194
FXUS62 KRAH 170626
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
225 AM 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 Sunday night.

&&

.NEAR TERM /TODAY THROUGH TONIGHT/...
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 /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 /06Z SATURDAY THROUGH WEDNESDAY/...
As of 140 AM Saturday...

Generally VFR conditions are expected through 18z today. Scattered
thunderstorms with brief MVFR conditions are expected this afternoon
and evening, with the best chances from KINT to KRDU.

Looking beyond 00z Sun, a few showers and storms remain possible
at all sites through Sat night. A higher chance of showers/storms
exists on Sunday afternoon and evening, especially from KRDU east
and south. Generally VFR conditions should return and prevail Mon-
Wed.

&&

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

&&

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