Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 250027
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
827 PM EDT Mon Jul 24 2017

.SYNOPSIS...
Scattered showers and thunderstorms will raise the risk for heavy
rainfall and possible localized flooding into mid week. A cold
front will approach from the north and should slip into the area
later Tuesday night and on Wednesday before stalling and then
dissipating by Thursday. After a brief hot and dry period Thurs
day into Friday. the arrival of a stronger cold front this
weekend will bring numerous thunderstorms back into the eastern
Carolinas.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 730 PM Monday...Updated POPs across much of the ILM CWA
to account for current mosaic radar trends and sat imagery for
cloudiness. Added the tstrm attribute "Some thunderstorms may
produce heavy rainfall" to the convection mainly over the
southern portions of the ILM CWA for mainly this evening.
Hourly temps/dewpts adjusted to account for pcpn. Min temps for
tonight adjusted by a degree or so upwards due to clouds and
the threat of pcpn closer to the immediate coast.

Previous.....................................................
AS OF 230 PM Monday...Low cloud deck has played havoc with high
temperatures today and delayed destabilization. The area of clouds
will become increasingly scattered finally allowing parts of the
forecast area to warm up. Dewpoints remain in the mid to upper 70s
and the precipitable water is above 2 inches. SPC mesoanalysis shows
CAPE above 3000 j/kg but lifting mechanisms remain weak/limited
associated with the sea breeze front and inland trough. Will
maintain chance POPs through the afternoon and into the evening.
Scattered showers and thunderstorms possible again during Tuesday
with weak trough aloft and sea breeze inland trough providing lift.
Storm motion will be weaker tomorrow and the risk for localized
flooding in a high precipitable water air-mass will increase as a
result. Followed a blend of MAV/MET temperatures for tonight and
with highs in the lower 90s and dewpoints in the mid 70s the heat
index will be around 100 to 103 during Tuesday. Lastly, not
expecting water levels to exceed minor coastal flood thresholds at
downtown Wilmington tonight. Latest ETSS takes the gauge to just
below Coastal Flood Advisory criteria.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 300 PM Monday...Mid to upper trough and frontal boundary
remain strung out and become nearly stationary across the
Southeast through the period as high pressure reaches down from
the north behind it. This will leave a gradient of very moist
air to the south running most likely right through our forecast
area from SC east to northeast into the Atlantic. Pcp water
values will be greater than 2 inches to south of this boundary
and less than 1.5 inches to the north. The GFS is less bullish
and maintains a wetter more unsettled forecast for Wed, as
compared to other models showing boundary farther south and a
drier forecast. Overall, would expect a greater chc of stronger
storms to the south and east over the waters, but will maintain
higher PoPs across most of NE SC up to the Cape Fear coast with
gradient of lower PoPs as you head N to NW. The drier air may
reach into most of NC to produce a sunnier forecast with lower
end pops, but overall expect potential for shwrs/tstms but
confidence is low as to exactly where this boundary will be
located. Models also showing potential for low pressure to
develop along this boundary on Wed which could also push pcp
farther south into local forecast area. If this occurs, QPF
could be on the higher side. For now will show a trend to lower
end pcp and brighter skies end of day Wed but will show
potential for convective development through Wed aftn. The
weaker steering flow will also point toward greater potential
for slow moving storms and therefore higher end QPF which could
lead to localized flooding issues. It could end up with two
different atmospheric conditions with one to the NW and N being
drier mid levels with threat of gusty winds in storms while to
the south, expect mainly heavier rain. Temps will be in the mid
70s Tues night and up toward 90 on Wed. As drier air moves in
late Wed into early Thurs, dewpoint temps will drop a few
degrees allowing for overnight lows to drop to the lower to mid
70s on Wed night.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 300 PM Monday...Longwave trough which has affected the eastern
CONUS for what seems like most of the summer will re-intensify this
weekend after a brief period of warm and dry weather on Friday.

