Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 291421

Area Forecast Discussion
National Weather Service Wilmington NC
1020 AM EDT Thu Jun 29 2017

It will be dry through the day, but showers and thunderstorms will
return Friday and remain in the forecast each day, mainly during the
afternoon and evening hours. Summertime heat and humidity will
return for the weekend, becoming hot next week.


As of 1015 AM Thursday...Water vapor imagery shows a swath of dry air
across the forecast area with mid-level ridging in place. Morning
soundings indicate low precipitable water while better instability
was found farther south. As a result, the forecast will remain POP-
free into the evening. However, as surface high pressure slides
eastward the door will open for higher precipitable water and
increasing instability into the short term period. Regarding max
temperatures today, favor going slightly above guidance along the
coast and a blend farther inland. Overall, no significant changes
were made to the forecast with this update.


As of 300 AM Thursday...It will become warmer and more humid
during this period with the risk for thunderstorms returning.
High pressure off the Mid-Atlantic and mid-level ridging will
increase heights with 850 mb temps climbing to 17C on Fri and
19C on Sat. Highs in the mid 80s Fri will increase to the upper
80s and lower 90s Sat. Heat index values will be around 100
degrees on Sat. Lows will be in the 70s, mid and upper 70s Sat

As the ridge amplifies offshore, moisture gets channeled into
the eastern Carolinas which increases precipitable water values
to 2 to 2.25 inches. A trough coincident with a significant mid-
level shortwave lifting across the area Fri should allow for
scattered to perhaps numerous showers and thunderstorms. A
weaker impulse aloft on Sat combined with strong heating should
also allow for at least scattered thunderstorms. Forcing looks
stronger for convection on Fri while instability should be higher
on Sat.


As of 300 PM Wednesday...After the cool weather of the last couple
of days, summer heat and humidity should come roaring back next
week. Persistent upper level ridging across Florida and the Gulf
Coast and the Bermuda High offshore will allow heat and humidity to
build through the period. A time-series plot of forecast 850 mb
temps shows +17.5C Sunday, and +18C Monday through Wednesday.
The ECMWF actually has some forecast 850 mb temps near +20C by
Wednesday, however we`ve noticed over the past several years
there is a summer warm bias in the ECMWF at the extended range.

The airmass should be moderately to strongly unstable through the
period with CAPE values rising to 2000-3000 J/kg each afternoon.
West to northwest flow aloft, a pinned seabreeze near the coast, and
a well-defined Piedmont trough (perhaps evolving into an inland
thermal low for a few days next week) should set the stage for
scattered diurnally-driven storms each day. Precipitable water
values will fall to around 1.8 inches early next week.

Afternoon highs in the 90s and dewpoints in the lower 70s will
bring heat indices to 100 to 103 degrees in most locations away
from the beaches each day next week.


As of 12Z...VFR will continue into tonight with surface high to
the northeast providing onshore flow. Sea breeze will make its
way inland with some cumulus clouds developing along it. No
rainfall is expected, but marginal increase in low level
moisture will lead to some potential for MVFR or even IFR
ceilings as the forecast period comes to an end Fri morning,
especially at KILM and KCRE.

Extended Outlook...Brief MVFR/IFR possible in and near diurnal
driven convection starting Friday. Brief morning MVFR/IFR
possible from fog or low stratus between 08-12Z starting Sat.


As of 1015 AM Thursday...Surface ridge axis is situated just
north of the waters resulting in light NE-E flow. The flow will
strengthen during the afternoon and evening as the sea breeze
circulation evolves with some veering. Seas are expected to
be around 3 ft or less through tonight.

As of 300 AM Thursday...Wind speeds will be increasing during
this period, but are expected to remain below Small Craft Should
Exercise Caution criteria. Wind speeds will be 10 to 15 kt Fri
and Fri night increasing to 15 to 20 kt during Sat and through
Sat night as a thermal trough helps to tighten the gradient. The
wind direction will be SE to S on Fri, becoming SW beginning
Fri night. Seas will be 2 to 3 ft, building to 3 to 4 ft later
Sat and Sat night.

As of 300 PM Wednesday...Bermuda high pressure well offshore
will extend its ridge axis westward across Florida and into the
northern Gulf of Mexico Sunday and into early next week. With
the ridge remaining south of the area, mainly southwesterly
winds are expected through the period with the typical afternoon
seabreeze backing wind directions more southerly with an
increase in wind speeds.

With inland highs in the 90s and westerly winds aloft, there
should be scattered thunderstorms making their way down to the
beaches and offshore virtually every afternoon. Average sea
heights of 2-3 feet are expected.





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