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000
FXUS62 KRAH 240624 RRA
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
224 AM EDT Sat Jun 24 2017

.SYNOPSIS...
The remnants of Cindy will fill and lift quickly up the middle
Atlantic coast this morning. A trailing pre-frontal trough will
linger over the ern Carolinas today, ahead of a cold front that will
cross our region late this afternoon and this evening. The front
will stall along the southeast U.S. coast through Sunday, then
drift offshore Sun night.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1225 AM Saturday...

There would appear to be a risk of strong to severe storms during
the next several hours over the Piedmont, as the current band of
fast-moving, but generally weak convection crossing the Foothills
encounters an instability axis of 1000-1500 J/KG MLCAPE centered
over central NC. While the consensus of NWP guidance suggests this
activity will further weaken with time and ewd extent, observational
and objective analysis data would indicate otherwise.

The height gradient and associated deep layer wind fields on the
sern periphery of Cindy will remain strong for several more hours,
before weakening by around 09Z, as the remnant Cindy circulation
moves to the Mid-Atlantic coast. Resultant effective bulk shear and
SRH values of 35-40 kts and 200-300 m2/s2, respectively, would
support organized storm modes, including supercells/bows, with right-
moving supercells favored owing to strongly-cyclonically-curved
hodographs during the next several hours, before the height/wind
field weakens. Damaging wind gusts and an isolated tornado or two
may result, mainly west of U.S. Hwy 1. Radar trends indeed support
an uptick in convective intensity and organization from Statesville
to Gastonia, NC.

As of 950 PM EDT Friday...

Nothing on radar this evening except for a few sprinkles which is a
nice change from previous days. This is not the case to our west
however as the remnants of Cindy have combined with a frontal system
that runs along much of the expanse of the Appalachians with the
heaviest rainfall across the Ohio Valley. A relative minimum in the
rainfall over eastern Tennessee will make its way eastward overnight
but continuing to die out as it does so. It is possible to have some
showers into the Triad between 6-9z but should die out by 12z.

As far as stratus is concerned, some MVFR ceilings are possible in
the triad but further east conditions should remain VFR. Part of the
reason for this is that forecast soundings show good mixing down to
the surface overnight and we have already seen some gusts to 15 kts
start to make their way into the observations. This is expected to
continue overnight and will likely increase in frequency and
coverage.

Temperatures across the area remain the the upper 70s to lower 80s
with dewpoints in the upper 60s to mid 70s. Lows will only reach the
mid 70s.


&&

.SHORT TERM /SATURDAY THROUGH SUNDAY/...
As of 135 PM EDT Friday...

A cold front will approach the central Appalachians from the NW late
tonight. With the remnants of Tropical Cyclone Cindy progged to
track a bit further N/NW of central NC than previously anticipated,
the cold front is not expected to progress into central NC until Sat
evening/night. With central NC on the eastern periphery of the pre-
frontal trough, rich low-level moisture is likely to persist through
the afternoon. Strong insolation and rich low-level moisture are
expected to yield moderate instability by mid/late afternoon,
ranging from ~1000 J/kg in the NW Piedmont to ~2000 J/kg in the SE
Coastal Plain, in the presence of 30-40 knots of deep-layer shear.
Convection allowing models suggest scattered convection will develop
within the pre-frontal trough in vicinity of the I-77 corridor by
mid/late afternoon (19-20Z), then quickly grow upscale into a SW-NE
oriented line that progresses E/SE through central NC between 21-00Z
(roughly). Though diurnal timing will be optimal, rich boundary
layer moisture /relatively low T/Td spreads/ will yield marginal
DCAPE (500-750 J/kg) and line-parallel (southwesterly) deep-layer
shear will not favor new updraft development at the leading edge of
the consolidated cold pool. As a result, the potential for damaging
winds appears relatively marginal /isolated/. Expect highs ranging
from the mid/upper 80s (NW) to lower 90s (SE). -Vincent

Saturday night and Sunday, a sfc boundary trailing behind a low
pressure system crossing the northern Mid-Atlantic, will cross
central NC Saturday night and Sunday. This front interacting with a
moisture rich air mass will support the development of scattered-
numerous showers and thunderstorms Saturday evening. Bulk of
convective will dissipate overnight Saturday night though isolated-
scattered showers still probable due to the presence of the front
and available moisture. By Sunday, the main focus for convective
development should be primarily east and south of Raleigh as the
front should lie in this vicinity. Nwly flow behind the front will
advect a drier more stable air mass into the Piedmont Sunday,
leading to drier conditions. -WSS

&&

.LONG TERM /SUNDAY night THROUGH FRIDAY/...
As of 305 PM EDT Friday...

The drier air mass will overspread the remainder of central NC late
Sunday and Sunday night. Monday shaping up to be warm and dry with
wly flow aloft and a sfc high positioned over the TN Valley. A s/w
in the northern stream projected to drop sewd across the lower OH
Valley Monday night, and cross central NC Tuesday. 12Z ECMWF more
adamant about the potential for lift and isolated/scattered showers
compared to the drier GFS. Based on the favorable timing, potential
will exists for isolated-scattered showers, primarily late morning
through the afternoon.

A modifying Canadian high pressure system will initiate a stretch of
dry and relatively pleasant conditions (ie. less humid) across
central NC Wednesday into Thursday. By Friday, return flow on the
back side of the retreating high will signal a return to warm and
humid conditions by the end of the week.

No signals noted for extreme heat across our part of the country
through the next 5-7 days. In fact, high temperatures Tuesday and
Wednesday will likely average 3 to 8 degrees below normal. The
modifying air mass Thursday and Friday will permit temperatures to
return to seasonal norms.

&&

.AVIATION /06Z Saturday through Wednesday/...
As of 220 AM Saturday...

MVFR ceilings, both ahead of and within an approaching band of
showers and storms with gusty wswly convective wind gusts, will
spread east across central NC through about 09Z. Even away from
convection, strong swly surface winds, generally 12-15 kt sustained
with gusts of 20-30 kts, will also persist for several more hours,
beofr tapering off between 09-12Z, as the remnants of Cindy move to
the nrn mid-Atlantic coast.

Scattered showers and storms with associated sub-VFR conditions
are expected to focus along both a pre-frontal trough at ern
terminals by early this afternoon, followed by the west to east
passage, area-wide, of a broken band of convection along a cold
front between 21-03Z.

Outlook: There will be a chance of low stratus or fog over ern NC
Sun morning, including at FAY, followed by generally VFR conditions
through the middle of next week. The main exception will be a chance
of a shower or storm on Tue, especially at ern TAF sites.

&&

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

&&

$$

SYNOPSIS...MWS
NEAR TERM...MWS/Ellis
SHORT TERM...Vincent/WSS
LONG TERM...WSS
AVIATION...MWS