Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 232253
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
653 PM EDT Sat Jun 23 2018

.SYNOPSIS...
Hot and humid weather with isolated thunderstorms will continue
through Monday. Heat advisories are in effect Sunday, and are
possible Monday. A cold front will cross the area late Monday
and Tuesday bringing a good chance for showers and thunderstorms
and a relief from the heat through Thursday. Temperatures will
rebound to above normal again by next Friday but with good
chances for showers and thunderstorms.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 700 PM Saturday...A 300 mb jet streak probably helped
support a modest line of convection across the Cape Fear region
earlier this afternoon. This feature is now off the coast, and
a capped marine airmass wasn`t able to support the storms
anyway.

A cluster of showers and storms across eastern SC is also drying
up as it approaches the Santee River. I`ve maintained a 20 PoP
in the Georgetown, SC area for the next couple of hours,
otherwise I`m forecasting dry weather overnight. A southwesterly
low level jet should again keep the hot boundary layer mixed,
and similarly to last night lows should range from 75 degrees
west of I-95 to around 80 on the beaches. Minor edits have also
been made to PoPs for Sunday, dropping them into the 20-30
percent range given the magnitude of dry air aloft anticipated
to move across the area.
-TRA

Discussion from 300 PM follows...
An MCV should drive convection across eastern Georgia and
southern South Carolina through mid eve. Ongoing convection has
been fairly shallow owing largely to the amount of dry air in
the mid levels, but a few strong thunderstorms are still
possible late this afternoon across our FA. Will follow the
guidance offered by the high resolution models in keeping the
convection mainly isolated with an emphasis across the Cape Fear
area as a mid- level shortwave skirts the area as it moves off
the Mid-Atlantic late this eve. Will also keep the previous
trend with the risk for convection dwindling with loss of
heating as a mid-level shortwave pivots offshore of the Mid-
Atlantic states. Lows tonight will be in the muggy mid and upper
70s and a few spots will struggle to get as low as 80 degrees.

A Heat Advisory is in effect for Sun with heat index values mainly
in the range of 105 to 109 degrees. A few spotty 110 values are
possible. Highs will be in the mid and upper 90s and 100 degrees is
possible, especially across inland areas. A flat 500 mb ridge will
promote subsidence and downslope flow which will keep the seabreeze
pinned, allowing even the beaches to reach into the lower and mid
90s. Given the abundance of heat and humidity, expect isolated to
perhaps scattered showers and thunderstorms to develop with an
emphasis for later afternoon Sun and Sun night as the thunderstorms
struggle to overcome the drier air in the mid levels. The Piedmont
trough and seabreeze should be areas where convection initiates.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 300 PM Saturday...Bermuda high and flattening mid-level ridge
will hold on into Mon. A mid-level shortwave is expected to move
across the area Sun night and this trough will help push the
Piedmont trough to the coast. Stronger upper level support is
expected to arrive late Mon and Mon night. A cold front will slowly
sag S and should move into the FA Mon night and it is possible it
will be as far south as the South Santee River during the early
morning hours of Tue as a 500 mb trough exits the Northeast states.

Precipitable water values are forecast to be near or in excess of
2.25 inches Sun night and Mon and instability is expected to be high
with mixed layer CAPE values in excess of 3000 J/kg. For this
reason, we have raised POPs to the likely category Mon and Mon night
and show POPs trending higher Sun night as a cluster of
thunderstorms should reach the area during the eve. POPs may need to
be boosted with later issuances as timing details are ironed out
given the ingredients for a widespread and perhaps significant
rainfall event seem to be coming together.