Front will dissipate across the area Thursday with warm westerly
flow developing aloft. This will dry the column out on Thursday, and
while isolated tstms will be likely, coverage will be less than
earlier in the week and highs will climb towards 90. On Friday, WAA
drives 850mb temps towards 20C, and convective coverage will be even
more limited despite highs climbing into the 90s with heat index
values once again rising towards 105. Eastern trough re-loads
beginning Saturday driving another cold front into the eastern
Carolinas. This front will become aligned parallel to the flow
through the wknd and into early next week as an anomalous cutoff
digs towards GA. Deep moist advection, upper diffluence, and PWATs
over 2 inches all suggest periods of heavy rain and tstms Saturday
through Monday as more unsettled weather plagues the region. The
benefit to the forecasted rainfall is that temps will remain at or
below climo, mid to upr 80s, the latter half of the extended.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 00Z...Mainly VFR this evening with MVFR and possibly
brief IFR conditions from the waning thunderstorm activity.
FLO and LBT terminals will indicate VCTS for the time being as
the activity stays just south and east of the terminals. The
convective activity should dissipate by 04z leaving convective
debris clouds to contend with. Have indicated clouds
thinning enough across the inland terminals resulting in the
possibility of 3sm ground fog, especially with winds diminishing
to less than 4 kt or going calm altogether. The coastal
terminals should remain an active SW wind around 5 kt to keep
BR at bay.

Models indicate the threat for coastal thunder activity around
daybreak Tue thru midday. The inland terminals will see
convective activity pick up around midday thru the aftn. Have
indicated a PROB30 for this activity with subsequent TAF
issuances ironing out a more precise time-range.

The overall sfc pg will relax once the cool front settles and
stalls across the FA just inland from the coast thru Tue and
possibly thru Wed. This loosened gradient will result in winds
dropping to and below 5 kt tonight, with possible calm winds
across the inland terminals during the pre-dawn Tue hrs. Winds
are progged to increase to around 10 kt, mainly across the
coastal terminals during Tue aftn due to onshore SSE-S flow.

Extended Outlook...MVFR/IFR conditions are likely in showers
and thunderstorms Tue night thru Wed. Less chance of convection
by Thursday.

&&

.MARINE...
NEAR TERM /THROUGH TUESDAY/...
As of 730 PM Monday...Short term SCEC raised for the local
waters between Surf City and Murrell Inlet. Latest Buoy and OMR
wind and seas trends indicate the need for the SCEC thru 3 am
Tuesday. The sfc pg should relax some during the pre-dawn Tue
hrs with resulting winds diminishing-some. Significant seas will
be initialized at 3 to 5 ft and have indicated a subsiding trend
to 2 to 4 ft by daybreak Tue. Dominating periods will run 5 to 7
seconds.

Previous....................................................
As of 230 PM Monday...Trough across the inland Carolinas with
Bermuda High pressure will maintain a southwesterly fetch across
the waters tonight into Tuesday. However, the fetch will weaken
as the inland trough shifts eastward with a weaker pressure
gradient expected over the adjacent coastal waters. In the
meantime winds of 15-20 knots will prevail, especially away from
the coast tonight with seas in the 3 to 5 ft range. Plan on
continuing the Small Craft Should Exercise Caution headline
through the afternoon.

SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 300 PM Monday...A front will drop south and should reach
into the waters by Wed morning. This boundary will remain in the
vicinity producing light and variable winds through much of the
period, although initially the winds will be SW up to 10 to 15
kts ahead of the front into early Tues night. Once the front
drops south overnight Tues into Wed the winds will turn around
to the NE and should back to the E through Wed, but this is all
dependent on where the boundary ends up. Either way, expect seas
to diminish through Wed with seas up to 3 to 4 ft Tues eve and
down less than 3 ft Wed aftn into Wed eve. This front will
produce an increased chc of shwrs/tstms through much of the
period.

LONG TERM /THURSDAY THROUGH SATURDAY/...
As of 300 PM Monday...High pressure offshore will intensify through
Friday before weakening again in response to a cold front dropping
down from the north. SW winds around this surface high will slowly
increase to around 15 kts during Friday before weakening and then
shifting to the W/NW late on Saturday as the front encroaches on the
waters. Seas will be formed by a SE swell as well as an amplifying SW
wind wave through Friday, with significant seas building from 2 ft
Thursday to 3-4 ft late Friday into Saturday. Seas will fall slowly
late in the period as the winds ease and shift offshore.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...Beach Hazards Statement until 8 PM EDT this evening for SCZ054-
     056.
NC...Beach Hazards Statement until 8 PM EDT this evening for NCZ106-
     108-110.
MARINE...None.

&&

$$
SYNOPSIS...RGZ
NEAR TERM...DCH/SRP
SHORT TERM...RGZ
LONG TERM...JDW
AVIATION...SRP
MARINE...



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