Area NWS Forecast Discussion
FXUS62 KILM 231413

Area Forecast Discussion
National Weather Service Wilmington NC
1013 AM EDT Wed May 23 2018

A weak cold front approaching from the north will produce a
greater coverage of showers and thunderstorms this afternoon
and on Thursday. The front will dissipate over the area on
Friday. Low pressure developing across the Gulf of Mexico will
bring tropical moisture northward and help fuel a higher
probability of showers and thunderstorms with heavy rain across
the eastern Carolinas Sunday and into early next week.



As of 1015 AM Wednesday...showers have developed along a
boundary a this morning from near Conway to Topsail these
showers have decreased in the past half hour. Other showers have
developed in Georgetown and Williamsburg counties and this is
indicative of the very moist and unstable conditions across our
area. With abundant sunshine over most of the area expect
convection coverage to be more widespread than the past few
days. The morning soundings are indicating MLCAPE approaching
2000 J/KG this afternoon. Winds shear is weak and with a front
slowly sinking from the north SPC has shifted their marginal
area of severe thunderstorms to border northern portions of
Robeson, Bladen and Pender counties. Biggest threats appear to
be heavy rain, gusty winds. The convection is expected to
diminish after sunset.


As of 300 AM Wednesday...A weak cold front will be in close
proximity Thu and should become ill-defined to our S by Fri. An
area of high pressure will briefly nose into the area from the
N, moving progressively offshore late in the period. An upper
trough will lift out Thu followed by a building ridge Fri and
Fri night.

Precipitable water values will only drop very modestly as we
move from Thu into Fri with slightly more drying noted later Fri
and Fri night. Given a front will be slowly dissolving across
the area as it struggles to advance southward, it will be
difficult to refrain from including at least some risk for
showers and thunderstorms. Moisture profiles show the moisture
depth decreasing, especially later in the forecast period.

Will show chance to likely POPS Thu and this activity is expected
to lessen significantly or end with nightfall. Then on Fri, will
include mainly slight chance/small chance for convection, mainly
across South Carolina. Expect the convection Fri to be mainly
diurnally driven.

High temps will be near to slightly above normal for late May.
The beaches will be coolest as onshore flow prevents them from
rising above the upper 70s and lower 80s. Lows will be in the
mid 60s to lower 70s.


As of 300 PM Tuesday...A baggy upper level trough across the
lower Mississippi Valley and Gulf of Mexico will become better
defined Saturday and Sunday. Upper ridges building across the
Pacific coast of Mexico and out over the western Atlantic
between the Bahamas and Bermuda will help to spin this feature
up. A surge of Caribbean moisture very similar to what we saw
last weekend will be drawn northward in the deep southerly flow
between this upper trough and the offshore ridge, and this
could lead to another significant rainfall event Sunday into
Monday. The latest WPC QPF outlook for just Sunday and Monday is
around 1.5 inches across our area, with forecast 7-day totals
of 2-3 inches.

Latest models show there will probably be some sort of low
pressure development across the Gulf of Mexico late this week,
but FSU cyclone phase diagrams show only the Canadian
developing a significant warm core aloft. The 12z ECMWF (not
currently part of the FSU website) shows the cyclone keeping a
pronounced gradient in 1000-500 mb thickness above the surface
low, implying subtropical characteristics at best. The GFS is
the farthest east with its low pressure development across
Florida on Sunday, while other guidance is westward. While not
ruling out anything just yet, it`s expected the low will remain
too far west for any direct impacts on the Carolinas, but
enhanced southerly flow should help enhance our rainfall
potential Sunday and Monday when my highest rainfall chances
(50-70 percent) are currently forecast.

A warm day Saturday when there will be more sunshine and lower
shower chances. Highs should reach the mid to upper 80s inland,
several degrees cooler near the coast. Temperatures should top
out in the lower 80s Sunday, and lower to mid 80s Monday and
Tuesday. Lows in the upper 60s to lower 70s through the period
are evidence of the tropical airmass we`ll have in place.


As of 12Z...Fog/IFR/MVFR cigs will improve to VFR 12-14Z, with only
a brief MVFR cig possible the remainder of the morning. An upper
impulse will move across the terminals today. Mostly showers,
with possibly an isolated thunderstorm, is expected mid-morning
to mid afternoon at the inland terminals, and in the afternoon
at the coastal terminals. Will maintain VFR in TAFs attm
although tempo periods of MVFR possible with the showers. Since
thunderstorms will be isolated any IFR will be very very brief.

This evening models showing convection ahead of a cold front
moving south and affecting the KILM/KLBT terminals around 04Z
and the southern terminals 06Z. Confidence is higher this will
be the better shot at tempo thunderstorms and sub-VFR. After
activity dissipates there is moderate confidence MVFR/IFR with
BR/stratus will develop. Confidence of timing/duration is low.
Low cigs could persist through mid-morning with N-NE winds
Thursday morning.

Extended Outlook...Potential for MVFR/tempo IFR/Thunderstorms
southwest terminals Thu aftn/evng. will increase late Wed/Thur as a
cold front drops across the area and again during the weekend as
tropical moisture returns.


As of 1015 AM Wednesday...Currently winds of 10 to 15 knots at
the buoys this morning with seas running from 2 to 4 feet over
the coastal waters. As a front approaches from the north winds
are expected to increase to 15 to 20 knots this evening and
overnight. Significant seas remain in a 2-4 foot range with a
southeast swell.

As of 300 AM Wednesday...A weak cold front will be in close
proximity Thu and should become ill-defined to our S by Fri. An
area of high pressure will briefly nose into the area from the
N, moving progressively offshore late in the period.

The wind direction Thu will shift from W and NW early to easterly.
Easterly winds will then hold into Fri before veering to SE Fri
afternoon and S fri night. Wind speeds will be no higher than
around 10 kt through the period. Seas will be 2 to 3 ft. A SE
swell should gradually build across the waters late in the

As of 300 PM Tuesday...Bermuda high pressure will remain well
off the Southeast coast this weekend. By itself it would provide
a gentle southerly wind and typical summertime weather. However
models over the past few days have been showing the potential
for a tropical or subtropical cyclone to develop across the Gulf
of Mexico by Saturday. The GFS is the farthest east of any of
the models with its latest run showing a low reaching Florida
on Sunday, while the ECMWF and Canadian are farther west. While
it`s too early to completely rule out impacts, our latest
forecast has south winds increasing to around 15 kt Sunday, with
a lengthening fetch of stronger winds extending down into the
Bahamas. This could build seas up toward 6 feet, assuming our
wind forecast is correct.





NWS ILM Office Area Forecast Discussion