Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 120223
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
923 PM EST Mon Dec 11 2017

.SYNOPSIS...
The week looks dry although there is some risk for rainfall on
Friday. Sunshine will bring a modest temperature rise and we
will be close to normal by Tuesday. A 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 followed by a return to seasonable temperatures
early next week.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 900 PM Monday...With the sfc based inversion having
developed after sunset, winds have decoupled. This has resulted
in temps nose-diving rather quickly even where winds have not
decoupled entirely. The best rad cooling conditions and the
stronger sfc based inversion will occur across the Northeast
portions of the ILM CWA. With the sfc pg progged to tighten-some
tonight and a low level southwesterly 35+ MPH jet at 950mb,
SW winds will become active across the entire FA, wiping out
much of the sfc based inversion. As a result, temps will bottom
out this evening, close to their respective dewpoints, but then
hold steady initially, then look for a slow increasing trend
for temps. Lows tonight will likely occur late this evening or
just after the midnight hour.

Previous.........................................................
As of 300 PM Monday...A cool but beautiful afternoon ongoing
across the Carolinas as broad high pressure centered across the
Gulf Coast expands into the region. This is accompanied by very
dry air noted on WV imagery, and cloudless sky conditions are
present across the entirety of the Southeast. Well upstream into
the western Great Lakes, a surface low pressure beneath a
strong shortwave is producing clouds in that region, with the
accompanying cold front draping into the MO VLY.

This front will cross the area on Tuesday, but before this occurs
increasing WAA around the southern high pressure will create
relatively warm temperatures for the next 24 hours. This is due to
warm advection on increasing SW flow within the warm sector ahead of
the aforementioned front. Moisture will slowly increase within the
column, but latest RAP soundings show PWATs only to around 0.5
inches tonight, so the area will remain mostly cloud free. The
exception may be well NW where a few mid/high clouds may advect in
from the NW. Temperatures will drop quickly in the dry column after
dark, but then will begin to level off as S/SW LLJ increases to 25-
35 kts. This will keep mins from bottoming out as radiational
cooling gets inhibited, and mins are forecast to be 40-42 at the
coast, 36-39 inland.

SW winds increase Tuesday ahead of the front, and may gust above
25mph during the aftn/eve. THe strong cold front will cross the
region precip-free thanks to the dry column, but mid-level
cloudiness will increase during the aftn with FROPA occurring from
NW to SE during the evening. Strong CAA follows this front and 850mb
temps plummet from +1C to +3C early Tuesday, to -4C to -7C by the
end of the period. This will be accompanied by gusty NW winds, and a
very chilly night is forecast just beyond this period as temps begin
to crash Tuesday evening from aftn highs very near 60 degrees.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 300 PM Monday...An arctic blast will bring the coldest day
of this season so far. Temps will drop into the mid 20s most
places Tues night in a rush of cold and dry air with Wed afternoon
highs only making it into the 40s under bright sunshine. The
brisk NW winds will make it feel even colder with apparent temps
down in the teens right around daybreak Wed and feeling like
the 30s most of the day. A very dry air mass will remain in
place through Wed with dewpoint temps down in the teens and pcp
water values a quarter of an inch or less.

By Wed night, another shortwave will ride through the base of
the long wave trough in place over the eastern CONUS. The
associated sfc low will move by to our north, but may see some
passing clouds overnight Wed into Thurs morning. The winds will
back slightly but not expecting much of moisture return. Pcp
water values will not even reach a half inch with moisture
profiles showing potential for some mid level clouds as
shortwave passes through overnight Wed into early Thurs morning.
Temps overnight Wed may be a bit tricky as warmer air just above
the surface may mix down if winds spike up at all overnight.
Basically expect atmosphere to decouple allowing temps to drop
out down to the upper 20s to around 30 most places, a few
degrees warmer than previous night. Overall, a very cold and dry
period from Tues night through Wed night.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 300 PM Monday...The East Coast longwave trough will reload
late this week as another strong shortwave moves through the
Carolinas on Friday. This upper system should induce low pressure to
develop at the surface over North Carolina during the day Friday.
Moisture is going to be tough to find given deep layer winds have so
much offshore component, virtually eliminating Gulf of Atlantic
inflow. In fact the only moisture I can find arrives in the 850-700
mb layer from the northwest -- most likely Pacific moisture that
came onshore in British Columbia several days earlier. Dynamics are
going to be so strong that I still think there will be some light
measurable rainfall around, and I`m including a 30 percent chance of
showers in the forecast for Friday.

