Area Forecast Discussion
Issued by NWS Newport/Morehead, NC

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FXUS62 KMHX 280638
AFDMHX

Area Forecast Discussion
National Weather Service Newport/Morehead City NC
238 AM EDT Thu Mar 28 2024

.SYNOPSIS...
A coastal low will move along the Crystal Coast on Thursday,
followed quickly by a cold front passage. High pressure then
builds in from the south over the weekend with another frontal
passage likely early next week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
As of 230 AM Thursday...Issued a SPS for patchy dense fog with
visibilities as low as 1/4 miles for NOBX and Mainland Dare Co.
until 1015Z.
Previous discussion...As of 145 AM Thursday...A couple of weak,
upper level waves will lift northeast through the coastal
Southeast through tonight, and interact with a stalled, SW to NE
oriented low- level boundary. A moist, southwesterly flow will
be enhanced with the passage of each wave, leading to increased
low- mid level moisture transport along the stalled boundary.
This will lead to multiple waves of showers and thunderstorms
lifting north through the area through tonight. Training showers
have reached the extreme western portions of the CWA. At this
time they have light to moderate rainfall rates, but will be
getting heavier as we progress through the night into the
morning Thursday. Axis of heaviest rainfall totals through
tonight will be west of hwy 17 along the very slow moving
boundary, moving east as we get into the morning with the help
of an upper level wave approaching from the west.

Despite strong deep layer shear in place,
elevated instability is forecast to be weak (<250 j/kg), which
should keep the risk of severe weather very low through the
night.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 AM FRIDAY/...
As of 200 PM Wednesday...

**Coastal low to impact ENC with heavy rain, gusty winds, and
coastal impacts on Thursday**

An upper level trough will translate east from the TN Valley to
the Carolinas on Thursday. Strong mid-level height falls
beneath the trough, plus a modestly diffluent flow aloft, will
support the development of a deepening surface low along an
eastward- moving frontal boundary. Guidance has remained
consistent with a surface low track very near, or just offshore,
of the Crystal Coast/Southern OBX. As the low quickly deepens,
the surface winds will also quickly respond, with a period of
moderate N/NW winds developing from west to east through the
day. For most of the area, this will likely equate to a period
of 25-35 mph winds. Closer to the coast where the gradient will
be the strongest, gusts of 35-40+ mph appear plausible. Worst
case scenario, a few gusts to 45+ mph may occur. Based on the
above, we`ll hold off on a Wind Advisory for now due to lower
confidence in reaching 45 mph along the coast.

As the low deepens, a warm front will lift north and stall
along the coast. This will setup an area of enhanced low-level
convergence near and north of the low and warm front.
Additionally, ahead of the advancing wave, an area of diffluent
flow aloft will overspread the area, supporting increased large-
scale forcing for ascent. Strong WAA will occur ahead of the
low as well. The strong dynamics plus anomalously high PWATs
will support a period of moderate to heavy rain during the
morning and early afternoon hours. Instability will be weak,
which will tend to keep rainfall rates from being overly
excessive. However, ensemble guidance still suggests rainfall
rates of 0.50"+/hr will occur for several hours, with event
total rainfall topping out in the 1-3" range for most areas.
Where convection occurs, rainfall amounts as high as 3-5" will
be possible. This will especially be the case for areas that see
multiple rounds of rain this evening and tonight. HREF mean QPF
guidance have shifted the axis of heaviest rainfall west some,
but not drastically so. The ongoing Flood Watch covers this
potential well for inland areas. Along the coast, rainfall
amounts may not be as high as further inland. However, the coast
is where the heaviest rainfall fell during the last coastal
low, and is where soils may be more susceptible to some hydro
issues. Therefore, the Flood Watch has been expanded to cover
the entire area. For additional details, please see the "Hydro"
section of the AFD. For additional details regarding the coastal
flooding potential, please see the "Coastal Flood" section
below.

Like tonight, instability is forecast to remain low (<250 j/kg)
which should keep the risk of severe weather very low as well.
Additionally, from a climatological standpoint, a surface low track
offshore is typically less favorable for severe weather locally.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
As of 400 AM Wed... Coastal low will quickly exit off to the
north and east Thursday night with high pressure building in
from the south on Friday bringing much quieter weather to
Eastern North Carolina through the weekend. Next potential
frontal system begins to near the area early to mid week next
week.

