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859
FXUS62 KILM 251344
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
944 AM EDT Sat May 25 2024

.SYNOPSIS...
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Unseasonably hot and humid conditions are expected to continue
through Tuesday with scattered mainly afternoon and evening
thunderstorms continuing. An approaching cold front should
enhance thunderstorm coverage late Monday into Monday night.
The front will stall near the coast on Tuesday and Wednesday
before a second front pushes through Wednesday night, bringing
cooler and drier weather.
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&&

.UPDATE...
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No significant changes have been made with the forecast with
this morning`s update. Inland temperatures should still approach
90 degrees - but remaining 5 degrees cooler at the beaches with
a well-defined seabreeze anticipated to develop in the next few
hours. Isolated seabreeze convection this afternoon will be
joined by southeastward-propagating cells developing in
association with a shortwave moving across the Carolinas late
this afternoon and this evening. Some enhanced mid level wind
speeds could help organize these line segments sufficiently for
a damaging wind threat to emerge.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
Subtle northwest flow aloft develops today as weak ridging expands
north over the western Gulf of Mexico. Not a big shift, but enough
to run another cluster of shortwaves northwest to southeast across
the forecast area. This is something that tends to lead to active
weather, even with marginal environmental parameters (not the case
today). Continued temperatures above normal today and dewpoints in
the mid to upper 60s will push SBCAPE over 2500 J/kg in some areas.
The pinned sea breeze will likely be where the first batch of storms
develop, with SC favored due to some PVA enhancement early
afternoon. From there outflow will generate some additional
convection with areas farther inland starting to see some action
later in the afternoon as the next batch of shortwave enhancement
arrives. There may also be some boundary interaction inland by mid
to late afternoon. The steady stream of shortwave energy that had
been moving across the area comes to an end this evening. Do not
expect convection to continue overnight as it has in past nights.
Patchy fog may be a concern in areas that see high rainfall amounts,
but boundary layer winds will limit duration and coverage.

Some potential for training/backbuilding storms given the storm
motion/steering flow, however the lack of a deep warm cloud layer
and precipitable water marginally above climo suggest flooding is a
localized concern at best. As was the case on Fri, the environment
is not really supportive of organized/widespread strong/severe
storms, but pulse storms have the potential to produce a few
damaging wind gusts or large hail hence the marginal risk.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
On Sunday, rising mid-level heights during the day should keep a
lid on convection through the morning and into the early
afternoon due to subsidence. However, within a moist low-level
environment, large SBCAPE is still expected to develop. Subtle
impulses embedded in the mid-level flow combined with surface
convergence along the Piedmont trough and sea breeze should be
enough to help get at least isolated convection going during
peak heating in the mid-late afternoon. Given the CAPE profile,
any storms that do develop will be capable of frequent lightning
and small hail, but weak to modest effective shear should keep
their lifetimes limited. High temps across the region are
expected to breach 90F except where marine influences are felt
early enough in the day.

Any storms should tend to weaken and dissipate with the loss of
daytime heating and the passage of the impulses aloft, with
subsidence bringing PoPs into the slight chance range for
Sunday night. An approaching cold front, courtesy of a forecast
sub-1000 mb low pressure system over the Great Lakes region,
should bring at least subtle warm advection during Sunday night,
keeping nighttime lows in the low 70s.

On Monday, the front crosses the Appalachians and draws nearer
to the coast, with mid-level shortwave energy accompanying it.
However, considerable subsidence and dry air well-ahead of these
features should keep much of Monday dry except for isolated
convection which can break through the cap aloft. This should
make for the hottest day in this string of 90-degree days, with
abnormally warm mid-level temperatures (reaching or exceeding
the 90th percentile at 850mb) supporting highs in the 91-93F
range, with heat indices forecast to reach the upper 90s.

