002
FXUS62 KRAH 171831
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
230 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 230 PM Thursday...

...There is a slight risk (level 2 of 5) for severe storms from
Raleigh south and east Sunday afternoon and evening...

...There is also a risk for Isolated Pocket of Heavy Rain and Flash
flooding along and east of US 1...

An unseasonably strong()~3 S.D. below normal) and amplifying upper-
level trough will dig SEWD into the Eastern US Sunday during the
period.  At the surface, a  pre-frontal sfc trough in the lee of the
Appalachians will get overtaken by the accompanying cold front that
will move east across central NC during the late afternoon and
through the overnight hours. As daytime heating commences, moderate
destabilization is expected area-wide, maximized across the
Sandhills and southern coastal plain. Coincident with the arrival of
the cold front and core of the stronger 40-50 meter H5 falls into
the area, showers and storms are expected to develop across the
western Piedmont between 18-21z, with convection thereafter
increasing in coverage and intensity(becoming better organized) as
the progresses eastward into the central Piedmont and western
Sandhills between 20-00z, and then across eastern Sandhills and
coastal plain counties between 23-04z. Deep layer shear of 30-35 kts
will likely favor multi-cellular severe threat, with damaging winds
the primary threat. Given recent wetness and with area streams and
creeks still running high, the convective downpours could also lead
to some instances of flash flooding, especially in poor-drainage and
urban areas. The severe threat appears greatest between 3 to 10 pm
with generally dry conditions after midnight.

Highs ranging from mid 80s north to lower 90s south. Lows in the
mid/upper 60s to lower 70s south.

&&

.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...CBL
LONG TERM...Swiggett
AVIATION...Green