Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 201733

Area Forecast Discussion
National Weather Service Wilmington NC
130 PM EDT Wed Sep 20 2017

Disturbances aloft will bring isolated showers today through
Friday. High pressure will build in from the north for the
remainder of the week while Jose spins nearly stationary off the
Mid-Atlantic coast. Dangerous hurricane Maria will bring
increasing southeast swell and strengthening rip currents to the
Carolinas beginning late week. Maria is expected to move north
and offshore of the Carolinas early next week.


As of 1030 AM Wednesday...Latest 12Z WRF in agreement with current
forecast in that POP trend will not follow the normal diurnal trend.
Rain chances (though remaining slim overall) rise this evening after
peak heating height falls and PVA impinge upon the region. May also
add a degree or two to highs.

As of 515 AM Wednesday...

The westerly flow aloft will transition to a bit of troughing
later today and extend into Thursday morning. At the surface a
weak trough will move across this evening which may kick off a
few showers and possibly a thunderstorm. Guidance is not overly
agressive and some model suites show little to nothing. I have
maintained the slight change pops. The best forcing appears to
occur around 03 UTC this evening. Highs today will tack on a
degree or two from yesterdays readings as the airmass continues
to modify. Overnight lows Thursday morning will also add a
degree or two with some areas remaining above 70 degrees.


As of 3 AM Wednesday...Amorphously broad high pressure
dominates eastern CONUS during the short term, with an upper
trough extending SW from Jose off of the New England coast and
distant Hurricane Maria emerging from the Carribbean. Model
soundings show a moderately unstable column developing both
afternoons with P/W amounts in the 1.5 inch range. The moisture
will mainly be confined below 700 mb, but this will be enough
for isolated to widely scattered convection to develop both
afternoons and into the evenings. Ill-timed upper disturbances
hinted at in the guidance, and this could extend convection into
the overnight hours. Given limited moisture depth and
unfavorable wind profiles do not expect strong or severe
convection. Temperatures will remain around or above climo
through the short term.


As of 3 PM Monday...At onset Friday Jose will be meandering off
the New England/Mid-Atlantic coasts while Maria approaches the
eastern Bahamas with weak high pressure in place across the
Carolinas. Weak high pressure will remain across the Carolinas
early next week as Maria moves northward off the Southeast U.S.
coast. We will obviously need to keep a very close eye on
Maria`s progression, however in the least we expect very
hazardous surf conditions as large swells impact the coast. Held
onto a small POP for primarily SC areas during Friday, then no
POPs thereafter (ultimately dependent on Maria`s track early
next week). Favored a blend of MEX/ECE highs/lows through the
long term period.


As of 18Z...Generally expect VFR conditions except for possible
predawn MVFR fog. Guidance showing some randomness as to where
favored locations may end up so have shown it area-wide. IFR hinted
at for FLO but given anticipated gradual increase in cloud cover
this was not given much credence unless some showers materialize
beforehand near the airport.

Extended Outlook...Mainly VFR conditions through the period are
expected with the exception of a few hours of early morning low
clouds or fog most mornings through the period. The highest
risk of IFR conditions will be in the 0900-1200Z timeframe each


As of 3 AM Wednesday...A weak pressure field will continue to
reside over the area and waters with a continuation of light
wind fields. A light west to southwest flow of ten knots or less
will continue through most of the day. Speeds may briefly
increase this evening by a couple of knots as a surface trough
moves across. Significant seas will continue to be 2-3 feet.

As of 3 AM Wednesday...Although a broad area of high pressure
over the coastal zones will keep winds light through the period,
generally around 10 kts, expect that swell from very distant
Hurricane Maria will bring seas up to 3 to 5 ft by Friday night.
Until then, seas will stay in the 2 to 4 ft range.

As of 3 PM Monday...Very hazardous maritime conditions expected
during the long term period as large waves emanate outward from
Maria. At this time Maria is likely expected to remain offshore
as it moves northward from the Bahamas, but all marine
interests should closely monitor the progression of this storm
given forecast track uncertainty at this time. Winds on Friday
will be around 10 knots from the northeast to east with similar
conditions Saturday. Speeds will increase during Sunday out of
the northeast as the peripheral circulation of Maria begins to
come into the picture. Wavewatch III guidance indicates
significant swells impacting the coastal waters, especially Sat
into Sun. Very steep waves are possible, especially near inlet
entrances during the falling tide.


NC...Coastal Flood Advisory from 9 AM this morning to noon EDT
     today for NCZ107.



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