-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KILM 251023
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
624 AM EDT Sun Sep 25 2016

.SYNOPSIS...
A backdoor cold front will stall across the area today before
lifting back to the north on Monday. This will create periods of
showers and isolated thunderstorms through Monday. A stronger cold
front will move across the Carolinas late Tuesday and Wednesday
with continued chances for showers. Cooler temperatures are
expected behind this front for late in the week and into next
weekend as high pressure builds southward from Canada.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 300 AM Sunday...A backdoor cold front was positioned from near
RDU to MHX. This front will move slowly south and is expected to
push into the forecast area this morning. The front is currently
being nudged to the south by high pressure across the Great Lakes
and northeast states. The center of the high is expected to move
across New England tonight. The front will likely get hung up as it
tries to push through the the forecast area today and should stall
in close proximity tonight before drifting back to the N late
tonight and Mon. Low clouds across northeast NC will continue to
push south behind the front and we expect clouds to be on the
increase today, especially across NC. Still a fair amount of dry air
in the mid-levels today. Moisture will be increasing below 25 kft or
so. Instability will be increasing with mixed layer CAPE values
peaking this afternoon in the 800 to 1200 J/kg range, highest across
SC. There is no appreciable upper level support and the high
resolution HRRR is not showing any convection developing until mid
afternoon. Will show POPs increasing above threshold early to mid
afternoon and include isolated thunderstorms by mid afternoon and
into early this eve. Depth of moisture should largely preclude heavy
rainfall amounts despite the slow storm motions.

Given the proximity of the front, will keep a mention of showers in
the forecast through the eve and overnight, but the moisture
depth will be restricted to about the lowest 15 kft of the column
and so will pull any mention of late night thunderstorms.

Highs today will be in the lower to mid 80s, warmest across the
Pee Dee. Lows tonight, mid 60s to lower 70s.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 300 AM Sunday...High pressure across New England will drift
offshore and this will allow the cold front to push back N of the
area during the day with surface winds turning onshore and
eventually to the SE Mon afternoon and eve. A subtle mid-level
shortwave will sneak up the coast late in the day Mon and Mon night.
A vigorous trough carving out across middle America is expected to
drive a cold front into and eventually through the eastern Carolinas
Tue night or Wed. Moisture will increase steadily during Tue and Tue
eve and then begin to drop off sharply with frontal passage
overnight, lastly along the coast Wed. Will show convection through
the period, but include the highest probability Tue afternoon and
night.

Highs will be about normal, lower 80s. Lows will be in the upper 60s
to lower 70s Mon night and then cooling in the wake of the cold
front to mid and upper 60s.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 300 AM Sunday...Deep upper low will evolve across the Great
Lakes and then sink slowly SE through late week before ejecting into
Canada during the wknd. This will drive a cold front across the
Carolinas on Wednesday, but its overall progression is a low
confidence forecast due to model uncertainties into the evolution of
the aforementioned upper low. ECM is deeper and stronger with this
upper low, cutting it off entirely from the mean flow into next
wknd. The CMC is the fast solution with short cutoff followed by
rapid progression into the westerlies by late week. The GFS is a
decent compromise, although its ensembles show a very large spread
by D6. The biggest difference to the sensible weather from these
solutions revolves around precip potential, as temperatures will
likely be seasonable or slightly below regardless of which outcome
is correct.

Will favor the GFS attm which is supported by WPC, which
suggests the front will push offshore as the upper low begins to
move NE Thursday, with cool high pressure building down the coast
thereafter. Temperatures Wed/Thu will likely be around seasonable
norms or slightly above, but clouds and showers will be likely as
the front drifts towards, and then off, the SE coast. As the high
builds south late week and into Saturday, temps will cool to below
normal with mins potentially dropping to 60 or below, especially
inland, by the end of the period. If the ECM solution ends up being
correct, temperatures will still follow this trend, but both Friday
and Saturday could also feature periods of showers instead of the
drier forecast currently being shown.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
As of 12Z...A cold front is passing through our northern CWA at this
time. Predominately northeast flow and MVFR conditions are expected
with brief IFR ceilings possible early on. There will probably be a
shower or two around, however they will be very weak as things
should remain quite stable with low CAPE expected. The front will
stall over our southern counties with light northeast flow overnight.

EXTENDED OUTLOOK...Chance for SHRA/TSRA each day through Wed.
Otherwise expect VFR.
-- End Changed Discussion --

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 300 AM Sunday...A backdoor cold front will move into the
northern waters this morning and will likely stall across the
southern waters this afternoon and eve before moving back to the N
tonight and Mon. High pressure will be moving into and through the
northeast states today and tonight and then offshore Mon. Winds
across our coastal waters will be from the NE through the period at
speeds of up to 15 to 20 kt. Seas will be mainly 3 to 4 ft, but up
to 5 ft around Frying Pan Shoals in part due to a robust 9 to 11
second easterly swell.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 300 AM Sunday...High pressure across New England will move
offshore and this will allow winds to shift from NE and ENE Mon
morning to E Mon afternoon and to SE Mon night. As a cold front
approaches the waters, SE winds Tue will become S and SW Tue
night. If the front does not slow down, winds may shift to the N
as early as the wee hours of Wed morning. The highest winds this
period will be Mon and Mon eve, up to 10 to 15 kt. Seas of 3 to 4
ft Mon and Mon night will subside to 2 to 3 ft Tue and Tue night.

LONG TERM/WEDNESDAY THROUGH THURSDAY/...
As of 300 AM Sunday...Some uncertainty exists in the extended with
respect to the timing of a cold front moving across the waters, but
attm it appears the front will stall over the waters Wednesday and
then shift well offshore during Thursday. This leaves a period of
highly variable winds on Wednesday with speeds of 5-10 kts, before
the front moves away Thursday followed by N to NE winds of 10-15
kts. Seas Wed and most of Thu will be 2-3 ft with residual 11-12 sec
swell remaining in the spectrum combined with low-amplitude wind
waves. Late in the period a northerly 4-5 sec wave will amplify, and
seas may build towards 3-4 ft late Thursday.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.

&&

$$
SYNOPSIS...JDW
NEAR TERM...RJD
SHORT TERM...RJD
LONG TERM...JDW
AVIATION...43
MARINE...RJD/JDW