Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 291852
Area Forecast Discussion
National Weather Service Raleigh NC
250 PM EDT THU SEP 29 2016
A large upper level low will hold over Kentucky and southern Indiana
through Friday, as a surface front holds along the North Carolina
Foothills. The upper low will weaken and drift north and
northeastward over lower Michigan through the weekend, as the
surface front pushes slowly eastward across central North Carolina.
.NEAR TERM /through tonight/...
-- Changed Discussion --As of 250 PM Thursday...
Flash flood watch for the far eastern and southeast sections of the
forecast area will continue for now, and may need to be extended in
area based on further assessment of developing convection. This
morning`s band of heavy rain and storms which instigated countless
flooding reports this morning was oriented along a band of strong
low level moisture transport, strong upper divergence, and focused
deep IVT, all of which have weakened and shifted eastward, along
with the greatest coverage of moderate to heavy rain. Bands of
showers and storms are developing once again over NC this afternoon,
pivoting around the KY upper level low, and while the strongest
storms are expected to be in the Triad region to the north and NW
(where deep layer bulk and effective shear is quite strong and where
low level lapse rates are approaching or exceeding 7 C/km) over the
next 6-8 hrs, a few strong storms are possible this afternoon into
early evening over the remainder of central NC with surface
dewpoints solidly in the upper 60s to lower 70s. Instability so far
has been marginal despite some insolation, but will continue to
monitor. Otherwise, still expect training cells given the band-
parallel cell motion, which could push local rain totals up to 2-3"
in spots, while many areas outside of such bands may see less than a
half inch. Locations which have seen considerable rainfall in the
last 24 hours cannot handle much more water and may see a rebounding
of flooding with even minor amounts of additional rainfall. Showers
and isolated storms will slowly decrease in intensity and coverage
later this evening and into the overnight hours with an expected
decrease in low level moisture transport, although the persistence
of upper divergence especially across the NE and far N CWA will
necessitate retaining a low chance there through the night. Areas of
fog and stratus should return late tonight. Lows from the low 60s
west to upper 60s east. -GIH
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.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
As of 445 AM Thursday...
On Friday, expect conditions similar to Thursday with the upper
level low stalled over the Cumberland Plateau and the attendant cold
front stalled over central NC. -Vincent
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 440 AM Thursday...
Stubborn upper level low over the Southern Ohio valley will lift
slowly north, back over the Great Lakes through the weekend. At the
surface, the lingering orphaned surface front will dissipate across
With Central NC on the eastern periphery of the deep cyclonic flow
and the back-edge of the deeper moisture plume (PWATS
~1.5")lingering over the coastal plain of NC, we`ll continue to see
a threat of mainly diurnal isolated to widely scattered showers
Saturday and Sunday, diminishing in coverage with each passing day.
Temperatures will continue to run slightly above normal with highs
ranging from upper 70s north to lower 80s south.
The closed low over the Great Lakes will finally open up and weaken
as it finally ejects eastward, moving off the New England Coast
Monday and into Tuesday. In it`s wake, sfc high pressure building
east and south down the Atlantic Seaboard will bring cooler, more
seasonable temperatures to the area by Tuesday/Wednesday.
Large uncertainty looms for the latter half of the upcoming work
week with respect to Tropical Storm Matthew. The NHC official
forecast has Matthew near Eastern Cuba Monday evening, with
questions as to whether Matthew will get picked up and directed
northward by an upper level trough over the Gulf of Mexico. Stay
tune and check with the National Hurricane Center for the latest on
Matthew. Users are reminded that the average NHC track errors at
days 4 and 5 are on the order of 180 and 240 miles, respectively.
.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
As of 215 PM Thursday...
Conditions have improved to VFR over all but FAY, where MVFR cigs
lingered, and near GSO where MVFR cigs returned with showers in the
vicinity. Periods of sub-VFR conditions -- mainly MVFR but briefly
IFR at times -- is expected at all central NC terminal sites through
the rest of the afternoon, as scattered to numerous showers and
storms form over the area and move swiftly toward the north,
generating brief heavy rain, periodic wind gusts, and possible small
hail. The shower/storm coverage will slowly decrease through the
evening and night from SW to NE, with RWI the last to see the rain
threat diminish. With a moist ground and light winds from the SE,
widespread IFR to LIFR cigs and MVFR to IFR vsbys are expected to
develop at all sites after 07z tonight, lasting until around 13z
Fri. VFR conditions expected after that, through the end of the TAF
valid period. A few showers may linger through the morning in the
east near FAY/RWI.
Looking beyond 18z Fri, another round of MVFR showers and isolated
storms are expected mainly at RDU/FAY/RWI Fri afternoon into early
evening as a surface front shifts slowly eastward into central NC.
This front will weaken and dissipate heading into the weekend,
allowing the better rain chances to shift to our east. Except for a
potential for MVFR or IFR fog/stratus at RWI early Sat morning, VFR
conditions will dominate through Tue with low rain chances. -GIH
Flash Flood Watch until 10 PM EDT this evening for NCZ028-042-043-