Area Forecast Discussion
Issued by NWS Wilmington, NC

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KILM 232316
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
716 PM EDT Sun Sep 23 2018

.SYNOPSIS...
A weak cold front will stall across the area Monday and Tuesday,
dissipating by Wednesday. Rain chances will increase Thursday
and Friday as a stronger cold front approaches the coast. Drier
and cooler high pressure will build in over the weekend, bringing
temperatures closer to normal for early Fall.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 700 PM Sunday...The cold front currently extends from
Greenville and Kinston southwestward across Pope Air Force Base
near Fayetteville, then westward beyond Charlotte. This boundary
is moving very slowly southward, but should pick up a little
speed overnight, making it through Myrtle Beach and possibly
Georgetown by sunrise Monday. Northeasterly winds behind the
front will be accompanied by increasing clouds but very little
cool advection, so the front`s expected impact on temperatures
will be subtle.

High-res models show the cluster of showers currently well
offshore of Cape Fear dissipating this evening, but new showers
developing there around midnight may become a little more
widespread after the front (and its enhanced low-level convergence)
arrives. Instability should remain rather shallow due to a subsidence
inversion between 800-700 mb. Steering flow in the surface-600
mb layer should turn easterly, increasing the chance of some of
these showers making it onshore late tonight. Forecast PoPs
range from 20 percent in Wilmington and Southport to 30 percent
in Myrtle Beach and Georgetown, no higher due to plenty of dry
air within and above the subsidence inversion.

Discussion from 300 PM follows...

Cool front pushing through tonight while flow above remains
southwesterly. This sets up an undercutting source of lift that
will increase cloud cover area-wide. The mid levels moisten up
but only in a relative sense compared to how dry they are now.
By midday Monday one can still easily find 20C dewpoint
depressions aloft. This does not bode well for appreciable
rainfall amounts, and this will be welcome news to the flood-
battered area. Even so, some very light rain will be tough to
rule out following FROPA. The cool advection will be quite weak
and so temperatures will remain elevated above their seasonable
norms.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 330 PM Sunday...Mid-level ridge remains just off the
Southeast coast through the period. Weak surface
wave/trough/low passes over or just east of the area Tue into
Tue night which may slightly enhance diurnal convection along
the sea breeze and Piedmont trough. For now have coverage capped
at high chance due to a few negative factors. Mid-level lapse
rates are weak, barely climbing above 6C/km and there is a fair
amount of mid-level dry air (likely due to the mid-level ridge).
Forecast soundings do have precipitable water above 2 inches,
but this is likely due to an abundance of moisture below 700mb.
Storm motion will be under 5 kt, and with the abundance of low
level moisture any convection that does develop will be able to
produce a decent amount of rainfall. Sea breeze and Piedmont
trough convection will have the potential to produce isolated,
nuisance flooding in those areas where the strongest storms
develop. Loss of diurnal heating should lead to a rather quick
end for any lingering convection on both Mon and Tue nights.
Nocturnal marine convection will be possible each night, some of
which could bleed onto the immediate coast. Temperatures will
run above climo on Tue and well above climo Mon and Tue night.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 330 PM Sunday...Agreement is good that a Bermuda to
Bahama upper ridge will be shunted slightly south and west by a
band of westerlies, associated with an amplifying upstream upper
trough Thursday and Friday. This looks to push a cold front to
the coast, where it may promptly stall just offshore or south of
the area. As such, abnormally warm temperatures to prevail Wed-
Fri, with tempering of daytime highs Friday in clouds and
showers, and weak cold air advection potentially into the
weekend with drying and cooling overall. Rainfall later in the
week ahead of, and through frontal passage, could reach 0.75-1"
over SE NC, and 0.25-0.50" average over NE SC, most of this
received Thursday through very early Saturday. This will not be
enough to aggravate flooding, or significantly raise rivers.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
As of 00Z...Overnight fog will be a persistence forecast as not much
has changed in the previous 24 hours. Moderate confidence in this
approach. Upper ridge begins to build and shift east from the
Midwest to the Great Lakes region on Mon. This will push the
boundary to the south and stall over the area tomorrow afternoon.
The surface boundary should initiate some evening showers over the
water which will make their way inland due to an easterly component
of the average wind in the 1000-500 mb layer. This will give us a
slight chance of showers in the morning with a higher chance south
including CRE and MYR. Afternoon showers and storms are possible but
will be concentrated mainly to the northern part of the CWA where
the signal is a little stronger and at inland terminals closer to
the boundary.