Expect scattered showers and storms to arrive along and ahead of
the cold front late on Monday and Monday night. The timing of
this arrival of convection will affect severe weather chances,
as moderate to strong instability during peak heating paired
with increasing effective shear attendant to the approaching
mid-level wave would yield an environment favorable for severe
weather. However, if the convection arrives after peak heating, nocturnal
cooling after sunset will decrease instability while the parent
mid- level wave pivots away, causing vertical shear to decrease
at the same time as the front slowing down and stalling near or
over the area. Therefore, only a "marginal" risk for severe
weather (threat level 1 of 5) is outlooked by the Storm
Prediction Center at this time, with a "slight" risk (threat
level 2 of 5) just to our north. Eventually, the passage of the
wave aloft will shift convective activity offshore by late in
the night. Overnight lows will remain mild, with upper 60s to
low 70s forecast.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
On Tuesday, despite the front lingering over the area or nearby,
a lack of upper support and considerable dry air aloft should
keep any convective activity isolated and short-lived at worst
during the afternoon and focused along the sea breeze. A second
mid-level wave pivoting to our north and subsequent height
falls will help to push the first cold front offshore, with a
wind shift to northwesterly expected across the area on Tuesday
night. A secondary cold front looks to approach as yet another
mid-level wave pivots to our north, with this dry cold frontal
passage expected on Wednesday night. Confidence decreases from
this point forward as guidance differs in the handling of a
possible closed low over New England on the east side of an
Omega Block feature that is depicted across the CONUS. In
general, the placement and somewhat progressive nature of this
modeled blocking feature should keep relatively cool, dry, and
precip- free conditions in place for Thursday and Friday. The
GFS remains a wet outlier for the end of the week, and I will
opt keep PoPs silent for now.

Temperatures follow a general cooling trend to below normal through
the period as a mean trough is carved out and cooler/drier air
filters in via surface high pressure to our north. Highs
initially around 90F and lows in the mid-60s on Tuesday and
Tuesday night should fall into the low 80s and upper 50s,
respectively, by Thursday and Thursday night.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
Patchy MVFR across coastal NC will quickly transition to VFR
between 12Z and 13Z, leaving VFR for the remainder of the
morning. May see some sprinkles/light showers at the coast SC
terminals through 13Z, but the heaviest activity will pass to
the south. Both ceiling and visibility should remain VFR.

Another round of SHRA/TSRA possible this afternoon and
evening as surface boundaries generate storms with enhancement
for disturbances aloft. Favored locations will be coastal SC
midday into early afternoon with activity expanding north and
west later in the day. Storm motion will be from the northwest
to southeast, meaning any storms that do develop over inland
areas will continue to affect coastal terminals into the
evening. Storms will wind down during the evening hours as the
last of the enhancement aloft moves southeast of the area.

Extended Outlook...Scattered mainly afternoon and evening
thunderstorms may be accompanied by periodic short lived IFR
conditions through Monday.

&&

.MARINE...
Through Tonight...
West to southwest flow this morning will quickly become southwest as
the Bermuda High and the sea breeze circulation overcome the weak
offshore push. Once again winds nearshore will be enhanced by
heating inland, with another round of afternoon and evening storms
moving offshore and across the waters. Southwest flow weakens later
tonight and with light west to southwest flow setting up after
midnight. Seas generally around 2 ft with potential for 3 ft seas
near shore where wind enhancement and thunderstorm come together.
The southwest wind wave continues to be dominant with periods around
4 seconds.

Sunday through Wednesday...
Relatively light south-southwest winds persist through late
Sunday around high pressure well offshore, with seas around 2
feet. South-southwesterly flow increases on Monday as a front
approaches from the west, with sustained peaking at 15-20 kts
Monday evening. Seas in turn increase to 3-4 feet for late
Monday as southerly wind wave builds. A cold front stalls near
the coast late Monday night, causing winds to veer to
southwesterly and weaken while seas subside into the 2-3 ft
range on Tuesday. A second cold front should push through on
Tuesday night, with winds veering to northwesterly behind it
while seas fall further to around 2 ft on Wednesday. The best
chance for thunderstorms over the local coastal waters during
the extended period will be Monday evening and night as the
first cold front stalls near the coast.

&&

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

&&

$$

SYNOPSIS...ILM
UPDATE...TRA
NEAR TERM...III
SHORT TERM...ABW
LONG TERM...ABW
AVIATION...III
MARINE...III/ABW