Area Forecast Discussion
Issued by NWS Wilmington, NC

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147
FXUS62 KILM 212221
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
621 PM EDT Mon May 21 2018

.SYNOPSIS...
Isolated to scattered showers and thunderstorms will become more
numerous by the middle of the week as a cold front sags into the
area from the north before slowly dissipating Friday. The upcoming
holiday weekend looks unsettled as a tropical airmass brings the
likelihood for showers and thunderstorms and possibly more heavy
rain.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 300 PM Monday...The deep tropical moisture plume responsible
for at many days of clouds and wet weather has temporarily shifted
westward, leaving the eastern Carolinas with just some scattered
showers today along the seabreeze front. The upper level ridge
supporting the Bermuda high offshore is responsible for allowing the
drier mid level air to advect across the area from the southeast.
Models show deeper moisture may start to return as soon as late
tomorrow afternoon across the Pee Dee region of South Carolina as a
trough moving across the Great Lakes knocks upper level heights down
and allows a westerly veering of the 700-500 mb flow to develop.

Today`s scattered showers should die away this evening from south to
north as the core of the drier mid-level airmass advects onshore.
Model-computed precipitable water values fall to 1.0 to 1.2 inches
tonight, a far cry from the 2.0 inch values we had over the weekend.
PW could return to 1.5 to 1.7 inches tomorrow afternoon along I-95,
and a chance of showers is back in the forecast accordingly.

Lows tonight should range from the upper 60s inland to around 70 on
the beaches. Some fog could even develop late tonight as winds
become light. GFS MOS has been running consistently too warm for
highs, so our forecast for Tuesday is much closer to a NAM/ECMWF
consensus: mid 80s inland with lower 80s near the coast.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 300 PM Monday...A northwest flow will be in place by the end
of the period after a transition from somewhat weak ridging. This
flow will allow a weak backdoor cold front to move across the area
at least briefly. Precipitable water values will have recovered
nicely especially by Wednesday afternoon and with good sea breeze
convergence and some distant forcing from the approaching front
likely pops remain in place. For overnight Tuesday and Wednesday
there will be a smattering of activity as well. Essentially no
changes to the temperature forecast.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 300 PM Monday...A brief break in the pattern is forecast Thu
into early Fri as a mid-level trough digs into New England driving a
surface cold front into the area. This front will stall over the
area Thursday and dissipate into Friday.  While scattered showers
and storms will remain possible Thu and Friday, it is possible that
northern areas of the FA will get a break from the showers and
storms and may see a little lower humidity for about 24 hours.

As southerly flow returns to the area Friday into the weekend,
shower and storm chances will ramp back up again for the holiday
weekend.  Temperatures through the extended range will remain in the
lower to middle 80s by day and upper 60s to lower 70s at night.

&&

.AVIATION /00Z TUESDAY THROUGH FRIDAY/...
As of 00Z...The two main concerns this TAF period will be possible
patchy dense fog, and possible convection on Tuesday in the
afternoon at the inland terminals. Moisture profiles look favorable
for fog, particularly inland, although CRE may get into the act. The
winds at the boundary layer are marginally favorable. Tuesday,
another summer like day with cu forming along the sea breeze by
midday. Some isolated convection is possible, but for the coastal
terminals the window will be small, say from 17-19Z. The best chance
for convection will be at the inland terminals as the next system
approaches. CAPES should be favorable for thunderstorms after 18Z.

Extended Outlook...MVFR and possibly IFR conditions will increase
late Wednesday into Thursday as a cold front drops across the
area.

&&

.MARINE...
NEAR TERM /THROUGH TUESDAY/...
As of 300 PM Monday...Bermuda high pressure well offshore is
extending a ridge axis westward toward the South Carolina coast. A
front stalled across the North Carolina/Virginia border should move
north and farther away from the Carolinas tomorrow, allowing modest
southwesterly winds to continue. Isolated showers should end quickly
this afternoon as the seabreeze moves inland from the coast, but
isolated showers are possible again Tuesday morning into the early
afternoon hours.

Although there is certainly a small wind wave out there, the
majority of our wave energy is due to an 8-second southeasterly
swell measured at 4 feet at Frying Pan Shoals buoy. This swell
should continue into Tuesday.

SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 300 PM Monday...For the most part a south to southwest flow of
10-15 knots will continue across the waters. There is a wind shift
very late in the period to a weak offshore flow via a front or what
is probably an outflow pushing offshore. As usual this time of year
the push will be rather weak and fleeting. Significant seas will be
2-4 feet.

LONG TERM /THURSDAY THROUGH SATURDAY/...
As of 300 PM Monday...A cold front will briefly turn winds to the
W/NW Thu before the gradient eases considerably as the front wavers
and then dissipates across the area into Fri. This brings a period
of light and variable winds Thu before E-SE winds develop late Thu
into Fri with a turn to the south Saturday. Winds look to be 15 KT
or less with seas of 2 to 3 feet through the period.

&&

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

&&

$$

SYNOPSIS...
NEAR TERM...TRA
SHORT TERM...SHK
LONG TERM...31
AVIATION...43



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