Scientific Forecaster Discussion
fxus62 kilm 212252
Area forecast discussion
National Weather Service Wilmington NC
652 PM EDT Thu Jun 21 2018
hot and humid conditions with scattered thunderstorms will
continue through the weekend. A cold front will move through
the area Monday night. Drier and cooler conditions are expected
to gradually develop Tuesday and Wednesday of next week and may
persist into next Thursday as high pressure builds in from the
Near term /through Friday/...
as of 645 PM Thursday...large cape values up to 3000 j/kg have
been feeding towering cumulus development all afternoon along
the seabreeze and inland as well, however dry air aloft has
limited the area to just a smattering of rainfall so far.
Shower activity should diminish almost entirely over the next
hour, however a weak trough associated with an enhanced area of
T-storms now entering western South Carolina may lead to a
resurgence of convection later this evening. Activity may
redevelop across Lumberton and the Pee Dee region by 10 PM, then
should clear out of the Cape Fear region by 3 am. I'm not
expecting severe weather, but scattered showers and thunderstorms
with 30ish percent coverage sounds reasonable.
Otherwise no significant changes have been made to the forecast.
Assuming convection doesn't become overwhelmingly widespread,
lows should remain very warm tonight with mid to upper 70s for
most areas. -Tra
Discussion from 300 PM follows...
convective temperatures being realized this afternoon. Goes_e
visible reveals storms firing along a west to east remnant
outflow to the north across central NC. A weak surface trough
axis was analyzed from around akq to ocw to eyf to kmni.
Vertical circulations from morning acc clouds has aided the
blossoming of convection over central and southeast NC. The present
steering flow will take some of the cells into the sea breeze
directly later this afternoon, which could pulse cores close to
severe thresholds. Still appears to be some inhibition aloft in
part due to short-wave thickness ridging ahead of the
approaching upper trough, however this influence will migrate
eastward into late afternoon and early evening.
Tonight, a broken line of convection ahead of an upper trough
should edge from west to east into our forecast area, with
diurnal cooling and remnant dry mid-level air serving to lessen
convective intensity. A few strong to severe storms may linger
north of Pender and Bladen counties into middle and late evening
where convergence and diffluence aloft will be stronger. The
line may bring a brief wind shift to northwest-north overnight.
Heat and humidity will be short of heat advisory criteria on
Friday, but apparent temperatures will reach 100 degrees.
Short term /Friday night through Saturday night/...
as of 300 PM Thursday...deep low pressure over the juncture of
the Ohio and Mississippi rivers Fri evening will continue to
lift north-NE leaving a broader, flatter flow by Sat night. A trough
will extend down from this low toward the Gulf Coast states
leaving a deep SW flow running up through the Carolinas but as
low lifts off, flow aloft will veer to a more westerly
direction. Looks like some shortwave energy rotating around the
trough may enhance some convective development which is always
tough to time exactly. But, there will also be some drier air
moving in with the SW to west flow aloft. Overall not expecting any
widespread development, but any storms that do Blossom could be
quite potent depending on the timing of the mid to upper
impulses moving through, with main focus along sea breeze
boundary and trough inland.
Temps will once again soar into the 90s with overnight lows in
the mid 70s most places. With slightly drier air moving into
the I-95 corridor Sat aftn, expect heat index values to hold
just shy of heat advisory criteria, but still hot.
Long term /Sunday through Thursday/...
as of 300 PM Thursday...ridge will be suppressed to our S sun
and Mon as an upper trough pivots across the northeast states
and then offshore Tue. Shortwave energy embedded in the west to west-northwest
flow will skirt across the Carolinas with one spoke moving
across and offshore Sun night into Mon morning and another late
Mon and Mon eve. This should help drive a surface cold front
south and into the area Mon night into Tue. High pressure will
then try to build S Tue and Wed which should push the front
further S where it will stall out Wed and Thu.
