289
FXUS62 KMHX 250759
AFDMHX

Area Forecast Discussion
National Weather Service Newport/Morehead City NC
359 AM EDT Sat May 25 2024

.SYNOPSIS...
A surface trough will reside across the piedmont while a series
of upper level shortwaves will generate multiple rounds of
shower and thunderstorm activity through the weekend. A stronger
cold front will move through early next week.

&&

.NEAR TERM /TODAY/...
As of 3:30 AM Saturday...Latest surface analysis shows a
positively tilted surface trough over ENC. Today, the surface
low will slightly deepen as it moves east and off the mid-
Atlantic coast. This will put the NOBX under moist onshore
northeasterly flow, which will keep fog and some lower clouds
around through the day. Across the coastal plain, any fog
development should dissipate by mid-morning.

As has been the case for the past couple of days, a series of
embedded shortwaves will move across the area and serve as the
upper level support for afternoon shower and thunderstorm
development. Aside from a few isolated showers across areas
north of HWY 264 later this morning, most of the area should
remain dry until later this afternoon when the seabreeze treks
inland. Wherever convection does form, the environment will be
supportive of some strong to potentially severe storms with
MLCAPE 1500-2000 J/kg, effective shear 20-25 kt (limiting
factor), and PWATs 1.5-2". The main hazards of concern will be
gusty winds, heavy rainfall, and hail. Clusters of storms will
move east and become widely scattered as we progress later into
the evening. All activity is expected to be offshore around
midnight. Highs will approach 90 across the coastal plain and
stay closer to 80 along the beaches.

&&

.SHORT TERM /TONIGHT/...
As of 3:45 AM Saturday...The surface low will continuing moving
offshore and the next surface trough will approach from the
west. Another round of fog is on the table late tonight due to
moistened soils and decoupling winds. Visibilities will likely
be the lowest along the OBX but the coastal plain will be
impacted as well. Lows will be in the low to mid 60s.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
As of 200 AM Saturday...

 - Watching thunderstorm risk Sunday-Monday

 - Elevated heat risk Sunday and Monday/Memorial Day

 - Not as hot mid to late-week

Synoptic Summary: Multiple shortwaves embedded within zonal flow
aloft will traverse the Carolinas through Sunday night, with each
carrying at least a chance of showers and thunderstorms. On Monday,
a stronger wave will glance the area, sending a cold front southeast
through the area Monday night or Tuesday. Guidance differ on how
quickly that front will get through Tuesday, and how far off the
coast it gets. Eventually, a potent upper level shortwave will move
through mid-week, pushing the front well offshore. A cooler post-
frontal regime then settles in to close out the work week.

Sunday: Boundary layer moistening beneath modestly steep mid-level
lapse rates should support MLCAPE climbing to 1000-2000j/kg during
the afternoon hours. During the daylight hours, it appears the main
source of lift will be the seabreeze, with isolated thunderstorms
possible. Deep layer shear of 20-30kt plus moderate instability
appears supportive of a pulse severe mode capable of wind and hail
(if storms develop). The limiting factors will be weak lift and a
modest cap with warm temps aloft. It may be that the better chance
of thunderstorms holds off until the evening/overnight hours as a
shortwave moves through. The boundary layer will be stabilizing, but
lift from the s/w, plus modest deep layer shear may support a low-
end risk of strong/severe convection. Warm low-level thicknesses
plus moderate to strong heating should support above to well above
normal temperatures, especially where thunderstorms or convective
debris don`t inhibit heating.

Monday/Memorial Day: Continued southerly low-level flow should
support dewpoints rising into the 70s beneath steep mid-level lapse
rates. Heating of the moist boundary layer in combination with the
steep lapse rates should support moderate to regionally strong
MLCAPE of 2000+ j/kg. Temps aloft will be warming as well, though,
which will lead to a seasonably strong capping inversion.
Synoptically, an upper level shortwave will lift NE from the Ohio
Valley into the northern Mid-Atlantic, with a glancing influence to
the south across the coastal Carolinas. The greatest chance of
thunderstorms should be focused just to our NW and N where the
greatest lift is expected. If storms manage to develop this far
south, the combination of moderate to strong instability, steep
lapse rates, and sufficient deep layer shear will be supportive of
severe thunderstorms. This will be a day to watch, especially given
the above-mentioned overlap of shear and instability, but
questionable forcing and a modest cap make confidence lower.
Thunderstorms aside, and barring more cloudcover than currently
forecast, Monday has the potential to see well above normal highs.
This combined with dewpoints in the 70s will support a "feels like"
temperature of 95-100 degrees, leading to an elevated heat risk.
While the heat risk is not forecast to reach high enough to warrant
heat headlines, it`s noteworthy coming on a busy holiday weekend,
with a lot of outdoor activities, etc. The risk will be highest for
those with extended time outdoors and/or those without a way to
sufficiently cool down.

