-- Discussion containing changed information from previous version are highlighted. --
765
FXUS62 KRAH 251857
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
255 PM EDT Sat May 25 2024

.SYNOPSIS...
Above normal temperatures along with humid and unsettled weather
will continue through Memorial Day. A cold front will move through
Monday night, bringing drier, cooler, and less humid conditions
Tuesday through Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
As of 255 PM Saturday...

The latest radar supports the hi-res models suggestion that
scattered thunderstorms will track off the Blue Ridge ESE into the
Triad late this afternoon. Differential heating may combine with
potential outflow boundaries to help initiate the convection. In
addition, 20-30 knots of bulk shear is forecast that will aid in
convection to become loosely organized for several hours late this
afternoon. Scattered thunderstorms may reach the Triangle and
Fayetteville areas between 7 and 9 PM.

Low-level lapse rates will become steep as surface temperatures rise
into the upper 80s to 90 and may pose a strong to severe wind gust
threat ahead of any organized clusters. Over the Piedmont into the
Coastal Plain, weaker instability (~1000 J/kg) and bulk shear (10-20
kts) will likely result in isolated pulse type storm mode.

Skies will clear behind the departing showers/storms with weak
pressure gradient over central NC overnight. This will favor another
night of patchy fog with areas of fog possible in locations that
receive the heaviest rainfall. Lows will mostly fall into the mid
60s.
-- End Changed Discussion --

&&

.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
As of 250 PM Saturday...

Sunday will start off dry across the area, some might see patchy fog
early morning but will clear shortly after sunrise. By the afternoon
an increase of showers and thunderstorms is expected. As the
enhanced shortwave trough progresses east from the IL/IN area during
the day, by the afternoon it is expected to be on the door step of
the Appalachian Mountains by late evening. Isolated to scattered
storms are expected to begin to evolve across the region late
afternoon. With loss of heating the severe threat is expected to
diminish through the overnight hours Sunday.  HiRes CAMs are showing
a bit more consistency with timing of the first round of storms
moving across the region late Sunday night through early Monday
morning. While this round of storms are expected to move across the
region swiftly, PW values are expected to be above normal (1.5-
2.0inches), thus some heavy rain could cause some minor flooding in
poor drainage areas. Drivers should be be extra cautious driving in
these storms at night. CAPE values will be lower than what is
expected with Mondays storms, but some storms could be strong. Kept
PoPs higher across the Northern Piedmont region, but chance PoPs are
generally across the region. Sunday will be warm, 5-7 degrees above
normal. Highs will be in the mid/upper 80s some areas reaching 90,
lows will range from upper 60s to low 70s.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 155 AM Saturday...

High rain chances Memorial Day into the night will yield to an
imminent pattern change to drier and less humid conditions starting
Tue and lasting through the week.

The details in timing and location of convection Mon/Mon night will
greatly depend on what culminates prior in situ and upstream, given
the outsized influence of various mid level perturbations (mostly
MCVs) and surface boundaries (differential heating discontinuities,
new and old outflows, and sea breezes) in focusing showers and
storms and guiding their tracks and evolution. And lingering debris
clouds from Sun/Sun night convection here and immediately upstream
may affect our heating and potential buoyancy Mon. What is of higher
certainty is the continued presence of a warm and humid air mass, a
deeply moist column, and increasing winds at all levels ahead of an
approaching surface cold front and a profound longwave trough/low
sweeping through the Midwest and Great Lakes region Mon. This will
create favorable conditions for scattered to numerous showers and
storms with improving organization late day heading into Mon night.
The LREF members have SBCAPE peaking at 1000-2500 J/kg (25th/75th)
over much of central NC, with mid level flow strengthening to 40-50
kts amid PW of 1.5-1.75". Incoming dynamic forcing for ascent in the
form of mid level DPVA (in particular with a late-day shortwave
trough swinging through W and N NC) and upper divergence should also
boost storm intensity and organization. Will have pops rising to
good chance to categorical, highest NW in the afternoon and in the
Coastal Plain in the evening, trending down overnight with cold
front passage. Highs in the upper 80s-lower 90s. With the front
passing through Mon night, lows should be in the lower 60s NW but
still mid 60s to near 70 S and E.

Mostly dry weather will follow for the rest of this period. The
longwave trough axis will still be to our W Tue, and while there may
be minor waves shifting through SC and SE NC, much of the deeper
moisture will have pushed E of our area or even offshore. Will keep
a slight chance of an afternoon shower or storm in our far SE, as
large scale models show the front slowing or lingering over our SE
sections where surface temps and dewpoints are apt to be elevated. A
dry NW flow will keep the column dry and stable Tue night through
Wed, although the notably cooler air will still be held up W of the
mountains until a secondary reinforcing dry cold front drops SE
through our area late Wed through Wed night. Behind this front,
dewpoints will drop even more, bottoming out in the 50s and perhaps
even some 40s Thu/Fri as surface high pressure sourced from central
Canada builds in from the NW and N. Temps will still be near to
slightly above normal Tue/Wed, before dropping to a few degrees
below normal Thu/Fri with low humidity and lots of sunshine. -GIH

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
As of 650 AM Saturday...

Periods of shallow MVFR fog around RWI should quickly dissipate
through 12z. The forecast remains on track for loosely organized
showers and storms in the vicinity of the Triad terminals (GSO/INT)
this afternoon that will continue to track to the ESE through the
late afternoon and evening hours. Timing and eastward extent of the
showers/storms related to RDU and FAY remains uncertain, but FAY may
have the better chance to see storms within its vicinity this
evening. These storms will bring the risk for strong and erratic
wind gusts as well as heavy rain and reduced vsby. Airmass
showers/storms will be possible near RDU and RWI, but expected
coverage will mostly likely be isolated enough to not include in the
12z TAFs at this time.

Looking ahead: Primarily diurnally driven showers/storms will be
possible at all terminals through Mon, with the best chances Mon
aft/eve ahead of a cold front, which should move through the area
Mon night.

&&

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

&&

$$
SYNOPSIS...Hartfield
NEAR TERM...Badgett
SHORT TERM...Hartfield
LONG TERM...Hartfield
AVIATION...Swiggett/KC