393
FXUS62 KMHX 190005
AFDMHX

Area Forecast Discussion
National Weather Service Newport/Morehead City NC
805 PM EDT Wed Sep 18 2024

.SYNOPSIS...
A weak cold front will cross the region tonight through Thursday
producing unsettled conditions across eastern NC. High pressure
will then build over the area over the weekend into early next
week with mostly fair weather conditions expected.

&&

.NEAR TERM /OVERNIGHT/...
As of 745 PM Wednesday...

 - Monitoring potential for fog overnight

Radar, satellite, and surface obs this evening reveal a cold
front sagging slowly south across the NRN OBX/Albemarle Sound
vicinity. Showers and thunderstorms associated with this front
have shown a quick weakening trend over the past 30-60 minutes,
likely due to increasing inhibition. Meanwhile, to the south
scattered showers and thunderstorms are ongoing from NE SC into
SE NC. This appears to be associated with a weak area of low
pressure that has been drifting east along the NC/SC border over
the past 24 hours. Downstream of this low, the airmass is only
modestly unstable, and inhibition is increasing. In general, I
expect this to keep the risk of thunderstorms low over the next
few hours. However, as the low begins to lift NE into ENC, there
may be just enough lift and instability to allow a few showers
and isolated thunderstorms to fester through the evening and
into tonight. This may especially be the case as the above-
mentioned cold front continues to sag south, perhaps increasing
low-level convergence and lift. The previous forecast handles
this fairly well, so no significant changes were needed. We`ll
continue to monitor the shower/thunderstorm potential through
the night, as some adjustments to the chance may be needed.

Regarding the fog potential, recent guidance appears to be
favoring more of a low stratus scenario, and less of a fog
signal. Satellite imagery shows low clouds already beginning to
spill slowly south out of NE NC, and this should continue to
expand across the area overnight. I left a mention of fog in the
forecast, but the risk of dense fog appears to be lowering.

PREVIOUS FORECAST...Upper troughing persists with the remnants
of PTC #8 over far western NC and SC. Off the VA/NC coast, a
secondary low is gradually moving northeast. A stalled boundary
across ENC will begin moving eastward this evening, which could
spark some widely scattered showers and some isolated
thunderstorms across the CWA. The best chance for this activity
will be across far western and northern counties (north of
Highway 70 and west of Highway 17). A slight chance (15-20%) of
widely scattered showers will persist overnight with lows in
the upper 60s to low 70s.

Light winds and saturated soils will prime the environment for
another round of fog and low stratus beginning around or just
after midnight. The coastal plain will likely experience the
most impactful fog with visibility down to a mile or less at
times.

&&

.SHORT TERM /THURSDAY/...
As of 3:30 PM Wednesday...The mid/upper trough will deepen as
it moves slightly to the east tomorrow. At the surface, two low
pressure systems will be offshore: one off the SC/NC coast and
another near DE/MA. Guidance shows a surface low developing over
eastern North Carolina as the base of the trough swings through,
which will be the main forcing mechanism for any shower or
thunderstorm activity. Chances will increase through the day and
peak in the afternoon (45-50% for the coastal plain, 25-40% for
the beaches). Modest instability (MLCAPE 500-1500 J/kg) could
support a few stronger thunderstorms, but these would be
isolated in nature.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
As of 300 AM Wednesday...Mid/upper level trough lingering over
the region through the end of the work week brings daily precip
chances through Friday, and ridging starts moving in from the
north and west through the weekend as a low spins up well
offshore confining precip chances generally east of hwy 17
through the remainder of the long term period. Seasonable (or
just below) temps through the period.

Thursday:
Mid and upper level trough starts shifting eastward over ENC
Thursday and its surface counterpart low pressure system starts
to strengthen offshore of the delmarva peninsula and NJ. We will
have enough mid and upper level forcing directly above us paired
with PWATs near 1.75" and CAPEs near 500-750 J/kg for scattered
showers and thunderstorms (PoPs near 50%). Current expectation
is for most of the convection to remain thunder free with lower
instability, but if CAPEs start trending higher thunderstorm
coverage would increase as a result. Deep Layer Shear generally
below 20 kts will limit the severe potential and storms aren`t
expected to become tall enough for damaging microbursts. If
there is any hazard to be mindful of Thursday, it would be slow
to moderate storm motions allowing for rainfall to accumulate
over areas that already have saturated soils from the recent
rainfall. Northerly flow would allow the sea breeze to remain
close to the coast (if it develops at all), which could cause
problems for Carteret County as the sea breeze would provide
additional stationary forcing. However this a low probability
outcome and we will have a better idea once more hi-res guidance
comes in. Showers and Tstorms will scour our with the loss of
daytime heating Thursday evening/night.

