Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 200157

Area Forecast Discussion
National Weather Service Wilmington NC
957 PM EDT Mon Mar 19 2018

Low pressure will move east toward the Carolinas on Tuesday, dragging
a cold front through Tuesday night as it tracks northeast and
deepens off the North Carolina coast. Possible strong to severe
thunderstorms will occur ahead of the low on Tuesday with
potential for a few flurries in the mix as colder air moves in
on the back end on Wednesday. Cold and dry high pressure will
extend down into the Carolinas Thursday and Friday. The weekend
may become unsettled and remain cooler, with clouds and periods
of rain possibly through early next week.


As of 930 PM Monday...01Z surface analysis show low pressure
centered over middle TN and north-central AL, with a warm front
extending to just south of Charleston, SC. The low will track
east-northeast through the remainder of the overnight, as the
warm front lifts north. Showers and thunderstorms associated
with the surface low will track across the forecast area between
09Z-12Z, and although they should be weakening with diminishing
upper support, the presence of shear along the warm front will
necessitate a close watch for potential rotation.

After a lull in activity in the 12Z-18Z window, a vigorous mid-
level trough and associated surface cold front will approach
from the west in the afternoon and evening hours Tuesday. This
will give the atmosphere an opportunity to destabilize, with
surface-based CAPE values reaching 1500-2000 j/kg. SPC has
included the CWA in an slight to enhanced risk of severe storms
for Tuesday afternoon, noting the possibility of a few
tornadoes considering the amount of low-level wind shear.


As of 300 PM Monday...Complex storm system will be exiting the
area albeit slowly through the period. The latest guidance has
shown a considerable drying trend with precipiation through the
period. It appears the mid level cyclone will just be pulling in
too much dry air to allow any significant showers to develop.
Overall I have trended pops down through the period.
Temperature guidance continues to show some differences but in
general maintained a blend.


As of 300 PM Sunday...Although I would not discount a few
flurries as potent shortwave swings through the back end of the
upper trough early Thurs, the moisture will be very limited.
Therefore will not include any pcp in forecast early Thurs
morning as upper trough swings off the coast. CAA continues
through Thurs into Friday in strong NW flow as high pressure
builds in from the north. The 850 temps drop down around -4c and
do not return above 0c until Sat. Temps will drop into the 30s
most places with some frost or freeze potential in spots again
early Fri morning. Temps both Thurs and Fri may not reach above
60. Low pressure system will brush the Carolinas Fri night into
Sat as it moves toward the Mid Atlantic coast. This will produce
increase in clouds and greater chc of rain across the area late
Fri into early Sat. The latest model runs show a possible wedge
type scenario setting up for the weekend with clouds and periods
of rain possible. Overall, the weather may turn out to be cooler
and more unsettled than originally forecast.


As of 23Z...The next 24 hours should be a roller coaster, especially
for the coast. The first batch of convection will be associated with
the warm front which will move through the region through the
overnight hours. The HRRR model has some pretty rigorous convection
hitting the western CWA around 08Z, rolling to the coast by 10Z.
Gusty southwest winds and brief IFR visibilities in heavy showers
are possible. Thunder can not be ruled out, but the convection will
likely weaken as it nears the coast.

Tuesday, a possible wild day in store as the cold front approaches
from the west. The convection will be strongest near the coast, as
it will have the best moisture and possible sea breeze interaction.
Strong thunderstorms are possible as we are in a favorable region
for convection with strong shear, with moderate cape and helicity.

Extended outlook...Periods of MVFR/IFR through Wednesday.


As of 930 PM Monday...A weak pressure gradient is in place
across the waters this evening on the north side of a warm
front, which will progress north overnight. Winds will remain
light, generally 10 knots or less, and mainly east-southeast
until the front lifts through after midnight. At that point,
winds will become south to southwest and increase to 15 knots,
and shower and thunderstorm activity is expected to be moving
off the coast in the few hours before sunrise.

Conditions will deteriorate Tuesday, as SW winds pick-up ahead
of a cold front. An advisory may not be needed but a few lines
of showers, and even strong TSTMS could impact the 0-20 NM
waters Tuesday morning, and again in the afternoon. Mariners can
expect SW gusts near 20 kt Tuesday, outside of showers and
TSTMS. Seas will build to 3-5 ft Tuesday afternoon, and an
`Exercise Caution` headline may be needed. A radar update is
recommended before venturing out, as some storms may become
capable of gusts in excess of 35 kt Tuesday morning and again in
the afternoon.

As of 300 PM Monday...Expect a rough and tumble period for the marine
community. A complex storm system will be exiting the area with
initially gusty southwest winds. The winds will shift to northwest
by Wednesday evening but the speeds will remain elevated in a 20-25
knot range. Some guidance is showing higher winds and subsequent
shifts may need to increase the wind forecast with gales a
possibility. Not surprisingly considering the winds,  seas are
expected to be high from 4-8 feet with the higher values across the
outer waters.

As of 300 PM Monday...Cold and dry high pressure will extend
down over the local waters Thurs through Saturday. Strong off
shore flow up to 15 to 20 kts early Thurs will weaken and become
more northerly through the period down to 10 kt or less by Sat.
This will allow seas to subside from close to 3 to 5 ft early
Thursday down less than 3 ft by Fri aftn into Sat.





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