Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 251905

Area Forecast Discussion
National Weather Service Wilmington NC
300 PM EDT Sun Sep 25 2016

A cold front will stall across South Carolina tonight before
returning north Monday. A stronger cold front will move across the
Carolinas late in the week though its timing is highly uncertain.


As of 300 PM Sunday...This morning`s cold front has nearly stopped
moving southward and is stalled over eastern South Carolina in the
vicinity of Georgetown, Florence, and Hartsville. With northeast
winds on both sides of the boundary it`s a bit nebulous exactly
where the front is. Dense low clouds never burned off across
northern and central North Carolina, but fortunately the post-
frontal airmass never became that well established here before the
sun rose this morning. Northeasterly low-level flow should push
these lower clouds southwestward after sunset.

So far we`ve seen virtually nothing on radar. The HRRR appears to
have been right all along and I`ve trimmed PoPs back to just a small
20 percent chance through this evening from west of Wilmington to
around Conway and Marion.

Weak cool advection should be felt most strongly across coastal SE
North Carolina tonight as the high over New England points its ridge
axis down in that direction. Broken low clouds will help to hold
heat in overnight and my forecast lows are close to the warmer NAM
MOS guidance, except at ILM where a slug of dry air after midnight
associated with the ridge may allow better radiational cooling to
occur. Lows mainly upper 60s with some lower 70s on the beaches.


As of 300 PM Sunday...The 500 mb ridge over the Southeastern U.S.
will get beaten down over the next two days as an upper level trough
begins to dig southward across the Great Lakes. The surface high
will move off the New England coast Monday; return flow behind this
high should lift today`s cold front back to the north again, with
the boundary moving back into Virginia by Monday evening. A weak low
in the northern Bahamas will get lifted northward by the same low
and mid-level flow. While this feature should remain 50-75 miles off
the coast as it moves northward Monday into Tuesday, its closest
approach late Monday night into Tuesday morning could enhance
rainfall potential, at least along the coast.

By Tuesday, attention will shift to a cold front entering the
western Carolinas, preceding the upper level trough over the Great
Lakes. This front should stall as the upper trough deepens and cuts
off. With a humid tropical airmass in place Tuesday ahead of this
stalled front, scattered showers and t-storms appear quite possible,
especially inland. Assuming there are no unresolved upper level
disturbances present, precipitation should diminish Tuesday evening
with the loss of daytime heating.



As of 3 PM Sunday...Interesting weather early in the period with a
very large trough on Wednesday turning into a major cutoff low well
into the weekend. Trouble is, models are not in agreement regarding
the longitude of the cutoff. As a result it is difficult to
determine whether we see a FROPA locally or spend most of the long
term in the warm sector of the deeply occluded surface low. Even
FROPA model solutions do not push the boundary very far offshore so
either way the weather appears to be unsettled. The main
ramifications of the aforementioned uncertainties then will likely
affect temperature/dewpoint forecast. The ECWMF has been seemingly
leading the way in figuring out how this system will evolve and it
has been showing the least progression. It now delays the front
until about Saturday morning and it is not indicative of any
significant airmass change. The GFS looks like it is trending in the
direction of the EC so the forecast will be hedged in that


As of 17Z...Favored a blend of the models for this period with
more confidence in the NAM and GFS then the ECMWF due to the
handling of the H5 low across the nrn portion of the country
during the next few days. Cold front south of KILM and KLBT at
this time and right near KCRE/KMYR/KFLO. Predominately northeast
flow and MVFR conditions are expected with mention of vcsh along
the coastal terminals but will leave out mention inland. HRRR a
bit overdone with the pcpn potential across the region but as
mentioned in the near term forecast best chances for pops are just
behind the front so that is enough reason for the vcsh. BUFKIT
seems to agree with this scenario as well with pcpn ending around
00z across the coastal terminals. Moderate confidence in MVFR due
to ceilings during the overnight period with improvement to vfr
after daybreak. Winds will stay up along the coast but I will
lower across KLBT and KFLO overnight.

EXTENDED OUTLOOK...Chance for SHRA/TSRA each day through Wed.
Otherwise expect VFR.



As of 300 PM Sunday...This morning`s cold front has made it only a
short distance down the South Carolina coast this afternoon. The
boundary will settle somewhere near the Santee River tonight where
it should remain stalled through Monday. A healthy northeast breeze
around 15 knots with gusts to 20 knots should continue most of the
night as high pressure builds south across New England. Seas 3-5 ft
across the NC waters and 3-4 feet across the SC waters consist of a
mix of 11-second easterly swell from former Tropical Storm Karl and
4-5 second wind waves.


As of 300 PM Sunday...As high pressure moves off the New England
coast Monday and out to sea Tuesday, our synoptic wind direction
will veer from northeasterly Monday morning to southeasterly by
Monday night. Normally it would hold this direction, however it
appears that a weak area of low pressure in the Bahamas will move
north along the Gulf Stream Monday, approaching to within 50-75
miles of Cape Fear Tuesday. Circulation around this feature may turn
our winds back to the northeast for at least the first half of
Tuesday before the southeasterly winds redevelop Tuesday afternoon
or evening. Wind speeds should average 10-15 kt Monday, but lighter
through Tuesday and Tuesday night.


As of 3 PM Sunday...Confidence is very low for the long term. A cold
front driven southward by a cutoff upper low is being handled very
poorly by various models. Solutions range from a somewhat clean
FROPA on Thursday to the front lingering to our west until Saturday
morning. Have trended the forecast towards the slower timing since
models do tend to be gravitating in that direction. While the
current wind direction forecast may be way off given the
uncertainties at least that is some confidence that both wind speeds
and seas will remain quite manageable for most mariners.





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