Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 231453
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
1053 AM EDT Sun Jul 23 2017

.SYNOPSIS...
A Heat Advisory remains in effect today. A cold front will
approach from the north and may slip into the area mid week
before stalling and then dissipating during Thursday. Showers
and thunderstorms with heavy rain will increase in coverage
Monday through Wednesday and this will serve to knock down the
heat although the high humidity will remain. Drier air may
briefly work into the area Thursday, but the arrival of a
stronger cold front will bring more thunderstorms by the
weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1050 AM Sunday...Strong insolation across the area this
morning has allowed temperatures to climb into the upper 80s at
several locations thus far. Heat indices will be problematic,
especially during the afternoon given the hot temperatures expected
with dewpoints in the mid to upper 70s. No changes planned to the
Heat Advisory that is currently in effect. The mid-level subtropical
ridge has become pinched across the Carolinas with a mid/upper low
off the GA coast and a band of westerlies from the Ohio valley to
the Mid-Atlantic Region. Thermally the column is similar to
yesterday however the precipitable water has increased. Think the
sea breeze will be a little more active during the day, and the
Piedmont trough will serve as a lifting mechanism as well. Any
severe weather should remain north of the forecast area, closer to
the belt of westerlies an main track of impulses aloft. Stronger low-
level winds will result in gusty winds, especially at the coastal
areas and the onshore wind will provide some relief at the immediate
coast, especially the south facing beaches. Enough southwesterly
wind tonight will keep low temperatures in the upper 70s for many
areas tonight. Lastly, new moon tides will likely result in the
issuance of another Coastal Flood Advisory for downtown Wilmington
for high tide tonight.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 300 AM Sunday...This forecast period will be marked by
increasing shower and thunderstorm coverage. The hot ridge will
have retrograded back to the Southern Plains while the Bermuda
ridge remains offshore and suppressed to our S. This will allow
an east coast trough to dig which will coax a surface cold front
slowly southward. The front should be in close proximity by Tue
morning and will likely stall overhead by Wed. In addition, the
Piedmont Trough is expected to be displaced further E. This
scenario should allow for a likelihood of showers and
thunderstorms. These thunderstorms will be enhanced by mid-level
short wave troughs. Currently models are showing one of these
upper level impulses will move across the area Mon afternoon and
eve and another Tue afternoon and night. The later impulse may
actually close off across the Carolinas and linger. Rainfall
rates should be very high given precipitable water values will
be on the order of 2.25 inches or higher for much of the period.
Excessive rainfall is certainly possible given slow storm
motions and the expectation that cells will train along the
front. Rainfall amounts could easily reach 2 to 3 inches across
a majority of the area during this time with more rainfall
possible on Wed as well.

The clouds and widespread and significant rainfall will knock
down high temps, but the high humidity will remain. Highs both
days will be around 90, averaging just above 90 on Mon and just
below 90 on Tue. Heat index values will be in the 100 to 105
degree range Mon and around 100 Tue. Lows will be in the muggy
lower to mid 70s.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 300 PM Saturday...The upper air pattern will transition
to a cooler pattern for the eastern U.S. next week.

The upper ridge will retrograde to the Four Corners region by
Saturday. A downstream trough will develop along the East Coast,
enhanced by a shortwave that almost cuts off across the
Carolinas mid week, and a progressive shortwave that moves
through New England Friday.

At the surface, low pressure should sink down to coastal South
Carolina by Wednesday night. This will drag a weak cold front
down from the north. While yesterday`s ECMWF kept the front
across central North Carolina, today`s run is in agreement with
the GFS that the front will sink all the way down into the
Charleston, SC area. With low-level convergence focused along
the front and cooler upper-air conditions with the disturbance
aloft, expect thunderstorms to be fairly widespread into Wed.
There is the potential we`ll see 1-3 inches of rain area-wide.

As the upper disturbance kicks offshore Thursday afternoon
and drier mid-level air bleeds in from the west, the surface
front should dissipate. Friday should be the warmest day in the
extended period with highs popping back into the lower 90s and
heat indices over 100 degrees again. By Saturday, the GFS and
ECMWF are in surprisingly good agreement that a stronger cold
front will dive southward and into area, with another
enhancement in the potential of thunderstorms.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
As of 12Z...VFR conditions are expected. At KLBT, included
tempo MVFR in thunderstorms 23-03z as this terminal will be
closest to organized convection to our N which will tend to
shift southward toward KLBT late afternoon and tonight ahead of
a slowly sagging cold front. Otherwise, convection should be
diurnally driven and there should be isolated to perhaps widely
scattered showers and thunderstorms developing along the
Piedmont Trough and perhaps the seabreeze. The probability for
one of these cells to result in flight restrictions at any one
terminal this afternoon/early eve is too remote for inclusion in
the TAF at this time. Wind gusts up to 15 to 25 kt, strongest
this afternoon and early eve, are expected at KCRE and KMYR and
to a lesser extent at KILM due to the seabreeze circulation.
Winds will tend to stay elevated at the terminals tonight due
to modest low level jetting.

Extended Outlook...MVFR/IFR possible in showers and
thunderstorms Mon through Wed.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 1050 AM Sunday...Small Craft Should Exercise Caution
headline will continue as is given the southwesterly fetch in
place across the adjacent coastal waters. The fetch will likely
lead to steep conditions given the wave height and periods in
the 5-6 second range. The gradient between the Bermuda High and
the inland trough will remain in place through tonight.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 300 AM Sunday...A cold front will sag south and be in
close proximity Tue and may stall overhead Tue night or Wed. The
eastward displaced Piedmont Trough will serve to keep a rather
tight pressure gradient in place and this will keep sustained
southwest winds near 20 kt Mon and Mon eve. As the cold front
gains proximity late Mon night and through the remainder of the
period, wind speeds will decrease to no higher than 10 to 15 kt
with 10 kt or less by late Tue night as the wind direction
becomes variable. Seas will be 4 to 5 ft through the first half
of the forecast period, subsiding to 3 ft or less during Tue
and Tue night. Thunderstorms will be increasing across the
waters during this time and mariners should expect poor
visibility in very heavy rain along with locally higher winds
and seas.

LONG TERM /WEDNESDAY THROUGH THURSDAY/...
As of 300 PM Saturday...A cold front will become increasingly
ill-defined on Wednesday, and by Thursday afternoon should wash
out as southwesterly winds increase ahead of a stronger front
that should affect the area next weekend.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...Heat Advisory from 11 AM this morning to 7 PM EDT this evening
     for SCZ017-023-024-032-033-039-053>056.
NC...Heat Advisory from 11 AM this morning to 7 PM EDT this evening
     for NCZ087-096-099-105>110.
     High Rip Current Risk through this evening for NCZ110.
MARINE...None.

&&

$$

NEAR TERM...III
SHORT TERM...RJD
LONG TERM...TRA
AVIATION...RJD


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