120
FXUS62 KMHX 170101
AFDMHX

Area Forecast Discussion
National Weather Service Newport/Morehead City NC
901 PM EDT Mon Sep 16 2024

.SYNOPSIS...
An area of low pressure to our south will slowly drift
northwest towards the Carolinas and bring heavy rain, coastal
flooding, and a threat of severe weather to the area. Troughing
will remain over the Eastern Seaboard through next week as well
keeping unsettled conditions across ENC.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 815 PM Monday...

 - Flash flooding risk continues overnight

Surface observations and regional radar show an area of low
pressure centered near Lumberton, NC. East of the low, a
confluent, and very moist, low-mid flow continues to support
bands of heavy rain and embedded thunderstorms pivoting W/NW
through the southern half of ENC. While convection within these
bands has shown some signs of weakening, radar is still
estimating 1"/hr+ rainfall rates is occurring at times. As the
SFC low drifts westward, guidance is insistent that the ongoing
bands of rain will shift northward as an associated frontal
boundary lifts north. However, short-term guidance differ on how
quickly this northward progression will occur. The timing
difference lends itself to very different rainfall outcomes
through the night. The slower guidance, for example, suggests
another 3-6"+ of rain over the southern half of ENC, while the
quicker guidance keeps amounts lower thanks to the more
progressive nature of the rain. The slower guidance are favored
at this time, based on trends seen on radar and satellite, and
given the general synoptic pattern. In light of this, the
heaviest rainfall through tonight is forecast to fall over
already saturated soils, leading to a heightened flood/flash
flood through the night. A large Flash Flood Warning was
recently issued to capture the area most at risk through
midnight. We`ll continue to evaluate this potential and issue
additional warnings as necessary. The Flood Watch continues, and
not changes were needed to that area.

One note about the flash flooding potential. Some of the worst-
case guidance is suggestive of additional rainfall amounts of
5-10" possible near the coast. Should this occur, there would be
a much higher flash flood risk, which would be more problematic
given that this would occur at night. Stay tuned for updates on
the flash flood potential.

Forecast-wise, a kept a higher chance of rain and storms across
our southern counties, with the assumption that the bands of
rain will be slower to lift north. Otherwise, the forecast is
on-track, and no other major changes were needed.

PREVIOUS DISCUSSION...Low pressure continues to move onshore
with its rainbands dumping heavy rainfall across the Carolinas,
especially in the Wilmington, NC area. This system has been
slowly (5 mph) moving towards the NNW, but it will pick up speed
as it gets picked up by the upper ridge.

The hazards from this low pressure will be flash flooding,
coastal flooding, and tornadoes.

- Flash Flooding: As the system moves NNW, the axis of heavy
  rainfall (PWATs of 2-2.25") will transition from the
  southwestern to northeastern region of the FA. QPF has
  remained roughly the same for areas north of HWY 70 but has
  increased for areas to the south. Areas north of HWY 70 are
  expected to get 2-3" while areas south of HWY 70 are in the
  4-7" range with locally higher amounts up to 8-9" possible. A
  Flood Watch is in effect for the entire area, but the highest
  likelihood to see flooding remains south of HWY 70.

- Coastal Flooding: The coastal flooding threat remains largely
  unchanged, with the potential for up to 3 feet of water AGL
  in low lying areas. See the TIDES/COASTAL FLOOD section for
  more details.

- Tornadoes: The current forecast track of the low brings the
  tornado-favorable right front quadrant across eastern NC. The
  highest low level helicity will be displaced to our west,
  along the I-95 corridor, but 0-3 km SRH of 100-250 m2/s2
  combined with afternoon CAPEs between 1000-1500 J/kg support
  at least an isolated risk of a brief tornado or waterspout
  especially this afternoon and early evening.

- Strong Winds: Winds will strengthen to 30-40 mph along the
  coast today, especially south of Ocracoke Island. Sporadic
  wind gusts up to 50 mph are possible in passing rain bands.
  These may cause sporadic power outages and/or tree damage.

The axis of deepest moisture will transition northeastward
overnight. Greatest rainfall amounts will likely be along and
just north of HWY 70 with overnight QPF in the 2-3" range.
Dry air entrainment will start to cut PoPs back from south to
north late tonight and temps will reach the low 70s.

&&

.SHORT TERM /WEDNESDAY THROUGH 6 PM TODAY/...
As of 3 PM Monday...The axis of deeper moisture will continue
its northeastward movement into tomorrow morning, which will
bring the focus of heaviest rain to the Outer Banks. The QPF in
this area is 1-2" with locally higher amounts possible in
stronger rainbands. The Flood Watch for areas south of HWY 70 is
scheduled to drop at 8 AM while the Flood Watch for areas north
of HWY 70 is scheduled to drop at 2 PM.The low will finally
lift north of the area tomorrow afternoon. This will decrease
PoPs from south to north through the day.

Highs will be in the low 80s for everywhere except the Northern
Outer Banks where longer lasting rain will keep high temps in
the upper 70s.

&&

.LONG TERM /TONIGHT THROUGH SUNDAY/...
As of 400 AM Mon... Eastern North Carolina will remain
unsettled through the entire period as an impactful low moves
out of the area Tuesday. Beyond that, troughing over the Eastern
Seaboard will continue to bring daily chances for showers and
thunderstorms across the region into next weekend.

