Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 200745
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
245 AM EST Wed Feb 20 2019

.SYNOPSIS...
A front will lift into coastal communities today while inland
areas remain on the cool side of the boundary. Warmer air will
move on on Thursday and again be most pronounced along the
coast. Seasonable weather Friday will give way to another warmup
over the weekend. A cold front is due later Sunday.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 300 AM Wednesday...A particularly difficult forecast is
shaping up for today as models are struggling to initialize the
position of the front offshore and struggling to depict the very
cold, dry low-level air across the eastern Carolinas. A general rule
of thumb in these situations is that the cold wedge will last longer
than you`d think possible and that NAM typically performs much
better than the GFS. I can`t find a compelling reason to think
otherwise, and this forecast is very close to the 00z NAM today
through tonight.

A developing coastal front extending from 40 miles east of
Jacksonville FL out along the western edge of the Gulf Stream east
of Cape Fear should move westward toward the coast today. Modest 300-
305K isentropic lift over the frontal inversion across the eastern
Carolinas should result in solid clouds and waves of light rain
today. Forecast rain chances range from 70-90 percent with the most
substantial QPF expected along the coast. After starting out this
morning in the upper 30s to lower 40s, temperatures should only
slowly crawl through the 40s through early afternoon. As the coastal
front reaches Cape Fear by mid-afternoon temperatures should pop
into the mid 50s in Wilmington and Southport. The boundary should
also make it into the Grand Strand area by late afternoon with
temperatures also rising into the 50s. Inland temperatures should
remain stuck in the 40s all day as there`s simply no mechanism to
dislodge the cold, dense air at the surface given solid cloud cover
above.

The coastal front should become more diffuse tonight. As the parent
Canadian high moves farther off the New England coast we`ll lose our
connection to any influx of cold, dry air in the low levels. With no
further evaporational cooling and substantial warm advection ongoing
aloft, temperatures should remain steady or rise slightly overnight.
Thursday`s forecast is no easier than today`s as the NAM maintains
enough of the wedge airmass inland to produce a large temperature
gradient either side of I-95. While the bust potential is high, it
appears along the coast we`ll see enough sunshine to mix up into the
subtropical air aloft with temperatures punching well into the 70s.
West of I-95 it`s possible low clouds could linger all day with
temperatures stuck in the 60-65 range. Colleagues at NWS Columbia
and Raleigh are all on-board with this idea as well.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 300 AM Wednesday...Backdoor cold front slides into the region
from the north Thursday night bringing some rain along with it
though models not in good agreement with respect to QPF. Friday into
Friday night the wedge to the north of the boundary pushes more into
the Carolinas. Expect cloudy but only slightly cool conditions with
generally light rain or drizzle as very low amplitude ridging aloft
over Bahamas leads to little mechanism for ascent locally.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 300 AM Wednesday...High pressure wedge remains firmly
entrenched on Saturday while coastal warm front approaches. This
boundary will lift through Saturday night into Sunday allowing for
much milder air to flood into the region. A largely moisture-starved
front then moves through on Sunday, it`s parent low all the way up
in the Area Lakes. Post-frontal high pressure to bring dry and
fairly seasonable weather Monday and Tuesday.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
As of 06Z...VFR conditions across the area will worsen around
daybreak as the dry low-levels saturate and lower stratus decks
develop. IFR conditions appear likely most of the day with periods
of light rain expected. A warm front approaching from offshore
should reach the coastal airports by late afternoon, but will likely
do little to improve aviation weather conditions. Low IFR conditions
could develop tonight as stratus ceilings fall below 400 feet AGL.

Extended Outlook...Thursday morning IFR ceilings should lift along
the coast, but could linger through a good portion of the day
inland. The front lingering in the area could lead to more IFR
ceilings and/or vsbys Friday into Saturday as another round of
overrunning rain develops.

&&

.MARINE...
As of 300 AM Wednesday...Strong northeast winds this morning have
built seas to 8 feet at the Frying Pan Shoals buoy and 12 feet at
the Edisto buoy east of Charleston. The worst of the marine weather
conditions are ongoing now, and improving winds/seas are expected as
a coastal front begins to move westward toward the coast this
afternoon. Northeast winds should bend easterly around noon, then
should become light and southerly as the front moves through. Models
are not in any sort of agreement with the position or timing on the
front, but my best forecast has it reaching the Cape Fear coast
during the mid-afternoon hours, and the Grand Strand during the late
afternoon. The preferred model today is the 00Z NAM.

The front should weaken near the coast tonight with light south to
southwest winds continuing into Thursday. Subtropical moisture
creeping up the coast could lead to areas of sea fog developing
tonight into Thursday, and it`s even possible some of the fog could
become dense given a favorable wind trajectory and high moisture
content of the incoming airmass.

Thursday night through Friday night... Backdoor cold front moving
south across the area Thursday night turning winds onshore and
dropping dewpoints that should bring and end to the sea fog. Mariner
problems then transition to wind and seas behind the front, both of
which could reach Advisory levels. The high pushes in more Friday
night but the local change of winds and seas will be minimal and the
Advisory may continue.

Saturday through Sunday... Cool air wedge breaks down Saturday
albeit somewhat gradually. Winds will be veering in direction and
abating in speed. No headlines are expected. Sunday will bring SW to
W flow around a large storm system in the Great Lakes. Advisory-
worth 6 ft seas could return.

&&

.TIDES/COASTAL FLOODING...
As of 300 AM Wednesday...Large tidal ranges associated with this
month`s full moon will be further enhanced by strong northeast winds
this morning. The current tidal anomaly measured at gauges at
Wrightsville Beach and Myrtle Beach ranges from +1.2 to +1.4 feet.
This may begin to subside slightly by the time high tide occurs
around 745 AM, but adding this anomaly to the astronomical tide
easily yields minor coastal flooding all along the coast. The most
significant flooding is expected in the Myrtle Beach/Murrells Inlet
area where water should reach a solid half foot over flood stage.
This could be sufficient to make some flood-prone streets impassible
around high tide.

Minor coastal flooding will also occur during daytime high tides on
the Cape Fear River at downtown Wilmington this morning and again
tomorrow.


&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...Coastal Flood Advisory from 7 AM to 10 AM EST this morning for
     SCZ054-056.
NC...Coastal Flood Advisory from 7 AM to 10 AM EST this morning for
     NCZ106>108-110.
MARINE...Small Craft Advisory until 7 AM EST Thursday for AMZ250-252-
     254-256.

&&

$$
SYNOPSIS...mbb
NEAR TERM...tra
SHORT TERM...mbb
LONG TERM...mbb
AVIATION...TRA
TIDES/COASTAL FLOODING...tra


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