Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 221956
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
357 PM EDT THU SEP 22 2016

.SYNOPSIS...
Low pressure over the Carolinas will weaken and move slowly east and
eventually offshore by Friday night. A moisture starved backdoor
cold front will push south through the area Saturday night.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 341 PM Thursday...

DCVA in tandem with ample low-level moisture convergence and weak
destabilization, will support scattered to numerous showers and a few
storms across central NC this afternoon/early evening. While
isolated pockets of heavier rain are possible today within the above-
normal PW environment, amounts should be notably less overall given
the weaker dynamic forcing for ascent and slowly filling mid level
low over the eastern Carolinas.

With closed low devolving into an open wave trough, decreasing upper
level support and shallower saturation through the column
will support less in the way of rain/drizzle overnight. Lows 65-69.


&&

.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
later runs.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
As of 350 PM Thursday...

Mixing of drier air from aloft to the surface, has allowed ceilings
to improve/lift to VFR at eastern and central TAF sites. However,
with numerous showers across the area, could see additional restrictions
in association with these showers over the next couple of hours.

Meanwhile across western terminals, IFR to MVFR ceilings have persisted
throughout the day. Latest visible satellite imagery suggests,
these ceilings too, will soon improve to MVFR or low end VFR.

However, ceilings will quickly lower this evening and overnight,]
with widespread IFR and possibly LIFR stratus developing between
06 to 12z. Ceilings will gradually improve from west to east
between 15 to 18z as drier air spreads in from the west.


Looking beyond the 24 hour forecast: Aside from some early
morning fog/stratus, VFR conditions will dominate through
early next week.



&&

.RAH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...Hartfield/CBL
NEAR TERM...CBL
SHORT TERM...CBL
LONG TERM...mlm
AVIATION...CBL


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