Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 260546

Area Forecast Discussion
National Weather Service Blacksburg VA
146 AM EDT THU MAY 26 2016

High pressure is centered just off the southeast Atlantic Coast.
This feature will remain nearly stationary through the end of the
week, clockwise flow around the high resulting in a warm
southwest wind. Increasing moisture from the southwest will result
in increasing cloudiness along with scattered showers and a few
thunderstorms. an area of low pressure is forecast to develop over
the Bahamas Friday. This feature is expected to impact the beaches
along the southeast Atlantic coast this weekend.


As of 1020 PM EDT Wednesday...

Any shower threat overnight will be mainly confined to areas west
of the blue ridge, and primarily west of I-77 where deeper
moisture will have a chance to make inroads. Per regional
radars...Deeper moisture is advancing across the OH/TN
valleys...showers and thunderstorms ongoing from western TN
northeast into KY. This activity is progged to move east northeast
overnight. Have trimmed back probability of showers in all but the
far western county warning area tonight.

High pressure is currently building just off the southeast
Atlantic Coast, clockwise flow around the high resulting in a warm
southwest wind from the Gulf Coast into the Tennessee and Ohio
Valleys. This southwest wind flow is also advecting moist air
northward with dewpoints in the 60s. A broad upper level trof of
low pressure resides over the western U.S. and a short wave has
ejected from this trof, this disturbance currently moving
northeast through the mid-upper MS Valley. It is the tail end of
this short wave that is associated with the area of showers/storms
over wrn TN/KY. Models show this short wave moving down stream and
weakening with time as it encounters the building upper level
ridge over the southeast and mid-atlantic regions. Never the less,
this increase in moisture and lift will be enough to contribute
to widely scattered shower and thunderstorm formation Thursday.
Since dynamics are waning, the thunderstorms are not expected to
be severe.

With the influx of warmer air, high temperatures Thursday will
reach the middle and upper 80s east of the Blue Ridge with upper
70s and lower 80s elsewhere. Lows tonight and again Thursday night
will generally be in the upper 50s to lower 60s. With higher dew
points tonight, have introduced patchy valley fog toward morning.


As of 400 PM EDT Wednesday...

Synoptic pattern will continue to feature an upper level trough
in the southwestern U.S. with a ridge of high pressure over the
east, the primary surface high still centered along the southeast
Atlantic Coast. Southwest flow will provide warmth and moisture to
the forecast area, daytime heating allowing for pop-up
showers/storms, but lack of dynamic support leading to little or
no organization. Net result is a summertime sort of pattern with
shower threat mainly tied to the peak heating part of the day.

Models are in agreement that an area of low pressure will develop
in the vicinity of the Bahamas on Friday, with potential impact to
the beaches along the southeast Atlantic Coast this weekend. For
the central Appalachians we should escape any influence through at
least Saturday.


As of 410 PM EDT Wednesday...

Forecast challenge this period will hinge on track of the area of
tropical low pressure along the southeast Atlantic Coast. The
upper flow will remain quite stagnant with an upper high to our
north and a broad upper low continuing in the western U.S.
Therefore, if the tropical system does drift into the GA/SC/NC
area as most models suggest, although there are notable
differences in the distance it will track inland, it will likely
linger for several days with non-existent steering currents and
blocked upper flow. The upper high to the north could keep the
system lingering in place for several days. Rainfall may become a
concern depending on how far inland the system tracks. The ECMWF
continues to paint the least ominous solution, keeping the bulk
of the precipitation and higher PWATS closer to the coast. At a
minimum, we can expect scattered diurnal convection with
warm/humid conditions through the period. Max temps will remain
mostly in the 70s mountains and 80s elsewhere, with lows mainly
in the 60s. Have not made any drastic changes to the extended QPF
as there is still considerable uncertainty in exactly how much
precipitation we will see.


As of 140 AM EDT Thursday...

Generally VFR conditions expected through the TAF valid
period...with a few exceptions...mainly in the form of early
morning fog in some of the mountain valleys/BCB/LWB. Expect some
mid and high cloud debris from showers and thunderstorms well to
the west of the region. Medium confidence that this cloud cover
will not be enough to hamper fog formation.

A short wave ejecting from a broad upper low over the southwest United
States moves northeast Thursday, bringing a better opportunity
for showers and a few storms to over the mountains and across
areas east of the Appalachians Thursday afternoon. MVFR ceilings
and visibilities are likely in any of these storms. Coverage will
be limited enough to just have VCTS in the TAFs for now.

Extended discussion...

Wind flow through Friday will be out of the southwest with the
weather pattern more reflective of summer conditions, primarily
VFR except for widely scattered afternoon and evening showers
during the peak heating part of the day. Nightime fog also
possible in the mountain valleys, but mainly after midnight up
until an hour or two after daybreak.

Potential wind flow change is advertised by the models this
weekend per development of a storm system off the southeast
Atlantic Coast. Models differ quite a bit on timing and movement
of this feature so low confidence forecast beyond Saturday attm.




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