Friday:
Mid/upper level trough starts moving offshore to the east Friday
PM as high pressure starts moving in from the west. Decreased
forcing and a drop in PWATs will lead to clearing skies and
precip chances highest offshore and along OBX. Thunder possible
offshore, but expecting just showers over land Friday. Rain
chances east of hwy 17 are 20-30% Friday with drier condition
expected for the coastal plain. Low continues meandering off the
delmarva coast, sandwiched between ridging from all directions.

The Weekend:
Low precip chances, 10-20% for offshore and OBX, as low
continues meandering to our east. Substantial ridging builds in
over ENC from the north, which provides a stronger pressure
gradient through the weekend and early next week. This will
result in a slight uptick in winds, but skies are expected to
remain partly/mostly cloudy through the weekend.

Monday-Tuesday:
Ridging and drier conditions continue through Monday, and
Tuesday the high shifts offshore reintroducing slight chances of
rain again.

&&

.AVIATION /23Z WEDNESDAY THROUGH MONDAY/...
SHORT TERM /through 00z Friday/...
As of 745 PM Wednesday...

 - Risk of IFR conditions expected to increase through the
   night

 - LIFR conditions possible tonight (30-50% chance)

A weak cold front is forecast to sag slowly south through
eastern NC late this evening and overnight, with an increased
risk of IFR, or lower, conditions. IFR/LIFR CIGs are already
ongoing across parts of the Northern OBX, and the expectation is
for this to expand south through the remainder of ENC
overnight. Guidance has trended more towards low CIGs/stratus,
with a lower risk of FG. In light of this, I continued with more
of a low stratus/BR scenario in the TAFs. If the low CIGs end
up not as widespread overnight, then the risk of FG would
increase. With daytime heating/mixing, CIGs should gradually
improve, with MVFR conditions becoming increasingly likely by
mid- morning. Lastly, the front moving in from the north, plus a
weak low moving up from the south, will lead to a risk of SCT
SHRA and a few TSRA. The highest TSRA risk is expected to be
early this evening and again on Thursday. Confidence in TSRA is
too low to mention in the TAFs for now, though.

LONG TERM /Thursday night through Monday/...
As of 400 AM Wednesday...Continued unsettled weather will bring
a chance for brief/occasional sub- VFR conditions across ENC
Thursday due to widely scattered to scattered mainly afternoon
and early evening showers and thunderstorms. Friday onward VFR
conditions expected, although Saturday morning could see some
fog as skies clear and winds calm.

&&

.MARINE...
SHORT TERM /Through Thursday/...
As of 745 PM Wednesday...

 - Quieter boating conditions

Seas across the coastal waters are laying down quicker than
anticipated, and the forecast has been adjusted to reflect this
trend.

PREVIOUS DISCUSSION...Sub-SCA conditions persist through the
period. 3-5 ft seas will decrease to 2-4 ft by Thursday morning.
Winds will remain around 10 kt or less through the period with
variable wind directions becoming northwesterly by late tonight
and northerly by Thursday afternoon.

LONG TERM /Thursday night through Monday/...
As of 400 AM Wednesday...Northerly winds increase to 10-15 kt
Fri then become 15-20 kt Sat. and 20-25 kt Sunday. There is a
30-40% chance of seeing gale force gusts for the central and
northern waters and the Pamlico Sound Sunday into early Monday.
The strength of the winds depends on the position and strength
of the low developing offshore to our northeast, and how strong
the ridging pushing in from the north is. Seas will be 2-4 ft
through Friday, then increase to 3-6 ft Saturday and 4-7 ft
Sunday as gusty winds + the low offshore results in higher
swell.

&&

.TIDES/COASTAL FLOODING...
As of 4 PM Wednesday...Coastal flooding will continue to be a
risk given the higher than normal astronomical tide cycle. The
Coastal Flood Advisory for Ocracoke has been extended and new
Coastal Flood Advisories have been issued for all remaining
oceanside coastal areas, which are currently set to last
through Saturday.

&&

.MHX WATCHES/WARNINGS/ADVISORIES...
NC...Coastal Flood Advisory until 10 PM EDT Saturday for NCZ195-196-
     199-203>205.
     Beach Hazards Statement through Thursday evening for NCZ196-
     203>205.
MARINE...None.

&&

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