Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 241948

Area Forecast Discussion
National Weather Service Raleigh NC
345 PM EDT Sun Sep 24 2017

High pressure centered over the Great Lakes and northern Mid
Atlantic states will extend south into our region through Monday.
Hurricane Maria is forecast to move north through the western
Atlantic, paralleling the SE Coast through midweek.


As of 259 PM Sunday...

Subsidence associated with the stacked anticyclone centered over the
NE and Mid-Atlantic states will support dry and stables conditions
across central NC. Under mostly clear/fair skies, lows tonight will
once again fall into the lower to mid 60s.


As of 259 PM Sunday...

Deep layer ridging centered over NY will prevail across the region
on Monday, before weakening/breaking-down Monday evening/night as
Maria continues to move north-northwest, paralleling the Carolina
Coast. Expect a gradual increase of high level cloudiness throughout
the day as the outer outflow cirrus bands push west into the area,
which should be sufficiently opaque along and east of I-95 to temper
afternoon heating. Highs ranging from lower 80s in the east to
mid/upper 80s SW. The pressure gradient between the high to our
north and Maria will also begin to tighten, producing wind gusts in
the mid to upper teens.

Strengthening NELY low-level flow will advect some Atlantic maritime
moisture in the form of low clouds/stratus into the eastern half of
the forecast area Monday night. Owing to the increase in
clouds/moisture, low temps Monday night will be a few degrees warmer
than past recent nights. Lows in the mid to upper 60s.


.LONG TERM /Tuesday through Sunday/...
As of 345 PM Sunday...

Tue through Thu night: Hurricane Maria is expected to drift slowly
northward off the NC coast Tue-Wed, before getting caught up in the
westerlies and taking a turn NE and out to sea Thu. The official
forecast track follows the op GFS more closely than the ECMWF, which
tracks Maria`s center a bit closer to the NC and about 18 hrs slower
than the GFS by Thu. Will hew more closely to the op GFS for
sensible weather. Based on the latest NHC wind radii forecasts, we
are very unlikely to see tropical storm force winds into our
forecast area. However, momentum transfer noted on forecast
soundings suggests that frequent gusts to 20-25 kts are likely in
our eastern third, especially when Maria`s center makes its closest
approach Wed. Skies Tue should trend to fair west, with streaks of
thin high clouds streaming off the top of Maria northwestward over
NC, with partly to mostly cloudy skies east where greater low level
influx of Atlantic moisture should result in scattered to broken
stratocu. As Maria tracks up to and north of the latitude through
central NC, the backing of low level winds to be from a more
northerly or northwesterly direction should help draw drier air back
in, such that clouds should thin out Wed, and likely be primarily
partly cloudy through Thu. Shower chances appear to be small, with
models generally confining small chances of measurable precip to the
east. Will continue with isolated shower pops Tue through early Thu,
as far outer bands may work into the Coastal Plain at any time.
Highs 80-86 Tue and 81-89 Wed, with narrow ridging aloft NW and then
W of Maria and thicknesses 10-15 and 15-20 m above normal
respectively. By Thu/Thu night, broad mid level troughing over much
of NOAM (all but the far S and W) begins to dig over the Upper
Midwest, pushing a moisture-starved cold front to the SE, over the
NC mountains and through the state late Thu through Thu night.
Expect highs of 83-90 Thu with thicknesses likely to be nearly 20 m
above normal. Lows in the mid 60s to lower 70s Tue night and Wed
night, slipping to the low-mid 60s post-front Thu night.

Fri through Sun: The digging mid level trough shifts eastward over
the weekend, while cool high pressure drifting from the Upper
Midwest across the Great Lakes to the Northeast ridges down through
NC. The GFS develops a baroclinic zone near the SE Coast, along
which low pressure tracks. While this is far from certain to occur,
given some disagreement in the models, will still leave in a low
chance of showers over the SE, mainly late Sat through Sat night,
still below climatology. Otherwise, expect fair to mostly sunny
skies. Highs in the upper 70s to lower 80s Fri, then in the 70s
Sat/Sun, making for a pleasant fall weekend. -GIH


As of 115 PM Sunday...

24 Hour TAF Period: VFR conditions are generally expected to
continue through the 24 hour TAF period as high pressure extends
into the area from the north. A steady 3 to 5kt northerly breeze
should preclude any widespread fog development overnight.

Outlook: As Hurricane Maria moves northward through the western
Atlantic near a latitude of the NC coast, eastern terminals could
see some sub-VFR ceilings as early as Monday night/Tuesday morning
with breezy northerly winds developing by Tuesday and lingering into
Wednesday. Based on the latest NHC official track, precipitation and
resultant aviation impacts will be minimal and confined to eastern





LONG TERM...Hartfield
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