Clouds and convection Mon should allow temps to back off as
compared to Sun and we are currently forecasting mainly lower and
mid 90s. However, given the high dewpoints, at least some of the
area may again require a Heat Advisory. Lows Sun night will be in
the mid and upper 70s. Lows Mon night should be slightly lower,
mainly mid 70s with perhaps a few lower 70s in rain cooled
environment.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 300 PM Saturday...Cold front will be meandering to the south
early on Tuesday before washing out closer to the Gulf Coast on
Wednesday. This will bring a reprieve from the heat and humidity,
but will also feature good shower and tstm chances, especially
Tuesday during FROPA. This front will be followed by Canadian high
pressure bringing much cooler temperatures and lower humidity during
Wednesday. This will also bring lower convective potential
Wednesday, and continuing into Thursday as the high begins to
rebuild both at the surface and aloft. Thursday is interesting
because the guidance shows a weak surface low trying to develop
along a remnant trough just offshore in response to PVA associated
with one final shortwave drifting across the SE. While low pressure
development seems plausible, most of the precip will likely remain
offshore and will keep POP low Thursday despite this development.

This ridge will expand across the eastern CONUS into next weekend,
but the orientation is progged to drive the highest heat to our
north, keeping the Carolinas warm and humid but unsettled as onshore
flow becomes entrenched and PWATs climb to well above 2 inches
again. Will show temps climbing back to above normal along with
above climo precip chances Friday and Saturday.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 00Z...VFR conditions should continue through at least 16Z
on Sunday, before isolated showers and t-storms develop during
the heat of the day. Coverage should average only 20-30 percent
during the 16-23Z timeframe. Southwest surface winds could
exceed 15 knots along the coast with Sunday afternoon`s
seabreeze.

Extended Outlook...Mostly VFR. Mainly afternoon showers and
thunderstorms each day with short duration flight category
restrictions possible. A cold front will bring a higher
probability for showers and thunderstorms Monday into Tuesday.

&&

.MARINE...
NEAR TERM /THROUGH SUNDAY/...
As of 700 PM Saturday...Breezy winds gusting up to 25 knots
across the entire marine area should continue overnight away
from shore even after the seabreeze dies away. Latest buoy
reports agree closely with our forecast sea heights, and no
significant changes are being made to the forecast with this
early evening update. Discussion from 300 PM follows...

Nocturnal jetting on the order of 30 kt at 1500 ft will keep
winds elevated tonight, mainly 15 to 20 kt. A robust seabreeze
circulation and inland trough will allow winds to peak in the 15
to 20 kt range during the afternoon. Seas will be 3 to 4 ft
with a few 5 ft seas possible across the outermost waters.

SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 300 PM Saturday...SW winds will dominate Sun and through Mon
eve with winds then shifting to NE and NNE late Mon night and Tue
morning in the wake of a cold front sagging across the waters from N
to S. Wind speeds will be mainly 15 to 20 kt Sun night with
nocturnal jetting in place. Wind speeds Mon should be slightly
lower, mainly 10 to 15 kt. Wind speeds will lower to 10 kt or less
late Mon night. Seas will be 3 to 4 ft Sun night with perhaps some 5
ft seas observed, mainly across the outermost waters. Seas on Mon
should be closer to 3 ft with 2 to 3 ft seas currently forecast late
Mon night. Of course winds and seas will be stronger in
thunderstorms which will be numerous, especially Mon night.

LONG TERM /TUESDAY THROUGH THURSDAY/...
As of 300 PM Saturday...NE winds will surge behind a cold front
Tuesday to 10-15 kts before veering slowly to the east through
nightfall. High pressure will ridge into the region Wednesday but
maintain its ridge axis to the north. This will keep winds from the
E on Wednesday before the high pushes away turning winds to the S at
the end of the period. Wind speeds Wed/Thu will be around 10 kts.
Wave heights will be generally 2-4 ft through the period, with a NE
wind wave giving way to a E/SE wind wave and swell later in the
week.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...Heat Advisory from 11 AM to 8 PM EDT Sunday for SCZ017-023-024-
     032-033-039-054>056-058-059.
     Beach Hazards Statement until 8 PM EDT this evening for SCZ054-
     056.
NC...Heat Advisory from 11 AM to 8 PM EDT Sunday for NCZ087-096-099-
     105>110.
     Beach Hazards Statement until 8 PM EDT this evening for NCZ106-
     108.
MARINE...None.

&&

$$

SYNOPSIS...JDW
NEAR TERM...RJD/TRA
SHORT TERM...RJD
LONG TERM...JDW
AVIATION...TRA



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