FXUS62 KILM 161128

Area Forecast Discussion
National Weather Service Wilmington NC
728 AM EDT Wed Aug 16 2017

Summertime heat and humidity will build and Heat Advisories
will likely be required for at least portions of the area
through Friday. Showers and thunderstorms will be on the
increase during the weekend as a cold front approaches from the
north. This front may stall in close proximity early next week.


As of 300 AM Wednesday...Synoptic conditions will be very similar
to Tuesday across the area through the near term period. For
the most part the mid level pattern will be westerly with slight
ridging building in tonight. At the surface the Piedmont Trough
will once again be the main feature. Guidance is fairly
consistent on mostly sea breeze convection today. Temperature
guidance seems almost identical to Tuesday which means Heat
Advisory criteria will be met in places, mainly in South
Carolina and along the coast. The lack of longevity precludes an
actual headline however.


As of 300 AM Wednesday...The center of warm high pressure will
be positioned across portions of FL and the Southeast states
Thu into Fri. As a longwave trough progressively digs across
the eastern third of the nation late Fri and Fri night, it will
help drive a surface cold front to the SE. This front should
reach central portions of central North Carolina and the
upstate of South Carolina by Sat morning.

850 mb temps will be 19-21 deg C during this period. This will
allow high temps to rise into the lower to mid 90s. These temps
are fairly typical for the later half of Aug. However, dewpoints
will be in the mid and upper 70s with perhaps an 80 deg dewpoint
for portions of the coast. This will make it uncomfortable to
be outdoors as afternoon heat index values will be near or above
105 and as high as 109 deg both Thu and Fri. These conditions
will likely require a Heat Advisory. The nights will be in the
muggy mid and upper 70s.

As for the risk for convection, it will be hit or miss Thu with
the seabreeze being the primary impetus for convection along the
coast and the Piedmont Trough for areas further inland. Morning
and early afternoon convection that does develop along the coast
should tend to migrate inland and away from the beaches as the
afternoon progresses. Convection should tend to wane and come to
an end with loss of heating Thu night. Fri should tend to be
more active convectively later in the day and Fri night as a
cold front gains proximity. Will cap POPS in the chance category
with a likelihood for greater thunderstorm coverage on Sat.


As of 300 PM Tuesday...Vertically stacked high pressure
offshore will strengthen into Saturday ahead of a shortwave and
associated cold front dropping into the OH VLY. The front will
drop into the area and then likely stall as the shortwave hangs
back, the front becomes flow-parallel, as ridging persists to
the east. Convection chances will ramp up significantly
Saturday, with still good chances Sunday as the shortwave digs
through the Mid-Atlantic and offshore. Temps for the wknd will
remain above climo as well.

Concern then shifts to Monday, the day of the total solar eclipse.
Guidance has backed off on a clean FROPA, and has the front
dissipating overhead during Monday. This is much more typical for
late August. While this could create more clouds and unsettled
conditions for Monday across the area, mid-level flow does become
W/NW behind the aforementioned shortwave which brings some drier
air into the mid-levels. At this time a fairly typical August day is
expected with aftn CU and convection, especially focused along the
stalled boundary wherever that may set up. This does not suggest the
eclipse will not be visible, but may be temporarily blocked by
convection at times.

On Tuesday offshore high pressure re-asserts itself, but yet another
weak cold front will approach from the NW creating good convection
chances with continuing above climo heat and humidity.


As of 12Z...VFR is forecast through the period. However,
isolated to perhaps scattered showers and thunderstorms that do
develop along the seabreeze and Piedmont Trough will have the
potential to briefly drop conditions to MVFR or lower. However,
the risk that a thunderstorm will move directly over a terminal
is low and so flight restrictions are not referenced in any of
the TAFs. Afternoon and early eve VCTS was confined to the
coastal terminals where the probability for thunderstorms is
slightly higher than across KFLO and KLBT. Did include sct
stratus below 1kft after 09z at the coastal terminals as model
profiles are most supportive of some low cloud development here
in very weak onshore flow. However, this low status may very
well develop toward the tail end of the valid TAF period across
the inland terminals as well.

Extended Outlook...A brief period of MVFR or lower conditions
can not be ruled out in isolated to scattered showers and
thunderstorms through Fri. The risk for flight restrictions due
to showers and thunderstorms will increase significantly on
Sat and Sun. Low stratus and some fog during the overnight and
early morning hours may result in flight restrictions as well
each day.


As of 300 AM Wednesday...Winds have a mostly westerly component this
morning as a weak trough has pushed across the waters. The weak flow
will remain in place through the period with more of a southwest
flow developing later this morning then south to southeast with the
sea breeze influence. Weak high pressure may build in tonight
turning the winds to northeast but once again the flow will be very
light, ten knots or less. Regarding seas, the influence of Hurricane
Gert will wane as seas will be in a range of 2-4 feet dropping to
around two feet by Thursday morning.

As of 300 AM Wednesday...A trough will wash out by/during Thu
morning and the Piedmont Trough and Bermuda High will be in
place for the balance of the forecast period. A cold front will
approach the waters from the NW Fri night. Initially, the wind
direction may be light E or SE with the direction veering to S
Thu afternoon and SW Thu night. SW winds will then persist
through the end of the period, increasing to 15 to 20 kt Fri
afternoon and night. The strengthening winds will allow seas to
build from 2 ft Thu and Thu night to 3 ft Fri afternoon and 3
to 4 ft Fri night.

As of 300 PM Tuesday...A cold front approaching from the NW
will sandwich the waters with a pinched gradient as high
pressure spins offshore. This will result in SW winds of around
15 kt into Sunday morning. This front will stall and begin to
dissipate inland from the waters on Sunday, causing the gradient
to relax and wind speeds to fall to around 10 kt while
maintaining a SW direction. Initially seas will be 2 to 4 ft,
but will increase thanks to an amplifying SW wind wave,
becoming 3-5 ft by Saturday night. Conditions should remain just
below any cautionary statements. As the winds begin to ease
Sunday, seas will follow, with wave heights falling to around 3
ft at the end of the period.






NWS ILM Office Area Forecast Discussion