336
FXUS62 KMHX 251957
AFDMHX

Area Forecast Discussion
National Weather Service Newport/Morehead City NC
357 PM EDT Wed Sep 25 2024

.SYNOPSIS...
Warm front lifts north of the Carolinas today as weak high
pressure builds in from the west. End of the week trends unsettled
as TC Helene lifts across the eastern Gulf of Mexico and into the
southeastern CONUS.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
As of 345 PM Wed...Meridional flow pattern in place across the
eastern CONUS today as upper ridge remains anchored off the
coast of the Carolinas, while a deep upper trough digs into the
MS River Valley. The ridge will not move much through the short
term as the trough digs further into the southeastern CONUS and
cuts off, eventually interacting with TC Helene as it lifts into
the southeastern CONUS.

At the surface, warm front has lifted north into Virginia as
weak high pressure attempts to build in from the west. Moist,
unstable, and uncapped airmass intruding behind the front is
supporting spotty shower activity, although subsidence from the
offshore ridge is preventing any deep convection. A weaker area
of showers is ongoing along a surface trough offshore.

Inland activity is being diurnally driven and will quickly
collapse after sunset, giving way to dry conditions but with
increasing clouds as cirrus from distant TC Helene begins to
overspread the region. An early morning shower threat remains
for the southern coastal counties like this morning as trough
moves little offshore. Cloud cover keeps low temps elevated at
around 70 inland, and low to mid 70s for area beaches.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
As of 345 PM Wed...Isolated to widely scattered shower threat
will continue Thursday in southeasterly surface flow in tandem
with weak WAA, in the absence of any frontal boundary. Like
today, upper ridge will continue to provide some mid-level
subsidence and keep activity from blossoming into deeper
convection. Therefore, rainfall amounts should remain light at a
quarter inch or less. By early evening, heavier showers
emanating from the outer bands of TC Helene may briefly impinge
on the inner coastal plain.

Warm and muggy tomorrow, with highs in the low to mid 80s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
As of 4 AM Wed...

Friday/Friday Night...The main item of interest will be the
impacts from TC Helene, which the center of the storm will be
moving through GA and then into the TN Valley. With the large
size of the system, some outer rain bands will be propagating
through ENC during the day. 25/00z deterministic and ensemble
guidance in good agreement with the track of the system. Strong
moisture advection east of the center should allow a plume of
tropical moisture to quickly overspread the coastal Carolinas
throughout the day from w to e. At the same time, a broadly
diffluent flow aloft plus increasing WAA should support a period
of strong forcing, leading to a quick period of moderate to
heavy rain and scattered thunderstorms, some of which may become
severe and contain a few tornadoes. MLCAPE vals inc to aoa
1,500 J/KG with plume of mid/upr 70s TD`s overspreading the
region. Strong backing of sfc winds to the SE will produce
enhanced low lvl helicity, and a favorable environment for a
tornado or two will develop. While quick- hitting, guidance has
been showing a consistent signal for a brief period of heavy
rain and localized flooding, though the good news is the band or
bands of heavy rain will be progressing eastward fairly
quickly, with rain ending as early as mid afternoon for many
areas save for the OBX, and all areas by day`s end. Attm, 0.75"
to 1.00" are forecast, with locally higher amounts in heavier
cells. Breezy conditions will be present as well, with sserly
breezes gusting to 20-25 mph inland, with 25-30 mph close to the
coast. Quick drying with all rain ending and winds diminishing
rapidly and becoming swrly Fri evening, with temps still muggy
in the low 70s.

Saturday...Mainly dry with subsidence in place behind the
system, and upr low pres well west of ENC. Warm and humid
continues with swrly flow, and highs in the mid 80s.