This scenario should allow for the greatest coverage of showers
and thunderstorms early in the week, especially Mon and Mon
night when precipitable water values will peak near or in excess
of 2 inches. Convection should be scattered sun, initiating
along the seabreeze and Piedmont trough. A greater number of
thunderstorms may arrive Sun night coincident with upper level
support which should be able to sustain upstream thunderstorms
as they move into our portion of the Carolinas. The arrival of
progressively drier air from the north Tue and Wed should result in
a decrease in convective coverage and silent pops may be
warranted for at least portions of the area Wed and Thu.
850 mb temps will reach 20-21c sun and so expect the heat and
humidity to still be high with high temps reaching the mid and
upper 90s. This will bring the heat index to near 105 to 109
which would require a heat advisory. We should be at least a
degree or two cooler Mon with more clouds and developing
convection and then seasonable temps Tue through Thu as
dewpoints lower to the mid and upper 60s which will keep heat
index values below 100 degrees. Lows Sun night will still be
muggy, mid and upper 70s, but lower 70s should be more common
for the remainder of the week.
Aviation /00z Friday through Tuesday/...
as of 00z...there will some instability overnight and it should be
enough to kick off some late evening convection as a weak impulse
movers through around 03z. The hrrr model does not do much with it,
but it does have some good convection developing in the Morehead
City area after midnight. Will keep vcsh as a hedge. Little or no
fog expected. Friday, another hot one with isolated convection by
Extended outlook...VFR with possible short duration MVFR fog or
IFR cigs inland terminals early each morning. Scattered
afternoon showers and thunderstorms likely each day with short
duration restrictions possible. A cold front will bring a better
chance for showers and thunderstorms Monday.
near term /through Friday/...
as of 645 PM Thursday...only a modest seabreeze was able to
develop today despite firecracker heat inland. It's so warm over
the ocean now in late June that even 95 degrees inland isn't
that great a temperature difference anymore. Background
southwesterly winds 10-15 kt should continue through the
evening, but the passage of a weak trough offshore late tonight
should veer winds more westerly with speeds dipping to 10 knots
or less before sunrise. Seas currently 2-3 feet could briefly
build toward 4 feet near Cape Fear later this evening, but
should average 3 feet through the night. -Tra
Discussion from 300 PM follows...
SW winds prevail into evening, because of thunderstorm steering flow,
it is advisable that mariners get a radar updated before heading
out because of potentially active marine weather tonight, most
of it north of Cape Fear and the Gulf Stream. Seas will hold at
around 3 ft, with dominant wave periods of 5 seconds. No
advisories or caution headlines are expected but periodic gusts
to 20 kt can be expected both tonight and on Friday, and 4 ft
seas outer waters at times. Winds and seas will be higher and
Short term /Friday night through Saturday night/...
as of 300 PM Thursday...low pressure over the Ohio Valley will
lift north through Saturday and tighten the gradient flow late
Sat into Sat night a bit. Overall expect SW winds 10 to 15 kts
with gusts to 20 kts, but winds should reach up to 15 to 20 kts
late Sat into Sat night. This should push seas up a bit with
some 5 fters possible in the outer waters and beyond through Sat
night into early sun. Also, expect a spike in winds and gusts
in afternoon sea breeze, especially close to the coast.
Long term /Sunday through Tuesday/...
as of 300 PM Thursday...south-southwest to SW winds sun will be mainly SW
Mon and then shift to the north and NE in the wake of a cold front
late Mon night and then NE to east-northeast Tue as high pressure begins
to assert a southward push across the waters. The strongest
winds will be in the range of 15 to 20 kt later Sun afternoon
and eve, the result of a robust seabreeze circulation, and into
Sun night due to some nocturnal jetting. A tightening gradient
ahead of a cold front approaching from the north may keep wind
speeds close to this range into Mon. Wind speeds will diminish
to 10 kt late Mon night. A modest push of drier and cooler air
should bring wind speeds up to around 15 kt Tue. Seas will be 3
to 4 ft with a tendency to build to 4 to 5 ft during Tue.