256
FXUS62 KRAH 090823
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
423 AM EDT Fri May 9 2025

.SYNOPSIS...
A cold front will move south across VA this morning and NC this
afternoon and evening. A couple of areas of high pressure will
follow and build from the Great Lakes to the Middle Atlantic and
Carolinas through the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 420 AM Friday...

* Stratiform rain and widespread multi-layered overcast this morning

* Seasonably warm, partly sunny, with widely scattered
  showers/storms this afternoon-evening

* Cooler tonight

A slowly progressive mid/upr-level cyclone will dig from the lwr
Great Lakes to cntl PA through this evening, then rotate newd to srn
New England by 12Z Sat. It will be preceded by a strongly-sheared
perturbation over cntl KY, the remains of a former cyclone over the
mid MS Valley this time Thu, which will continue to shear enewd and
across and offshore the srn Middle Atlantic through early this
afternoon and be accompanied by a belt of seasonably strong, ~40-50
kts of swly mid-level flow. Related mid-level height falls and
forcing for ascent will be maximized at 20-40 meters/12 hr over cntl
NC this morning, then lift newd and along the Middle Atlantic coast
through tonight. Following rising heights and subsidence will spread
ewd and across the region late this afternoon and especially
tonight.

At the surface, a lead cold front, reinforced by extensive
convective outflow from earlier and ongoing convection over the
Carolinas, stretched at 08Z across cntl SC swwd across cntl GA and
AL, the lwr MS Valley, and the wrn Gulf. This boundary will move
discontinuously sewd across the Southeast and well south of cntl NC.
Convective overturning and stabilization, and the development and
maintenance of a mesohigh centered over srn NC, was situated between
the lead front and a trailing nrn stream one that extended from a
~1012 mb low over DE, wswwd across n-cntl through swrn VA, then wwd
roughly along both the KY/TN and MO/AR border. This reinforcing
boundary will move in backdoor fashion swd across cntl and srn VA
this morning and through cntl NC this afternoon and evening.
Following, ~1026 mb Canadian high pressure centered over the upr
Great Lakes this morning will settle swd and extend from the mid MS
Valley ewd to the OH Valley and srn Middle Atlantic by 12Z Sat.

Given the stabilizing influence from earlier and ongoing convection
over cntl NC, and early day large-scale forcing for ascent and mid-
level flow/shear that will progressively decrease through this
afternoon, coverage and intensity of thunderstorms in cntl NC will
be somewhat limited today. Nonetheless, diurnal heating into the upr
70s to lwr-mid 80, of a continued seasonably moist airmass
characterized by surface dewpoints in the upr 50s-lwr 60s ahead of
the aforementioned cold front, will support generally weak
destabilization of up to 1000 J/kg in cntl NC, with pockets of
moderate instability of up to 1500 J/kg in ern NC, and with minimal
convective inhibition. As such, low-level convergence along and
ahead of the advancing cold front may be sufficient to force
isolated convection over the Piedmont, to generally scattered
coverage across the Sandhills and Coastal Plain. A few storms may
become strong to locally severe, especially from MEB to RWI and
points ewd, with a risk of both hail and damaging wind gusts.

Tonight will feature noticeably cooler and drier air and a nly
breeze that may gust to near 15-20 mph at times, as the post-frontal
airmass advects into the region, with lows in the upr 40s to 50s.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 145 AM Friday...

Sat will be seasonably cool and dry for most of the area, as the
surface front settles to our S. Models are in good agreement with
the mid level pattern consisting of a deep closed low over New
England moving NE to the Canadian Maritimes during Sat, while
upstream energy diving through Quebec maintains broad troughing down
through the Mid Atlantic region. This trough connects to a second,
nearly stationary closed low that will hold over LA through Sat
night. While this mid level shear axis appears likely to hold to our
NW through Sat night, a weak but cool/dense surface high will build
over NC during the day, then shift E off the coast while a portion
of a stronger high builds from the NW into NC right behind it,
resulting in dry low levels and limiting pops to nothing more than
isolated patches of light rain over the extreme S, within a
shallower and less dry subcloud layer. Otherwise, we will see
considerable high cloudiness spreading out of the central and E Gulf
coastal region to the NNE across NC, yielding a trend to mostly
cloudy skies Sat that will hold through Sat night. Expect below
normal highs of 70-75, followed by lows from around 50 to 55. -GIH

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 255 AM Friday...

