Area NWS Forecast Discussion
FXUS62 KILM 181821

Area Forecast Discussion
National Weather Service Wilmington NC
121 PM EST Sun Nov 18 2018

A weak area of low pressure near the coast could produce a
little light rain tonight into Monday. A dry cold front will
sweep offshore Tuesday evening. Cooler weather is expected for
Wednesday and Thanksgiving Day as high pressure builds in from
the west. A complex area of low pressure could bring substantial
rain to the area next weekend.


As of 100 PM Sunday...Have increased cloud cover over the SC CWA
and contemplating on placing any pcpn. Earlier model MOS
guidance indicated pcpn to start later, mainly tonight over the
SC CWA and spreading northeast across the NC CWA. Have kept the
pcpn threat to light rain. With insolation a bit hier across the
ILM NC CWA, have tweaked max temps a degree or 3 hier.

As of 300 AM Sunday...Weak coastal trough taking shape off the coasts
of GA and NE FL will sharpen through the morning then slowly lift
northwest as surface high exits New England. Increasing mid level
moisture as the flow around 850 becomes southerly will spread
shallow moisture over the southeast later today into tonight. The
result locally will be an increase in cloud cover this evening and
overnight with chances of light rain increasing from south to north
across the area after midnight. Any rain that develops will be
light, due to the weak nature of the isentropic lift and the shallow
nature of the moisture. Despite the limiting factors think there a
decent chance for areas seeing measurable rain from the event,
especially closer to the SC coast. More typical coastal trough
starts to develop overnight, just off the NC/SC coast as the high
departs. This may lead to another area of enhanced precip chances
just off the coast, brushing the Cape Fear during the pre-dawn
hours. Again, anything that develops will be light/weak but in the
coastal zones may be enough to produce measurable rain. Increasing
cloud cover today will limit temperatures, especially across inland
SC where highs will only be a degree or 2 warmer than yesterday.
Lows will end up above to well above climo with cloud cover and
increasing warm advection keeping coastal areas in the low 50s and
inland areas in the mid to upper 40s.


As of 300 AM Sunday...An active jet stream is forecast over the
next several days as a northern stream shortwave moves across
Iowa on Monday, then across the southern Great Lakes and into
New England by Tuesday. A speed max in the subtropical jet will
move across the Carolinas Monday night, but lags a little
behind and never phases with the northern stream disturbance.

At the surface a weak coastal trough that develops today along
the GA coast will advect north toward the Cape Fear coastline
Monday. Models have a large spread in potential positions for
this trough, ranging from near Wilmington (ECMWF), to Myrtle
Beach-Whiteville (GFS), to Marion-Lumberton (NAM). The trough
should remain weak enough that sensible weather shouldn`t vary
much on either side, but its position will determine local wind
directions and temperatures as well. I`ve gone with a more
coastal location for the trough, following the GFS and ECMWF.
The trough will lift out to the northeast Monday night as
synoptic low pressure developing across the Mid-Atlantic states
becomes the dominant player for local wind directions.

Modest isentropic lift and even a bit of elevated instability
Monday should lead to patchy light rain or showers, particularly
near the coast during the morning hours. Forecast PoPs range
from 20 percent inland to 30-50 percent along the coast, but
with QPF of only a few hundredths of an inch. Moisture should
thin out during the afternoon with dry weather expected by

The low developing across the Mid-Atlantic states on Monday will
deepen as it moves near coastal New England on Tuesday. This
will drag a dry cold front southeastward and through the eastern
Carolinas Tuesday evening. Cold advection will develop behind
this front for Tuesday night with morning lows dipping back
into the 30s inland.


As of 500 PM Saturday...The longwave upper pattern to continue
through this period as identified in the short term. However,
mid-level s/w troughs during this period remain active and
possibly a bit more potent. The influence of the subtropical
jet over the polar westerlies continues across the FA, with the
sfc CFP Tuesday followed by CAA that brings temps back down to
at or slightly below normal as a good chunk of Canadian high
pressure breaks away and dives to the Gulf Coast States by Wed
and across the FA Thu. A potent s/w trof within the polar
westerlies pushes across the NE States early Thu followed by
very cold Canadian high pressure that follows a secondary CFP
across the FA during the day on Thu. A portion of this cold high
is progged to work it`s way across the local CWA due to another
wedge setup late Fri into Sat. Will see cloud development and
light stratiform pcpn occur by Sat. Flow aloft is not conducive
to pull completely onshore the coastal trough that will
eventually develop late Fri into Sat.


As of 18Z...Models identify a weak area of mesoscale lift
associated with weak isentropic lift mainly for late tonight
into Monday daytime morning. Will be looking at continued
developing layered stratiform type cloudiness with
bases/ceilings dropping to MVFR across NC terminals after dusk.
And for the SC terminals, will see prevailing MVFR thru and
after dusk with occasional IFR for coastal SC terms due to
the moist onshore low level flow. The IFR and potentially LIFR,
may occur in a 7 hr span between 05z and 13z. This also includes
vsby lowering due to patchy light rain/drizzle and fog.
Improving conditions will occur toward 18z Mon.

Extended Outlook...CFP Tuesday with threat of MVFR showers. VFR
returns Wednesday through Friday.

As of 100 PM...Winds dropping slowly as expected. Sig. seas
still holding strong as the 9+ second period ground swell
becoming more dominant and the short period wind wave continues
to slowly drop off.

As of 300 AM Sunday...High pressure off the New England coast
will maintain northeast flow through the period. Gradient will
slowly weaken later today into tonight as the high slowly
departs and weak coastal trough starts to develop. Speeds will
drop from around 10 kt this morning to closer to 5 kt overnight.
Seas will run 2 to 3 ft through the period.

As of 300 AM Sunday...A weak coastal trough developing today
to our south will work its way north to the coastal Carolinas
Monday. This feature should remain very weak, but models are
still having difficulty determining where the boundary will set
up during the day. Wind speeds will remain 10 kt or less, but
directions will vary depending on precisely where the trough
moves. I`m penciling in the trough right on the coast Monday,
maintaining mainly a northeasterly wind direction during the
day, shifting westerly Monday night as the trough moves offshore
in response to low pressure developing up across the Mid-
Atlantic states.

A dry cold front will push offshore Tuesday evening, followed by
a reinforcing shot of cold air on north winds. At this time it
appears wind speeds will increase to 15-20 kt Tuesday night, but
remain below advisory criteria.

As of 500 PM Saturday...Eventually, the entire CWA waters from
Surf City to South Santee River will be under a SCA after the
secondary CFP. With N to NE winds at 15 to 25 kt as the sfc pg
tightens in response the wedge setting up. Significant seas will
run 3 to 6 ft by the end of the long term period. This slow
building process is due to a shortened fetch. However, with
winds progged to further veer to the NE or ENE by the end of
this fcst, sig. seas will likely further build.





NWS ILM Office Area Forecast Discussion