Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 231318

Area Forecast Discussion
National Weather Service Wilmington NC
918 AM EDT Mon Apr 23 2018

An approaching storm system will bring wet weather the next day
or two, along with windy coastal conditions, dangerous surf, and
high beach tides. Easing winds and a warming trend will follow
into mid-week in wake of this system. Several lows emerging
from the Gulf states, will bring rain chances late Thursday into
Friday, and again Saturday. Drying and seasonable temperatures
are expected Sunday into early next week.


As of 334 AM Monday...Complex storm system moving into the TN
Valley today will generate periods of widespread heavy rain over
the forecast area today and tonight. First round of heavy rain
is likely to spread over southwestern areas during the late
morning hours, with period of light to moderate rain ahead of
it. Although the surface warm front will be well south of the
area strong low level moisture advection through the day, low
level jet strengthens from 25 kt to 55 kt, is married to low
level convergence, strong divergence aloft, and 850/700 mb
frontogenesis. GFS/ECMWF also show 850 Theta E ridge just
upstream from the forecast area, something which usually helps
produce periods of heavy rainfall.

Low level convergence really starts to increase late in the day
and during the evening as the warm front moves closer to the
region. Not sure the warm front will ever reach the area, the
occluded surface low may end up moving into the area as the
period ends. Forecast soundings show an extended period of near
saturation through the column as well as increasing elevated
instability late today and overnight. Surface layer remains
stable through the forecast period, suggesting affects of
deeper/stronger convection that is likely to develop during the
second half of the period may remain disconnected from the
surface. Cannot rule out strong wind gusts, especially with a
tightening gradient pushing wind speeds over 30 kt late in the
day and overnight. However, the chance for any strong/severe
storms seems remote. Extended period of heavy rain seems highly
likely, with potential for 2 to 4 inches of rain in some areas.
Warm cloud layer is on the order of 3.5 km, right in the sweet
spot for high rainfall efficiency. The good news is that the
area has been relatively dry and heavy rain will be occurring
over the span of a day or more. So while there is some potential
for flooding, think overall the chances are low.

Given the abundance of cloud cover and heavy rain/moisture it is
not surprising that low temperatures will run well above climo
and diurnal ranges will be limited. Less than 10 degrees for
many areas. Highs will end up close to 10 degrees below climo.

Will continue the coastal zones wind advisory with guidance
continuing to shows sustained winds in excess of 20 kt along the
coast (worth noting MOS typically is too low on sustained wind
forecast). Couple the gusty winds with an abundance of rainfall
and it becomes likely that broad leaf/shallow rooted trees
will be susceptible to uprooting.


As of 334 AM Monday...`Wet and Mild` begins the period, rain
ongoing, but by now, the axis of greatest rainfall has shifted
offshore, and a decreasing rainfall coverage and intensity
trends takes root, as mid-level drying digs deeper, down to 850
mb by day`s end Tuesday. The `snap-back` of upper heights in
wake of the upper cool pool, and S-SW low-level wind flow, will
bring a warm-up into upper 70s or near 80 Tuesday and Wednesday.

Hazards: Very rough surf early Tuesday. Urban and small stream
flooding from 2-3 inch rainfall run-off, much from overnight,
and locally higher and lesser in spots. Strong and gusty S-SE
coastal winds Tuesday morning. Any of these could bring about
additional or extended advisories, through Tuesday morning.


As of 3 PM Sunday...May see a weak boundary or front drop down
into the Carolinas early Thurs. The second low will track down
from the Upper Midwest, becoming an open wave as it digs down
into the lower Mississippi Valley by Thurs. The GFS and ECMWF
both show this low moving northeast through the Coastal
Carolinas Thurs night into Fri, but the GFS is deeper and
showing greater QPF and winds overnight Thurs. By Friday, this
system will lift off to the northeast with a decent day in
store. The GFS and ECMWF differ quite a bit heading into the
weekend with the GFS showing a much drier forecast. Either way,
a trough will move across the east coast producing below normal
temps through much of the late week period.


As of 12Z...Conditions will slowly deteriorate through the afternoon
hours as low pressure and associated front move northeast. Light
rain will overspread the CWA by mid to late morning as isentropic
lift increases. Ceilings will hang on to VFR until this afternoon,
except FLO as they are expected to lower to MVFR in a few hours.
Tonight, heavy rain expected with ceilings and visibilities
eventually becoming IFR . Easterly winds will be quite strong, with
gusts to 30 kts possible.

Extended outlook...Tue morning MVFR/IFR in heavy rain. late
Tue- Fri VFR, except for possible MVFR Thu night.


As of 334 AM Monday...Conditions will continue to deteriorate
across the waters this morning with Small Craft Advisory
conditions giving way to Gales later this morning. Sustained may
struggle to reach 34kt given the below normal near shore water
temps but gusts will frequently exceed 34 kt. Guidance is
showing a low level jet over 50 kt developing later in the
afternoon which continues into the evening. Strong onshore flow
will persist into the evening before winds start to veer to
southerly. The extended period of increasing onshore flow will
build seas through the day and into the early evening. Double
digit seas are likely across SC zones by mid afternoon and by
the end of the day across NC zones. Conditions will remain
treacherous through the end of the period.

As of 334 AM Monday...An ugly and dangerous marine period to
usher in Tuesday, but gradual improvement late Tuesday onward,
as a low pressure system pulls away from the waters. Seas of
6-11 feet early Tuesday, will drop below 6 feet by daybreak of
Wednesday, thus after the Gale, and Advisory will be needed to
close out most of Tuesday. Rain may limit visibility to less
than 1 NM Tuesday morning. Inlets will be turbulent in exposure
to direct, onshore and strong winds, much of Tuesday.

As of 300 PM Sunday...A cold front may drop in early Thurs with
winds shifting around to a more N-NE direction on Thurs. Fairly
low confidence forecast Thurs into Fri as another area of low
pressure may affect the waters. Seas should drop down to 2 to 4
ft by Thurs morning. Winds and seas will be dependent on
strength and track of low pressure late Thurs into Fri, but for
now have left them in the 3 to 5 ft range, although the WNA
shows potential for SCA conditions early Fri.


SC...Wind Advisory until 5 AM EDT Tuesday for SCZ054>056-058-059.
     High Rip Current Risk until 8 PM EDT this evening for SCZ054-
NC...Wind Advisory until 5 AM EDT Tuesday for NCZ105>110.
     High Rip Current Risk until 8 PM EDT this evening for NCZ106-
     Beach Hazards Statement until 8 PM EDT this evening for NCZ110.
MARINE...Gale Warning until noon EDT Tuesday for AMZ250-252-254-256.


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