Area Forecast Discussion
Issued by NWS Wilmington, NC

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599
FXUS62 KILM 101103
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
603 AM EST Sun Dec 10 2017

.SYNOPSIS...
Bright sunshine finally returns today and Monday with dry
weather expected this week. Sunshine will bring a modest
temperature rise and we will be close to normal by Tuesday.
Another strong cold front will move across the area late Tuesday
with Arctic air returning Tuesday night through Wednesday night.
Temperatures will moderate late week. A cold front may bring a
brief cool down to start the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1000 PM Saturday...Though sunshine will abundantly return today
seasonable temperatures will not. Forecast model soundings show PW
values drop to just 0.25" indicative of dry air through the entire
column. Northwesterly flow in the mid levels will push a thermal
trough across the areas with 850mb temps bottoming out at -6C around
daybreak before some weak recovery gets underway. Such chilly values
should readily cap afternoon high temperatures in the 40s once again
(though with sunshine and less wind today will arguably have a less
raw feeling than yesterday). Wind turns more southerly at the
surface tonight, a harbinger of the warming trend slated for
Monday. Forecast soundings do not show a hard decoupling, but
rather a deep nearly isothermal layer developing supportive of
low temps within a few degrees of the freezing mark for most
locales.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 300 AM Sunday...Bright sunshine will remain across the
area for Mon. A deep westerly flow will develop with a low-level
SW flow and this will allow temps to reach the mid 50s Mon
afternoon despite below freezing temps at sunrise. We will be
under the influence of warm air advection Mon night and with
stronger winds aloft, we will not fully decouple and this will
keep lows from dropping below the mid and upper 30s with lower
40s at the coast.

Upper trough digs across the Ohio Valley Mon night and then
pivots across the Southeast states, moving across the eastern
Carolinas late Tue and Tue eve. This will drive a cold front
across the Forecast Area. Arctic air will plunge across the
region in the wake of this front, bringing a brief return to the
deep freeze. Still looks like airmass will be too dry to support
precipitation, but should see a period of partly cloudy skies
as the front moves through with clearing overnight Tue.

It will be breezy on Tue with high temps likely just about the
warmest of the week, reaching the upper 50s in most locations
before the arrival of much colder air. 850 mb temps will drop to
minus 5 to minus 9C by daybreak Wed. As dewpoints crash into
the teens late Tue night, lows will drop to the mid and upper
20s by daybreak Wed with the beaches perhaps holding onto
readings near freezing.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 300 PM Saturday...Change in 850 temps from Tue to Wed is
almost 15C, +3C to -11C. Highs Wed will struggle to reach mid
40s despite full sun should that verify. Next shortwave crosses
the area Thu morning, again starved of moisture, and lacks any
cold air. Wave exits northeast on Thu as the 5h trough starts to
flatten ahead of the next, stronger shortwave. As the 5h trough
amplifies to the west, deep southwest flow will develop over
the southeast, pushing temps closer to climo.

Duration of the return flow is brief and precipitable water values
barely reach half an inch. Clouds will increase Thu night as the
wave approaches and then passes early Fri morning. Not sold on any
measurable precip based on moisture profiles despite the strength of
the feature. Cold front trailing the wave quickly crosses the area
and shifts offshore early Fri, bringing another round of cold
advection to the region late Fri. Advection arrives too late to have
a big impact on highs for Fri, but Fri night temperatures will drop
below climo. Although this air mass does not look as cold as the one
during the middle of the week, temperatures for the end of the
period will still be close to 10 degrees below climo.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
As of 12Z...SKC/VFR today and tonight. Northwest winds could
gust to 16-18 kt along the coast this morning, but becoming
much lighter by mid afternoon.

Extended Outlook...VFR.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 300 AM Sunday...Cold and dry surge of air underway,
keeping gradient rather tight. The surge is weakening however
and so wind and waves should be abating, the latter trend aided
by the increasingly offshore trajectory in the veering flow. The
Advisory currently in effect has been marginal and uncertain
for a while now. Given that wind and waves are still close to
criteria and that dominant wave period is a choppy 6 seconds
have decided to err on the side of caution and leave it as-is.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 300 AM Sunday...Benign winds and seas on Mon. Gradient
will tighten Mon night and Tue ahead of a strong cold front
which will move across the waters Tue eve. W to WSW winds on the
order of 10 to 15 kt Mon will be WSW to SW Mon night and
increase to 15 to 20 kt. WSW winds Tue will become W and
increase to around 20 kt in the afternoon. The passage of the
cold front will shift winds to the NW Tue eve. Winds Tue night
will peak near Small Craft Advisory criteria, 20 to 25 kt. Seas
will be 3 ft or less Mon, building to 3 to 5 ft Mon night and
Tue and perhaps up to 4 to 6 ft Tue night as cold and dry surge
intensifies, although the strong offshore component should
drive seas lower near shore.

LONG TERM /WEDNESDAY THROUGH THURSDAY/...
As of 300 PM Saturday...Winds of 20 to 25 kt at the start of
the period. Offshore component may keep seas within 20 nm of the
SC coast under 6 ft, but NC nearshore waters seem likely to hit
6 ft and possibly 7 ft at times. Cold advection and gradient
slowly weaken on Wed with offshore flow gradually dropping to 20
kt around midday and 15 to 20 kt by the end of the day. Seas
will mimic wind speeds, slowly subsiding Wed into Wed night.
Flow remains offshore Wed night, before backing to southwest Thu
and starting to increase as next cold front approaches from the
west. Southerly flow will increase to a solid 20 kt Thu
afternoon and evening with seas increasing from around 2 ft Thu
morning to 3 to 5 ft Thu evening.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...Small Craft Advisory until noon EST today for AMZ250-252-254-
     256.

&&

$$

SYNOPSIS...
NEAR TERM...MBB
SHORT TERM...RJD
LONG TERM...III
AVIATION...TRA
MARINE...



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