Area Forecast Discussion
Issued by NWS Wilmington, NC-- Highlight Changed Discussion --
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FXUS62 KILM 230042 AAA
Area Forecast Discussion...UPDATED
National Weather Service Wilmington NC
842 PM EDT FRI JUL 22 2016
Seasonable temperatures today will yield to hotter weather over the
weekend. The heat wave will last into the early or middle part of
next week all while rain chances remain minimal.
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
-- Changed Discussion --As of 840 PM Friday...Just a quick public update to shift the
highest anticipated coverage of storms to just east of
Bennettsville across Robeson county. Storms are actually quite
healthy with some impressive cores aloft in recent radar cross-
sections near Red Springs in northern Robeson county. Activity
should die down over the next couple of hours as it slides south-
southeast at around 15 mph. Discussion from 730 PM follows...
Convection diving southward from the Southern Pines to Uwharrie
Mountains area is moving along a corridor of relative maximum
instability and low LFC heights. 18z GFS suggests a mid-level
disturbance near or just above the 700 mb level is involved as
well. Since there is some synoptic support this cluster of storms
may survive for at least an hour or two after sunset. I have
expanded the region of slight chance (20%) pops southward through
Marion and Florence, and raised pops as high as 60 percent across
the northern third of Marlboro County between 8-9 pm. The latest
HRRR did not have a particularly good initialization and I am not
completely willing to trust its output on the 21z run. Otherwise
few changes have been made to the overnight forecast. Discussion
from 300 PM follows...
Warm and mostly sunny conditions persist this aftn as ridging
from the midwest slowly expands towards the Carolinas. While the
very hot temperatures across the midwest are on the doorstep and
will encroach upon this area during the weekend, today has been
actually a nice respite with highs around 90 and dew points which
dropped below 70 at times.
This increasing ridge is also functioning as a convective lid to
most updrafts, which is clearly evident by the shallow cu on visible
imagery. A few showers have developed north of the area, likely
along a weak mid-level impulse aided by some differential heating,
and these will try to advect southward towards the far NW counties.
The HRRR wants to bring a few storms into the CWA, but it has been
running far too "hot" with its convective initiation today, and very
dry mid-level air should preclude much of this making the trip
south. However, have left an hour of two of SCHC for Darlington,
Marlboro, and Robeson counties this evening before convection wanes
with loss of heating. Additionally, an an isolated shower or tstm is
possible along the sea breeze through this evening, but coverage
will remain quite isolated. The soundings are very dry in the mid-
levels however, making even lightning difficult since the charge
separation zone is so far into the dry air, but have left TRW- as
the primary Wx type as there are a few lightning strikes upstream.
After nightfall, any diurnal cu will wane and a warm and mostly
clear night is forecast. Have forecast mins a degree above a MAV/MET
blend based off previous verification, and the presence of a 20-25
kts LLJ keeping mins elevated. Have lows forecast to be 72-75,
warmest at the coast.
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.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
As of 330 PM Friday...Hot with increasing humidity forecast for
the weekend as this hot July continues. Massive ridge across the
central part of the country will expand to become a broad feature
across nearly the entire southern tier of the CONUS. As this
occurs, a weak closed mid-level low off the SC coast will be
suppressed to the SW, driven by increasing heights to its north.
This keeps this feature weak and away from the Carolinas, moving
across Florida Sunday night. No surface reflection is progged with
this impulse, but as it moves overhead Florida late, it will cause
a better SE moisture tap and increasing clouds are forecast Sunday
The big story this wknd is a return to uncomfortable and dangerous
heat as the mid-level dome of high pressure expands overhead. This
occurs in conjunction with persistent Bermuda ridging, and 1000-
500mb thicknesses approach 580dm by Sunday. Developing SW flow this
wknd will pump in additional moisture, and this means humidity will
be on the rise at the same time temperatures climb back well into
the 90s. While isolated convection is possible each aftn during peak
heating, widespread tstms are not forecast thanks to warm and
relative dry air aloft, and will carry only SCHC along the sea
breeze and piedmont troughs, highest Sunday. Very little airmass
change is forecast Sat to Sun, so highs both days will be in the mid
90s, slightly warmer Sunday, and a bit cooler at the coast each day,
with lows in the mid to upr 70s. The combination of these hot temps
and high dew points will create heat index values just below 105
(heat advisory criteria) on Saturday, but a heat advisory will
likely be needed on Sunday and will mention in the HWO.
.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 330 PM Friday...The extended period as would be expected,
offers little change in the summertime pattern. The eastern
Carolinas will be in between a subtle northwest flow aloft and at
times ridging building in from the central Atlantic. Any synoptic
forcing mechanisms are relegated to the Piedmont trough with the
more local feature being the seabreeze. Precipitable water values
remain somewhat unimpressive with perhaps an increase later next
week. This warrants no more than either slight or low chance pops
for any period. 850mb temperatures remain pegged right around 20
degrees C so surface readings should be a few degrees above
normals for both daytime highs and overnight lows.
.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
As of 00Z...VFR this evening at all terminals. Showers and
thunderstorms were moving S towards KLBT early this evening.
Attm activity is expected to dissipate before reaching the
terminal, but will indicate VCSH at KLBT just in case a rogue
shower makes it to the terminal. Convection should dissipate
with loss of heating. Confidence is high for VFR overnight.
The impulse causing the convection this evening is forecast
to continue to move to the SE. A few models indicate showers
re-developing overnight, but confidence is low. Although winds
will be light, the chance for fog development should be low
due to 20kt boundary layer winds.
By sunrise a few showers will be possible along the coast but
confidence is moderate to high VFR will continue. Winds will
be WSW, but winds will shift to the SSW-SW by afternoon. Any
afternoon convection will be isolated.
EXTENDED OUTLOOK...Brief periods of MVFR/IFR from isolated
afternoon convection Sunday through Wednesday. Otherwise expect
NEAR TERM /THROUGH TONIGHT/...
As of 730 PM Friday...No significant changes to the forecast with
this early evening update. Discussion from 300 PM follows...
Weak Bermuda high pressure will exert its influence through
tonight, but a weak gradient will persist. Winds will gradually
veer to the SW tonight, with speeds rising to around 10 kts. Seas
will be formed almost exclusively through a 3ft/9sec SE swell,
producing wave heights of 2-3 ft.
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 330 PM Friday...Bermuda high pressure will be the dominant
feature this weekend as it expands again into the Carolinas. This
produces SW winds around 10 kts Saturday, increasing to up to 15
kts Sunday thanks to a sharper piedmont trough. Seas will be
formed through an amplifying SW wind wave and a persistent SE
swell, producing wave heights of of 2-3 ft Saturday, and more
widespread 3 ft on Sunday.
LONG TERM /MONDAY THROUGH WEDNESDAY/...
As of 330 PM Friday...South to southwest winds of 10-15 knots
will continue across all waters through the period. There is a
little hint of higher winds overnight Tuesday into Wednesday
morning with the low level jet and this is reflected in the
forecast. Significant seas will be mostly in a range of 2-3 feet.