An overall wet period is ahead, with rain chances ramping up Sun/
Sun night, peaking Mon through Tue night, before finally decreasing
gradually and shifting E Wed/Thu. Periods of heavy rain are
possible, which may lead to flooding.

Sun: The mid level low wobbles but holds over LA through Sun, but as
it deepens a bit, the mid level S flow out of the N Gulf into SC
will increase and deepen, suggesting a further-north drift of 1"+ PW
into S NC. While northern sections of the CWA should still be dry
Sun as the surface high drifts offshore, enough of the latest
deterministic models and ensemble suites are indicating precip
spreading N into W and far S NC during the day that warrant drawing
chance pops further N into the CWA Sun. Any precip across our S Sun
should be light, however, given the weak forcing for ascent
including initially muted moist upglide. Below normal highs should
persist with cloudy skies, again mainly 70-75, although the NE and
far N CWA should be the warmest with lower readings in the S and SW.

Sun night through Tue night: Confidence is increasing that much of
the CWA, but particularly the S and W sections, could see at least a
couple of rounds of heavy and potentially flooding rainfall during
this time frame. By Sun evening/night, as the surface high pushes
over and just off the New England coast with a tightening MSLP
gradient between the high and deepening surface low pressure over
the central Gulf Coast, the increasing low level E/SE flow into the
Southeast will produce strengthening and deepening moist isentropic
upglide, with a long fetch of Atlantic moisture driving high
moisture transport into the Carolinas. Terrain upglide may enhance
lift, and LREF probabilities of 1.5-2" of rain in 24 hours is over
30% across our SW half. The LA closed low will open a bit but drift
only slowly NE into the Mid South through Tue night, while the MSLP
gradient remains tight between the surface high over the NW Atlantic
and developing low pressure over SC into GA, keeping us within a
surge of 1.5-1.9" PW (150-170% of normal) over the entire CWA Sun
night through Mon night, followed by a focus over our E half Tue
into Tue night as the slow-moving H8-H5 trough axis shifts gradually
ENE through the area, nudging the best moisture transport into E NC
and E VA. Models agree on cycles of enhanced forcing for ascent,
including strong and deep moist isentropic upglide Sun night through
Mon night, with DPVA from energy lifting out of the NE Gulf, and a
shot of upper divergence in the exit region of the S mid level jet
late Mon night through the first half of Tue. With good agreement
among deterministic models and ensemble means on this pattern, will
carry high pops (likely to categorical) through much of Tue, with a
NE shift in higher pops out of the CWA late Tue through Tue night as
a dry punch arrives from the S. Still expect a smaller-than-usual
diurnal temp range, with slightly below normal highs and above
normal lows.

Wed-Thu: An improving trend is expected mid week, although our
eastern areas may stay unsettled longer. Cold/deep mid level
troughing over the W CONUS and downstream ridging developing over
the Miss Valley will nudge our Ohio Valley low/trough slowly E as it
continues to slowly weaken. While confidence in the forecast details
declines, we`re likely to see the trailing mid level trough extend
from OH/PA/WV SSE through central NC Wed before easing ENE Wed night
and Thu with the encroaching Miss Valley ridge. Will keep above-
climo pops E through Wed with a surface frontal system or low
expected to track slowly E through the state, with pops then
trending to near climo by Thu. -GIH

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
As of 205 AM Friday...

Light to moderate stratiform rain, and showers/storms near and
southwest of FAY, will end from west to east later this morning.
Isolated showers/storms will probably redevelop along and ahead of a
cold front over the Piedmont by early this afternoon, then grow in
coverage (to scattered) and intensity across the RWI and FAY
vicinity through late afternoon-evening.

Outlook: Flight restrictions and rain, some moderate to heavy, will
become widespread next Mon-Tue.

&&

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

&&

$$
SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...Hartfield
LONG TERM...Hartfield
AVIATION...MWS