Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
127 PM EDT Thursday Jul 10 2014
a cold front will stall across the region tonight...persisting
into early Saturday. This will bring good chances for
thunderstorms the next few days...with periods of heavy rainfall.
This front will dissipate late in the weekend with a return to
typical summertime conditions...with a warming trend developing
early next week. Another cold front will approach on Wednesday.
Near term /through tonight/...
as of 1100 am Thursday...shwrs/tstms and clouds over Cape Fear
this morning have lowered temperatures into middle 70s...lower than they
have been for past few days. Should see this convection weaken
through the morning before other storms develop along sea breeze
boundary and other outflow boundaries just inland of the coast
early this afternoon and translating inland through later this
afternoon. Overall expect greater coverage of storms through
tonight as cold front slows down as it approaches from the
northwest through tonight. Very moisture rich air lies ahead of
the front with pcp water values up close to 2 inches. Convergence
along localized boundaries will remain the Focal Point for
convection over most of area with best coverage just ahead of
front. Upper level support will increase through the day as trough
shifts east. Looks like best jet dynamics will be located to the
northwest of forecast area. With a storm motion out of the
southwest at 10 miles per hour...some training of cells could produce
potential for flooding through this afternoon. Although cell
motion will be from southwest to northeast...the storms will shift
eastward through time as upper level trough pushes front slowly
east. Lapse rates remain fairly neutral with less overall heating
in most places limiting the convection potential but cloud free
spots will heat up producing areas of differential heating adding
to storm development. Storm Prediction Center mentions coastal plain as Focal Point
with risk of damaging wind gusts.
Clouds and pcp will keep temperatures from reaching as high as past
couple of days with highs of 85 to 90 most places. Areas that
cooled down from rain this morning will be slower to rise reaching
the middle 80s by this afternoon. The clouds and showers will keep
overnight lows higher once again...remaining in the middle to upper
70s most places. The cold front will hang over the area tonight
with potential for convection into Friday.
Short term /Friday through Saturday night/...
as of 330 am Thursday...Friday continues to look very wet locally as
elements combine to produce widespread convection with heavy rain.
At the surface...a weakening cold front will be wavering across the
County Warning Area...and this...along with remnant outflow boundaries from
convection on Thursday...will serve as foci for updrafts on Friday.
Aloft...shear line demarcating the longwave trough axis will swing
overhead and northeast during the day...while 300mb 100kt jet moves
over New England...leaving the Carolinas within the favorable rfq
difluent region...in a setup that resembles quite well a
Maddox-type event from literature for heavy rain.
All this occurs in a thermodynamic environment characterized by
SBCAPE of 800-1000 j/kg...precipitable waters over 2 inches...and warm cloud
depth approaching 11 kft. The "long skinny" cape profile suggests
efficient precipitation processes (longer parcel residence times
within strong collision-coalescence environment) in updrafts
Friday as well...so all signs point to a very active day with
heavy rainfall the primary threat within thunderstorms. Although
drier air will slowly begin to filter into the middle-levels as an
embedded shortwave pushes offshore late Friday...still anticipate
a significant quantitative precipitation forecast day...highest eastern half of the County Warning Area. Temperatures
will be tempered by the widespread clouds and rain...rising only
into the middle/upper 80s. Lows at night will drop into the middle 70s at
the coast...but around 70 well inland where drier air will become
more pronounced late.
Saturday will be a transitional day as ridging from the southwest
tries to Blossom across the area. It will get shunted east by the
aforementioned longwave trough...but the westerly flow between these
two features will help to dry the column from Friday. At the same
time...the subtle thickness increase will help to further erode the
front which should become indistinguishable on Saturday.
However...it will continue to help drive convection...albeit in a
less significant manner than Friday. Still anticipate scattered
thunderstorms Saturday area-wide...with temperatures again just below normal in
the upper 80s to around 90...and lows a few degrees above 70.
Long term /Sunday through Wednesday/...
as of 330 am Thursday...seasonable conditions to begin the period as
ridging develops aloft and high pressure offshore ridges back
towards the coast. Middle-level westerly flow will cause a relatively
dry column on Sunday...so only isolated convection is
anticipated...likely less than climatologically normal. With heights
building aloft and return flow developing...temperatures Sunday will warm
to seasonable values. Thereafter...heat will slowly build again
through Tuesday thanks to subtle thickness increase downstream of a
large trough across the Midwest...and continued return flow at the
surface. This drives more typical convection chances
Monday/Tuesday...before a cold front approaches and stalls across
the area by Wednesday. This will bring much more widespread precipitation
chances for the middle of next week...along with temperatures
cooling back to seasonable levels.
Aviation /18z Thursday through Tuesday/...
as of 18z...shra/tsra expected to develop just inland of the coastal
terminals this afternoon...and there is moderate to high confidence
this activity will translate towards kflo/klbt as the afternoon
progresses. Convection will move from kflo/klbt to near the coastal
terminals this evening...but could re-develop and continue through
06z at kflo/klbt. Overnight...additional rain showers/thunderstorms and rain could develop at
the coastal terminals...but confidence is low as to the
Due to uncertainties in timing and coverage will indicate MVFR
conditions with convection...but short term IFR is almost certain to
occur...especially at kflo/klbt...and may add to tafs depending on
radar trends. IFR should not last 15-30 minutes at any one terminal
unless cells train over any one terminal for an extended period of
time. MVFR visibilities in br could also occur 09-12z at kflo/klbt. Despite
copious amounts of low level moisture confidence of IFR is low due
to cloud cover.
After sunrise showers will be likely at the coastal terminals with
tempo MVFR conditions. Less activity is expected at kflo/klbt.
Extended outlook...a front stalls over the region with a decent
chance for rain showers/thunderstorms and rain through Saturday morning. Rain showers/thunderstorms and rain are again
possible Monday and Tuesday. Brief IFR conditions are possible in
the heavier showers and storms. Otherwise VFR.
near term /through tonight/...
as of 1100 am Thursday...southwesterly flow will continue over
the waters through tonight as high pressure over the western
Atlantic interacts with an approaching cold front well inland.
Seas will remain 2 to 4 feet most waters.
Short term /Friday through Saturday night/...
as of 330 am Thursday...a weakening cold front will waver in the
vicinity through Saturday...likely remaining just west of the
coastal waters during this period. That leaves a weak
gradient...and S/southeast winds Friday and Saturday at 10 kts or less.
Late Saturday the cold front will wash out...and as high pressure
becomes dominant offshore...winds will veer to become more
southwesterly...remaining around 10 kts. Wave heights will be highest on
Friday...thanks to winds easing from Thursday...with 3-4 feet seas
likely on a southerly wind chop. These heights will drop to 1-3 feet
on Saturday on the lighter winds.
Long term /Sunday through Monday/...
as of 330 am Thursday...more typical summertime pattern will develop
late in the weekend and early next week as high pressure offshore
exerts its influence across the coastal waters. SW winds will slowly
increase through the period...becoming 15-20 kts late Monday. The
combination of these rising winds and an amplifying ground swell
will drive seas up from 2-3 feet Sunday...to 3-5 feet Monday...and
cautionary statements may be needed early next week.