Sunday through Tuesday...Aforementioned upr low migrates slowly
eastward, with chances for showers each day, with perhaps a
surface low developing near or over ENC. Have capped pops at 30%
attm due to uncertainty on synoptic and mesoscale features this
period. Temps will cont to near or slightly above climo, with
highs in the low/mid 80s to 60s for lows.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
SHORT TERM /through today/...
As of 145 PM Wed...VFR conditions in place across eastern NC
terminals this afternoon as warm front is lifting northward into
central VA this hour. Behind the front, moist and tropical
airmass is overspreading the region with spotty shower activity
developing in tandem with the diurnal maximum. Upper ridge and
associated subsidence offshore is prohibiting deeper convection,
and only expect an isolated shower threat until sunset.

Dry conditions expected overnight, although signal remains for
some low stratus across the inner coastal plain. Fog formation
looks unlikely due to a steady increase in thick cirrus
associated from TC Helene encroaching from the south.

LONG TERM /Thu through Sun/...
As of 4 AM Wed...A few iso to sct showers will dot the region
on Thu with onshore serly light winds. On Friday, a tropical
system is forecast to pass well west of eastern NC, but still be
close enough to produce a period of gusty winds, RA, TSRA, and
sub- VFR conditions. Sub- VFR end by late Fri afternoon into
evening as dry air moves in behind the system.

&&

.MARINE...
SHORT TERM /Through Thursday/...
As of 345 PM Wed...Seas continue to slowly fall under as light,
5-10 kt southeasterly winds remain behind a departing warm
front currently in Virginia. Seas are sitting at around 5 feet
north of Cape Hatteras, but 2-3 feet south. Little change in the
overall weather pattern is expected as southeasterly winds
persist into Thursday, but winds will begin to increase late
Thursday, especially across Raleigh and Onslow Bays, as TC
Helene makes landfall in the northeastern Gulf Coast and pinches
the pressure gradient.

No changes were made to SCAs from the previous forecast.

LONG TERM /Thu through Sun/...
As of 4 AM Wed...Building seas occur on Thu ahead of TC Helene
well south and west of ENC, and have added the remaining ctrl
and srn waters into the SCA suite, with seas building to 6+ ft
Thu morning. On Fri, gradient inc to 20-25 kt sustained and
gusts to 30 kt for the coastal waters, esp ctrl and srn waters,
and seas build to 7-10 ft with the sserly winds. Attm it appears
winds will remain below gale/trop storm force, though the large
wind field will cont the high seas into Fri evening. Winds
quickly diminish and turn swrly Fri night and cont into Sat with
seas subsiding to below SCA by Sat afternoon.

&&

.TIDES/COASTAL FLOODING...
As of 4 PM Wed...The coastal flood threat continues for all of
coastal North Carolina through tomorrow as tide levels remain
elevated, including the Neuse, Bay, Pamlico, and Pungo Rivers as
reported water levels remain elevated. Water levels will
continue to trend slightly lower, but will still remain high
enough to result in up to a foot of inundation. Along and north
of Ocracoke, swell offshore is weakening but may still result in
some minor overwash where dune structures are compromised or
vulnerable.

Looking ahead, we`ll continue to closely monitor the track of
TC Helene as distant coastal impacts could be felt across a
portion of ENC on Fri into Fri evening thanks to southerly
onshore winds and large waves.

&&

.MHX WATCHES/WARNINGS/ADVISORIES...
NC...Coastal Flood Advisory until 5 PM EDT this afternoon for
     NCZ080-094-194>196-199-203>205.
     Beach Hazards Statement until 8 PM EDT this evening for NCZ203-
     205.
MARINE...Small Craft Advisory until 2 PM EDT Saturday for AMZ150-152-
     154.
     Small Craft Advisory from 10 AM Thursday to 2 PM EDT Saturday
     for AMZ156-158.

&&

$$
SYNOPSIS...MHX
NEAR TERM...MS
SHORT TERM...MS
LONG TERM...TL
AVIATION...TL/MS
MARINE...TL/MS
TIDES/COASTAL FLOODING...MHX