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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 260155
AFDRAH

AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
955 PM EDT Wed May 25 2022

.SYNOPSIS...
High pressure will remain north of the area through Thursday,
bringing continued cool weather to the region tonight. Low pressure
will approach the region Thursday night into Friday, bringing the
potential for showers and storms, along with locally heavy rainfall
on Friday. Weak high pressure will follow the front into the
weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
As of 955 PM Wednesday...

Thick low clouds and patchy drizzle will be the story tonight, esp
across northern & NE sections. The latest surface analysis shows low
pressure just off the central Outer Banks along an inverted trough
off the Southeast coast and connected to a CAD front stretching
across S SC into N GA, while a narrow ridge of cool/stable high
pressure noses in from the NE. The strong low level stability is
evident on the 00z GSO sounding, with high RH through the surface to
850 mb depth across central NC and to the NE and E. The nearshore
surface low will reinforce the diffluent NE flow into central NC,
and this is topped by E and ESE flow around 930-900 mb, generating
sufficient weak moist upglide for patchy drizzle esp across the NE
sections. This should persist overnight as the low drifts WNW to the
central and N coast of NC. The surface cool air advection is rather
weak, and with the clouds inhibiting radiational cooling, current
temps are already within a category or so of expected low over much
of the area, except in the far S where clouds have been minimal thus
far this evening but where stratus should eventually spread into by
midnight or soon thereafter. Lows in the upper 50s to lower 60s. -GIH

Earlier discussion from 215 PM: CAD regime remains in place across
the area this afternoon but as expected, some of the cloud cover to
the south has eroded considerably. This has yielded mostly sunny
skies across the Sandhills along with an increase in temperatures
into the mid 70s. Meanwhile to the north (generally along and north
of US 64), skies remained overcast with temps still lingering in the
low to mid 60s.

For the rest of the afternoon, expect the clearing line to continue
moving northward up to, and through, the Triangle and at least parts
of the Triad, before returning southward again as stratus
redevelops by mid evening into the overnight hours. Where clearing
is realized, there could be a quick late-day jump in temperatures
into the mid 70s but elsewhere (along the NC/VA border) expect temp
to remain steady in the mid 60s. Tonight temperatures will be fairly
uniform with upper 50s to lower 60s the most likely range for low
temps.
-- End Changed Discussion --

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
As of 215 PM Wednesday...

Warm advection aloft will increase during the day tomorrow as a
590dm H5 ridge slides farther off the coast. A deepening upper low
and associated upper divergence (presently over the southern Plains
and Deep South) will migrate eastward throughout the day, beginning
the process of eroding the wedge front and ushering in a return of
warm temps and elevated dewpoints. As WAA strengthens throughout the
day, a few showers should develop across the far western Piedmont
and should eventually make a run at the Triad during the afternoon
hours. Instability and shear aren`t terribly impressive tomorrow
ahead of this approaching low, but 0-1km shear could be maximized in
the vicinity of the rapidly retreating wedge front across the Triad
late in the day. Will carry some likely PoPs in the west, tapering
down to less than 10 percent from the Triangle eastward where the
upper ridge will remain the dominant factor in tomorrow`s weather.
Surface based instability wanes quickly with the loss of daytime
heating Thursday night but with falling heights aloft and steepening
mid level lapse rates, some degree of elevated instability is likely
to persist through the overnight hours and I`ll maintain a mention
of thunder throughout the night. Showers are likely to develop and
re-develop at times Thursday night into Friday morning in the west
and I will keep PoPs elevated west of the Triangle through 12Z
Friday. Ridging to the east should keep conditions dry elsewhere.

Temperatures will be noticeably warmer tomorrow with highs returning
to the low/mid 80s. Lows on the mild side within the pre-frontal
warm sector in the mid/upper 60s.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
As of 300 PM Wednesday...

Friday and Friday night: A potent mid/upper low (around two standard
deviations below normal) across the Ohio Valley Friday morning will
lift northeast towards the Mid-Atlantic by Friday night and weaken
through the period. The associated trough will swing across central
NC Friday during the day, and exit east off the coast Friday
evening. A surface low will follow a similar path to the mid/upper
low, with the cold front lagging behind the trough and not pushing
across our region until late Friday.

Precipitable water values will increase to around 1.75" (around two
standard deviations above normal) ahead of the trough as south to
southwesterly flow at H500 increases to 50 kts. Heavy rainfall and
training storms on already saturated soils will increase the risk of
flash flooding across the region. WPC has increased the Excessive
Rainfall Outlook to a Slight Risk of flash flooding throughout the
period.

MLCAPE of 2000-2500 J/kg, 0-6km shear of 40-50 kt, plentiful
moisture and diurnal heating will all help develop organized strong
to severe storms across the region as the main line of storms pushes
east during the day. Damaging wind gusts and large hail are the main
threats, however 0-1 km shear to 30 kt and 0-1 SRH of 200-300 m2/s2
will increase the chance of tornadoes, as well. Timing of the main
line of convection still varies among model solutions, however
general consensus has slowed down the line slightly, moving across
the western half of the region by early afternoon and the eastern
half of the region by late evening. SPC still has most of our area
under a Slight Risk of severe thunderstorms through the period.

Showers and thunderstorms should exit the region by late Friday
night as conditions dry out behind the weak cold front. Highs will
range from the mid 70s to mid 80s, with lows in the 60s.

Saturday through Sunday: The mid/upper trough exits off the coast
early Saturday, then heights slowly build through the weekend as an
upper ridge builds north from the Deep South to the OH Valley. At
the surface, high pressure will build across the Mid-Atlantic, and
switch surface flow from westerly to northerly to easterly by the
end of the weekend. Subsidence will help keep conditions dry for
most of the holiday weekend, with highs slowly increasing to just
above seasonal normals by Sunday. Lows will be near normal, ranging
from the upper 50s to mid-60s.

Memorial Day through Wednesday: The large ridge will remain to our
north through the period, and slightly flatten over time. PWs will
increase early to mid-next week, and increase chances of diurnal
showers and thunderstorms through the period, with less confidence
in storms Memorial Day compared to later in the period on Wednesday.
Highs will slowly increase to the upper 80s and low 90s, with lows
in the 60s.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
As of 819 PM Wednesday...

The CAD regime will remain firmly in place tonight over central
NC with predominantly northeasterly flow at the surface. MVFR
stratus this evening are expected to steadily lower tonight to
IFR/LIFR area wide. A weak low pressure system just off the NC coast
will retrograde inland tonight and bring the potential for LIFR fog
to northeast NC. Confidence is medium-low on whether or not this fog
will reach the RWI terminal or if just enough flow/moisture will
lead to a light drizzle. As for the 00z TAF package, have opted for
the fog scenario, but this may need to adjusted as the surface low
creeps inland tonight. Conditions will slowly improve Thursday
morning with VFR returning to all terminals expect for the Triad
(GSO/INT) which will likely have some lingering MVFR ceilings
through the remainder of the TAF period.

Looking beyond 00z Friday, showers and storms currently over MS/AL
border will slowly move northeast Thursday and begin encroaching on
INT/GSO after 00z Friday, but recent guidance depicts the heaviest
precipitation remaining west of the terminals until Friday morning.
Sub-VFR conditions likely at times at all sites on Friday as a slow
moving strong cold front moves through the area. Thunderstorms with
gusty winds and locally heavy rain possible at all terminals. A
gradual improvement in conditions is expected Saturday through
Monday.

&&

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

&&

$$
SYNOPSIS...Leins
NEAR TERM...Hartfield/Leins
SHORT TERM...Leins
LONG TERM...JJT
AVIATION...Swiggett/Leins