Tuesday-Wednesday: Model guidance begin to differ during this time.
The main challenge is how quickly Monday`s front moves offshore, and
whether or not it stalls for a time. The slower guidance keeps a
risk of showers and thunderstorms potentially lasting all the way
into Wednesday, while the faster and further offshore guidance
paints a much drier picture. Blended guidance holds onto a chance of
precip Tuesday, but is dry on Wednesday. This seems reasonable for
now, but be aware that the potential exists for precip to last
longer than currently advertised. Temperatures will begin to "cool"
during this time, but how cool will depend on how quickly the front
moves through.

Thursday-Saturday: There remains a fairly solid signal in guidance
depicting a potent shortwave moving through the US East Coast,
sending a strong cold front through the coastal Carolinas Wednesday
night or Thursday. It`s expected that this will usher in a
noticeably "cooler" airmass for at least a couple of days, with
dewpoints falling back into the 50s, and lows bottoming out in the
50s and 60s. Highs are expected to be in the 70s to near 80. While
the airmass will be drying, this may not equate to a lack of
precipitation. The potential is there for a shortwave, or two, to
move through supporting at least a low-end risk for showers and
thunderstorms, especially towards next weekend.

&&

.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
SHORT TERM /through Saturday/...
As of 1:45 AM Saturday...All shower and thunderstorm activity
has cleared the coastal plain and we should remain dry through
the rest of the night. It will be a tricky forecast over the
next 12 hours with low stratus and fog at play. Given the light
overnight winds and wet soils from today`s rain, widespread fog
is expected. Confidence is high in all TAF sites seeing at least
low-end MVFR to IFR visibility within the next 1-2 hours. LIFR
visibility is certainly not out of the question, especially for
OAJ and ISO, so have added a TEMPO group for 1/2 SM FG from
10-11/12Z. As for ceilings, conditions will gradually
deteriorate over the next few hours and bottom out between
8-12Z. Confidence is high in low-end MVFR ceilings. IFR and LIFR
ceilings are a strong possibility, especially between 9-12Z, and
confidence is highest in this occurring at EWN, OAJ, and ISO.
Flight cats will improve to VFR by mid to late morning, but OBX
terminals are expected to remain sub-VFR through the period.

LONG TERM /Saturday night through Wednesday/...
As of 200 AM Saturday...

There will be daily risk of TSRA Sunday through Tuesday, with
accompanying sub-VFR conditions. Outside of TSRA activity, mostly
VFR conditions are anticipated. On Monday, gusty southerly winds
appear likely (60-80% chance) ahead of an approaching cold front,
especially Monday afternoon into Monday evening. SHRA/TSRA risk may
linger into Wednesday before drier air works in by Thursday.

&&

.MARINE...
SHORT TERM /through Saturday/...
As of 4 AM Saturday...Quiet marine conditions persist through
the period. Winds will be variable at 5-10 kt with 1-2 ft waves.
The southern waters will shift from NW this morning to SW by
this afternoon. The northern and central waters will shift from
NW to NE. Greatest shower and thunderstorm chances will exist
over the Pamlico Sound, rivers and sounds, and the southern
waters.

LONG TERM /Saturday night through Wednesday/...
As of 230 AM Saturday...

 - Approaching Small Craft conditions Monday/Monday night

 - Periods of thunderstorms through early next week

Several upper level waves will move through the ENC coastal waters
through early next week. Each wave will bring with it a chance of
showers and thunderstorms. A stronger wave, and associated cold
front, then moves through Monday/Monday night. Southerly winds will
increase to 15-20kt ahead of this front, and may approach 25kt for
some waters. Right now, though, the risk of widespread 25kt winds
appears low (<10% chance). Seas of 1-3 ft over the weekend will
increase to 3-4 ft Monday with the building winds. The highest seas
are expected south of Cape Hatteras.

&&

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

&&

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