Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 310819
Area Forecast Discussion
National Weather Service Raleigh NC
415 AM EDT WED AUG 31 2016
Tropical Depression 8 will track northeast into the Atlantic today
as central NC remains in a relatively warmer and drier pattern. A
cold front will move in for Thursday, before Tropical Depression 9
will move northeast near and along the front on Friday and Saturday.
.NEAR TERM /THROUGH TONIGHT/...
As of 320 AM Wednesday...
Tropical Depression 8 is scheduled to move further offshore today to
the northeast and away from the state. In its wake a small wave is
forming along the South Carolina coast that will track northeastward
into along the coast today. This is best illustrated in the 500 mb
vorticity field and this could be a small focus for some convection
across the east today with a few showers extending into our eastern
counties. Convective allowing models are quiet until after 21Z when
some light shower activity moves across the area from the south.
Chances will be slight at best and most locations should remain dry.
Highs once again near 90 with lows around 70 on Wednesday night.
.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
As of 320 AM Wednesday...
A cold front approaches the area on Thursday which is being forced
into the area by a deepening upper level trough spurred on by an
upper low moving out of Quebec and into New England. There is not
much of a surface low with this system and as a result the front is
ragged as it approaches with not much in the way of instability or
shear to speak of but there will be enough to kick off some
convection albeit most likely sub-severe. Forecast soundings
indicate that the front will not actually make it though the area
until Friday morning when winds become more northeasterly and drier
air moves at least into the northwest Piedmont. Further south and
east the story will be much more complicated as the front hangs up
and a meso low develops right on the coast all while moisture
increases greatly ahead of TD 9. This could lead to a period of
showers and storms in the south and east on Thursday night into
Friday morning. Thursday highs are still expected to be in in the
upper 80s to low 90s with the late frontal passage and lows will be
very tricky as the northwest Piedmont could see lows in the low 60s
with lower 70s across the southeast.
.LONG TERM /Friday through Tuesday/...
-- Changed Discussion --As of 415 AM Wednesday...
Fri/Fri night: The official NHC forecast for what is now TD9 takes
it on a northeastward track just off the Carolina coast Fri/Fri
night, likely to result in a scattered to numerous tropical showers
over the SE CWA, along with enhanced surface winds and gusts from
the northeast. While the bulk of the winds directly around the
cyclone are expected to hold just SE of the CWA, we could still see
winds become enhanced by the tightening pressure gradient between
the tropical circulation and the cool high pressure ridge extending
in from the north. Expect max winds in our SE to be near 15 mph with
periodic gusts to 20-25 mph possible, although these may need to be
adjusted upward as the track gets better defined with greater
confidence. Similarly, the precip chances and amounts will be
refined in the next 24-48 hrs, but for now expect 50-70% pops over
the SE half, with little to no precip over the NW CWA. Will have max
rainfall amounts around three-quarters of an inch in our far SE
sections, with highest totals along/east of a line from Maxton to
Fayetteville to Goldsboro. Tough call on the southeastward
progression of the surface cold front moving in from the northwest,
given that the narrow mid level trough extending from the Canadian
maritimes into the OH valley early Fri will drift very slowly SSE
while shearing out and leaving a weak low over eastern KY/TN by Sat
morning. But the effects of the cyclonic circulation drawing cooler
thicknesses into the area combined with the enhanced cloud cover
should hold temps down into the 79-83 range for highs. Lows Fri
night from 60 NW to 67 SE with decreasing clouds and wind speeds.
Sat-Tue: In the wake of the tropical cyclone, our weather heading
into the weekend will be largely driven by the cool surface high
pressure building in from the north, pulling in below-normal
thicknesses and a markedly drier air mass that will last into at
least Mon, albeit with some modification as the mean weak trough
eases ENE just off the East Coast, with heights aloft building in
the west due to the mid level ridge building over the lower Miss
valley and Gulf states. Conditions may remain unsettled with some
cloudiness over the CWA Sat into Sun morning resulting from the
baggy upper trough axis, but expect a dry forecast thereafter as the
trough axis eases gradually east of the area. Highs should be mostly
in the lower-mid 80s with lows in the lower-mid 60s through Mon,
followed by warming temps to upper 80s for highs Tue with rising
heights aloft and modifying surface air mass. -GIH
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.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 745 PM Tuesday...
24 hour TAF period: A few more MVFR visibilities already popping up
this morning compared to yesterday as dewpoint depressions near zero
are in place across the east. This would lead me to believe the KRWI
will be soon to experience MVFR visibilities but all other TAF sites
are carrying at least a 5 degree dewpoint depression so if KFAY or
KRDU were to go down to MVFR it will be much later this morning.
Otherwise another mostly dry day is expected although models do show
a little more shower activity after 21 Z through the end of the TAF
period. Will keep showers out of the TAFs at this time as the
probability is less than 30 percent. Winds will begin easterly and
shift to a more southeasterly direction by the end of the period.
Wind speeds near 5 kts.
Long Term: An uptick in convection is in order for Thursday as a
cold front approaches from the northwest and then the influence of
tropical depression 9 will affect at least eastern terminals on
Friday through Saturday morning with some gusty winds and rain