Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 291022
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
622 AM EDT Mon May 29 2017

.SYNOPSIS...
Today should be the hottest day of the week with temperatures in
the 90s away from the beaches. Thunderstorms may return tonight
and Tuesday ahead of a cold front. This front should stall
across the area Wednesday and Thursday, returning north again on
Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 300 AM Monday...A strong round of convection last night
beneath a mid-level impulse has moved offshore, with a surface
trough exiting the coast this morning. While mid and high level
debris cloudiness will again scatter through the sky this morning,
subsidence behind the departing impulse and increasingly dry air
behind the convection will create a hot but sunny Memorial Day
across the area.

Elongated high pressure which has been stretched along the Gulf
Coast for days now, will recenter offshore today in response to mid-
level ridging blossoming up the Southeast coast. This thickness
advection will push the strongest band of mid-level westerlies NW of
the area at least through this evening, and the combination of
subsidence beneath this along with the factors mentioned above will
create a hot and dry day. Today is forecast to be the hottest day of
this stretch, with widespread 90s forecast even right to the beaches
as westerly wind pins the sea breeze at least into the late aftn.
However, drier air aloft noted on soundings will allow for the
dewpoints to mix out, and thus have kept all heat index values just
below 100 degrees today - but still the hottest so far of 2017.

Guidance is in very good agreement that a vorticity impulse rotating
SW to NE around the ridge will spawn another round of convection
this evening W/SW of the area, and then push NE into the CWA. Most
of this activity is forecast to occur tonight, but forecast soundings
suggest considerable MUCape of 1000-15000 J/Kg of MUCape above the
nocturnal inversion along with 35-40 kts of 0-6 km shear. This will
likely manifest as increasingly organized convection beneath the mid-
level impulse, and another MCS with the potential for strong winds
and hail may move across the area tonight. Inland locations may have
the best chance with this setup, but have carried CHC POP for nearly
the entire CWA tonight. Any convection will move offshore before the
end of this period, leaving drier conditions and mins a degree or
two either side of 70.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 300 AM Monday...500 mb high pressure will move farther
offshore Tuesday and Wednesday to near Bermuda. Upper level low
pressure will dig a trough across the Great Lakes. In between
these two systems will be a flow of mid to upper level moisture
originating from the western Gulf of Mexico streaming northeastward
across the Carolinas. This moisture should remain overhead
Tuesday, but will thin out below 600 mb on Wednesday.

Tuesday appears to have favorable conditions for convection,
perhaps arriving in two rounds. The first could be ongoing as
the sun rises Tuesday morning as the last in a series of Monday
night vort maxes pass overhead. After a lull in the late
morning through early afternoon hours, another round of
convection should develop during the mid to late afternoon hours
with the arrival of a second vort max. Forecast PoPs have been
bumped up to 40-60 percent, highest just inland from the coast
where seabreeze convergence should exist. Model forecast CAPE as
large as 3000 J/kg will coexist with weaker mid-level winds than
we`ve seen the past couple of days. Despite the good buoyancy
the organized severe weather threat is overall not as high as we
saw yesterday or today.

A weak cold front sinking southward from the Mid-Atlantic region
will settle into the area Wednesday morning. Any northwest winds
behind the front will be fleeting as Wednesday afternoon`s
seabreeze should send the boundary back to the north. A cooler
and much drier lower atmosphere will make it harder to generate
showers and storms Wednesday and our forecast PoPs are only 20
percent. Forecast highs are in the upper 80s both days, with
nighttime lows in the upper 60s to near 70.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 300 PM Sunday...GFS/ECMWF in agreement on the evolving H5
pattern in slowly migrating a broad but low amplitude trough
eastward across the Great lakes and Ohio valley then into
New England and SE Canada this period, while holding an upper
ridge of varying amplitude over Florida and the Bahamas. This
will allow a series of weak fronts and upper disturbances to
move to our coasts, offering daily chances of thunderstorms.
Late May/early June heating coupled with PWATS values between
1.50-1.80", and numerous surface boundaries, will support
convection much of the extended forecast period. Next weekend
potentially could turn wet, as enhancement of column moisture is
drawn from the Gulf of Mexico by low pressure over Texas on
Saturday, tracking to the Ohio Valley during Sunday. With the
abundance of clouds, daytime temperatures will run near normal
for the season, middle to upper 80s, but above average minimum
temperatures in the upper 60s to low 70s.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
As of 12Z...VFR conditions will continue through at least
sunset this evening. High pressure well offshore will provide
southwesterly winds 5-10 kt which will turn southerly 10-15 kt
along the coast this afternoon with the seabreeze. A train of
upper level disturbances will reach the area tonight, possibly
accompanied by showers and thunderstorms developing inland as
early as 01Z and at the coast by 04Z. Ceiling and visibility
restriction will occur beneath any of these convective cells.

Extended Outlook...MVFR/IFR conditions are possible in
thunderstorms Tuesday, mainly during the afternoon and evening.
More typical scattered showers and thunderstorms are possible
Wednesday through Friday.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 300 AM Monday...Weak trough will move offshore this morning,
causing winds to shift to the west while easing to 5-10 kts. This
change will be short lived however, as high pressure expands from
the south, winds will quickly return to the S/SW and increase once
again to 10-15 kts and persist at these speeds through tonight. The
exception will once again be within the near shore sea breeze
circulation, where a local backing along with gusts up to 20 kts are
forecast this aftn/eve. A low amplitude SE swell will again be
masked by a 5 sec SW wind wave, and seas will become uniformly 2-3
ft today and tonight.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 300 AM Monday...1023 mb high pressure anchored offshore
well south of Bermuda will move little through the period. This
should maintain a light to moderate southwest wind across the
Carolina coastal waters. A weak cold front will slide into the
area from the north Wednesday morning, however any shift to
northwesterly winds appears to be brief as the afternoon
seabreeze should push the front back inland. Seas should average
2 feet through the period.

Thunderstorms will be a concern for mariners, particularly
Tuesday and Tuesday night as models show a series of upper level
disturbances and good moisture crossing overhead. By Wednesday
the atmosphere dries out enough to hopefully make thunderstorms
more isolated in coverage.

LONG TERM /THURSDAY THROUGH FRIDAY/...
As of 300 PM Sunday...Near typical summer-like marine
conditions this period as SW winds prevail with 2-3 foot seas.
High pressure will remain centered just to the SE and E of
Bermuda, and weak troughing inland should maintain SW wind flow
Wed to Fri. The sea spectrum will be comprised of S-SSW waves
1-2 feet every 5 seconds and ESE waves 1-2 feet every 8 seconds.
TSTMS will be active this period, moving generally from land to
the coastal waters, and some may be strong from afternoon
heating. Getting a radar update before heading out may be in the
best interest of safely this period as we transition into a
more active lightning and TSTM wind gust season.

&&

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

&&

$$

SYNOPSIS...TRA
NEAR TERM...JDW
SHORT TERM...TRA
LONG TERM...MJC
AVIATION...TRA



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