Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 250652
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
252 AM EDT Tue Jul 25 2017

.SYNOPSIS...
Scattered showers and thunderstorms will raise the risk for heavy
rainfall and possible localized flooding into Wednesday. A cold
front will approach from the north and should slip into the
area late tonight and on Wednesday before stalling and then
dissipating by Thursday. The arrival of a stronger cold front
this weekend will bring numerous thunderstorms back into the
eastern Carolinas.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 300 AM Tuesday...Weak cold front will stall just north of
the area this morning. The front will end up lifting back north
around midday as diurnal heating helps surface southerly flow
and the sea breeze kicks up. Mid level troughing today will be
weaker than past days and drier air aloft will be spreading over
the region. Deep moisture may linger along the coast and this
is the area with the best potential for any showers and
thunderstorms. Pattern aloft lacks any significant features and
mid/upper level winds struggle to reach 30 kt. Although there
will be surface based instability the lack of mid level
mositure, precipitable water will be anywhere from 1.5 to 1.75
inches, will hamper development of deep convection. Do expect to
see a few storms on the sea breeze and possibly the Piedmont
trough but coverage overall will be limited. Light steering flow
will keep storm motions at or below 10 kt and flooding will be
a concern with any storms that do develop. Bulk of todays
activity will be diurnally driven with activity quickly
diminishing as the sun sets. Cold front will slowly sag south
overnight but the abundance of mid level dry air combined with
lack of forcing should keep most areas dry overnight.

High temperatures will be near climo today with mid to upper 80s
along the coast and lower 90s inland.  Heat index will end up
similar to or even slightly cooler than yesterday, peaking around
100 degrees this afternoon. Lows overnight will continue to run
above climo with debris cloud and low level moisture keeping lows in
the mid 70s inland with upper 70s along the immediate coast.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 300 AM Tuesday...Turning decidedly drier with time during
this forecast period as mid/upper trough gets shunted S/SE of
the area with some brief ridging taking place aloft. A cold
front will be near or just to our S at the start of the period
and should dissipate by Thu. Precipitable water values will
still be 2 inches or greater to begin the period, trending to
1.5 inches by Wed night and Thu as the mid levels dry significantly.
This drier air will result in POPs lowering from N to S through
the period. Still can not rule out some heavy rain in showers
and thunderstorms Wed, most probable across our southern zones
and points south where significant drying will occur last. Slow
storm motions heighten the risk for excessive rainfall, at
least on a localized basis. As high pressure, centered off the
New England coast noses into the area, only a small risk for
showers and thunderstorms should remain across southernmost
areas Thu with no mentionable POPs slated along and N of a FLO
to CRE line.

Highs on Wed should be higher N portions of Forecast Area, the
result of less convection and more hours of sunshine as compared
to communities further S, mid and upper 80s. Typical summertime
highs for Thu, upper 80s and lower 90s with mid 80s at the
beaches. Lows will be in the lower to mid 70s.

&&

.LONG TERM /FRIDAY 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.

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 /06Z TUESDAY THROUGH SATURDAY/...
As of 06Z...Convective debris clouds linger over the area this
morning but should gradually decrease in coverage prior to
daybreak. This may allow for patchy MVFR fog development at
inland terminals while along the coast slightly higher boundary
layer winds will prevent any fog development. May see some
marine stratus spread onshore at coastal sites through sunrise
or so but do not think ceilings drop below MVFR.

Another day with afternoon and evening showers and thunderstorms
expected. Storms will develop along the sea breeze and the
Piedmont trough with a gradual southeastward drift. Storm
motion will be slow so any storms affecting a terminal could do
so for an extended period of time. What storms do develop will
dissipate shortly after sunset with debris cloud lingering
overnight. Weak cold front will drop in from the north overnight
which may introduce some IFR ceilings and/or visibilities at
LBT and FLO, something to keep an eye on.

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

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 300 AM Tuesday...Bermuda High remains off the coast but gradient
over the waters has weakened somewhat. Southwest flow around 15 kt
this morning will dip into the 10 to 15 kt range today. Speeds may
climb back toward 15 kt late in the afternoon but increase will be
short lived. Southerly flow weakens in the evening before a weak
cold front drops in from the north. Winds become light and variable
with the front in the vicinity as the period ends. Seas 3 to 4 ft
this morning will drop to 3 ft this afternoon and evening and 2 to 3
ft by the end of the period.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 300 AM Tuesday...A cold front will lie across the waters
or just to out S on Wed before dissipating Thu. The wind
direction should start the day on Wed from the NE, but veer
quickly to the E. Easterly winds should hold Wed night and Thu
morning before veering to the SE and then S Thu afternoon. The
wind direction Thu night should be mainly from the SW. The
highest wind speeds will be 10 to 15 kt both Wed and Thu night.
Seas will be 2 to 3 ft Wed into Wed night and mainly 3 ft late
Thu night, otherwise seas will be 2 ft or less. The risk for
thunderstorms will be greatest Wed with POPs trending much lower
Thu and Thu night.

LONG TERM /FRIDAY 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 kt 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 Friday, with
significant seas building 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...None.
NC...None.
MARINE...None.

&&

$$

NEAR TERM...III
SHORT TERM...RJD
LONG TERM...JDW
AVIATION...III



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