831
FXUS62 KRAH 161837
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
237 PM EDT Fri Aug 16 2024

.SYNOPSIS...
High pressure will persist over the Carolinas today then shift
offshore late today and tonight. A cold front will approach
the region from the west on Saturday.

&&

.NEAR TERM /TODAY THROUGH TONIGHT/...
As of 237 PM Friday...

Embedded in the W-NW flow aloft between the upper ridge centered
over the Southern Rockies and the large troughing over the Great
Lakes and Ohio and Tn Valleys, a ribbon on higher moisture,
featuring PWATs 2-2.2", will advect west to east across central NC
through night as weak perturbations traverse the area. Steered by
the W-NWLY flow, showers and storms moving into and/or developing
over the higher terrain will progress east, in weakening fashion,
into the NW Piedmont during the late afternoon and evening. By
midnight, only isolated showers are expected to persist in the
relatively stable airmass in place across central and eastern NC.

Shear, instability and forcing are all weak. Thus, no severe storms
are expected.

The onset of SWLY low-level flow will result in continued warming
and a slight uptick in humidity levels. Lows 65-70.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 215 PM Friday...

A cold front will loop from Lower Michigan southeast into the Ohio
Valley and then southwest into the Tennessee Valleys Saturday
morning, slowly moving to the southeast and moving into western
North Carolina by Sunday morning. A thunderstorm cannot be ruled out
northeast of Raleigh Saturday morning left over from tonight`s
precipitation, then it appears coverage could expand a little bit in
the afternoon. Different synoptic and high-resolution models are
really all over the place with predictions for where convection will
occur. There does seem to be some broad agreement that the southern
Piedmont will remain dry Saturday afternoon, so with the
uncertainty, painted slight chance pops north of I-40 as well as
east of I-95. This is a very low confidence forecast considering the
lack of agreement from the computer models. There is slightly more
agreement in some thunderstorms moving into the region late Saturday
night as the cold front approaches, but this will also be occurring
at a time when convection is normally at a minimum, and have gone
with chance pops to the northwest of I-85. Saturday`s highs will be
within a degree or two of today`s values, generally in the mid to
upper 80s. Lows will be in the upper 60s and lower 70s.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
As of 220 PM Friday...

Sun/Sun Night: The leading edge of trailing cold front from a low
over the Great Lakes will likely be pinned west of the Appalachian
mountains into Sun afternoon with a pre-frontal lee-troughing
positioned east of the Appalachians into the VA/NC Piedmont. Surface
dew points in the low/mid 70s within and east of this boundary will
contribute to 1000-2000 J/kg of MLCAPE by peak heating. The
approaching trough should help support deepening convection by early
afternoon. Some storm organization is to be expected with 20-30kts
of 0-6km shear, but flow parallel to surface boundary will prompt
congealing updrafts and linear clusters along common cold pools.
Strong winds 30-40 mph will be most common, but isolated severe
winds will be possible for well organized clusters that can take
advantage of DCAPE around 1000 J/kg, theta-e diff of 25-30K, and low-
level lapse rates > 8C/km.

A conditional threat for isolated flooding will also exist Sun
evening, mainly in urban and poor drainage locations. Storm motions
should be quick enough with 20-35kt of mid-level flow, but back-
building storms may be possible. Point soundings east of the trough
axis show a deep warm-cloud layer > 10,000 feet and strengthening
low-level jet after 21z with lingering MUCAPE of 1000-1500 J/kg.
Most likely rainfall will range from a couple tenths to around three
quarters of an inch, but where any back-building and/or training
occurs, locally higher amounts of +2" would be possible.

Mon through Fri: An effective front will slowly progress through the
area through Mon with another reinforcing front and dropping low-
level thicknesses Mon night into Tues. High pressure will continue
to build over the Northeast and extend through the Mid-Atlantic into
the Southeast through the remainder of the forecast period. Mostly
quiet through the work week with only rain chances along the
seabreeze. Highs in the upper 70s to mid 80s will become common Tues
onward with lows in the upper 50s to mid 60s.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
As of 155 PM Friday...

Upstream showers and storms moving into and forming along the higher
terrain will apt to move eastward into the western Piedmont later
this afternoon and into the evening, potentially bring a brief
period of associated sub-VFR restrictions at KINT and KGSO. The
convection is expected to weaken significantly and could dissipate
all together as the remnant showers continue further east into the
central Piedmont and northern/central coastal plain. With the
exception of KINT and KGSO, the probability of occurrence is too low
to include any mention of shower/storms. Additionally, a brief period
of sub-VFR ceilings is possible at KINT and KGSO towards daybreak.
Otherwise, VFR conditions are expected through 18z Saturday.

After 18Z Saturday: Isolated to scattered shower/storms are expected
again Saturday afternoon and evening as a cold front approaches from
the west. The front will then move slowly east through the area
Sunday through Sunday night/early Monday. Sunday will be the most
convectively period with numerous showers and storms expected across
all of central NC. Drier conditions return Monday and should remain
predominately VFR through mid week.

&&

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

&&

$$
SYNOPSIS...PWB
NEAR TERM...CBL
SHORT TERM...Green
LONG TERM...Swiggett
AVIATION...CBL