National Weather Service United States Department of Commerce

 


000
FXUS62 KILM 302255
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
655 PM EDT THU JUN 30 2016

.SYNOPSIS...
A stalled front will bring unsettled weather through Sunday with
most of the activity shifting slightly northward by Monday. The
midweek period will bring seasonable temperatures as well as
normal coverage of afternoon thunderstorms.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
As of 730 PM Thursday...An increasingly diffuse front lies across
the inland Carolinas, probably across the interior Coastal Plain
of North Carolina arcing more westward across central South
Carolina according to latest sea level pressure plots. This
boundary has been enhancing the coverage of showers and storms
across South Carolina, however a drier airmass just above the
surface across much of North Carolina has kept the cumulus clouds
from growing into precipitating clouds much of the afternoon. This
is beginning to change as moisture is increasing in the 950-925 mb
layer -- observable in SPC mesoanalysis plots by rising MLCAPE
values but steady SBCAPE. Developing showers and storms along the
I-95 corridor should persist for the next hour or two as they move
northeastward, but a cooling boundary layer should lead to a
diminishing trend in this activity later this evening.

A baggy mid-level trough along the central Gulf Coast will
maintain southwesterly mean flow and plenty of deep moisture
across the area tonight. Precipitable water ranging from 1.5
inches at the coast to 1.8 inches inland will steadily increase
overnight, reaching 2.0 inches by daybreak Friday. Plenty of
convective debris cloudiness should persist until at least
midnight as well. I cannot completely remove pops from the
forecast, even after midnight, as elevated parcels remain
conditionally unstable. 500 mb forecasts all show various weak
disturbances moving northeastward very near the coast overnight,
any of which could help fire new convection. The best potential
for new convection overnight should exist offshore where larger
surface-based CAPE will remain and where climatology suggests we
typically see nighttime convective activity.

Forecast lows have been tweaked upward just a little inland, no
change near the coast. Lows 72-75.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
As of 3 PM Thursday...The short term forecast will be a function
of embedded shortwaves and daytime heating. in a mid level flow
that will be turning more zonal through the period. The surface
pattern remains all but unchanged with a front or Piedmont trough
meandering in the area. The highest pops occur Saturday afternoon
as a mid level shortwave should be coupled with the best forcing.
SPC has some of the area in a marginal risk for Saturday. No
changes in the temperature forecast other than a little cooler
than previous thinking for Friday.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 3 PM Thursday...With a front stalled in the area Sunday
still looks like the most unsettled day of the long term. It`s
still tough to say where the highest POPs are warranted as models
aren`t in great agreement as to where the boundary stalls. They do
seem to be gravitating towards keeping it to our north (though the
Canadian pushes it all the way through) so will show slightly
higher values over northern zones. Some energy then streaks across
the Ohio Valley on Monday drawing the boundary further to the
north. Not necessarily good news locally as copious moisture and
outflow boundaries will be left behind. Pair these with the
seabreeze and you`ve still the makings for a rather unsettled day.
Flow aloft changes enough to minimize the sea breeze inland
penetration on Tuesday while a well defined piedmont trough
develops. With any storms moving eastward some fairly normal
30-ish POPs are warranted everywhere. Rain chances may then
increase on Thursday as mid level flow tips to the NW and starts
to house some vorticity centers.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AS of 18Z...A synoptic front and seabreeze boundary have merged
and showers and thunderstorms have begun to develop along this
convergent zone as subsidence has now waned in the wake of
offshore showers and thunderstorms. The synoptic boundary snakes
back westward across our inland zones and will waver through
Friday. Strong heating in the absence of thick cloud cover will
ramp up instability and this will serve to increase the coverage
of thunderstorms across the inland terminals. Thus, we have
included tempo MVFR ceilings and visibilities from about 20z
through about 01z at KLBT/KFLO. After that time, convection should
generally wane, but did include VCTS/VCSH for the later eve hours.
The seabreeze had pushed inland of KILM/KCRE/KMYR as of 18z and so
did not include convection, but did include tempo BKN025/030 for
the first two hours of the valid TAF period, otherwise, expect VFR
at the coastal TAF sites. For KLBT/KFLO, MVFR in BR is possible
between 09z-11z.

EXTENDED OUTLOOK...Mainly VFR. Possible brief MVFR/IFR from
scattered convection each day. Possible brief MVFR from fog or low
ceilings each morning.

&&

.MARINE...
NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
As of 730 PM Thursday...A diffuse front stalled inland from the
coast will weaken further overnight, but is still helping organize
some thunderstorms inland from the beaches. Much like we saw last
night this inland convective activity should weaken this evening,
allowing nighttime showers and t-storms to develop over the ocean.
Latest high-res HRRR models suggest the first storms may begin to
fire up south of Cape Fear around midnight, and should move
northeastward from there.

Across the coastal waters winds are from the south at 10-15 knots
with seas around 3 feet on the latest buoy observations. Wind
directions should gradually veer more southwesterly with time
with speeds diminishing to 10 knots or less late tonight.

SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
As of 3 PM Thursday...Little in the way of synoptic change
through the period. South to southeast winds of 10-15 knots will
continue as will the 1-3 foot seas. There is some indication of
slightly stronger winds with enhanced low level jetting for a few
hours early Sunday morning but longevity isn`t there (if it comes
to fruition) for any change in seas, at least through this time
frame.

LONG TERM /SUNDAY THROUGH TUESDAY/...
As of 3 PM Thursday...A southwesterly wind will persist through
the period. On Sunday a front will be stalled nearby over land but
it does not appear to lead to any wind-increasing gradient pinch.
This boundary will lift slightly to the north for Monday and
Tuesday but again this should have little impact on marine
conditions. What will be the main issue for mariners to watch for
are thunderstorms that will cause higher wind and waves as well as
reduced visibility each day. Seas look to be a steady 2 to 4 ft,
highest offshore.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.

&&

$$

SYNOPSIS...MBB
NEAR TERM...TRA
SHORT TERM...SHK
LONG TERM...MBB
AVIATION...RJD