Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 121526
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
1026 AM EST Tue Dec 12 2017

.SYNOPSIS...
Today will be breezy and the warmest day of the week. The passage
of a strong cold front later today will usher in Arctic air
tonight and through Wednesday night. Temperatures will quickly
moderate Thursday and Friday. A cold front may bring some light
rain Friday and a brief cool down Saturday before seasonable
temperatures return Sunday followed by the risk for showers on
Monday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1000 AM Tuesday...Strong cold front has just crested the
mountains and will race SE today. WAA in a strong pre-frontal
regime will lead to rapid temp rises this morning along with
increasingly gusty SW winds. However, peak temperatures will
likely occur a few hours before typical maximums, as the front
races across the area, moving offshore around 2 pm. This will
lead to a rapid wind shift to the NW with continued gusts of
20-25 mph, along with cooling through the aftn. So, temperatures
will peak mostly in the 59-63 degree range today, before falling
through the late aftn rapidly on strong CAA. Post-front stratus
is likely, as noted by current visible imagery, and RAP
soundings suggesting a 2-4 hr period of saturation around 3-5
kft, and have increased cloud cover late this aftn/eve.

After a clearly atypical temperature curve during the daylight
hours, tonight`s temperature curve may be fairly typical due to
conflicting/offsetting factors. It will be breezy enough for
mixing and thus normally a slower, flatter temp curve. This will
be offset by the fairly robust CAA behind the front, and mins
will fall into the mid and upr 20s most places, with wind chills
falling below 20 towards Wednesday morning.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 300 AM Tuesday...The Arctic surge will drop dewpoints into
the single numbers and teens on Wed as 850 mb temps drop as low
as -11C. It will be sunny and cold with highs in the lower to
mid 40s. NW to W winds of 10 to 20 mph will make it feel as if
it were below freezing for much of the day. Minimum relative
humidity will be as low as 25 to 30 percent Wed afternoon.

As one deep trough lifts out Wed, another will begin to dig
more modestly across the Great lakes and Midwest and then across
the east coast late Wed night and Thu. It now looks like the
brunt of the cloud cover will brush us by to the N. However, an
impressive wind field will overspread the area with 50-60 kt of
wind lowering to around 2 kft. These very strong winds will tend
to keep the air near the ground moving and with the brunt of the
cold and dry advection having passed, it should not be as cold
Wed night. We should see dewpoints recover Wed night with low
temps no lower than the upper 20s and lower 30s. The strong
winds in the lower levels of the column will lift out Thu and
under the influence of SW flow, highs should reach the mid 50s
with plenty of sunshine. Light surface winds will return Thu
night and we will begin to see clouds increasing from W to E
ahead of yet another deep trough and surface cold front. These
clouds will cap minimums in the mid and upper 30s with lower 40s
at the coast.

&&

.LONG TERM /FRIDAY 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 /15Z TUESDAY THROUGH SATURDAY/...
As of 12Z...Based on latest soundings and KLTX VAD wind data will
continue LLWS through 14-16Z.

VFR through 13/12Z. Have indicated FROPA KLBT/KFLO around 17Z and
coastal terminals 19Z. Soundings suggest mainly high level cigs if
any. Time height progs indicate a slug of post frontal moisture
around 4k which could give tempo cigs this afternoon into early
evening. Otherwise skies should clear out this evening and
overnight. Winds may stay gusty into the evening although winds
should decrease to less than 10 kt by 06Z.

Extended Outlook...VFR.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 1000 AM Tuesday...Small Craft Advisory remains in effect
for all waters as winds become gusty in the vicinity of a cold
front today and tonight. These will be from the southwest ahead
of this front through this aftn, quickly becoming NW this
evening and tonight. Wind speeds will reach up to 25 kts pre-
FROPA, and may be higher than that tonight after the passage.
Seas of 4-6 ft with isolated higher faces are likely, with a
short period wind wave dominant. Near shore seas will fall
quickly tonight as the offshore flow develops.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 300 AM Tuesday...Small Craft Advisory conditions are
expected to linger across at least portions of the waters Wed
morning with the dry and cold surge slowly waning during Wed.
However, a developing deep and strong WSW flow should keep winds
elevated through much of the period. Winds will likely be near
Small Craft Advisory criteria, 20 to 25 kt, Wed night into Thu
with a 50 kt jet at 2 kft. Seas Wed morning will be highest
offshore, up to 4 to 6 ft. Seas will subside during Wed before
building to 3 to 5 ft Wed night into Thu with perhaps a few 6 ft
seas across the outermost northern waters. Diminishing winds
late Thu and Thu night will result in subsiding seas.

LONG TERM /FRIDAY THROUGH SATURDAY/...
As of 300 PM Monday...An active and windy weather pattern will
continue Friday as a Canadian cold front slides across the area.
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 until noon EST Wednesday for AMZ250-252-
     254-256.

&&

$$
SYNOPSIS...
NEAR TERM...JDW/MBB
SHORT TERM...RJD
LONG TERM...TRA
AVIATION...MRR
MARINE...



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