Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 240459
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
1259 AM EDT SUN JUL 24 2016

.SYNOPSIS...
A ridge of high pressure will expand across the Carolinas bringing
increasingly hot and humid conditions through the weekend and
much of next week. Isolated showers and thunderstorms are possible
each afternoon, and heat advisories will likely be needed each day
beginning Sunday.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
As of 1 AM Sunday...No changes to the forecast with the latest
update. Previous discussion follows:

A hot subtropical ridge is centered near Memphis, TN and extends
back into Texas while the Bermuda ridge is well offshore. As upper
level heights continue to rise across West Virginia our steering
flow is turning more northeasterly since we are south of the ridge
axis. This was apparent with this evening`s thunderstorms which
tended to move slowly toward the southwest when they weren`t
following boundary collisions. These storms formed within a
moderately unstable environment with weak shear but rich low-level
moisture. The strongest cell of the night near Fairmont in Robeson
County, NC displayed some interesting radar velocity signatures
prompting a Special Weather Statement for possible 50 mph winds.
Radar rainfall estimated were up to 3.7 inches in southern Robeson
County. No reports were received from the public.

Unlike last night there are no identifiable upper impulses to help
sustain or redevelop convection overnight. In fact temperatures
should warm at the 700 and 500 mb levels by about a degree C
overnight which will help stabilize things further. With the
evening convection now pretty much done, the only reason I can
find to maintain any mention of rain in the overnight forecast is
as the landbreeze pushes off the coast it may be able to develop a
few showers or t-storms offshore. Steering flow will tend to push
any developing cells back toward the southwest which means the
coast of South Carolina could see some activity very late tonight.
I`m holding pops at only 20 percent for now, redeveloping between
4-6 AM.

Very few changes have been made to the rest of the forecast. Lows
should fall into the mid 70s for most locations, perhaps a little
cooler where rain fell earlier and winds have gone calm.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH MONDAY NIGHT/...
AS OF 330 PM SATURDAY...Hot and dry will be the rule beginning
Sunday as a massive ridge of high pressure envelops much of the
southern tier of the CONUS. Although the ridge itself does not have
tremendous latitudinal amplitude, it is quite strong and 1000-500mb
thicknesses rise towards 580dm Sunday and Monday, with heights
climbing towards 595dm directly overhead the Carolinas by Monday
aftn. At the same time, 1000-850mb thicknesses approach 1435m,
fueling 850mb temps around 20C.

This ridge suppresses a weak mid-level low to the SW, moving overhead
Florida late Sunday, with easterly flow developing through all but
the lowest 100-150mb of the column. Typically this is a moistening
flow direction, but in this case trajectories originate from a dry
air mass offshore, and PWATs drop towards the bottom quartile for
late July by Monday. At the surface, return flow prevails however, so
ample sunshine combined with warm/moist flow and bulging thicknesses
aloft will create hot and humid conditions but with very few tstms.
Highs Sunday will rise well into the 90s, with mid 90s expected
inland and around 90 at the beaches. On Monday, temps will be just a
bit cooler thanks to the aforementioned upper low causing slightly
reduced thicknesses, but will still rise into the low 90s. These
hot temps combined with dewpoints climbing back into the low/mid
70s, will necessitate a heat advisory for Sunday, and one has been
issued, valid from 11am to 8pm, for all zones. Slightly cooler
temps and and lower dewpoints Monday will keep heat index values
just below advisory thresholds. Mins both nights will be well above
climo, mid and upr 70s.

While the airmass will be very unstable this period, convection will
be isolated at best, thanks to increasingly dry air aloft and
warming mid-level temps. Although 500mb and 850mb temps drop a bit
on Monday, the airmass dries even further, so will cap POP at SCHC
Sunday and Monday, with the highest values along the sea breeze in
SC.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 330 PM SATURDAY...Overall medium range guidance is pointing
to strong mid level ridging, on the order of 594DM Tuesday into
Wednesday. Heights slowly fall from that point onward through the
remainder of the period. Other than the Piedmont trough, still not
much in the way of forcing for convection. Certainly subtle mid
level features will help to kick off activity but all but
impossible to pinpoint at this time. The forecst of slowly
increasing pops still looks good with the best chance Thursday
when PWs jump to just over two inches. No changes to the
temperature forecast.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
As of 00Z...Synoptically, little has changed over the past week.
Convection will wind down this evening. The HRRR has some weak
convection toward morning near the coast. Do not really see the
impetus for this. Sunday, any isolated convection will form first on
the sea breeze resultant, with a secondary region along the thermal
trough. Predominately southerly flow.

EXTENDED OUTLOOK...Isolated to scattered afternoon convection
Tuesday through Thursday may create periods of MVFR/IFR.
Otherwise expect VFR.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 1 AM Sunday...No changes to the forecast with the latest
update. Previous discussion follows:

Bermuda High Pressure well offshore is maintaining southwesterly
winds across the Carolinas at 10-15 knots. This is the
climatologically typical pattern for mid summer. Winds should veer
a little more westerly overnight as a weak landbreeze forms. The
latest several HRRR model runs suggest the landbreeze front could
ignite a few showers or t-storms late tonight, especially south of
Cape Fear. Steering winds would tend to push whatever showers
might develop toward the southwest. Seas are only 2 feet with
dominant 8-9 second periods.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 330 PM SATURDAY...Bermuda ridging will remain the most
influential feature through the short term, creating consistent wind
and wave conditions. SW winds will prevail both days, with speeds
increasing from around 10 kts Sunday, to 10-15 kts on Monday. A
persistent but weak 2ft/8sec SE swell will exist in the spectrum,
but avg wave periods will gradually shorten as a SW 4-5 sec wave
amplifies. Wave heights will be 2-3 ft through Monday, becoming more
uniformly 3 ft late.

LONG TERM /TUESDAY THROUGH THURSDAY/...
AS OF 330 PM SATURDAY...Expect south to southwest winds of 10-15 knots
through the period as the Bermuda Azores high pressure system and
the Piedmont trough are the main drivers of winds. Significant seas
will be 1-3 feet with wave periods mostly confined to shorter period
wind waves.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...Heat Advisory from 11 AM this morning to 8 PM EDT this evening
     for SCZ017-023-024-032-033-039-053>056.
NC...Heat Advisory from 11 AM this morning to 8 PM EDT this evening
     for NCZ087-096-099-105>110.
MARINE...None.

&&

$$

SYNOPSIS...SHK
NEAR TERM...REK/TRA
SHORT TERM...JDW
LONG TERM...SHK
AVIATION...DL
MARINE...REK/TRA/SHK


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