Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 261147

Area Forecast Discussion
National Weather Service Raleigh NC
747 AM EDT Tue Sep 26 2017

A narrow ridge of high pressure will remain centered over the
Appalachians through Wed, while Hurricane Maria tracks northward,
offshore the coast of the Carolinas. Meanwhile, a dry cold front
will approach from the northwest, then cross NC late Thu and Thu


As of 340 AM Tuesday...

A mid level ridge now centered over the nrn middle Atlantic states,
and underlying surface ridge extending from New England swwd along
the Appalachians, will both weaken during the next 24 hours, as
height falls aloft from Hurricane Maria and a shortwave trough
lifting across the nrn Plains both converge upon the ridge. This
development will ultimately cause Maria to turn ewd and away from
the NC/VA coast later Wed and Wed night. Until that time, however,
the MSL pressure gradient between Maria and the (weakening) ridge
will result in both the continued wwd expansion of a low overcast
this morning, and the development of breezy conditions with diurnal
heating over the ern half of the forecast area (from the ern
Piedmont and Sandhills to the Coastal Plain). Resultant partly sunny
conditions over the wrn Piedmont, to mostly cloudy ones over the
Coastal Plain, will result in an atypical temperature distribution
characterized by middle to upper 80s west to upper 70s to lower 80s

Initially partly to mostly clear skies this evening will become
cloudy or mostly so over portions of the Coastal Plain and ne
Piedmont, as moist nely flow will favor the wwd expansion of low
overcast there once again overnight. Lows will range from the middle
60s to lower 70s, mildest east owing to both the aforementioned low
clouds and a continued nly breeze.


As of 355 AM Tuesday...

Based on the official NHC forecast track, by-then Tropical Storm
Maria will be ~150 nm east of HSE by 12Z Wed, after which time a
turn to the east and an increase in forward speed will occur. The
low level flow will consequently back to a (drier) nwly to nnwly
direction and result in partly to mostly sunny conditions on Wed.
Projected low level thickness values around 1425 meters at GSO will
favor well above average temperatures in the upper 80s to lower 90s.
Lows in the 60s.


As of 325 AM Tuesday...

Thursday will be our final unseasonably warm day as Maria
accelerates eastward and a dry cold front pushes south down the
Atlantic coast. Highs Thursday will reach the mid and upper 80s,
with some lower 90s possible along the southern tier of central NC.
Strong cold air advection will be getting underway Thursday night as
high pressure builds east across the Mid Atlantic. This high
pressure will then surge south down the Atlantic seaboard over the
weekend, with highs falling to mostly upper 70s on Friday, and even
further to mostly the mid to upper 70s though Monday. Mins will
similarly fall from 60 to 65 Friday morning to the low and mid 50s
Saturday through Monday.


As of 745 AM Tuesday...

A shield of IFR-MVFR ceilings, in moist nely low level flow on the
nwrn periphery of Hurricane Maria, will lift and scatter to VFR by
this afternoon, though they may persist in the 2000-3000 ft range
all day at RWI. The low clouds will then edge wwd once again
tonight, in a similar fashion as right now, though they will likely
not make it much farther wwd than RWI (to perhaps near or just east
of RDU) at that time. It will also become breezy with diurnal
heating today, mainly at RWI/FAY/RDU, owing to the MSL pressure
gradient between Maria and high pressure centered over the
Appalachians. Lastly, an isolated shower will be possible this
afternoon, mainly at RWI.

Outlook: Any lingering IFR-MVFR ceilings Wed morning at ern TAF
sites will quickly lift and scatter to VFR, as Maria accelerates ewd
and loses influence (Ie. the flow will assume a drier nwly
component), with a subsequent long stretch of mainly VFR conditions
for the next several days.



Record high temperatures across central NC for September 27 and

        RECORD MAX (9/27)       RECORD MAX (9/28)
RDU         94 / 1998               95 / 1998
GSO         90 / 2007               92 / 1939
FAY         94 / 1986               95 / 1933




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