Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
119 PM EDT sun Jul 13 2014
high pressure ridging west across the area will bring a seasonable
and mostly dry day today...before hot and humid conditions develop
Monday and Tuesday. Heat indices early in the week will exceed
100 degrees. A cold front will approach late Tuesday...and then
stall across the area through the upcoming week. This will bring
cooler than normal temperatures and good chances for showers and
thunderstorms each day.
Near term /through tonight/...
as of 1 PM Sunday...overall idea of previous forecast still looks
good though probability of precipitation for southern areas have been upped to chance
category for this afternoon due to current shower activity. Expect
showers to wane as ridge builds into the area aloft. Discussion
from 7 am follows.
As of 7 am Sunday...a few weak showers have tried to develop along
the coast this morning but these have so far been of limited
duration. Moist boundary layer and lingering surface boundaries are
likely the culprit but the dry air aloft continues to be a
hindrance. Showers are having a little more Success over the waters
where there is more low level moisture. It is possible some of the
activity over the near shore waters could move onshore so have added
slight chance to low chance in these areas. Activity along the coast
and over the waters should start to wane in the next few hours now
that the sun is coming up. Otherwise no major changes to the
Previous discussion follows:
as of 2 am Sunday...light winds will become calm overnight allowing
some radiational cooling...especially inland. This will allow temperatures
to drop into the upper 60s in places as well as increase potential
for fog. Boundary layer winds are forecast to be a little higher
than last night and do not expect widespread visibilities below 1sm.
Abundant middle level dry air and subsidence in place today will keep
skies mostly sunny and severely limit precipitation chances. Precipitable
water values hang around 1.2 inches...well below the 1.75 inches
typical for middle July and middle level lapse rates are in the 5 to 5.5
c/km range. Cannot rule out isolated weak showers along or just
behind the sea breeze...similar to yesterday...but most areas will
remain dry. Any showers that do develop will be hard pressed to last
for an extended period of time given the harsh middle level
Highs today will again climb into the lower 90s away from the coast.
Sea breeze should make good progress inland given the south to
southeast synoptic flow. Along the coast early sea breeze
development will keep highs in the middle to upper 80s. Light southerly
flow overnight will keep lows near to slightly above climatology.
Short term /Monday through Tuesday night/...
as of 330 am Sunday...hot and humid with increasingly unsettled
weather will define the short term.
Very uncomfortable weather expected both days for the early
work-week period...as return flow pumps warm moist air into the
Carolinas...and the much-discussed approaching cold front gets hung
up west of the area until Tuesday evening. This leaves high
thicknesses...850mb temperatures of 17-19c...and dew point temperatures well into
the 70s...both Monday and Tuesday. Temperatures on Monday will soar into
the middle 90s everywhere except the immediate beaches...and will only
be a degree or so cooler on Tuesday. This represents a
several-degree jump in forecast highs for Tuesday...but guidance has
backed off on the longitudinal progression of the cold front during
Tuesday...so a jump is required. These temperatures will combine with the
high dewpoints...causing heat indices to approach 105 on
Monday...and around 100 on Tuesday. Lows both nights will be
similarly warm...mid/upr 70s Monday night...and a few degrees cooler
While heat will be the big concern early week...convection will
become increasingly widespread into Tuesday ahead of the advancing
cold front. Monday will feature only isolated storms...focused
primarily on the typical sea breeze and Piedmont trough
boundaries...but lowering thicknesses and the cold front will cause
more widespread storms Tuesday...and especially Tuesday night when
column saturation occurs and the cold front reaches the ilm County Warning Area.
Long term /Wednesday through Saturday/...
as of 330 am Sunday...cool and wet conditions are expected for the
entirety of the long term as a highly amplified 500mb pattern drives
an anomalous trough into the eastern Continental U.S.. beneath this trough...a
cold front will push into the local area by the beginning of the
extended...and then stall across the East Coast. Although this
trough is quite strong...causing lowered thicknesses all way to near
Cuba (!)...it remains positively tilted with an axis from SW to NE.
This is unfortunate for the local area since that causes flow to
become boundary parallel...hence causing the front to stall...pretty
much overhead...into next weekend. At the same time...moist flow
from the Gulf of Mexico will remain tapped as the SW flow originates
from that area...and thus an extended period of wet weather is
anticipated. Wpc has 2-4" of quantitative precipitation forecast across the area next week...and
although there is some uncertainty into how much the front will
waver inland/offshore...expect the majority of the period to feature
slightly below normal temperatures and good chances for precipitation.
Aviation /18z Sunday through Friday/...
as of 18z...there is enough moisture in place to support isolated
convection along the sea breeze by around middle afternoon...pushing
inland by 20-21z. Brief downpours are possible...but they will be
isolated in nature. South to southwest flow will pick up in the
afternoon to around 10 knots and diminish after sunset. SW flow and
low level moisture above the surface tonight should preclude fog
Extended outlook...increasing chances for showers/thunderstorms and MVFR
conditions Tuesday through Friday as a cold front stalls over the
near term /through tonight/...
as of 1 PM...showers over most of the waters waters have dissipated
except southernmost areas where they will persist for another two or
three hours. Otherwise...a largely quiet remainder of the day is
expected on the waters with S winds of 10 to 15 knots and seas around 2
feet. Conditions much the same tonight though seas could peak at 3 feet.
Short term /Monday through Tuesday night/...
as of 330 am Sunday...high pressure well offshore...and a cold front
approaching from the west...will keep the waters sandwiched in
between through the period. This drives a pinched gradient...and
forces SW winds to increase to around 20 kts much of the beginning
of the week. These strong winds will drive wave heights up to 3-5 feet
much of the short term...possibly reaching 6 feet on Tuesday.
Cautionary statements are likely for a portion of the early-week
time-frame...and conditions necessitating an Small Craft Advisory may be possible.
Long term /Wednesday through Thursday/...
as of 330 am Sunday...high pressure centered well offshore will
gradually lose its influence over the waters as a cold front stalls
across the area. At this time expect the front to remain just west
of the waters...but will have the effect of weakening the
gradient...and thus SW winds will ease from around 15 kts
Wednesday...to 10 kts or less on Thursday. This will cause wave
heights to slowly fall from 3-5 feet early...to 2-4 feet late
Thursday...even as a southeast ground swell begins to amplify.