Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
808 PM EDT Wednesday Jul 1 2015
Bermuda high pressure will persist through the remainder of the
week and into the upcoming Holiday weekend. This will create
slightly above normal temperatures...along with typical summertime
thunderstorm chances each afternoon and evening. A front may stall
to our north over the weekend.
Near term /through tonight/...
as of 800 PM Wednesday...a large area of showers and
thunderstorms associated with a potent middle- level shortwave across
the Tennessee Valley and the southern Appalachians will continue
to move eastward and across the eastern Carolinas late evening and
early overnight hours. The cloud tops to our west have been very
slowly cooling. The airmass with eastward extent is more stable
and will continue to stabilize with loss of heating. The
convection was moving east at near 35 knots. Although a slow erosion
of thunderstorm coverage is expected over the next several
hours...at least scattered showers and thunderstorms should make
it into our western zones before midnight. The convection will
struggle to make it to the coast after midnight.
Otherwise...skies will be or will become mostly cloudy. These
clouds along with modest jetting on the order of 25 knots should keep
minimums elevated. We expect lows in the lower to middle 70s.
Short term /Thursday through Friday night/...
as of 300 PM Wednesday...a general long wave h/5 trough pattern
will persist aloft over eastern Continental U.S. Through the short term. At
the surface we can expect a typical summertime pattern with
Bermuda high pressure offshore and a Piedmont-style thermal trough
inland. This combination will continue to advect in a moderately
unstable and very moist airmass. Model soundings show deep
moisture increasing significantly with p/west values up around 2
inches Thursday and Friday. In addition...a series of short waves
will round the base of the upper trough. For these reasons we can
expect at least scattered convection both days. Timing of the
short waves will be iffy so do not think we can yet pin down when
the strongest convection will happen. Other triggers to convection
will also exist...with remnant outflow boundaries and the sea
breeze front further complicating the picture.
Long term /Saturday through Wednesday/...
as of 300 PM Wednesday...Bermuda high will maintain a southwest flow
across the area through most of the period...but shortwave trough
will drive a boundary south into North Carolina over the weekend.
Both the GFS and European model (ecmwf) flatten the middle level flow leaving a more
westerly flow aloft. This will keep shortwave energy rotating around
through the area and will act to deepen Lee side troughing and
enhance localized convection across the area through the weekend.
The decent westerly flow aloft may also contribute to enhance sheer
and should keep sea breeze pinned closer to the coast. Also will
drive any storms that develop and debris clouds eastward toward the
coast. The shortwave should push east Monday into Tuesday and should
push any lingering surface boundary south and east. Therefore may see
less coverage for Tuesday but another shortwave should push another
front or may enhance leeside troughing once again come Wednesday.
Overall expect showers and thunderstorms each day. Temperatures will be
right around normal through much of the period...close to 90
during the day and 70 to 75 at night.
Aviation /00z Thursday through Monday/...
as of 00z...VFR expected this taf valid period outside of showers or
thunderstorms. Showers and thunderstorms northwest of kflo/klbt should
weaken to showers as it moves southeast to the kflo/klbt terminals this
evening. By midnight best shower potential will shift to the coastal
terminals...but activity is expected to remain generally isolated
overnight. Broken cloud cover along with light SW winds should
prevent fog development overnight.
VFR with west winds during the morning. By late morning/early
afternoon winds become south-southwest at the coastal terminals with isolated
showers and thunderstorms again possible in the afternoon.
Extended outlook...predominately VFR with a chance of showers and
thunderstorms each day.
near term /through tonight/...
as of 800 PM Wednesday...small craft should exercise caution has
been headlined through 6 am for all of the coastal waters. Low
level jetting on the order of 25 knots ahead of a potent middle-level
shortwave should keep wind speeds near 20 knots through the night.
The direction will be SW overnight. These wind speeds and their
persistence will result in 4 to 5 feet seas.
Short term /Thursday through Friday night/...
as of 300 PM Wednesday...southwesterly flow will continue through
the short term with Bermuda high pressure offshore and a thermal
trough inland. A tightening gradient will pump winds up into the
15 to 20 knots range by Thursday afternoon...with seas building to 3
to 5 feet on Thursday night and 4 to 7 feet on Friday. Expect that we
will Post exercise caution headlines on Thursday night and then
small craft advisories on Friday for these conditions.
Long term /Saturday through Monday/...
as of 300 PM Wednesday...continued southwest flow around Bermuda
high through the period. A shortwave riding around main middle to upper
trough will push a weak boundary south. Not expecting this boundary
to reach into our waters...but should act to tighten gradient flow
into early Sat. Winds and seas will be on a downward trend through
Sat afternoon but Piedmont trough and sea breeze may act to increase
winds again through Sat afternoon. Overall expect seas up near 5 feet in
outer waters with some 6 fters through the morning hours on Sat...to
decrease down to 3 to 5 feet and keep on a diminishing trend through
Sunday down to 2 to 4 feet. The trough will move east by Monday and
flow may become more off shore which will drop seas even further.