Extended Outlook...Increasing chances for showers and storms Monday
and Tuesday, also Thursday and Friday. Light morning fog possible
each day. Satellite imagery over the past few evenings has shown
some dense fog in areas where the front has passed and that could be
true for our area on Tue morning.

&&

.MARINE...
NEAR TERM /THROUGH MONDAY/...
As of 700 PM Sunday...A cold front still across east-central
North Carolina should move southward tonight, spreading out
across Cape Fear after midnight, and potentially arriving in
Georgetown by daybreak Monday. Behind the front winds will turn
east to northeasterly around 10-12 knots. Scattered showers have
been sitting most of the day across the offshore waters 50-100
miles east of Cape Fear. As the front arrives it should help
showers develop closer to shore after midnight. Seas currently
1-2 feet is primarily in 8 to 10 second swell, but will build a
bit late tonight as wind waves develop with the east-northeast
wind increases behind the front.

Discussion from 300 PM follows...

A slow moving cold front will really take its time backing
winds to NE as previously anticipated. This is also due to the
approaching low from the east, slated by NHC to open to a wave.
The fate and strength of this feature are a little iffy, but
onshore E to ENE flow appears to be in the cards for much of the
period. Onshore flow allows some slightly bigger waves to get
into the 20 nm forecast zones and so some areas could see their
forecast open up to 3-4 ft from their current minimal values.

SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 330 PM Sunday...Weak surface high to the northeast will
maintain  light northeast flow Mon night into Tue. Approaching
surface wave/low/trough passing over or just off the southeast
coast during Tue will result in a 180 degree wind shift Tue
afternoon. Strongest winds will be Mon night into Tue when
pinched surface gradient pushes speeds into the 10 to 15 kt
range. Gradient starts to relax Tue and remains on the weak side
Tue night with speeds 10 kt or less. Increasing northeast flow
Mon night could build seas to 3 to 5 ft but decreasing winds Tue
and Tue night, along with the wind shift, will drop seas to 3
to 4 ft later Tue and 2 to 3 ft Tue night.

LONG TERM /WEDNESDAY THROUGH FRIDAY/...
As of 330 PM Sunday...Briefly at daybreak into Wednesday
morning W winds to prevail as a low off Cape Lookout or
Hatteras, lifts off to the NE through the day, allowing SW winds
to trend much of this period, generally 17 kt or less. Seas may
still be 3-4 feet early Wednesday from the departing low. TSTMS
and showers can be expected from Wednesday night through very
early Saturday before daybreak, and radar updates are encouraged
this period.

&&

.TIDES/COASTAL FLOODING...
As of 330 PM Sunday...Long fused coastal flood event on the
Cape Fear river ongoing. High tides will exceed warning level
(6.7ft MLLW) for the next several days as not only the flood
wave moves down river but astronomical tide builds with the
waxing moon. This evening`s high tide at 9:38 PM should reach
about 7.2 ft MLLW. Amazingly the normal tidal range on the river
of 4-5 ft is being confined to about 2.5 ft by the flood wave.
So not only are we expecting record-challenging high tidal
reading early this week, but low tides may not get below
Advisory levels.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...Coastal Flood Warning until 1 AM EDT Monday for NCZ107.
MARINE...None.

&&

$$

SYNOPSIS...MJC/TRA
NEAR TERM...TRA/MBB
SHORT TERM...III
LONG TERM...MJC
AVIATION...21
TIDES/COASTAL FLOODING...MBB


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.