Thurs night through Fri... Negatively tilted upper level trough
and deepening mid level shortwave will be overhead to start the
period but will quickly exit off to the north and east with
upper level zonal flow beginning to set up across the region on
Friday as the trough departs. AT the surface low pressure system
that had brought inclement weather through much of the day
Thursday will be located just offshore near Cape Hatteras and
will be pushing further north and east while strengthening as
the evening progresses. Any leftover rainfall associated with
this low will finally end from west to east through THursday
night thus ending our heavy rainfall threat with just the
potential for an additional 0.1-0.25 inches of rain to fall
overnight Thursday, WInds will still remain elevated overall
across ENC with NW`rly winds gusting to 20-30 mph across our
inland zones and 30-45 mph across the coast and OBX overnight as
the gradient tightens between the deepening low and encroaching
high. As we get into Friday low pressure continues to pull
further away from ENC while high pressure builds in from the
south. THis will keep things dry and mo clear across the region
while winds gradually ease and become W`rly Fri afternoon. Low
temps Thurs night get down into the 40s while high temps on Fri
get into the low to mid 60s as W`rly downslope flow offsets any
ongoing CAA behind the departing low.

This weekend... Dry weather remains across the FA through this
weekend as upper and surface ridging builds over the area with the
surface ridge quickly pushing off the coast and into the Sargasso
Sea on Sun. After some partly cloudy skies across the area on Sat,
expect increasing cloud cover late Sunday as a weak mid level
shortwave ridges along the boundary of the upper level ridge
promoting some weak lift. The GFS does hint at the potential for
some isolated shower activity to develop across ENC on SUn but
given that has been the outlier model so far with respect to
precip potential kept PoP`s below mentionable through the
weekend. Either way looks to be a pleasant weekend overall with
highs getting into the 70s to near 80 inland and into the 60s
to near 70 along the OBX. Lows through this time period increase
each night as well going from the 40s Sat to the 50s on Sun

Monday into midweek next week... Frontal boundary then begins to
approach the area on Mon and eventually makes its way into ENC
closer to mid week next week. This will bring our next chance
for precip to the area with partly to mo cloudy skies expected
from Mon on. Temps generally remain above avg through this time
period.

&&

.AVIATION /07Z THURSDAY THROUGH MONDAY/...
SHORT TERM /through 00z Thursday/...
As of 125 AM Thursday...Sub-VFR conditions to start off the
night for much of the CWA, with a narrow region of VFR along and
just west of hwy 17. Conditions will continue deteriorating
through the night, with widespread IFR expected before daybreak
with the eastward progression of the slow moving boundary and
northward progression of a warm front. Light showers are moving
NNE through the coastal plain and will become heavier and more
widespread as the night progresses, especially as we approach
daybreak. Light winds tonight will strengthen in the daytime
Thursday, out of the north at 10-15 kt with 20+ kt gusts across
all TAF sites. Low CIGs, VIS, and heavy rainfall will continue
through most of Thursday with flight categories liking jumping
back and forth from low- MVFR to IFR (possibly brief periods of
LIFR). Slight chance of thunderstorms moving NNE along the
boundary are possible but not likely. CIGs and VIS will start
to improve after 0Z Friday as the boundary turned coastal low
departs and dry air moves in. However, windy conditions will
continue through the end of the TAF period, particularly for
coastal regions where low level wind shear will also be a
concern.


LONG TERM /Thursday night through Monday/...
As of 4 AM Wed... We likely start the period out with sub-VFR
conditions heavy rain and reduced vis remain over Enc Thursday
morning and afternoon as a deepening low gradually departs the
area to the north and east Thurs night. Lowest ceilings and vis
will be found across the OBX to start with slightly higher
ceilings and vis the further west you go. Ceilings and vis then
rapidly improve from west to east overnight Thurs into Fri as
the low exits the area. However, gusty NW`rly winds overnight
Thurs will become W`rly on Fri while gradually easing. VFR
conditions are then expected Fri night through the end of the
period.

&&

.MARINE...
SHORT TERM /through Thursday/...
As of 1530 Wednesday...

Webcams along the coast of the Outer Banks still low to very
low visibilities over nearby waters (1SM or less). With light
winds, it`s likely that reduced visibilities will last for at
least a few more hours before easterly winds increase. In light
of this, I have extended the Marine Dense Fog Advisory through
8pm for the coastal waters north of Ocracoke Inlet, the Pamlico
Sound, and the northern rivers/sounds. There is potential that
this could need to be extended as long as into tomorrow.

N/NE winds 10-15 kt across the waters currently, with
subsiding, but still rough seas 3-5 ft south of Hatt, and 4-7
ft/12-13 sec north. Stubborn offshore low pressure is pushing
ESE, with seas slowly subsiding. Seas will continue to subtly
subside tonight. SCA criteria to continue for the coastal waters
but they were wiped from the map/products when we upgraded the
existing Gale Watches to Gale Warnings.

LONG TERM /Thursday night through Monday/...
As of 1530 Wednesday...

