National Weather Service United States Department of Commerce

 


000
FXUS62 KILM 292020
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
420 PM EDT FRI JUL 29 2016

.SYNOPSIS...
High pressure will continue to bring oppressive heat and humidity
to the region through Saturday. The high will begin to break down
beginning Sunday. A cold front will drop slowly across the area
Tuesday into Wednesday bringing good chances for thunderstorms.
Cooler temperatures will follow for the middle and end of next
week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
As of 330 PM Friday...Latest heat indices remaining running just
below heat advisory levels most places. Drier moderate to strong
westerly downslope winds were keeping sea breeze pinned closer to
the coast with some minor backing to the SW expected through this
afternoon as sea breeze becomes stronger. Therefore dewpoint temps
were running several degrees lower than yesterday at the same time
in places while 850 temps were running below 19c keeping overall
temps a couple of degrees less than yesterday. Therefore, although
it is hot, heat indices will remain just below 105 most of the
day, which is below heat advisory thresholds.

Overall high pressure ridge remains to the southeast and a
Piedmont trough continues to the west. Cu field was developing and
clustering mainly I-95 corridor and west with flatter cu along
sea breeze boundary. Convective indices point to best chc of
convection inland along trough or even farther west toward the
mountains where better upper level support is. Otherwise could
see isolated shwrs/tstms pulse up along sea breeze boundary mainly
from Cape fear northward where best convergence and lift will be
as winds back slightly in response to sea breeze this afternoon.
The westerly steering flow will guide any shwrs/tstms east but
expect them to dissipate as upper level ridging and drier air
remain to the east.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
As of 330 PM Friday...The heat indices will kick back up above
advisory levels once again on Saturday. It appears the atlantic ridge
may push back toward the northwest a bit with heights rising a
bit and 850 temps up a couple of degrees, mainly eastern two
thirds of area. Temps should reach the mid 90s for highs.
Therefore we will once again issue heat advisories mainly I-95
corridor east where dewpoint temps will increase as aftn sea
breeze draws atlantic moisture inland. The main focus for
convection will be along Piedmont trough and along sea breeze
boundary. The overall chance for convection will increase and may
decrease the overall length of heat advisory, but for now, have
issued it from noon to 8 pm. some needed rain and may temper some
of the heat.

By Sunday, Atlantic ridge gets pushed south and east a little
farther as mid to upper trough makes a little headway east. The
fight between the ridge and trough will be tricky in delineating
the area of greater convective potential. Overall expect moisture
to increase through the atmosphere and greater potential for
convection mainly along Piedmont trough inland and sea breeze
boundary. This should also keep temps from reaching heat advisory
criteria with greater amount of clouds and shwrs/tstms. Temps
should reach into the low to mid 90s on Sunday.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 300 PM Friday...Significant airmass change occurs...finally as
the calendar flips to August. The tremendous heat and humidity
through which we have been suffering will persist one last day
Monday with highs in the 90s and high humidity once again, but a
return to seasonable or even slightly below normal temps is forecast
by mid week. The cause of this change is a sharp mid-level trough
driving a cold front through the Carolinas Tuesday and Wednesday.
Guidance is in agreement this front will slow across the area, but
eventually will sink south of the region on Wednesday as the upper
ridge breaks down. Guidance can frequently be too aggressive and
quick with the breakdown of these ridges, so will lean on the slower
solution and dissipate the front Wednesday just south of the area to
blend with inherited, but much cooler temperatures are forecast
Tue/Wed/Thu with a slow return to warmer temperatures possible late
in the period. Along with these cooler temperatures, tstms should
become more numerous Monday night through Wednesday associated with
the fropa, decreasing back to seasonable POP at the end of the
week.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
As of 18Z...VFR through the valid taf cycle. SCT040 in CU/TCU but
upper ridge may suppress VCTS development. Any formation of TSTMS
will be very isolated in scope. Winds W-SW 7-12 KT gusts to 19 KT
between 18z-22z. WSW winds overnight 4-9 KT, increasing aft 15Z
Sat to W-WSW 7g16 KT.

EXTENDED OUTLOOK...Isolated to scattered afternoon convection
Sunday and onward through the forecast will create fleeting and
localized MVFR/IFR. Otherwise expect VFR.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 330 PM Friday...Southwest winds will continue as the
Bermuda High remains suppressed to the south of the coastal
waters. The stronger westerly component to the wind has kept sea
breeze pinned to the coast with winds basically 10 to 15 knots or
less. Seas will continue to run 2 to 3 ft with 4 ft seas
especially 10 miles off the coast with stronger off shore
component.

SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 330 PM Friday...The Bermuda High and Piedmont trough will
continue to be main players with a SW wind 10 to 15 knots through
much of the period. As mid to upper trough pushes a cold front
into North Carolina Sun night the gradient should tighten and
winds will increase to 15 to 20 knots. Seas will remain 2 to 4
feet through the period.

LONG TERM /MONDAY THROUGH WEDNESDAY/...
As of 300 PM Friday...Bermuda high pressure remains dominant one
last day Monday before a mid- level trough drives a slow moving
cold front across the waters through mid-week. This causes a wind
shift, so after 10-15 kts of SW winds on Monday, the gradient
becomes diffuse as the front drops south and weakens, with winds
gradually becoming NE at 5-10 kts by Wednesday. Highest seas will
be Monday with the SE swell and SW wind wave producing 3-4 ft
seas. Wave heights will fall slowly Tuesday, and then down to 2-3
ft Wednesday with a confused spectrum likely as a NE wind wave
develops atop the residual SE swell.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...Heat Advisory from noon to 8 PM EDT Saturday for SCZ032-033-
039-053>056.
NC...Heat Advisory from noon to 8 PM EDT Saturday for NCZ099-
105>110.
MARINE...None.

&&

$$
SYNOPSIS...JDW
NEAR TERM...RGZ
SHORT TERM...RGZ
LONG TERM...JDW
AVIATION...MJC
MARINE...JDW/RGZ