Wednesday into the weekend... Previously mentioned upper trough
will remain over the Eastern Seaboard through the end of the
week while at the surface previously mentioned low is forecast
to be to the north and likely dissipated. As we get into the
weekend, there remains uncertainty with the forecast as the
upper trough over the Eastern Seaboard is forecast to cutoff
into an upper low as upper ridging builds across the Northeast.
As is typical with upper lows, spread in timing and depth of
the feature remains large and forecast confidence remains below
average.

Either way, daily chances for showers and thunderstorms will
remain possible across ENC into the weekend as favorable
troughing remains overhead. Continued onshore flow will keep
clouds around the region while temps remain at or below avg.

&&

.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
SHORT TERM /through 00z Tuesday/...
As of 815 PM Monday...

 - Widespread IFR conditions through tonight

 - TSRA risk continues into Tuesday

Widespread RA and SCT TSRA will impact ENC through the night,
with occasional LIFR conditions. On Tuesday, the rain may
scatter out some, with precip becoming more showery and less
widespread, along with rising CIGs. Guidance isn`t in great
agreement on when this scattering out will occur, if at all. For
now, I focused the greatest aviation impacts through tonight,
then trended towards improving conditions on Tuesday. Just be
aware that confidence in improving conditions on Tuesday is low.

LONG TERM /Tuesday through Friday/...
As of 405 AM Mon...Continued unsettled weather will bring a
chance for sub-VFR conditions across ENC tomorrow as a low
pressure system moves out of the area. After the low moves to
the north we will still see at least a low end threat for the
rest of the week for sub- VFR conditions as daily chances for
afternoon and evening showers and thunderstorms will remain.

&&

.MARINE...
SHORT TERM /Today and Tonight/...
As of 3:30 PM Monday...Dangerous boating conditions are ongoing
this afternoon as winds remain strong on the northern periphery
of an area of elongated low pressure impacting the Carolinas.
Observations south of Cape Lookout show easterly winds of 20-30
kt, with seas ranging 8-11 feet.

Strongest winds will be focused over Onslow Bay and southern
Raleigh Bay this afternoon with gusts up to 35-40 kt. Farther
north, winds are slightly weaker but still peak at 25-30 kts.
Winds will peak this afternoon, then subside as the low shifts
onshore and fills. Seas will continue to be quite hazardous
today, peaking at 10-14 ft. Conditions begin to slowly improve
into Tues morning.

LONG TERM /Tuesday through Friday/...
As of 415 AM Mon...Dangerous marine conditions continue into
Tuesday, but gradually improve from south to north with winds
easing down to 15-20 kts with gusts up around 20-25 kts by Tue
morning and veering to a SE and eventually SW direction while
seas fall down to 5-8 ft along our coastal waters. Winds and
seas fall even further Wed with winds remaining S`rly at 10-15
kts while seas along our coastal waters finally lower down to
3-5 ft by Wed morning. This should then end SCA criteria across
all waters with more benign boating conditions forecast for
Thurs. Daily chances for showers and thunderstorms will remain
possible through the period with locally enhanced winds and seas
possible within the strongest storms that may develop.

&&

.HYDROLOGY...
As of 3:30 PM Monday...Widespread heavy rain is expected to
continue through tomorrow as a poorly organized low pressure
drifts northwestward towards the coast of South Carolina.
Abundant tropical moisture with this system will lead to
extremely heavy rainfall rates, which could cause flooding
issues over areas that have become saturated over the last
week. So far today the axis of heaviest rainfall has been along
Duplin and Onslow Counties, and this will transition to the
north and east as the low moves inland. Areas north of HWY 70
are expected to get 2-3" while areas south of HWY 70 are in the
4-7" range with locally higher amounts up to 8-9" possible.

&&

.TIDES/COASTAL FLOODING...
As of 3:30 PM Monday...There will be potential for coastal
flooding of up to 1-3 ft AGL today as winds slowly strengthen in
association with a poorly organized low pressure system to our
south. Additionally, coastal flooding may be worsened due to
the astronomically high tide cycle we are entering.

Ahead of this system, strong ENE/E winds will buildup water
along the SE portion of the Pamlico Sound as well as the Neuse,
Bay, and Pamlico Rivers. Oceanside, high water levels in
addition to strong wave run up will likely produce ocean
overwash along NC 12 on the Outer Banks at times of high tide.

Additionally with this system we can expect a high threat of
rip currents, rough and dangerous surf/shore break, and beach
erosion.

Current Coastal Flood and High Surf headlines remain unchanged
with the afternoon update.

&&

.MHX WATCHES/WARNINGS/ADVISORIES...
NC...Flood Watch through Tuesday afternoon for NCZ029-044>047-
     079>081-203>205.
     Coastal Flood Advisory until 8 AM EDT Tuesday for NCZ080-094-
     194>196-199-203>205.
     Flood Watch until 8 AM EDT Tuesday for NCZ090>092-094-193>196-
     198-199.
     High Surf Advisory until 8 AM EDT Tuesday for NCZ195-196-199-
     203>205.
     Beach Hazards Statement from 8 AM EDT Tuesday through Tuesday
     evening for NCZ195-196-199-203>205.
MARINE...Small Craft Advisory until midnight EDT tonight for AMZ131-
     135>137-230-231.
     Small Craft Advisory until 6 AM EDT Wednesday for AMZ150-152-
     154.
     Small Craft Advisory until midnight EDT Tuesday night for
     AMZ156-158.

&&

$$
SYNOPSIS...MHX
NEAR TERM...RM/OJC
SHORT TERM...OJC
LONG TERM...MS
AVIATION...RM/MS
MARINE...MS/OJC
HYDROLOGY...MHX
TIDES/COASTAL FLOODING...MHX