Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 211330
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
930 AM EDT Wed Jun 21 2017

.SYNOPSIS...
Bermuda High pressure will remain offshore of the Eastern
Carolinas. A stalled front just inland from the coast will
slowly move east and wash out today. Tropical moisture will
continue over the area through Friday. The remnants of Cindy
will arrive this weekend as a stalled front, moving offshore
early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 930 AM Wednesday...Plenty column moisture across the
region, but decreasing support aloft and a near absence of
surface warming today, may result in lighter rain rates and low
hourly accumulations compared to yesterday. POP values remain
elevated but the flooding threat appears low. No significant
changes to the forecast except that will remove any wording or
grid depiction of heavy rain as this appears to be a low-end
threat. Clouds will keep maximums in the low to middle 80s and
no big changes are planned with this.

As of 300 AM Wednesday...Tropical moisture continues to stream
up from the Gulf in deep S-SW flow through today. Although
deeper convection was confined to eastern half of CWA early,
the I-95 corridor west was also seeing some lighter pcp through
early this morning, and shwrs and thunderstorms will again
become more widespread as the day progresses. A cold front will
get nudged eastward and essentially wash out over the eastern
Carolinas, as mid to upper trough pushes eastward. Overall
dynamics aloft, this surface boundary and the sea breeze front
will act as main players producing showers and thunderstorms
through this afternoon. Pcp water values over 2 inches will
produce potential for localized flooding in mainly brief periods
of heavier rain.

Some drier mid level air will try and work its way south and
east behind exiting mid to upper trough through tonight, but
plume of deep layer moisture from Tropical Storm Cindy in the
Gulf will continue to feed into the Carolinas. Therefore, should
see pcp chances diminish and clouds may thin a bit in westerly
flow aloft behind exiting mid to upper trough. Max Temps will
be in the lower to mid 80s while overnight lows will hold in the
70s in very moist air mass.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 300 AM Wednesday...The upper level pattern Thursday and
Friday will feature a 500 mb high just off the Florida east
coast which will deflect the main jet stream flow well to our
north across the Great Lakes and northern New England. A lobe of
vorticity sheared off the outer circulation of Tropical Storm
Cindy will move northeastward around the periphery of the ridge
and should cross the Carolinas on Thursday.

At the surface Bermuda high pressure will remain offshore while a
cold front will advance southeastward across the Ohio Valley by
Friday, compressing the pressure gradient across the Carolinas and
producing a breezy day, particularly near the beaches where surging
inland temperatures should fuel a healthy seabreeze circulation.
Wind gusts could exceed 25 mph at the beaches Friday afternoon.

With plenty of low-level moisture both days, my attempt at
assembling a thunderstorm forecast hinged on mid level moisture and
temperatures. With the upper impulse from Cindy shearing out to the
northeast across the area on Thursday, mid-level temps should cool
slightly. Add to that the deeper moisture associated with the
disturbance and my forecast PoPs range from 40-60 percent, highest
in a band just inland from the coast where seabreeze wind
convergence should enhance t-storm coverage. By Friday, much warmer
and drier mid level conditions should develop with both the GFS and
NAM forecast soundings indicating a strong enough subsidence
inversion to limit, if not eliminate, deep convection. I have
trended PoPs back to 20-30 percent, but have not removed them
entirely to retain continuity with the previous forecast.

A good number of showers and storms and their attendant cloud cover
Thursday should help keep temperatures from rising any higher than
87 most places inland. But by Friday much more sunshine should allow
temps to soar to 90 or better inland. Nighttime lows will remain
quite warm with low to mid 70s expected, except some upper 70s
possible Friday night near the beaches.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 300 PM Tuesday...Seasonably warm and unsettled weather
will continue through at least Monday as the Bermuda ridge
retreats eastward, with a cold front slowly descending from the
NW. Confidence is not high regarding an actual clean FROPA for
this time of year, but a consensus of guidance for now moves the
front offshore Monday night, followed by dryer and slightly
cooler weather.

&&

.AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...
As of 12Z...Eroding low clouds should ensure predominant VFR
ceilings today. Dense mid and high level cloud cover should
hold tough most of the day streaming northeastward off Tropical
Storm Cindy in the northern Gulf of Mexico. This cloud cover
will reduce surface temperatures and should help keep afternoon
showers and thunderstorms limited in coverage compared to
yesterday. The best chance for afternoon showers or
thunderstorms should be along the coast after 19Z, with
precipitation chances diminishing after dark. Surface winds
should be south-southwest less than 10 knots today.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 930 AM Wednesday...Seas around 3 feet every 6-7 seconds
will prevail in the waters, but as low as 2 feet in the near
shore waters off SC. No significant changes to the marine
forecast at this time.

As of 300 AM Wednesday...Winds generally will be S to SW 10 to
15 kts around Bermuda High pressure. This will maintain seas
mainly 2 to 3 ft, dominated by a southerly 5-6 second wave
period. Showers and thunderstorms will be more widespread,
especially this morning as deep layer moisture continues to feed
into area waters from the Gulf.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 300 AM Wednesday...Bermuda High Pressure will remain anchored
offshore through the period, maintaining a warm and humid airmass
along the Southeast coast. The GFS model has the best definition of
a weak front stalled over coastal South Carolina Thursday morning
that should lift northward and out of the area Thursday night.
Thursday`s winds should be light as a result of the baggy pressure
gradient near the front, but Friday`s winds will be much stronger,
15-20 knots with gusts to 25 knots, as the pressure gradient
tightens up between the Bermuda High and an approaching cold front
in the Ohio Valley. Seas could build to 5 feet by late Friday.

Tropical Storm Cindy and its remnants should remain too far west of
the Carolinas through Friday night for any direct impacts on our
weather.

LONG TERM /SATURDAY THROUGH SUNDAY/...
As of 300 PM Tuesday...Expect SWly winds of 10 to 15 kts on
Friday increasing to 15 to 20 kts on Saturday as the gradient
around the backside of the Bermuda Ridge tightens. Seas will
likewise increase and it is possible that a Small Craft
Advisory may need to be raised for Saturday. Some improvement
is expected as the gradient again loosens on Sunday.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.

&&

$$

SYNOPSIS...RGZ/8
NEAR TERM...RGZ/8
SHORT TERM...TRA
LONG TERM...REK
AVIATION...TRA/SGL



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