528
FXUS62 KRAH 161323
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
923 AM 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 923 AM 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, an area of showers and storms, currently across
central portions of TN an KY, will progress east across the southern
Appalachians later this afternoon, and in weakening fashion move
into the western Piedmont between during the late afternoon and
evening. Then overnight, some isolated shower activity is possible
as the lingering convection  continues to move east 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. Highs 85-90. Lows 65-70.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 320 AM Friday...

The mid and upper level trough will be approaching from the Ohio
Valley Saturday and Saturday night. A cold front will remain to our
NW, but will approach the mountains Saturday night. There will be a
better chance (40-50) of mainly afternoon and evening showers and
thunderstorms in the west, with a 30 percent chance east. Highs will
be mostly in the mid to upper 80s, with lows in the lower 70s.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 400 AM Friday...

A surface low will move east from Lake Huron to Upstate NY on Sunday
and Sunday night, as a secondary low develops along the northern Mid-
Atlantic coast. This will push a surface trough and cold front
through central NC. Looking aloft, shortwave energy diving down from
the NW will deepen the mid/upper troughing in place to our west over
the Appalachians, increasing height falls across the area. Deep SW
flow will help bring dew points into the lower-to-mid-70s, which
will contribute to moderate instability (1500-2500 J/kg of MLCAPE)
by the afternoon. The upper-level forcing and cold front will
combine with the unstable air mass to result in scattered to
possibly numerous showers and storms developing during the afternoon
and evening along and ahead of the front. One somewhat limiting
factor will be the deep-layer moisture which doesn`t look overly
impressive, as PW values look to be around 1.5 to 2 inches (close to
normal). Widespread heavy rain doesn`t look like a big concern as
the latest WPC QPF is only in the quarter to half inch range on
average in most places (highest east), but locally higher amounts
will be possible. Still have close to 80% of GFS/ECMWF/CMC ensemble
members depicting measurable precipitation on Sunday
afternoon/evening, so raised POPs to likely (around 60%) in most
places. Mid-level flow continues to look as high as 30-40 kts, so
some strong to severe storms can`t be ruled out, and SPC has placed
all of central NC in a marginal (level 1 of 5) risk for severe
storms on Sunday. The main threat will be isolated damaging winds.
High temperatures will be in the mid-80s to 90, which is within a
few degrees on either side of normal. Rain chances will end from NW
to SE on Sunday night as somewhat drier air works in behind the cold
frontal passage. Lows will be mid-60s to 70.

More showers and storms will be possible on Monday as the mid/upper
trough lingers overhead, but moisture and instability will decrease
as the low-level flow turns more W/NW. Shear also doesn`t look as
impressive. So coverage should be fairly isolated, and POPs are only
in the low chance range. Temperatures will start a downward trend as
highs range from lower-80s far north to upper-80s far south
(slightly below normal) and lows Monday night are in the 60s.

A cooling and drying trend will continue from Tuesday through
Thursday behind a secondary cold front that looks to move through on
Monday night. Surface high pressure will build down from the Great
Lakes and Northeast US as the cold front stalls well to our south.
The mid/upper trough axis will gradually lift NE, favoring height
rises W/NW flow aloft. This will bring below-normal PW values and
help dew points mix out well down into the 60s from Tuesday through
Thursday. In fact, some guidance even shows some 50s dew points on
these days. So largely dry weather and mostly sunny skies are
expected. Highs will drop to upper-70s to lower-80s by Wednesday and
Thursday, with lows in the upper-50s to lower-60s as there should be
decent radiational cooling conditions.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
As of 640 AM Friday...

Showers/storms will be possible (15-30% chance) at INT/GSO during the late
afternoon into the evening hours as upstream convection leaks across
the mountains, although likely in a weakening state. Otherwise,
generally

After 12Z Saturday: A slow moving cold front will approach this
weekend, producing increasing convective rain chances through the
weekend with Sunday being the most active/widespread. Showers/storms
will potentially linger into Monday as the front finally moves
through the area.

&&

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

&&

$$
SYNOPSIS...PWB
NEAR TERM...CBL
SHORT TERM...Badgett
LONG TERM...Danco
AVIATION...PWB/Swiggett