread flooding this time of year.
This convection will move into central North Carolina during the
evening with high pressure building in from the west. Partial
clearing is possible Tuesday night which could lead to fog forming
in low lying areas.

High pressure should remain dominate Wednesday but could see a few
pulse storms firing along the Blue Ridge in the afternoon. These
storms may drift east over the foothills before fading in the
evening. Fog will be possible overnight in areas that see rain
during the afternoon. Temperatures will warm above normal Wednesday
with readings in the 80s, possible lower 90s across Southside VA.
Dew points will also increase into the upper 60s to mid 70s.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 1130 AM EDT Sunday...

Looking into the second half of the week, believe most of the shower
and thunderstorm activity will be hit-and-miss variety, driven by
daytime heating, as the weather forecast models do not indicate any
highly organized disturbances moving our way. Models are hinting at
a cool front approaching from the northwest by week`s end, which may
bring greater coverage of rainfall, however given the weak push from
high pressure behind the front, it remains uncertain how far south
this front will progress.

Temperatures enter a modest warming trend towards the end of the
workweek as a weak warm front lifts across the region, allowing
surface winds to shift more southwesterly, tapping more humid air
from the Gulf of Mexico. Temperatures may be a degree or two cooler
next weekend, depending on the amount of cloud cover associated with
the cold front approaching the mid Atlantic.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
As of 715 AM EDT Monday...

Wedge in place with southeast flow will keep cigs in the MVFR to
at times IFR range this morning, with lowest cigs along the Blue
Ridge. For taf sites, appears mainly MVFR. Two areas of showers
this morning, one from ROA-LYH, and scattered southward toward
INT. Another area near LWB and points west. Will maintain VCSH
most of the time with some tempo groups this morning to account
for radar/high res trends. Overall rainfall will be light-
moderate and can drop vsbys to 3-4sm.

As of the this discussion, not too impressed with thunder
chances, given extent of clouds, but some instability is
possible, especially outside the wedge toward BLF. At the moment
will keep VCTS out of the tafs.

Better coverage of showers will be along/west of the Blue Ridge
today, then from MKJ-TNB east to DAN tonight. Cigs overall
should mainly stay MVFR though periods of IFR/VFR are possible.

Late tonight models show less shower coverage and could see
MVFR to IFR fog at most sites.

Extended Aviation Discussion...

Surface high pressure moves east Tuesday, but with weak wedge
still in place could see lingering sub VFR cigs into midday
Tuesday over BLF/LWB. Wed-Fri will have more instability and
scattered to numerous showers, with thunderstorms and MVFR
ceilings and visibilities possible during the afternoon and
evening. Thursday-Friday appear a little more active than
Wednesday.

&&

.EQUIPMENT...
As of 755 PM EDT Saturday Aug 12th...

KFCX doppler radar will continue to be down for the rest of the
month due to a failing bull gear. It will only be operational
during this time frame for brief periods if an imminent
significant widespread severe weather and/or hydrologic event
occurs. Operating the system for any amount of time until the
bull gear is replaced risks a catastrophic failure that would
further extend system downtime. From the 17th through the 27th
the radar will most likely be down completely as the repairs
are expected to be made during this period.

&&

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

&&

$$
SYNOPSIS...DS/WP
NEAR TERM...DS/WP
SHORT TERM...RCS
LONG TERM...NF
AVIATION...AMS/DS/WP
EQUIPMENT...RAB/WERT



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