-- Discussion containing changed information from previous version are highlighted. --
067
FXUS62 KMHX 301142
AFDMHX

Area Forecast Discussion
National Weather Service Newport/Morehead City NC
742 AM EDT Tue Apr 30 2024

.SYNOPSIS...
A weak cold front will move through the area on Wednesday. High
pressure then builds in for a couple of days before yet another
cold front impacts the area over the weekend.

&&

.NEAR TERM /TODAY/...
-- Changed Discussion --
As of 730 AM Tuesday...

Mid/upper level ridging will shift offshore today as a
shortwave shifts east out of the TN Valley. Despite continued
low-level moisture advection, the combination of residual
subsidence and warm temps aloft are expected to keep the risk of
showers at a minimum again today as the seabreeze moves inland.
Yesterday the chance of showers was close to zero. Today it
will be about 5-10%. Once again, temperatures this afternoon
will top out in the mid 80s inland(~10 degrees above normal),
and the 70s along the coast (close to normal).
-- End Changed Discussion --

&&

.SHORT TERM /TONIGHT/...
-- Changed Discussion --
As of 200 AM Tuesday...

SFC low pressure is forecast to pass south of Southern New
England tonight, with an associated weak frontal boundary moving
slowly east from the Appalachians to the Carolinas and
Virginia. A modest LLJ is forecast to develop ahead of the
advancing front, with steady low- mid level moistening expected
through the night. Mid-level lapse rates will be weakening with
time, but a deepening layer of moisture appears supportive of a
zone of modest instability, especially on the nose of the
strongest elevated moisture transport. Within this zone, SREF
probs give a 50-70% chance of MUCAPE > 500j/kg developing ahead
of the front and an upper level shortwave approaching from the
west. Large-scale forcing for ascent is forecast to be on the
weak side, but a weak coastal trough moving inland plus modest
low-mid level convergence appears supportive of scattered
showers and thunderstorms developing from coastal SC northeast
through SE NC after midnight. Weak effective shear (~20kt) is
expected to limit any severe weather potential tonight. Where
thunderstorms manage to develop, rainfall amounts as high as
0.25-0.50" will be possible. Otherwise, amounts are forecast to
be less than 0.10".

With increasing clouds, and steady boundary layer moistening,
temperatures tonight are expected to be very mild for late
April, only dropping into the mid 60s. For perspective, normal
lows this time of year are in the mid to upper 50s.
-- End Changed Discussion --

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 330 AM Tuesday...

KEY MESSAGES

- Inland highs in the low to mid 80s for the rest of the week

- Best rain chances Wednesday and then an unsettled weekend and
  start to the new week

FORECAST DETAILS

A shortwave trough will move east across the area on Wednesday
and support shower and thunderstorm chances (30-60%). As for
severe potential, the threat appears low but non-zero with the
high CAPE/low shear environment being painted by the CAMs. Highs
will reach the low 80s with dew points in the low 60s, which
will generate plenty of instability to support thunderstorms. The
CAMs are showing large MUCAPE of 1500-2000 j/kg but weak
effective shear. However, it should be noted that the CAMs are
showing a higher amount of shear than they were 24 hours ago.
This is especially true along counties south of HWY 70 near the
coast, so this will be a trend to keep an eye on.

We return to warm, dry weather on Thursday and Friday with a
ridge building over the southeast US. Highs will be in the mid
80s across the coastal plain and low 70s at the beaches.

Unsettled weather returns this weekend with multiple chances for
showers and thunderstorms. Surface high pressure will be
gradually washed out as a surface low forms due to a shortwave
trough moving across the southeast. At the same time, a cold
front associated with a deep low over south-central Canada will
move into our area and stall. PoPs increase west to east on
Saturday with shower and thunderstorm activity possible through
Monday (15-30% chance).

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
SHORT TERM /through 12z Wednesday/...
As of 715 AM Tuesday...

KEY MESSAGES

- Sub VFR conditions possible late tonight (30-50% chance)

- TSRA possible after 06z/2am tonight (20-40% chance)

FORECAST DETAILS

SCT cumulus clouds are developing off the coast of GA/SC this
morning, and this is a sign of increasing moisture ahead of an
upper level wave moving through the TN Valley. Low-level
moisture will continue to steadily stream north through tonight,
leading to a modest increase in the risk of SHRA, TSRA, and
lowering CIGs late tonight. The greatest risk of the above-
mentioned conditions is after 06z/2am tonight. Prior to then,
gusty S to SW winds will be common, with an added boost along
the advancing seabreeze this afternoon. Despite the increasing
moisture, I expect a mostly dry seabreeze this afternoon, with
the SHRA risk being <10%.

Of note for tonight, the coverage of SHRA and TSRA is expected
to be scattered in nature, and guidance differs on where the
greatest risk will be. Because of this, I opted to leave out any
mention in the TAFs for now. In a similar fashion, guidance
continues to differ on where/when/if sub-VFR CIGs will develop.
Because of this, I decided to introduce a SCT025 layer, but held
off on going MVFR just yet.

LONG TERM /Wednesday through Saturday/...
As of 330 AM Tuesday...Pred VFR expected through the period but
a few instances of unsettled weather are expected. An
approaching disturbance will bring chances for showers and
thunderstorms on Wednesday (30-60%). By Saturday, a cold front
will be moving into the area and bring another chance for
showers and thunderstorms (15-30%). Lowered CIGs and VIS are
expected during these times.
-- End Changed Discussion --

&&

.MARINE...
SHORT TERM /through tonight/...
As of 200 AM Tuesday...

Background northeasterly long-period swell continues through
tonight, and will combine with a modest southerly wind swell,
producing seas of 3-5 ft. Like yesterday, breezy southwesterly
winds of 10-20kt will be common through tonight, with a few
gusts to near 25kt where the thermal gradient in maximized.
Because of the marginal nature of the winds, we`ll continue to
run headline-free.

Late tonight, an upper level disturbance and a developing weak
coastal trough is expected to support an increasing risk of
showers and thunderstorms, especially for the southern
waters/rivers/sounds.

LONG TERM /Wednesday through Saturday/...
As of 330 AM Tuesday...

KEY MESSAGES

- Sub-SCA conditions with multiple chances for showers and
  thunderstorms

FORECAST DETAILS

Although marine conditions are forecast to remain below SCA
criteria, opportunities for showers and thunderstorms are
possible Wednesday and this weekend. Winds will be variable
through the period due to several systems moving through but
will remain around 5-10 kt with 2-4 ft seas.

&&

.MHX WATCHES/WARNINGS/ADVISORIES...
NC...None.
MARINE...None.

&&

$$
SYNOPSIS...MHX
NEAR TERM...RM
SHORT TERM...RM
LONG TERM...OJC
AVIATION...RM/OJC
MARINE...RM/OJC