235
FXUS62 KRAH 301854
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
254 PM EDT Tue Apr 30 2024

.SYNOPSIS...
A slow moving surface trough will shift across central NC through
Wednesday afternoon. Weak high pressure will linger over the area
through Friday before sliding offshore ahead of a cold front
Saturday into Sunday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 245 PM Tuesday...

A compact shortwave is evident in water vapor imagery over the
southern Tennessee Valley and is forecast to drift east-southeast
across the Carolinas through tonight. The best H5 height falls (30-
50m) and DPVA near the core of the PV anomaly will traverse the
NC/SC border and shifting towards the coast by Wed morning. The
synoptic ascent associated with this feature will overlap with a
trough axis and weakly unstable airmass to initiate scattered
showers and isolated thunderstorms late this afternoon over western
NC and slowly shift east towards the Triad and southern Piedmont by
this evening. Storm organization will likely be limited to loosely
organized multi-cell clusters along common cold pools. Sub-severe
wind gusts and lightning will likely be the primary hazards.

Boundary layer cooling after sunset will likely limit surface based
convection, but the overall moist thermo-profile will support
elevated convection to continue for a few hours although with a
continuing weakening state through midnight. Dependent on the amount
of rain and potential clearing over the western Piedmont, some
patchy fog, dense in spots, would be possible especially for
locations that receive 0.5 to 1" of rain. Lows tonight will be
coolest in the Triad and southern Piedmont in the upper 50s with
low/mid 60s in the Coastal Plain underneath thick overcast.

&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
As of 245 PM Tuesday...

The shortwave will be positioned over the Coastal Plain of the
Carolinas by Wed morning with the trough axis shifting out over the
western Atlantic by Wed evening. NWP models have come in slightly
stronger with the shortwave ridging building in behind the departing
shortwave. The result will be a stronger subsidence inversion
overspreading central NC through the afternoon and evening hours and
suppressing any showers potential over the Piedmont. Wed morning
into the early afternoon some showers/storms will be possible over
the NC Coastal Plain where the core of the shortwave will overlap
with 500 to 1000 J/kg of MLCAPE as well as a surface trough axis and
sea-breeze interaction. Once again, storm organization will likely
remain confined to multi-cell clusters along common cold pools given
15-25 kts of 0-6km shear, a majority of which is located above 700mb.

Low-level thickness will be on average around 1-3m greater compared
to Tuesday and with greater sunshine chances most places will be
able to rise into the low/mid 80s once again. Lows will be more
indicative of a radiational cooling night with mostly clear skies
and most locations able to go calm relatively early in the night,
supporting temperatures in the mid 50s to low 60s. Patchy to areas
of fog seem probable in the Coastal Plain by early Thurs morning
with the lingering rich low-level moisture in addition to moderate
radiational cooling.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 310 AM Tuesday...

* Much above average temperatures expected for Thursday and Friday
  with temperatures cooling off a bit for the weekend.
* Not a washout but chances of scattered, mainly afternoon and
  evening, showers and thunderstorms this weekend have nudged
  upward.

In the wake of the departing short wave trough, mid and upper level
ridging will build into the Carolinas on Thursday. After some
morning fog/stratus clouds across the Coastal Plain and Sandhills,
expect mostly clear skies on Thursday. Morning low level thickness
values range between 1385-1395m which combined with a good deal of
sunshine will result in highs in the mid and even upper 80s. Highs
will be a little cooler to the northeast with highs in the lower 80s
across the northern Coastal Plain. Thursday should be the warmest
day of the week with highs 8 to 13 degrees above average. Lows will
range in the upper 50s to lower 60s.

The mid and upper level ridge axis across the Carolinas will quickly
shift and fold east/southeast on Friday with an elongated shear axis
moving southeast into the western Carolinas late Friday. A backdoor
cold front will drop south across the mid Atlantic on Friday and
move into northeastern NC on Friday night but it appears is will
remain northeast of our region. With the deep layer flow becoming a
little more southwesterly, deep layer moisture increases with PW
values generally climbing above an inch by Friday evening. With the
ridge axis shifting east and an approaching disturbance aloft along
with more moisture, expect a good deal more cloudiness on Friday.
Some widely scattered showers driven largely by the mid level
vorticity axis may move east into the western Piedmont late in the
evening and overnight. Highs on Friday will be similar to Thursday,
perhaps just a shade cooler with the extra clouds. Highs will range
in the mid to a few upper 80s. With the extra moisture and clouds,
lows Friday night will be a little milder and primarily range in the
lower 60s.

Forecast uncertainty increases significantly for the weekend as the
threat for scattered showers/storms increases. The mid and upper
flow becomes more perturbed across the Southeast for Saturday into
Monday with a series of disturbances move across the area. At the
same time a backdoor front stalls just to our northeast late Friday
into Saturday. Another weakening cold front will approach from the
west late Friday and move into the region over the weekend. At the
same time, deep layer moisture increases with PW values ranging
around 150% of normal for Saturday and Sunday before decreasing a
bit for Monday. These features will support a bit more active
pattern with largely diurnal showers and thunderstorms over the
weekend. Don`t expect a washout at all and lowered PoPs about 10%
from the NBM guidance, but it will be a tease of a more summerlike
pattern with the greatest rain chances during the afternoon and
evening. With the increased cloud cover, highs will be a little
cooler and range in the upper 70s to lower 80s over the weekend with
the warmest temperatures in the Sandhills. It may feel a bit muggy
with dewpoints in the lower 60s for much of the weekend, some mid
60s are possible in the southern Coastal Plain. With a little drier
regime on Monday, highs recover a bit into the lower to mid 80s.
Morning lows will largely range in the lower 60s. -Blaes

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
As of 155 PM Tuesday...

Early morning cumulus has lifted to VFR everywhere across central
NC. A unorganized line of showers and isolated storms are expected
to develop from the NC Foothills south into central SC and reach the
vicinity of INT/GSO around 21z and eventually FAY around midnight
with a little help from the seabreeze. Confidence is low whether
this line of showers will remain intact to affect RDU or RWI, but
best timing would be 4z and 7z respectively. Dependent on the amount
of rain and clearing behind this line of showers, some model
guidance is hinting at the potential for fog development near the
Triad terminals into the southern Piedmont late tonight, but
confidence is low at this time. Cumulus will again redevelop Wed
morning with a brief broken MVFR cig most probable at RWI and RDU.

Beyond 18z Wed, scattered showers and isolated storms will be
possible in the NC Coastal Plain, potentially impacting RWI, Wed
afternoon. Clearing skies, calm conditions and continued moist low-
levels may support the development of fog in the Coastal Plain early
Thurs morning. Scattered shower/storm chances increase late Fri
through Sat with the potential for sub-VFR conditions including
early-morning fog.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SYNOPSIS...Swiggett
NEAR TERM...Swiggett
SHORT TERM...Swiggett
LONG TERM...Blaes
AVIATION...Swiggett/Hartfield