700 
FXUS62 KILM 150817
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
417 AM EDT Tue Aug 15 2017

.SYNOPSIS...
Summertime heat and humidity will build and should peak Wednesday
through Friday as showers and thunderstorms gradually become 
fewer in number. Showers and thunderstorms will be on the 
increase during the weekend as a cold front approaches from the 
north. This front may actually push to our south early next week
as cooler high pressure builds from the north.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 300 AM Tuesday...A quiet early morning period with a few, 
mainly coastal showers and areas of fog. 

Deep SW flow will veer to the west aloft through this morning 
with continued pcp water values up at or above 2 inches. A very
broad mid to upper level trough remains mainly north as models 
show ridging up the southeast coast in weakness between trough 
and Hurricane Gert well to the east riding up around ridge in 
the Atlantic. This ridging will weaken slightly later today as a
shortwave pushes front/trough south, but should keep SC with
less convection. This boundary will drop south into our local 
forecast area this evening with winds shifting to the W-NW 
behind it. By daybreak on Wed it looks like a weak boundary will
be extending back along the Carolina coast, but ridging will 
build up into the area keeping generally quiet weather. 

The high res models show some iso to sct convective development
into this aftn mainly associated with sea breeze, with westerly
steering flow driving shwrs/tstms toward the coast and off to 
the east, but better chc late day as boundary drops south. Any 
showers or tstms that develop will drop some heavy rain as 
atmosphere remains very moist. The area remains in a marginal 
excessive rainfall outlook. 

Warm and humid conditions will persist with temps around 90
degrees combining with high humidity to produce heat index
values between 100 and 104 most places. Some spots over
Georgetown and Williamsburg counties should see heat indices up
to 105, but some drier air should advect into this area enough
to lower heat indices below heat advisory criteria.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 300 AM Tuesday...The period will be dominated by high heat
and humidity. A Heat Advisory may be required both days for heat
index values near or in excess of 105 deg. High temps will be
mainly in the lower to mid 90s with near 90 at the beaches where
the seabreeze should have a difficult time pushing inland given
the deep WNW to NW flow just off the surface. Lows will be in
the muggy mid and upper 70s.

A very warm ridge of high pressure will be centered across FL
and portions of the Southeast states during this period.
Subsidence and warmer temps aloft should help to decrease, but
not eliminate the number of showers and thunderstorms. A weak
front should be all but washed out and the seabreeze looks like
it will be the primary impetus for convection, especially on 
Wed when subsidence and warmer temps aloft will be building, but
not quite as strong as on Thu. The Piedmont Trough may also act
to focus showers and thunderstorms as it will be displaced 
further east given the flow aloft.

A NW flow will become established across the area and this flow
is often tricky for the Carolinas and will continue to monitor 
for any upstream impulses aloft which would warrant higher POPS.
However, at this time, will show higher POPs Wed than on Thu, 
mainly scattered. Eve convection should tend to dissipate 
quickly with loss of heating. 

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 300 PM Monday...Ridge building across the Southeast late 
in the week will bring increasing heat and humidity before a 
cold front drops into the region for the wknd. Highs Friday 
will likely climb well into the 90s away from the beaches as 
850mb temps climb above 20C, and this will combine with 
continued high dewpoints and humidity to produce heat index 
values above 100 degrees. This environment is supportive of 
typical aftn thunderstorms, but coverage is not forecast to be 
too widespread as the ridge aloft helps to minimize total 
convective development. Still, will carry CHC POP, focused 
along the typical boundaries, and any storm could produce 
torrential rainfall.

The cold front drops into the area Saturday as a 500mb shortwave 
digs into the OH VLY and then shifts east through Sunday. This will 
push the front through the area before stalling and beginning to 
dissipate on Monday thanks to increasing mid-level heights again 
behind the departing shortwave. Showers and thunderstorms will 
become widespread Saturday and possibly again on Sunday before W/NW 
flow behind the aforementioned shortwave begins to dry the column. 
Temperatures and humidity will remain elevated although cooler than 
late week.

First glance at the all-important Monday forecast is looking 
promising right now for the solar eclipse watchers out there. If the 
front can sag far enough south as currently shown by long-range 
guidance, the combination of surface high ridging from the OH VLY 
and increasingly dry W/NW flow aloft could support good viewing 
locally. Of course, if that front stalls overhead or begins to lift 
back to the north during Monday, it would create much more unsettled 
weather across the area. For what its worth, the 12Z/14 GFS average 
sky cover currently shows mostly clear sky conditions for the area 
Monday afternoon.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
As of 06Z...Vsbys slowly lowering across the area with areas of
dense fog expected into the early morning hours, especially for
KFLO and KLBT where LIFR conditions may develop. Scattered late
morning and afternoon showers and thunderstorms are expected 
Tuesday afternoon.

Extended Outlook...Scattered convection Wed through Fri, with
possible MVFR to brief IFR in TSRA. Low stratus and fog during 
the overnight and early morning hours through the period may 
result in flight restrictions as well.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 300 AM Tuesday...Expect SW flow remaining around 10 kts or so, 
but Hurricane Gert traversing the distant Atlantic waters will 
produce increasing SE to Easterly longer period, up to 12 seconds,
swells reaching into our waters. Have included some 4 to 5 ft 
seas to account for this swell, but overall seas will be lower. 

Winds will remain relatively light through the period with a 
southwesterly flow veering to a more westerly flow as a trough/front 
makes its way south through tonight. 

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 300 AM Tuesday...Winds Wed morning may be light from the
NW as trough pushes out across the waters. SW winds will return
Wed afternoon, but still less than 10 kt, as a pinned seabreeze
develops. Light and variable winds Wed night and Thu morning 
should settle on a SSE to S direction Thu afternoon, still less 
than 10 kt, as the seabreeze redevelops and a trough briefly tries
to amplify offshore. Seas will be highest Wed morning, 2 to 3 
ft with some residual 4 ft seas across portions of the outermost
waters as Hurricane Gert swell decays. Seas will be 2 ft Wed 
night through Thu night.

LONG TERM /FRIDAY THROUGH SATURDAY/...
As of 300 PM Monday...A messy wave spectrum expected late week 
as a weak gradient exists in the vicinity of offshore high 
pressure. This gradient will gradually tighten beginning late 
Friday and on Saturday as a cold front drops into the area from 
the NW. Although no wind shift is expected during this period, 
speeds will increase, becoming SW at 10-15 kt late Friday and 
Saturday, after being SW less than 10 kt. Wave heights will be 
2-3 ft Friday with a variety of low-amplitude wave groups 
comprising the spectrum. On Saturday seas will build to 3-4 ft 
as a SW wind wave becomes more significant.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...High Rip Current Risk from 8 AM EDT this morning through this 
     evening for SCZ054-056.
NC...High Rip Current Risk from 8 AM EDT this morning through this 
     evening for NCZ106-108-110.
MARINE...None.

&&

$$

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