Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 230514
Area Forecast Discussion
National Weather Service Raleigh NC
115 AM EDT FRI SEP 23 2016
A surface low and trough will hold along the Carolina coast through
today, before weakening tonight. Weak high pressure will hold over
the area through Saturday, then a backdoor front will push in from
the north Saturday night and Sunday.
.NEAR TERM /THROUGH TONIGHT/...
As of 1230 AM Friday...
Quick update to reduce rain coverage a bit for the remainder of the
night, according to current trends and recent hi-res model output.
No other significant changes. -GIH
Earlier discussion as of 939 PM Thursday... The threat of locally
heavy rain continues over the Coastal Plain.
The mid/upper low was still lingering near the NC/SC border area per
the latest WV satellite data. The surface low pressure was located
off the SC coast. Deep moisture continued to be pulled westward into
central NC (north of the mid/upper level low). The main areas of
heavy rainfall have been tied to an inverted surface trough
extending from near Fayetteville northeast to near Rocky Mount and
Halifax. A large swath of 1 to locally 2.5 inches fell across
Johnston, southern Wilson, and southern Edgecombe Counties earlier
this evening. Several other clusters showers with heavy rain have
been focused over the southern Piedmont and Sandhills under the mid
level low, but amounts not been quite as heavy across the south.
Overnight, the continued presence of the mid level low over southern
NC will bring a continued very moist flow and lift from off the
Atlantic over eastern and central NC. The more concentrated areas of
showers will weaken and decrease in coverage; however, there will
continue to be a chance of showers overnight mainly east of the
Triad cities. Locally heavy rain is still possible but most likely
to redevelop with heating on Friday. We will maintain higher POP in
the east and south overnight with considerable cloudiness. Lows
should be hard pressed to fall below 70 due to the current high dew
points and extensive cloud cover. The NW Piedmont will see some mid
and upper 60s with some drier air in place there.
.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
As of 341 PM Thursday...
Lingering mid/upper trough over the Carolinas will move east and
offshore, picking up the weakening sfc circulation left-over from
Julia`s remains along the way.
This will allow drier air across western NC to spread east
throughout the day, which will aide in the scouring out of the low-
level moisture/stratus cloud deck with increasing sunshine by the
afternoon for the western two-thirds of the forecast area. Abundant
sunshine over the western piedmont will propel temperatures into the
mid 80s, with slightly cooler highs in the lower 80s over
eastern areas, where low cloud cover will be slower to move out.
Isolated to scattered showers will be largely be confined along and
east of I-95, along the western/back edge of the deeper moisture and
in closer proximity to weakening moisture convergence along
the inverted coastal trough.
Drier air will continue to spread east Friday evening/night, with
clear skies expected everywhere. If sfc flow decouples, wet soils
could lead to some patchy ground fog development. Lows again in
the mid-upper 60s.
.LONG TERM /Saturday through Thursday/...
As of 250 PM Thursday...
Gradual amplification and eastward progression of an upper ridge in
the mid west will produce drier northwest flow aloft over the
weekend. Associated surface high building down the east coast pushes
a backdoor cold front south...with cool air advection surging into
the northeast as early as Saturday evening. Highs Saturday will
benefit from abundant sun and should reach mostly mid 80s. Low
cloudiness is expected to spread along and behind the front Saturday
night...with gradually increasing isentropic lift producing a small
chance of patchy light rain or showers by Sunday morning...mainly
around the southern and western periphery of the ridge. Absent
additional forcing...slight chance PoPs will be maintained through
Monday in the cool regime...again mainly south and west where
isentropic lift will be present...albeit weak. Highs Sunday will be
only in the mid 70s northeast...with cool air slower to reach the
southern tier which should reach low and perhaps mid 80s. Monday
will be the cooler cloudier day with highs mostly in the mid 70s
across the area. Morning minimum temperatures will be mostly in the
low and mid 60s through the extended period.
Divergent model solutions in the mid week periods maintain low
forecast confidence...particularly the max temperatures. The GFS is
still advertising a strongly blocked pattern...with very slow
eastward progression of the amplified upper ridge along the east
coast and the next surface front approaching from the west.
Meanwhile...the ECMWF also sets up a blocking pattern...but further
west with an upper trof digging into the mid Atlantic which shoves
the next front quickly south through the area in backdoor fashion on
Wednesday. No point in making dramatic changes that will likely
revert...so will maintain the ongoing slight chance PoPs and highs
from the upper 70s north to lower 80s south as we await consensus in
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --As of 115 AM Friday...
Confidence is high in widespread IFR to perhaps LIFR conditions
through daybreak this morning across all of central NC, a result of
light winds along with stable and very moist air in the low levels.
Cigs are expected to rise to MVFR between 14z and 16z, and then to
VFR between 16z and 18z west (INT/GSO), 18z-20z central (RDU), and
19z-21z east (RWI/FAY). Rain chances today are low west (INT/GSO)
trending higher east (RDU and especially RWI/FAY), with the highest
coverage near FAY, which could see a few hours of showers, and
perhaps a storm or two, with MVFR vsbys and cigs this afternoon.
Conditions will trend toward VFR everywhere after sunset tonight, as
weak high pressure starts to build in from the west with drier air
Looking beyond 06z early Sat morning, VFR conditions will dominate
into Sat evening, with the risk of sub-VFR stratus and fog returning
late Sat night/Sun morning as a backdoor front approaches from the
north. MVFR cigs may linger through much of Sunday and Sunday night,
although confidence is not high, as there is uncertainty regarding
the southward pace of the backdoor front through NC. After mostly
dry weather Sat, the chance for sub-VFR showers and storms returns
for Sunday along the backdoor front. Shower/storm chances will
increase further late Mon into Tue as an upper level low pressure
trough approaches from the NW. There may be a risk for low level
wind shear early Tue morning. -GIH
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