Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 310615
Area Forecast Discussion
National Weather Service Raleigh NC
215 AM EDT WED AUG 31 2016
-- Changed Discussion --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.
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.NEAR TERM /THROUGH TONIGHT/...
As of 920 PM Tuesday...
Latest surface analysis shows a meager Tropical Depression 8 off the
NC coast with a ridge of surface high pressure extending southwest
into the Mid Atlantic. A light east to northeast flow at persists at
the low to mid levels which has resulted in an increase in moisture
across central NC. Further aloft, an upper level low was located
across central SC and was drifting slowly northwest with weak
ridging across central NC. This setup should result in generally
fair weather overnight with isolated convection confined to the
coastal region with partly to mostly clear skies overnight. Lows
Wednesday morning will range in the upper 60s to lower 70s. -Blaes
.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
As of 1245 PM Tuesday...
As Tropical Depression 8 tracks NE away from the Carolina coast, a
baroclinic low attendant a weakening upper level low just offshore
the Southeast coast and strengthening cyclonic flow aloft over the
Mid-Atlantic is expected to track NE along/just offshore the
Carolina coast Wed/Wed night. By 12Z Thu, the low is progged to be
centered just south of Cape Lookout. Although the best potential for
precipitation attendant the aforementioned low will remain in
immediate vicinity of the Carolina coast, 12Z model guidance
suggests isolated or scattered convection (primarily showers) may
develop as far inland as the Coastal Plain. Additionally, diurnal
convection is expected to develop in the higher terrain of the NC
mountains in assoc/w differential heating and diffluent flow aloft
Wed aft/eve, and some of this activity could drift into portions of
the NW piedmont before dissipating Wed evening. With the above in
mind, will continue to indicate a slight chance of showers/storms
during the aft/eve hours in southeast portions of the Coastal Plain
and in the Northwest Piedmont. Expect highs on Wed in the upper 80s
to near 90F, lows Wed night in the lower 70s. -Vincent
.LONG TERM /THURSDAY THROUGH TUESDAY/...
As of 245 PM Tuesday...
Thursday-Thursday night: Amplifying northern stream trough and
attendant cold front will progress southeast into the region late
Thursday afternoon/evening and at the same time should cause what is
now T.D. 9 or possibly soon to be Tropical Storm Hermine to to bend
northeastward and move across northern Florida and along the
Southeast Coast. At this time, minimal to no impact from this
tropical system. Instead, frontal lifting underneath the entrance
region of a seasonably strong 90kt jet streak extending down the Mid-
Atlantic States will provide sufficient forcing within the moist 1.8-
2.0" PWAT airmass in place to support scattered to possibly numerous
showers and storms across Central NC between 18z to 06z.
With afternoon temps in the upper 80s to lower 90s and continued
BL dewpoints in the lower to mid 70s, steep low-level lapse rates
will result in 1000-2000 J/KG of MLCAPE across the area Thursday
afternoon, highest across the southeast. Thus, could see a uptick
in coverage and intensity late in the day as convection moves
east-southeast into the Sandhills and coastal plain. Given 25 to
30kts of deep layer shear, can`t rule a few strong to severe storms
during the afternoon/early evening, before nocturnal stabilization
In the wake of the frontal passage, cooler air begins to seep into
the area Thursday night with lows 65 to 70.
Friday through Tuesday: While there are some differences in the
forward speed/timing of what is now T.D. 9 as it interacts/merges
with amplifying trough into the Eastern US, the official NHC track
moves the system up the Southeast Coast and out into the Western
Atlantic Friday and into Saturday. Central NC could see some
lingering showers in the east on Friday as the front could temporary
stall along the coast with the approach of the tropical cyclone from
the south. Thereafter, will forecast dry conditions with cooler
temps as Canadian high pressure builds south in the area. Highs
Friday and through the weekend in the lower 80s north to mid 80s
south. Lows in the lower to mid 60s. Temperatures should start to
rebound early next week as upper ridging builds back into the region
from the west. -CBL
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --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
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