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847
FXUS61 KRNK 291118
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
718 AM EDT Thu Jun 29 2017

.SYNOPSIS...
High pressure off the coast of VA/NC will allow for increasing
humidity and temperatures today into tonight.  Showers and
storms will be on the increase Friday into the weekend as a
cold front approaches from the northwest.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 225 AM EDT Thursday...

Quiet wx for the most part today with high pressure over the coast
of the Carolinas. High clouds this morning may limit fog to the
river valleys. Will see increasing dewpoints, and during the
afternoon scattered cumulus will form. Looking at deeper moisture
plume over the Gulf Coast in assocation with an upper low/trough
near the Louisiana coast. Models are having this plume shift
northeast toward our area by tonight.

For this afternoon, overall looking dry and model soundings showing
shallow layer of moisture in the 850-800 mb layer. Still expect some
towering cu, though both nam/gfs showing a decent cap in place even
over the NC mountains. High-res models showing isolated coverage
along spine of the Blue Ridge and synoptic models are mainly keeping
any convection over the NC/TN border mountains to the Smokys. Will
keep pops on the low side with isolated wording. Some thunder
possible but with strong cap seems limited.

Should be somewhat of a lull this evening before the deeper moisture
and better upper support shift to the southern Appalachians. Still
appears best coverage stays southwest of us over the Smokys into the
Gulf Coast states, so pops no higher than 25 percent.

Should be mostly sunny today, but sun may be obscured by the high
clouds early. Warmer and slightly more humid with dewpoints rising
into the upper 50s to lower 60s. Highs to range from the mid 70s in
the higher ridges, namely the NC mountains, with lower 80s over the
rest of the mountains/valleys along/west of the Blue Ridge.
Meanwhile, Roanoke, east to the piedmont temps are going to reach
the mid to upper 80s.

Tonight, should be mild with lows in the upper 50s/around 60 west,
to mid 60s east.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
As of 350 AM EDT Thursday...

High pressure off the Mid Atlantic coast will gradually shift east
into Saturday night. Southerly surface winds on the backside of the
High center will advection warm and moist air into our region. A
weak disturbance drifts northeast from out of the northern Gulf
Coast states towards and through the Mid-Appalachian Region. This
system will likely significantly weaken and shear out by the time it
arrives. In any case, the threat for scattered diurnal showers and
thunderstorms will increase. The combination of weak forcing
combining with increasing lower and mid tropospheric moisture
supports the best chances over the mountains, with a lower potential
across the Piedmont which will be a bit further removed from the
weakening system. Increased pops Friday in the west especially along
the western slopes which match up nicely with RLX and GSP. High
temperatures Friday will range the lower 70s in the mountains to the
mid 80s in the piedmont. Convection slowly tappers off Friday
evening into Friday night with the loss of solar heating. Then,
patchy fog develop overnight into Saturday morning. Low temperatures
Friday night will vary from around 60 degrees in the west to the
upper 60s in the east.

The upper trough approaches Saturday with richer low level moisture.
The combination of instability and orographic lift will create
showers and thunderstorms Saturday afternoon into Saturday evening.
Held on to the likely pops west of the Blue Ridge mountains. The Day
three SPC convective outlook has the marginal risk of Severe
thunderstorms to our west across the Ohio Valley with the better
instability and lift. High temperatures on Saturday will climb into
the mid 70s in the west to the mid 80s in the east. Expect a few
showers and isolated thunderstorms to end Saturday evening as the
initial weak short wave trof moves away from the forecast area. It
will be a mild Saturday night with lows from the lower 60s in the
west to around 70 degrees in the east.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 350 AM EDT Thursday...

Several weak disturbances and associated weakening fronts are
expected to move east through nearly zonal upper flow during the
long-term period.

First wave expected to move into/through the area on Sunday, which
may lay down a weakening cool front that will stall out over/near
the area by Sunday - with additional weak disturbances moving east
and through the area through mid week. Both the GFS and ECMWF
are hinting the Monday behind the first wave may be the drier day.

However, exact timing of each wave is still somewhat problematic, but
daily proximity of waves combining with a moist airmass and an old
frontal boundary warrants a continuation of some widely scattered
mainly diurnally-driven shower/thunderstorm threat throughout the
long term period.

Overall forcing and thermodynamics will remain lackluster through
this period, so severe weather threat expected to remain extremely
limited.

&&

.AVIATION /11Z THURSDAY THROUGH MONDAY/...
As of 710 AM EDT Thursday...

Fog never formed at BCB/LWB, and given insolation taking place,
and vis sat showing no fog, will not have any this morning in
the tafs

Cirrus will be around thru the day, mainly thin. Some cumulus to
form in the afternoon, in the 5-9kft range, but overall few-sct
mainly south of a BLF-BCB line. Few showers possible late south
of HLX-TRI line.

VFR through tonight, but may see some increase in clouds late
toward BCB. With increase in dewpoints still cannot rule out fog
at LWB/BCB if they stay clear, so taking them down to IFR
overnight.

Extended Aviation Discussion...

Better threat of storms Friday, as deeper moisture pushes
northeast ahead of a frontal boundary and in associated with
upper trough/shortwave over the southern Appalachains. With any
storms expect localized, brief sub-VFR vsbys/cigs. Friday
night, the potential for IFR/MVFR fog will be greater, along
with some areas with sub-VFR stratus formation.

Saturday should see good coverage of showers and storms
with front moving to the eastern Ohio Valley southwest to the
mid-MS valley. Sunday looks like less coverage, with even drier
conditions expected Monday.

Aside from any storms moving over, and any late night/early
morning fog/stratus, expect VFR conditions.


&&

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

&&

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