Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 261114
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
714 AM EDT Wed Jul 26 2017

.SYNOPSIS...
Drier weather will work into the area behind a cold front today.
The front will dissipate to our south on Thursday. Mainly isolated
showers and thunderstorms will become numerous Friday into Saturday
ahead of an unseasonably strong cold front. Strong to severe
thunderstorms will be possible later Friday and Friday night. Much
drier air is expected in the wake of this system early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 600 AM Wednesday...A cold front was running right along
the South Santee River and will drift further south through
today. A mid to upper trough will run from GA to the east
northeast into the Atlantic. Low pressure developing and trying
to cutoff at the base of this trough over GA/SC will produce low
pressure extending down to the lower levels. This will produce
a deep NE to E flow through today and will also bring drier air
and subsidence down over NC and into SC by later today into
tonight. Initially, this boundary, along with the sea breeze
will remain the focal point for convection through today. An
area of lower clouds was easing south behind the front while
isolated thunderstorms were developing along and just south of
the front. Expect lower clouds to break up through the morning
and isolated to scattered convective development to be focused
along the cold front, sea breeze front and any localized
boundaries. Therefore the best chc of thunderstorms will be
across SC and along the coast up to Cape Fear while greater
amounts of sunshine and drier air can be found over much of NC
and N and NW portions of South Carolina. The NE to E flow
behind front will keep temps below 90 most places today.

Dry air will slowly work its way into the area, especially in
the mid to upper levels with clearing skies developing from N to
S into tonight. Pcp water values will drop below 1.25 inches by
tonight. Guidance shows dewpoint temps dropping to near 70 or
just below through late this afternoon into tonight. This will
allow overnight lows to fall into the lower 70s across much of
the inland areas under mainly clear skies.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 300 AM Wednesday...A cold front will be in the process
of dissipating to our S on Thu. Modest ridging aloft going into
Thu erodes rather quickly and is replaced with increasing
troughiness. Then as this trough deepens across the Eastern
third of the CONUS, it helps to drive a cold front southward.
This front will be very near our northwest zones by daybreak
Sat.

The expectation is that Thu will be a day of transition as
initially drier air will show some erosion as deeper mositure
begins to poke back to the N. Thus, slight chance or chance POPs
for showers and thunderstorms appear warranted for mainly our
southern zones, highest across the South Santee River area.
Convection may begin to blossom offshore Thu night, perhaps
skirting portions of the immediate coast. The deep moisture will
be feeding N and focusing along and ahead of impressive trough,
especially given the time of year. Precipitable water values
climb to more than 2 inches and peak at more than 2.25 inches
Fri night. At the same time, robust shortwave energy pivots
across the eastern Carolinas with a southwest low-level jet of
50 kt impinging on the area and diffluence aloft. This will
support increasing shower and thunderstorm activity during Fri
with the most widespread coverage late Fri and Fri night and
perhaps into Sat. This setup could very well support an
organized severe thunderstorm event. The Pattern should be
progressive enough to limit excessive rainfall concerns with
very high moisture content being mitigated by quick storm
motions.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 215 PM Tuesday...An unseasonably amplified upper trough
becomes the primary feature and key player for late week and
weekend sensible weather. This will translate to elevated rain
chances Saturday as this system ushers a fairly strong surface
trough across the coast. ECMWF and GFS clear this boundary off
the coast into early Sunday, the GFS much stronger. Both suggest
therefore some drying and cooling, but of differing magnitude.
A blend still brings surface dewpoints into the 60s early next
week, helping to take off the bite of high absolute humidity
values. A dry mid-level air intrusion will curtail deep
convection Sunday through early next week. A few showers could
linger and remain favored closer the coast in proximity to
higher moisture and the oceanic front, but the overall coverage
should trend down Sunday onward. Temperatures will be slightly
below normal as cool air advection pushes into the balmy sea
air.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
As of 12Z...Drier air continues to seep into the area from the
N in the wake of a cold front. This front will stall south of
the terminals today and slowly dissolve tonight and Thu. Drying
should be just deep enough at KLBT and KILM to keep mention of
showers out of the TAF forecast here. Elsewhere, will include
VCSH from about 16-00z. There may be a rumble of thunder, but
the probability is just low enough to keep thunder out of the
TAF forecast at KFLO/KCRE and KMYR. Thunderstorms will be
scattered to perhaps numerous across southern portions of South
Carolina and points S where the front will reside during peak
heating.

Will initialize with MVFR/IFR ceilings at all sites. Expect VFR
to develop at the remaining terminals in the 14-16z time frame.
VFR will continue through the remainder of the valid period,
but will introduce few/sct stratus at or below 1 kft after
07-09z. Moisture should be very limited overnight and thus not
supportive of ceilings or fog.

Extended Outlook...MVFR or lower flight restrictions are likely
in association with numerous thunderstorms later Fri and Fri
night. Some of the thunderstorms may be strong to severe. Flight
restrictions may persist into portions of Sat as well.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 600 AM Wednesday...In the wake of a cold front, the wind
direction has shifted to the NE or ENE and we expect this
direction to hold across the waters with speeds of 10 to 15 kt.
The on shore winds will push seas up from less than 3 ft this
morning to 3 to 4 ft later today into tonight.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 300 AM Wednesday...A cold front will be in the process of
dissipating to our S on Thu. A stronger cold front will be
approaching from the N Fri night. A light easterly flow early on
Thu will veer to SE and S Thu afternoon. Wind speeds will
increase Thu night as the direction veers to SW. SW winds will
then persist through the end of the period as they increase to
near 20 kt later Fri and Fri night. Seas will build in response
to the increasing wind, building from 2 ft Thu and Thu eve to 3
to 4 ft Fri afternoon and 4 to 5 ft Fri night. Small Craft
Should Exercise Caution conditions appear likely late in the
period. Thunderstorms will be few if any Thu but we do expect
them to become numerous during Fri and especially Fri night.

LONG TERM /SATURDAY THROUGH SUNDAY/...
As of 215 PM Tuesday...Wind direction will become changeable
this period, but the good news is that wind-speeds will decrease
as a front lays up along the coast then offshore. TSTMS will be
numerous along the front into Saturday, so a radar update
should be on the checklist for the first part of the weekend.
TSTMS will decrease in coverage Sunday, although the Gulf Stream
and outer waters may remain unsettled due to the offshore
front.

Gusts to 20 KT from the SW may persist into Sat morning ahead
of the front. Then once the front moves through later Sat and
Sat night, the wind direction will shift to the NW and N and
then NE on Sun. Wind speeds Sat afternoon through Sun will be on
the order of 10 kt.

Seas of 4 to 5 ft early Sat will subside to 3 to 4 ft, but a
modest NE push may bring some 5 ft seas back across portions of
the outermost waters on Sun.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.

&&

$$

NEAR TERM...RGZ/RJD
SHORT TERM...RJD
LONG TERM...MJC
AVIATION...RJD



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