Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
936 PM EST Thursday Dec 19 2013
high pressure will linger offshore through Sunday...with high
temperatures in the 70s expected from Friday through the weekend. A
cold front will likely bring showers late in the weekend and on
Monday. Dry weather and seasonable temperatures will return for
Tuesday and persist into Thursday.
Near term /through tonight/...
as of 9 PM Thursday...temperatures are expected to level off in the lower
to middle 40s through the late evening as warm air advection gains at least
a modest foothold. A few spots may dip to the upper 30s. Cirrus will
continue to stream across the sky. Overnight...a moistening low
level return flow around a departing area of high pressure will
allow lower clouds to develop as the moisture gets trapped beneath a
subsidence inversion. As these clouds develop and increase...temperatures
will stabilize if not rise a couple degrees. Will continue to
include patchy fog as dewpoints will creep higher...bringing
dewpoint depressions to near zero.
Short term /Friday through Saturday night/...
as of 3 PM Thursday...unseasonably mild weather in store for the
end of the week as an increasingly strong southerly flow brings
relatively warm air to the forecast area. Temperatures will
increase through the period...with highs of around 70 on Friday
and up in the middle 70s on Saturday...and lows in the 50s on both
Model soundings do show increasing moisture at the very lowest and
highest levels during the short term. This will manifest itself as
increasing cloud cover...especially cirrus throughout the area and
stratus near the coast. Guidance still hints at stratus and/or
light precipitation along the coast at times as unseasonably warm and
moist air moves over the colder shelf waters of the western
Atlantic. However...as models have been backing off from
precipitation and the European is silent on the issue have opted
to keep probability of precipitation silent. Stratus formation is a good bet however...and
there is a possibly that sea fog could also affect the coast.
Showers moving in advance of a cold front may enter our
northwestern-most counties after midnight early on Sunday
morning...but confidence is low on this event this far out. In any
event...middle levels will remain too dry for really significant
Long term /Sunday through Thursday/...
as of 3 PM Thursday...will start off the period with very warm
weather and finish with much more seasonable weather for Christmas
and middle week. Bermuda high and strong ridge planted off shore will
provide deep southerly return flow into the southeast ahead of an
approaching cold front. This front will be trailing from a low
pressure system racing off into the Canadian Maritimes late Sunday
through Monday. A high amplitude middle to upper trough will push this
front east through the Carolinas Sunday night into Monday. Still
counting on best lift and upper dynamics to move through earlier in
the day on Monday but pcp may linger through the day as ridge to our
southeast causes trough aloft to lift off to the northeast.
Therefore the surface front may be slower to move through while the
winds aloft remain SW through Monday night. The greatest quantitative precipitation forecast should
remain inland and to the west of local forecast area on Sunday but
expect this to March east through early Monday producing over a half
inch of rain in places. Dewpoint temperatures surge well into the 60s
through Sunday in increasing southerly flow. This warm southerly
flow over the cooler shelf waters may produce periods of sea fog and
low clouds. Although the airmass will be very warm there may be
quite a few clouds both low and high clouds to keep sun out of the
forecast through the first half of the extended. Expect temperatures well
into the 70s on Sunday and remaining very warm through Sunday night
into early Monday ahead of front. Once front moves through on
Monday...temperatures will lower through Monday night dropping about 30
degrees by Tuesday morning.
Tuesday will be the transitional day with clearing skies as middle to
upper trough finally pushes off shore and a deeper northwest flow develops
as high pressure builds in from the northwest. Pcp water values as
high as 2 inches in convection ahead of front will drop down less
than a quarter of an inch by Tuesday night into Wednesday...making for a cool
crisp Christmas. Cold air advection will bring temperatures below freezing most places
both Wednesday morning and Thursday morning with highs only reaching into the
50s both days.
By Wednesday night into Thursday...the high shifts off the coast and a
more typical wedge type pattern sets up. The cool air at the surface
will hold tight as warmer southerly flow develops aloft and coastal
trough becoming more prominent heading into Thursday. This should lead
to greater chance of clouds and chance of pcp overnight Wednesday into
Thursday...mainly closer to the coast. Then a relatively dry cold front
should move through from the west bringing cooler and drier weather
for late week.
Aviation /00z Friday through Tuesday/...
as of 00z...satellite images indicate a patch of thicker cirrus
passing over the terminals at this time. SC clouds are well south of kmyr.
Winds have decreased this evening. There is low confidence but MVFR
visibilities could occur at kcre/kmyr this evening due to higher dewpoints
as a result of onshore flow earlier this afternoon. Otherwise...VFR
expected until the cirrus clears out after 06z. Then with light
winds expect MVFR visibilities to develop. Low SC should begin to invade
the terminals...but any ceilings at this time expected to be 3-5k and mainly at
the coastal terminals. This could increase visibilities at the coastal
terminals. Visibilities may be slow to increase after sunrise...but expect
VFR visibilities at all terminals by middle-morning with low VFR ceilings at the
coastal terminals through the day. Winds will be S-SW around 8 kts.
Extended outlook...MVFR/IFR visibilities possible Saturday morning. Periods
of MVFR ceilings expected Saturday and Sunday. Showers with MVFR/tempo
IFR on Monday...becoming VFR on Tuesday.
near term /through tonight/...
as of 9 PM Thursday...a return southerly flow will become well
established and increase in the coming days as high pressure drifts
further seaward and a strong trough approaches from the west. S to
south-southwest winds will be around 10 knots or less through the night. Seas will
be largely comprised of a 9 to 11 second southeast swell which will result
in higher seas than wind speeds would normally produce. Seas will be
2 to 3 feet and up to 4 feet across portions of the outer waters.
Short term /Friday through Saturday night/...
as of 320 PM Thursday...south to southwesterly flow in the 10 to 15
knots range will dominate through the short term as high pressure
remains anchored over the western Atlantic. Winds will be closer to
the 10 knots figure on Friday...and closer to 15 kts on Saturday as the
gradient tightens in advance of an approaching cold front. Seas will
gradually build from 2 to 4 feet on Friday to 3 to 5 feet on Saturday.
Long term /Sunday through Tuesday/...
as of 3 PM Thursday...increasing southerly return flow through
Sunday into Monday ahead of approaching cold front from the west.
Southerly winds will increase up to 15-20 kts by Sunday. This
increasing southerly push will drive seas up to 4-6 feet by Sunday and
as high as 5 to 7 feet through early Monday. A Small Craft Advisory
will likely remain in effect through Monday until cold front passes
through by late Monday. Winds and seas will subside in off shore
flow behind front but deepest cooler and drier air will move over
the waters Tuesday afternoon into Wednesday morning. Therefore should see seas
drop below Small Craft Advisory thresholds by Monday night but will then pick up again
in northerly surge late Tuesday through early Wednesday. May reach above 6 feet
for a short time Tuesday night. May see sea fog over the waters Sunday
into Monday as warm moisture rich air moves over the cooler shelf