Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 250712

Area Forecast Discussion
National Weather Service Wilmington NC
312 AM EDT Mon Sep 25 2023

Summerlike temperatures will last only a couple more days. A
cold front on Tuesday will bring breezy northeast winds and
cooler temperatures in for the remainder of the week as high
pressure over Canada builds southward. Spotty showers will
become possible behind the front, especially near the coast.


Quiet conditions will continue through the near term period as
the area remains under the influence of a modest west to
southwest flow aloft. At the surface a weak pressure pattern
will continue with a back door cold front approaching the area
Tuesday morning. There may be some patchy fog later this morning
and again Tuesday morning but that`s about it from a moisture
standpoint. Temperatures will be a little on the warm side of
climatology with today`s highs in the middle to perhaps upper
80s and middle 60s for Tuesday lows.


1036 mb high pressure across Quebec will push a cold front
southward across the eastern Carolinas on Tuesday. Compared to
yesterday`s models, the new 00z guidance is a good 6 hours
slower with the arrival of this front, now implying a delay of
the wind shift into Tuesday morning. For this reason I`ve bumped
forecast highs up several degrees with mid 80s now expected for
most locations. I wouldn`t be surprised to see some upper 80s
Tuesday afternoon near and south of Florence. Models are
getting extremely hard to beat consistently but one of the
errors they seem to still make is overestimating the impact of
cool advection during a sunny daytime frontal passage.

Frontal and seabreeze low level convergence near and south of
Cape Fear within a region of 500-1000 J/kg CAPE could develop
isolated showers or t-storms Tuesday afternoon. No real changes
have been made to PoPs here with only a 20 percent chance in
the forecast.

The incoming cooler, drier airmass will finally win Tuesday
evening as temperatures slip into the lower 60s for most areas
by Wednesday morning. Forecast soundings show the cold air will
only extend about 3500-4000 feet deep, with a frontal inversion
evident aloft.


The upper level pattern will become very amplified this weekend
as a ridge builds up the Mississippi Valley and across the
Great Lakes while troughs deepen both upstream and downstream of
the ridge. The GFS and ECMWF are in general agreement with the
shape of the upper flow, but differ enough with details that
confidence is not especially high.

Tuesday`s surface front should advance southward across Florida
Wednesday through Friday with steady northeasterly winds
continuing between it and a large area of high pressure over
Quebec. Shortwave energy spilling southward downstream of the
upper ridge may induce low pressure to form across the western
Atlantic, but each model run shows a very different position.
Humid Gulf air riding up and over the stalled front across
Florida will maintain plenty of mid level moisture across the
Carolinas, but clouds and precipitation are less certain given
negligible lift within the moisture-bearing layer. The course
of least regret is to include 20-30 percent daily chances for
showers Wednesday through Friday, highest near the coast.
Yesterday`s 12z ECMWF was by far the wettest model, but its 00z
run has dried out considerably and looks more like the 00z GFS
and Canadian now.

Breezy northeasterly winds gusting to 25 mph will continue into
the weekend. Highs in the upper 70s and lows 60-65 are


A very weak pressure pattern resides over the area with a weak
stationary front to the north. VFR is currently being observed
but conditions appear somewhat favorable for fog development
especially inland. Guidance is of course split and opted for
MVFR prevailing inland for a handful of hours beginning at 0800
UTC as a compromise for now.

Extended Outlook...VFR conditions to dominate through the
period. Exception will be possible early morning flight
restrictions from fog Mon and Tue. MVFR conditions possible by
midweek as a wedge of high pressure sets up across the interior
Carolinas along with weak low pressure off the Coast.


Through Tonight...Benign conditions will continue across the
coastal waters through the near term period. Winds will be primarily
from the southwest hovering around ten knots. Significant seas will
be 2-3 feet.

Tuesday through Friday...Models continue to show a cold front
advancing southward along the Carolina coast Tuesday. Predicted
timing of the frontal passage has slowed by a good 6 hours
versus yesterday, and it now appears northeasterly winds won`t
reach Cape Fear until sunrise and the Grand Strand area until late
Tuesday morning. The front is still expected to sink well south
of the area Tuesday night into Wednesday. High pressure
centered across Quebec will build southward along the U.S. East
Coast, maintaining breezy northeast winds through Friday.
Although Small Craft Advisory conditions are not currently in
the forecast, by no means is fair weather expected. Wind speeds
of 15 to 20 knots and choppy seas of 3-5 feet will be the rule
Wednesday through Friday.





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