Scientific Forecaster Discussion
fxus62 kilm 250723
Area forecast discussion
National Weather Service Wilmington NC
323 am EDT Thu may 25 2017
a cold front will move offshore this morning. High pressure
will then build in from late today into Friday and persist into
the weekend, bringing dry weather and increasing heat. A cold
front will reach into the Carolinas early next week, finally
moving off shore by mid week.
Near term /through tonight/...
as of 3 am Thursday...deep 5h trough over the eastern Continental U.S.
Today will lift northeast overnight. Shortwave rotating around
the base of the 5h trough will push a cold front, currently just
west of the area, off the coast by mid to late morning. Not
expecting much from the broken line of showers moving across the
forecst area out ahead of the front. Surface layer remains
stable and even a storm of some significance would have trouble
getting any strong winds or rotation to the surface. Line has
had very little in the way of lightning with it and do not
anticipate that this will change. Deep dry air, very evident on
water vapor imagery, is poised to start moving into the forecast
area and this will bring an end to any shower activity until
Stacked low remains over the Ohio Valley today as the 5h trough
axis shifts overhead this afternoon before lifting northeast
tonight. Trough axis arrives overhead during peak heating, just
as a shortwave accompanied by mid level moisture moves around
it's base. Daytime heating combined with mid level cooling and
steepening mid level lapse rates is usually a recipe for
isolated to scattered afternoon showers and thunderstorms.
Although temps today will be near climo, the anomalously cold
nature of the 5h trough will increase mid level lapse rates into
the 7-8c/km range for the afternoon. Although the MOS guidance
is showing a very low pop for this afternoon, past experience
has shown that just about any shortwave/5h trough with smallest
bit of moisture has the ability to generate convection. Will
remain on the wet side of guidance and carry chc pop across the
area this afternoon and evening. Cold pools aloft frequently
generate small hail and can always lead to a few storms with
larger hail and/or damaging winds, but it appears the best
chance for severe weather will be just north of the area. Any
activity that does develop will end around sunset with the loss
of heating and Post shortwave/trough subsidence bringing a rapid
end to any lingering storms.
Cold advection behind the front is delayed but by evening
cooler and drier air will be spreading over the region. Skies
clear out and despite winds close to 10 mph for much of the
night lows will drop below climo. Away from the coast lows in
the mid to upper 50s are likely.
Short term /Friday through Saturday night/...
as of 3 am Thursday...weak high pressure centered over Florida
will extend north across the forecast area Friday, then will be
suppressed to the south as a slow moving cold front drifts south
towards the region. A dry column and lack of forcing will make
for a rain-free start to the Memorial Day weekend, at least up
until Saturday night. For overnight Saturday have introduced
slight chance for showers and thunderstorms with the front
lingering to our north. Confidence not high that we will see
precip in that time-frame though, as guidance not in good accord
with frontal placement.
Temperatures will gradually warm through the period, with highs
in the mid 80s for Friday and right around 90 for Friday.
Long term /Sunday through Wednesday/...
as of 300 PM Wednesday...ridge will build up from the Gulf
Coast on Saturday as surface high shifts east and off the
Florida coast. This will maintain a warm and increasing moist
flow with rising heights in the mid levels. The 850 temps will
be up to 16 to 18c on Saturday. Overall expect plenty of
sunshine and well above normal temps on Saturday, reaching
around 90 most places. A minor perturbation riding over the
ridge overnight Saturday should produce some clouds and maybe a
spotty shower but will move off the coast by early Sunday.
Expect high pressure to hold with plenty of dry air and
subsidence in the mid levels to maintain a cap on convection
through early Sunday. The European model (ecmwf) is more bullish with a digging
northern stream shortwave pushing a cold front south and east
toward the Carolinas on Sunday and suppressing ridge farther
south. This could lead to greater potential for clouds and
showers and slightly less warm temps, but for now will lean more
toward the GFS and keep a more optimistic forecast for sunnier
and warmer weather on Sunday. If GFS forecast holds, mid level
heights will continue to rise through the weekend as ridge
builds up from the south and temps will rise up around 90 again
on Sunday.Overall confidence is lower through early next week as
a slow moving cold front reaches into the Carolinas and finally
moves off the coast on Tuesday or possibly not until Wed.
Therefore should see increasing chc of showers sun aftn through
Mon. Temps will continue to rise well into the 80s Mon through
Wed. A moist summertime like air mass will keep overnight lows
Aviation /06z Thursday through Monday/...
as of 06z Thursday...scattered convection and breezy southerly
winds ahead of the approaching cold front will continue for the
next couple hours. Other than brief IFR possible at any
terminal where convection occurs, the remainder of the overnight
will see MVFR conditions becoming VFR around daybreak. Gusty
winds will continue through the day today and with increasing
clouds in the afternoon along with the development of scattered
showers and thunderstorms. Any convection that does develop will
dissipate around sunset.
Extended outlook...localized MVFR conditions are possible in
scattered showers and thunderstorms Sunday and Monday afternoons
near term /through tonight/...
as of 3 am Thursday...winds and seas warrant continuation of
Small Craft Advisory through today and into tonight. Strong
southerly flow will veer to southwest this morning before
ultimately ending up westerly late in the period. Gradient will
start to relax late in the day which will result in speeds
decreasing. Seas will follow a similar trend, running 5 to 8 ft
into late morning then gradually trending downward, eventually
dropping below 6 ft late tonight.
Short term /Friday through Saturday night/...
as of 3 am Thursday...expect generally west to SW winds through the
short term as high pressure builds in from the west. Seas of 3
to 5 ft Friday morning for our NC waters will subside as the
gradient relaxes, possibly ramping up again Saturday night as a
weak front inches down from the north. Seas for our SC waters
will be a bit more moderate and should not exceed the 2 to 4 ft
range through the short term.
Long term /Sunday through Monday/...
as of 300 PM Wednesday...high pressure to the south will
maintain a SW return flow 10 to 15 mph through much of the
period. Seas between 2 and 4 ft will rise up to 3 to 5 ft on
Sunday with increasing winds up to 15 to 20 kts as a cold front
makes its way toward the Carolinas. Tightened gradient flow
between slow moving cold front to the west and high pressure to
the south and east may push winds up to 15 to 20 kts through
early next week.
SC...beach hazards statement through this evening for scz054-056.
NC...beach hazards statement through this evening for ncz106-108.
Marine...Small Craft Advisory until 6 am EDT Friday for amz250-252-254-