Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
FXUS62 KRAH 292342 RRA
Area Forecast Discussion
National Weather Service Raleigh NC
741 PM EDT MON AUG 29 2016
An ENE to NE onshore flow will prevail through mid-week as Tropical
Depression 8 approaches the Carolina coast from the ESE and high
pressure shifts slowly east from the lower Great Lakes to the Mid-
.NEAR TERM /THROUGH TONIGHT/...
As of 135 PM Monday...
A dry low/mid-level airmass persists over the majority of central NC
this morning, as sampled by the 12Z GSO RAOB (PWAT 1.11") and
indicated by the latest 925/850 mb SPC mesoanalysis. Moisture
increases rapidly as one progresses east of the I-95 corridor in the
Coastal Plain where NE low-level flow has advected rich low-level
moisture from the Atlantic into Eastern NC, as indicated by the 12Z
MHX RAOB (PWAT 1.83"). Marginal destabilization (tempered by cloud
cover and NE low-level flow) will be confined to areas along/east of
I-95 this afternoon. Forcing for ascent will also be confined to
areas along/east of I-95, in the form of weak DPVA assoc/w a shear
axis extending N/NNE along the Southeast/Carolina coast, attendant a
stalled upper level low offshore the GA/FL coast. With the above in
mind, expect mostly cloudy skies and a slight chance of showers to
along/east of the I-95 corridor this aft/eve, with partly cloudy
skies and dry conditions elsewhere. Expect highs in the mid/upper
80s, coolest east of I-95. Lows tonight will range from the upper
60s (western and northern Piedmont) to lower 70s in the Coastal
Plain, primarily east of I-95. -Vincent
.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 135 PM Monday...
Moisture will increase over central NC on Tuesday as an E/NE onshore
flow expands westward across the state, with PWAT values rising in
comparison to today as , the shear axis extending N/NNW into the
area (from a stalled upper level low offshore the GA/FL coast) today
is expected to shift W/SW into western NC, upstate SC and northern
GA. As a result, forcing will largely be absent Tue/Tue night. In
fact, subsidence is likely to be present over portions of central/
eastern NC on the western periphery of TD #8 Tue aft/eve (progged to
be a marginal tropical storm by then) as it approaches the NC OBX.
With the above in mind, will indicate a dry forecast over central NC
Tue/Tue night, with the best chance for precip along the Carolina/
Southeast coast. Expect partly cloudy skies with highs in the upper
80s to near 90F. Lows Wed in the upper 60s to lower 70s. -Vincent
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 300 PM Wednesday...
Lots of interesting weather features to watch for during the mid to
late week period.
Wednesday: The approach of a northern stream shortwave trough diving
se through the Great Lakes and Ohio River valley on Wednesday will
erode the weakening ridge in place and cause T.D. 8 to recurve
northeastward and away from the NC coast. Meanwhile, nearly all
models indicate some weak sfc cyclogenesis along a weak coastal
trough and in proximity to the weakening mid-level
circulation/trough along the GA/SC coast. This feature too will feel
the influence of the approaching northern stream trough, and is
expected to quickly skirt ne away from the NC coast late
Wednesday/Wednesday night. Thus with no forcing mechanisms, central
NC will continue to see a continuation of mostly dry conditions with
temps in the upper 80s to lower 90s.
Thursday-Thursday night: Aforementioned northern stream trough and
attendant cold front will progress southeast into the region
Thursday afternoon/evening. Once again, this northern stream trough
will impact the tropics, with attendant belt of westerlies picking
up what is now T.D. 9 and inducing a north-northeastward
acceleration across northern Florida and up along the Southeast
Coast late Thursday night and Friday. Will have to monitor how the
track and timing evolves over the next couple of days, but if
everything lines up, it`s possible that convection along the front
could increase in both intensity and coverage Thursday afternoon and
Thursday night(possible PRE??),as it intercepts the tropical
moisture plume advecting poleward into the area. For now will
continue to feature a NW-SE pop gradient, highest pops se. Temps
will continue to remain above normal until the front moves through.
Friday through Monday: Official NHC track of T.D. 9 moves it off the
Southeast and Mid-Atlantic Coast Friday-Friday night. Could see some
lingering showers in the east early Friday, otherwise it will be dry
with cooler temps as Canadian high pressure builds south in the area.
Highs over 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 build back over the region.
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 741 PM Monday...
24-hr TAF Period through 31/0000z: Mainly VFR conditions are
expected during this time as dry air persists over most of central
NC. The dry air exception will be south and east of the Triangle
where NE winds are promoting a moist flow off the Atlantic. As
such, our eastern zones and sites including KRWI and KFAY, may see a
brief period of MVFR stratus toward daybreak Tuesday, however
outside of that, expect mostly VFR conditions and NE winds less than
10kt during this period.
Looking ahead: Forecast confidence decreases mid-week due to
uncertainty assoc/w the evolution of TD #8 offshore the Carolina
coast and an upper level low offshore the Southeast coast. Forecast
confidence remains low late this week into this weekend when a cold
front approaching from the NW is progged to interact with TD
#9 (located west of the FL Keys in the GOMEX this morning) as it
tracks NE across northern FL and emerges offshore the Southeast
coast. With the above in mind, VFR conditions are most likely to
prevail at western terminals (INT/GSO), and eastern terminals
(FAY/RWI) are most likely to see periodic showers and low ceilings
mid/late week. -Vincent