-- Discussion containing changed information from previous version are highlighted. --
455
FXUS62 KRAH 301016
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
615 AM EDT Tue Apr 30 2024

.SYNOPSIS...
A deep high pressure ridge will hold over and off the Southeast
coast through this morning. An upper level trough will drift
eastward over the Carolinas this afternoon through Wednesday. An
upper level high pressure ridge will then build over the Southeast
and Carolinas from the west Wednesday night through early Friday. A
weak upper level disturbance will move in from the west late Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 225 AM Tuesday...

While a few showers/storms remain possible late today through
tonight, mainly across the S, overall coverage should be low. Deep
ridging is holding over and off the Southeast coast this morning,
allowing for minimal eastward progress of the cirrus blowing off
from the broad convective band now extending from W Lk Erie through
central KY/TN into AL. This ridging aloft will slowly break down and
shift E as mid level shortwave trough seen on GOES layer WV imagery
over N MS approaches the Carolinas today, resulting in an increase
in clouds over our area as the current PW aob 1" gives way to a band
of 1.25-1.4" PW spreading in from the W. But the existing convection
to our west is likely to steadily dwindle as it gets into the W
Carolinas. The shortwave will weaken as it approaches with
decreasing mid level flow, leading to quickly lowering DPVA, while
the upper jet over the Great Lakes decelerates, leading to
diminishing upper divergence as its right entrance region moves in.
And while higher surface dewpoints will spread in from the S and SW,
the overall moisture flux through the low levels will be fairly low,
which should also keep coverage isolated to scattered at most, and
late-day CAPE is expected to be just a few hundred J/kg at best,
with poor deep-layer shear. Latest CAM runs support this scenario
with decreasing convective coverage and intensity as the waning
forcing for ascent and marginally moist column spreads into our
area. Following the overall picture painted by these latest CAM
runs, will spread low chance pops into the W late this afternoon
then track them E through the evening into the overnight, decreasing
to isolated in the process, focused largely along and S of Hwy 64.
WAA balanced by increasing clouds will keep thicknesses largely
unchanged from yesterday, so expect highs from around 80 to the mid
80s, several degrees above normal, highest E where clouds will be
fewest and thinnest for longer today. Lows tonight in the upper 50s
to lower 60s. -GIH

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
As of 245 AM Tuesday...

Expect a mix of sun and clouds Wed, with scattered mainly afternoon
convection possible across the E. With very weak surface troughing
over the Piedmont, the further-weakening mid level shortwave trough
is expected to be moving into the E Carolinas Wed morning, in tandem
with the eastward push of the 1+" PWs, as mid level ridging and
drier air in the wake of the trough moves into our area from the W.
Forecast soundings from the HREF show well the drying aloft from the
W across the Piedmont/W Sandhills Wed afternoon with deep mixing and
drying surface dewpoints, resulting in little to no CAPE. Further E
in the Coastal Plain, this drying and the exit of the shortwave
trough occurs later enough in the day to allow the daytime heating
to result in 500-750 J/kg of MLCAPE, mostly E of I-95, and some
interaction with a sea breeze may result in storm cluster or two.
Mid level flow will be very weak, though, producing continued low
deep layer shear. Thus, any storms will be poorly organized,
although we could see some gusty winds in/near storms in our extreme
E. Will maintain chance pops just in the E Wed afternoon, ending by
early evening as subsidence spreads in. Highs still above normal, 80-
85, followed by lows in the upper 50s to lower 60s. -GIH

&&

.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 /12Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
As of 615 AM Tuesday...

With a couple of low-probability exceptions, confidence is fairly
high that VFR conditions will dominate across central NC from early
this morning through tonight, as deep high pressure sitting just off
the Southeast coast will slowly give was to an approaching upper
level disturbance. Any cloud cover through this morning will be high
thin cirrus. Additional thicker high and mid clouds will slowly
spread in from the west from midday through the remainder of the TAF
period, with sct-bkn VFR cumulus based around 5-6kft possible after
18z esp at western terminals. The current solid band of
showers/storms over central/eastern TN will keep pushing E through
today but will decrease in intensity and coverage, such that only
isolated to scattered showers/storms are possible later today,
moving into our W sections (INT/GSO, although coverage is expected
to be greater to the S) after 21z. With coverage expected to be
fairly low, will include just a VCSH at INT/GSO for now. While this
activity is expected to spread E from mid evening through the
overnight hours, it`s uncertain if any showers/storms would impact
the eastern terminals (RDU/FAY/RWI). The better chance appears to be
at FAY, and will include a period of VCSH at FAY late, although
confidence in this is not high. Surface winds from the SSW or SW
will increase after sunrise, to 10-14 kts gusting to 17-20 kts after
13z, then decrease to under 8 kts toward sunset.

Looking beyond 12z Wed, bkn-ovc mainly VFR cloud cover is expected
through Wed, and additional isolated to scattered storms are
possible in the far E (perhaps near RWI/FAY) Wed, mainly afternoon.
VFR conditions with low to zero rain chances are expected Wed
evening through at least midday Fri. Sctd shower/storm chances
increase late Fri through Sat with the potential for sub-VFR
conditions including early-morning fog. -GIH
-- End Changed Discussion --

&&

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

&&

$$

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