043
FXUS62 KRAH 120849
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
449 AM EDT Mon May 12 2025

.SYNOPSIS...
A slow moving upper low centered over the lower Mississippi
River Valley will drift northeast through the Mid South to the
central Appalachians through Wednesday, bringing wet and unsettled
weather to the region.

&&

.NEAR TERM /TODAY AND TONIGHT/...
As of 340 AM Monday...

...A Flood Watch is in effect through Tuesday morning...

A nearly stationary upper level low that has been churning over the
mouth of the Mississippi this past weekend, will finally begin to
move north towards the Tennessee Valley. Weak insitu CAD will remain
hang on across much of the area, ahead of the attendant warm front
and potential weak triple point low forecast to extend along the SC-
NC state line by daybreak Tuesday.

Beneath increasing upper level diffluence, a plume of strong
southerly moisture transport will spread across the area through
early Tuesday. This anomalous moisture, combined with deep layer
ascent, will spawn repeated rounds of showers and thunderstorms this
morning through tonight. The slow progression of this system and
potential for training convection raise concerns for isolated to
widely scattered flash flooding, particularly by the afternoon and
evening in areas that experience multiple rounds of heavy convective
rainfall as BL dewpoints increase 65-70 and weak instability
develops.

Rainfall amounts through tonight are expected to average between 1-
2" across central NC, with localized heavier amounts of 2-4"
possible where training convective bands line up. Urban areas, poor-
drainage roads, and small streams will be the most susceptible. Some
river flooding is also possible, mainly along the Haw and Rocky
Rivers.

Highs ranging from near 70 across the northern Piedmont to mid 70s
across the coastal plain and eastern Sandhills. Lows in the lower to
mid 60s.

&&

.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 420 AM Monday...

* Showers/storms likely

On the ern periphery of a mid/upr-level cyclone that will move
slowly newd from the Mid-South to the OH Valley, a negatively-tilted
shortwave perturbation, and associated pocket of minus 12-15C
temperatures and 20-40 meter height falls at 500 mb, will pivot nwd
across the Carolinas on Tue and Virginias Tue night. That shortwave
perturbation will be preceded by a generally north to south-oriented
band of deep convection and convectively-amplified mid-level
vorticity, embedded within a plume of tropical moisture
characterized by PWs of 1.5-1.75" and 150-175% of normal, over ern
NC and near and just east of RAH`s Coastal Plain, at the start of
the period. That convective band and deep moist axis will translate
generally nwd across the Middle Atlantic through 12Z Wed.

At the surface, a triple surface wave and moist sector will migrate
nwd across the Carolinas Tue and w-cntl VA Tue night.

The aforementioned band of deep convection and main focus for flash
flooding, ongoing in or near the Coastal Plain at the start of the
period, will gradually edge newd and out of RAH`s area by mid-
morning. In its wake, partial clearing may result from ern SC nwd
and into srn and cntl NC, as a mid-level dry slot briefly streams
nwd across the region. Associated pockets of relatively maximized
insolation and diabatic heating will probably contribute to warming
into the upr 70s-lwr 80s over the Sandhills and parts of the Coastal
Plain and ne Piedmont, with generally mid-upr 70s elsewhere. When
combined with seasonably rich low-level moisture and cool
temperatures aloft, moderate instability of 1000-2000 J/kg will
result. That heating will erode any weak convective inhibition
present in the morning, with low LCLs and LFCs that will all favor
the redevelopment of numerous showers/storms through the day,
particularly given background forcing for ascent accompanying the
negatively-tilted shortwave perturbation. 15-25 kts of 0-1 km bulk
shear and slightly backed surface flow ahead of the triple
point/trough will yield clockwise-curved and somewhat elongated
hodographs in the lowest 2-3 km, with associated effective helicity
values up to 100-150 m2/s2. Associated low-level shear profiles,
beneath modest sswly mid-level flow of 20-30 kts, will probably
promote mostly weak low-level rotation in even shallow, cells (mini-
supercells). A conditional risk of a weak spin-up cannot be ruled
out where instability and low-level shear may locally maximize.

That convection may linger numerous in coverage especially across
the ne Piedmont and nrn Coastal Plain Tue evening, but otherwise
diminish in coverage and intensity overnight, with low temperatures
mostly in the lwr-mid 60s.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 445 AM Monday...

* Lingering showers/storms Wed-Wed night, then mainly dry until
  late Fri

* Turning hot, with scattered, possibly strong-severe convection Fri-
  Sat

A mid-level cyclone over the OH Valley at the start of the period
will become an open wave trough while weakening and lifting newd
across the lwr Great Lakes and Middle Atlantic through Thu night.
Progressive shortwave ridging will migrate from the MS Valley to the
Middle and South Atlantic through the same time, then offshore.
Meanwhile, yet another closed and cutoff low will develop across the
nrn Plains and nrn MS Valley and drift slowly ewd across the Great
Lakes and srn ON/QC through the weekend.

At the surface, a trough will linger over the Middle Atlantic and
Carolinas throughout the period, with a weak cold frontal passage in
cntl NC possible late Sat into early Sun.

Above average probabilities of convection will linger with the
slowly exiting mid/upr-level trough and cyclonic flow aloft mid-
week, followed by a mainly dry Thu-into at least early Fri, beneath
shortwave ridging and rising heights aloft. Convective chances will
then increase late Fri, and especially Fri night, as falling heights
and forcing for ascent, accompanying the cutoff low over the Great
Lakes, glance the srn Middle Atlantic. A belt of seasonably strong,
35-45 kts of mid-level at its base and into parts of the srn Middle
Atlantic would favor organized storms and risk of severe.

It will otherwise turn warmer, to hot particularly Fri, when
forecast temperatures will be in the upr 80s to lwr 90s, and with
heat index values in the upr 90s to near 100 mainly in the Sandhills
and srn-cntl Coastal Plain.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
As of 220 AM Monday...

Through 06z Tuesday: Conditions will continue to deteriorate with
ceilings lowering to LIFR to IFR through daybreak as widespread
showers and rain overspread the area from the south. Additionally,
before the rain moves in, a period of patchy fog is possible, with
VSBYs potentially dropping to less than a mile at times.

Expect little to no improvement through the forecast period as
widespread showers and isolated thunderstorms will continue to
redevelop across the area through tonight. Restrictions should
remain predominately IFR through the evening, before potentially
lowering to LIFR tonight/early Tuesday.

After 06Z Tuesday: Bands of moderate to heavy rain and IFR
conditions will more-or-less continue through Tuesday morning.
Diurnally driven scattered showers and thunderstorms will continue
Tuesday afternoon through late week. Early morning stratus and/or
fog (IFR to LIFR) will be likely.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Flood Watch from late tonight through Tuesday morning for
NCZ007>011-021>028-038>043-073>078-083>086-088-089.

&&

$$
SYNOPSIS...Badgett
NEAR TERM...CBL
SHORT TERM...MWS
LONG TERM...MWS
AVIATION...CBL/Badgett