663
FXUS62 KRAH 171803
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
203 PM EDT Sat Aug 17 2024

.SYNOPSIS...
A surface cold front and deep upper level trough will approach our
area from the west tonight through Sunday, then move through the
region late Sunday through Monday.

&&

.NEAR TERM /TODAY THROUGH TONIGHT/...
As of 835 AM Saturday...

Some scattered showers have developed around the Charlotte metro
area a little earlier than expected. Updated the pops across western
counties to account for the showers this morning, plus tweaked pops
northeast of Raleigh to account for a few small showers there. Have
not made any changes to the afternoon forecast at this time.
Previous discussion follows.

As of 225 AM Saturday...

A chance of mainly PM showers and thunderstorms in the west and
central areas (Piedmont) today.

An MCV associated with previous showers and thunderstorms over the
NW and W part of the Piedmont was still evident in the satellite
data tracking east across VA/NC. There continued to be mid
and high level cloudiness in all but the Coastal Area. Isolated
showers continued over central VA early this morning. CAMS suggest
that isolated to widely scattered showers are possible this morning,
mainly from the Triangle area north and east. However, it appears it
will be this afternoon and evening when the best chance (30-40
percent) appears in the Piedmont. The chances taper to slight
chances in the Coastal Plain this afternoon and evening. While
an isolated strong storms is possible, mainly over the Triad and
northern Piedmont this afternoon and early evening, the marginal
risk remained just to our NW. Highs will top out mainly between 85-
90.

The chance of showers/storms occurs as the mid/upper level trough to
our NW approaches the mountains later today. A weak lee pre-frontal
trough is expected over the Piedmont this afternoon and evening.
Isolated showers/storms will be possible tonight. Otherwise, most of
the convection will end by late evening. Lows in the lower 70s.

&&

.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
As of 300 AM Saturday...

There is a slight risk (level 2 of 5) for areas from Raleigh south
and east to the Coast Sunday afternoon and evening. There is a
marginal risk (level 1 of 5) for areas to the north and west
of Raleigh including the Triad Area.

The mid/upper level trough will through the Mountains on Sunday
afternoon and evening. A pre-frontal trough should be in place over
the Piedmont with the actual cold front trailing back over the
mountains. Surface heating of the very moist air mass over
the region will likely lead to moderate instability by afternoon
over the eastern Piedmont eastward. MLCape of 2000 to 2500 J/kg
is expected in the east, with 1500 to 2000 in the west depending
on cloud cover. Thunderstorms are expected to develop by early
afternoon with CAMS now suggesting the likely stronger storms (a few
possibly severe) in the areas of the eastern Piedmont to the Coastal
Plain. Some stronger storms will also be possible with the actual
cold front in the west during the evening. Convection should
diminish during the late evening with some potential for activity
along the cold front into the overnight hours of weaker intensity.
Locally heavy rain is expected, especially in the east. However,
widespread flooding is not expected.

Highs should range in the mid 80s NW to lower 90s SE. Lows in the
mid 60s north to lower 70s SE.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
As of 200 PM Saturday...

Sat/Sat night: A mid/upper level trough will be positioned over the
eastern CONUS with the trough axis extending from southern Quebec
trough the Mid-Atlantic and into FL. A leading effective front from
prior convection is expected to be situated near the coast with lee-
troughing extending through the Piedmont. Surface dew points within
and east of the lee-trough should still be in the mid 60s to near 70
and result in 500-1500 J/kg of MLCAPE through daytime heating. A
disturbance rotating through the backside of the trough will overlap
this weakly unstable airmass and a reinforcing cold front pivoting
across central NC to initiate scattered showers/storms during the
afternoon/evening hours.

The best overlap of synoptic forcing and available instability will
be over Northeast Piedmont into the northern/central Coastal Plain.
Mid-level flow in the core of the trough will be relatively weak,
but some directional shear (20-30kts of 0-6km shear) may lead to
some storm organization in this region where clusters organized
along a common cold pool will be most probable. DCAPE and theta-e
differences will be lower than previous days (around 600 J/kg and
20K, respectively) and lead to a marginal/conditional threat for
severe wind gusts.

Tues through Sat: The passage of a reinforcing front will mark a
pattern change with dropping low-level thicknesses through Tues.
High pressure will then shift over the Northeast and ridge down
through the Mid-Atlantic through much of the work week. Highs in the
upper 70s to mid 80s will become common each afternoon with dew
points in the 50s to near 60. Overnight, pockets of calm conditions
and clear skies will favor radiational cooling Tues night into Fri
morning with lows falling into the mid/upper 50s to near 60.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
As of 130 PM Saturday...

TAF period: There is a TEMPO group in the FAY TAF for some passing
showers at the beginning of the period. However, with less than a
30% chance of a shower/storm at any of the TAF sites during the
forecast period, did not mention precipitation in any of the TAFs,
although a shower/storm cannot be ruled out anywhere. The most
likely possibilities would likely be at INT/GSO in the late
afternoon or FAY after dark (as an area of precipitation may move
just to the west). As for late night restrictions, have gone with
persistence at INT/GSO where both sites developed low ceilings.
Considering how much the dewpoint has risen at RDU as of early
afternoon, also added a mention of LIFR ceilings to match INT/GSO`s
observations from this morning. There is enough confidence in lower
ceilings at FAY/RDU to go with prevailing ceilings, right around
1000 ft.

Outlook: Scattered showers/storms are expected at INT/GSO Sunday
afternoon, with prevailing shower/storms at the other 3 sites. A
chance of precipitation will linger at all sites on Monday, but the
rest of the outlook period should be dry.

&&

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

&&

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