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000 
FXUS62 KILM 121723
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
1223 PM 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 /18Z TUESDAY THROUGH SUNDAY/...
As of 12Z...VFR through 13/18Z. Front should be through 
KFLO/KLBT at TAF issuance and should move through the coastal 
terminals around 20Z. Soundings suggest high level cigs 
decreasing. Time height progs indicate a slug of post frontal 
moisture around 4k which could give tempo cigs mainly KLBT this 
afternoon into early evening. Otherwise skies should clear out 
this evening and overnight. Winds may stay gusty into the early 
evening. Winds should decrease to WNW-NW 7-10 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.

&&

$$

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