Dry weather will develop for Saturday and Sunday as a weak upper
level ridge pokes north from the Caribbean and surface high pressure
moves eastward along the Gulf Coast. Model depictions of another
shortwave trough arriving on the East Coast Monday vary quite a bit
from model to model, reducing confidence about what impacts we may
see. PoPs of 30 percent have been introduced into the forecast for
Monday along with some increased cloud cover.

Temperatures will be on a roller coaster ride through the weekend,
likely coolest on Saturday as the upper trough moves overhead and
offshore.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
As of 00Z...High confidence for VFR conditions through the forecast
period. Winds will go calm this evening, however they are expected
to pick up overnight with winds over 30 kts just above the surface.
Tuesday, a dry front will move through the region at the end of the
forecast period. Gusty west southwest winds are forecast ahead of
the front.

Extended Outlook...VFR.

&&

.MARINE...
NEAR TERM /THROUGH TUESDAY/...
As of 915 PM Monday...Light and variable winds early this
evening, will become southwest thruout at 10 to 15 kt by
midnight as the sfc pg begins to tighten. In addition, a low
level SW 30+ knot jet, will eventually partially mix down to the
ocean sfc late tonight into daylight Tue. Latest SSTS are not
quite cold enough yet for a deep sfc based marine layer to
prevent that mixing to the ocean sfc. With that said, winds will
reach SCA thresholds late in the pre-dawn Tue hours and
continuing thru daylight Tue. With the CFP slated for Tue aftn,
SCA threshold westerly winds will veer to the NW and become
gusty at times. The increasing NW winds will be the result of
a continued tightened sfc pg and CAA occurring across relatively
mild SSTs.

Previous......................................................
As of 300 PM Monday...Light S/SW winds across the waters are
occurring in response to broad high pressure ridging eastward
from the Gulf Coast. These winds will generally become all SW
and increase steadily tonight and on Tuesday in the warm sector
ahead of a strong cold front. The current wind speeds of 5-10
kts will become 20-25 kts this evening and on Tuesday, becoming
NW at these same speeds behind the FROPA Tuesday evening. These
winds will push seas quickly up from their current amplitudes of
2-3 ft to 4-6 ft by Tuesday morning, and the ongoing SCA
remains in place. Have started the hazard a bit earlier than
inherited to capture the 20-25 kt winds just before seas climb
towards 6 ft, and the SCA goes into effect at 6am Tuesday.

SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 300 PM Monday...A rush of cold arctic air will keep
marine layer well mixed in gusty NW winds up to 20 to 25 kts
Tues night. A Small Craft Advisory will remain in effect through
early Wed in this surge, but winds will back and diminish
through the day on Wed allowing seas to subside. Overall expect
seas up to 4 to 6 ft Tues night dropping down to 2 to 3 ft by
Wed night. The off shore flow will keep highest seas in the
outer waters.

LONG TERM /THURSDAY THROUGH SATURDAY/...
As of 300 PM Monday...An active and windy weather pattern will
continue into Thursday and Friday. Another Canadian cold front will
slide across the area on Friday. Low pressure is expected to develop
along the front, helping produce a surge of offshore winds Friday
night. The latest GFS model is actually showing gale-force winds
Friday afternoon and night, but other model guidance is not that
strong, instead keeping winds strong but below 30 knots. Our
forecast will go with this weaker wind forecast for now, implying a
period of Small Craft Advisory conditions (W winds 20-25 kt) Friday
into Friday night. Winds and seas should improve on Saturday as
Canadian high pressure builds in from the west.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...Small Craft Advisory from 6 AM Tuesday to 7 AM EST Wednesday
     for AMZ250-252-254-256.

&&

$$
SYNOPSIS...JDW
NEAR TERM...DCH/JDW
SHORT TERM...RGZ
LONG TERM...TRA
AVIATION...DL


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