Marine conditions will rapidly deteriorate on Thursday as a
coastal low tracks NE`wards and deepens Thu afternoon and
evening. 10-15 kt winds with 4-6 ft seas will be found across
our waters with winds becoming N-NW`rly behind the departing
coastal low and cold front and increasing rapidly with
widespread 20-30 kt winds with 25-40 kt gusts found across the
inland sounds and rivers Thu afternoon and evening with 25-35 kt
winds with 40-45 kt gusts found across our coastal waters.
Dangerous marine conditions then persist through the night and
into Fri morning before quickly easing from west to east as the
low departs and high pressure ridging builds overhead allowing
winds to fall to 10-15 kts coming from the W by Fri afternoon.
This will allow gales to end, however SCA criteria will be in
place likely into the weekend especially across our coastal
waters as seas will remain elevated. Winds will then generally
remain around 10-20 kts through the weekend and into early next
week.

Widespread 4-6 ft seas will be noted Thu morning as light winds
persist. However, this is short lived as seas quickly build
back up closer to 5-8 ft Thu afternoon and 7-11 ft Thu night as
strong winds bring increased wave action. Elevated seas then
persist through Friday before seas gradually fall back closer to
4-6 ft over the weekend with seas then falling to 3-5 ft by
early next week as the winds ease.

&&

.HYDROLOGY...
As of 200 AM Thursday...

A couple of rounds of showers and thunderstorms will impact
portions of ENC through tonight, followed by a final round on
Thursday. Showers have started moving into western portions of
the CWA at the time of this update. Rainfall rates are expected
to remain below 1"/hr due to a lack of stronger instability.
However, several hours of 0.50"/hr+ rainfall rates will support
a widespread 1-3" of rain, with higher amounts of 3-5" possible.
A Flood Watch is in effect for this potential, and has been
expanded east to cover the coast where soils are wetter, with an
increased runoff risk. While lower rainfall rates will tend to
keep the flash flood threat lower, the cumulative effect of
multiple rounds of rainfall should gradually increase the risk
of some runoff issues. 6hr flash flood guidance suggests event
totals of 3-4"+ would support an increased flood risk, which is
within the realm of possibility per ensemble mean/max QPF
guidance. The peak rainfall rates are expected from 5am-2pm on
Thursday, and this is when the greatest flash flood risk would
occur. This also falls during the morning commute which could
add to the impact. Smaller creeks and rivers will be the first
to respond, with larger rivers responding by this weekend,
especially as runoff from upstream works towards the coast.

&&

.TIDES/COASTAL FLOODING...
As of 415 PM Wednesday...

Deepening low pressure will move along the Crystal Coast and
Southern Outer Banks on Thursday, then shift out to sea by
Thursday night. Strengthening northerly winds will quickly
develop on Thursday, and last into Thursday night. An extended
period of northerly winds will lead to an increased risk of
soundside flooding for Ocracoke and Hatteras Islands. The
potential for coastal flooding may be exacerbated by weakened
dune structures from previous events. At this time, we are
expecting 1-2 ft AGL of inundation in those areas. With high
confidence in this event, we have issued a Coastal Flood
Advisory for the above-mentioned areas.

As the low pulls away, another round of large, breaking waves
and ocean overwash will impact oceanside areas from Ocracoke
north through the Northern Outer Banks. A High Surf Advisory is
in effect covering impacts from the system earlier this week,
and another High Surf Advisory will likely be needed to cover
impacts with this next system.

&&

.MHX WATCHES/WARNINGS/ADVISORIES...
NC...Flood Watch through this evening for NCZ029-044>047-079>081-
     090>092-094-193>196-198-199-203>205.
     High Surf Advisory until 8 AM EDT Friday for NCZ203-205.
     Coastal Flood Advisory from 8 PM this evening to 2 PM EDT
     Friday for NCZ204-205.
MARINE...Dense Fog Advisory until 5 AM EDT early this morning for
     AMZ131-135-150-152-154-230-231.
     Small Craft Advisory from 8 AM this morning to 10 AM EDT
     Friday for AMZ131-230-231.
     Gale Warning from 1 PM this afternoon to 6 AM EDT Friday for
     AMZ135.
     Small Craft Advisory from 10 AM this morning to 6 AM EDT
     Friday for AMZ136-137.
     Gale Warning from 2 PM this afternoon to 7 AM EDT Friday for
     AMZ150.
     Gale Warning from 2 PM this afternoon to 9 AM EDT Friday for
     AMZ152-154.
     Gale Warning from 11 AM this morning to 8 AM EDT Friday for
     AMZ156-158.

&&

$$
SYNOPSIS...MHX
NEAR TERM...RJ
SHORT TERM...RM
LONG TERM...RCF
AVIATION...RCF/RJ
MARINE...CEB/RCF
HYDROLOGY...MHX
TIDES/COASTAL FLOODING...MHX


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