678
FXUS62 KRAH 132330
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
725 PM EDT Sat Jul 13 2024

.SYNOPSIS...
A front will weaken over the NC Coastal Plain through this evening.
A strong subtropical ridge will otherwise remain over the Southeast
through early to mid-week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 310 PM Saturday...

Hotter, with widely scattered convection possible in both the
Coastal Plain this afternoon and nw Piedmont this evening.

An anomalously strong subtropical ridge, one which this morning
broke daily 500 mb heights at JAX and MFL and will produce
standardized anomalies of 4-5 sigma from the Bahamas to the DR and
Cuba, will remain across the Southeast and swrn N. Atlantic.
Poleward of the ridge and trailing a prominent but compact MCV over
the Chesapeake Bay --one related to convection that prompted the
issuance of a Flash Flood Warning over Franklin Co. overnight-- a
weak mid-level shear axis will move east across the srn Middle
Atlantic coastal region through this evening.

At the surface, a front and lingering wind shift extended from near
the aforementioned MCV swwd across the NC Coastal Plain and ern
Sandhills; and this boundary will move little while becoming
increasingly diffuse through this evening. Meanwhile, a weak lee low
now developing across the Shenandoah Valley to near ROA, within a
broader trough extending swwd along and just east of the NC Blue
Ridge, may drift ewd into the nw Piedmont this evening-tonight.

Weak to moderate destabilization, slowed by lifting and scattering
of morning stratus/stratocumulus, and (albeit weakening) convergence
along the front, may yet support the development of widely scattered
afternoon showers/storms in the Coastal Plain. Additional, more-
isolated cells have developed along the lee trough near UKF and HKY.
This regime of isolated cells  along the lee trough may drift into
the nw Piedmont before dissipating this evening. While HRRR
simulated reflectivity also depict what appear to be showers
lingering over the nw Piedmont throughout the night, associated
point soundings reveal that reflectivity originates from a layer of
altocumulus and saturation around 10 thousand ft AGL and would be
unlikely to overcome an otherwise dry and deep sub-cloud layer, and
should instead evaporate as virga. After a hot afternoon, and a
humid one over all but the nw Piedmont where dewpoints have mixed
out well into the 60s F, temperatures will slowly settle into the
lwr-mid 70s for most by Sun morning, with patches of altocumulus and
fair skies likely.

&&

.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
As of 257 PM Saturday...

Steady warming trend begins Sun with temperatures rising into the
mid/upper 90s and heat index values ranging from around 100 to near
105. A lee trough will develop over western NC in between an area of
high pressure over the LA riding up into the Ohio Valley and the
anchored Bermuda High in the Atlantic. This will prompt mostly
southwesterly flow at the surface up through 850mb and advect in
warmer temperatures aloft (850mb 19 to 21C). This will support temps
rising into the mid/upper 90s through the early afternoon. Point
soundings indicate some relatively drier air aloft that will mix
down to the surface and keep surface dew points in mid 60s (W) to
low 70s (E). This should temper heat indices a bit, but still reach
around 100 to near 105 degrees. Isolated locations will likely reach
105 during the afternoon for a brief time, but areal coverage and
confidence is low enough to not preclude a heat advisory at this
time.

Some isolated to scattered showers/storms will be possible Sun
afternoon within a hot and humid airmass. Greatest coverage will
likely be along the lee trough in the western Piedmont as a low
amplitude shear axis sags over the area as well as along the
seabreeze, with subsequent showers/storms possible along convective
outflows. Severe potential remains low as deep layer shear remains
weak (around 20 kts) and warm/dry air aloft will work to combat
sustained deep convection. Isolated strong winds cannot be ruled out
if deeper convection is able to develop with a deeply mixed boundary
layer and DCAPE > 1000 J/kg in place.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
As of 257 PM Saturday...

The main weather story for Monday and Tuesday will be the intense
heat, given the pattern which features weak ridging and flow aloft,
coupled with H8 temp anomalies of 4-6 deg C above normal.  This will
result in highs in the upper-90s both days, and some low-100s can`t
be ruled out.  Heat indices of 105+ are expected from the Triangle
eastward on Monday, perhaps reaching as far west as the Triad by
Tuesday.  In terms of precip chances those days... coverage should
be isolated at best both days given the overall weak forcing over
the region.

PoPs will increase on Wednesday as heights begin to fall in advance
of a trough moving across the Great Lakes. With increasing flow
above the BL, expect to see the Piedmont trough sharpen and improved
low level convergence and subsequent outflow boundaries should be
the primary lifting mechanisms for increased shower activity. Shower
and thunderstorm activity, which may begin by early afternoon, may
help keep high temps limited to the lower 90s.

Rain chances will continue to increase, with well-above climo PoPs
by Thursday and for Friday and possibly Saturday as well as the
aforementioned trough pushes a cold front into the Mid Atlantic and
Carolinas regions before stalling over us.  That boundary, coupled
with another plume of deep moisture will likely result in several
rounds of heavy rains.  However, that will also keep temps limited
to near-climo values.

&&

.AVIATION /00Z SUNDAY THROUGH WEDNESDAY/...
As of 725 PM Saturday...

A few isolated showers along along the slopes of the Appalachian
Mtns have been drifting east toward the Piedmont but have been
diminishing quickly.  One shower popped up SW of GSO earlier, so
another shower in the vicinity of INT/GSO cannot be ruled out
through around 02Z based on some hires guidance, but after that no
showers are expected overnight.  VFR will generally prevail
everywhere, with the lone and temporary exception most likely being
at RWI where some brief MVFR vsbys are more probable (but still low
confidence) after 06Z.

A similar day is expected on Sunday, with isolated showers and
storms developing over western NC and perhaps impacting INT/GSO late
in the afternoon.  The seabreeze could trigger a storm near FAY but
is less likely and will not be mentioned in the TAF for FAY.

Outlook: Isolated afternoon storms could result in sub-VFR conditions
at TAF sites early this week, but otherwise VFR conditions are
expected until the next front settles into the region with higher
chances of convection and flight restrictions late Wed-Thu.

&&

.CLIMATE...
Record High Temperatures:

July 15:
KGSO: 97/1974
KRDU: 99/1997

July 16:
KGSO: 99/1915
KRDU: 101/1887
KFAY: 103/1937


Record High Minimum Temperatures:

July 12:
KGSO: 76/2011
KRDU: 78/2011
KFAY: 80/1935

July 13:
KGSO: 75/2017
KRDU: 78/2017
KFAY: 78/2017

July 14:
KGSO: 77/1981
KRDU: 77/2017
KFAY: 80/2017

July 15:
KGSO: 74/2019
KRDU: 76/1992
KFAY: 78/2015

July 16:
KGSO: 75/2010
KRDU: 77/2010
KFAY: 78/1992

&&

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

&&

$$
SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...Swiggett
LONG TERM...np
AVIATION...BLS
CLIMATE...RAH