Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 231457

Area Forecast Discussion
National Weather Service Raleigh NC
1057 AM EDT FRI SEP 23 2016

An upper level low and the remnant low from Julia will linger and
weaken near the southern Carolina coast through Saturday. A cold
front will drop south into the area late Saturday and stall south
of the region on Sunday. A stronger cold front will push through the
region on Wednesday.

As of 1050 AM Friday...

Latest surface analysis shows a the persistent remnant low from
Julia located just south of Cape Fear. A weakening mid level
vortex that was located across the eastern Carolinas was beginning to
shear out and open up this morning. The air mass across the
eastern Carolinas remains very moist with precipitable water
values in excess of 1.9 inches in the southern coastal region and
Coastal Plain. Notably drier air with PW values of 1.5 inches or
less have reached the Richmond Va area and the western Triad. The
latest visible satellite imagery shows a large region of almost
exclusively low clouds across the eastern two thirds of NC with
some breaks and thin spots in the overcast developing. Shower
activity to the southeast of I-95 earlier this morning has

NWP guidance is in generally agreement that drier air over VA and
northwestern NC will push slowly south into central NC. Should
continue to gradually see a lifting of ceilings and brightening
of the sky this morning into this afternoon. Expect to see some
breaks develop in the overcast, especially in a slightly
divergent low level flow to the northwest of interstate 95 with
the clouds more stubborn to the southeast of I-95. Convection
allowing models develop scattered to widespread convection this
afternoon across the coastal region, with more widely scattered
convection in the RAH CWA across the southern Coastal Plain and
Sandhills region with little chance of rain elsewhere. A weakly
unstable air mass with thin CAPE should lead to a few
thunderstorms as well, but given the weak flow severe weather is
not expected but storms will be capable of producing locally heavy
rain as the move slowly.

Atypical highs are expected today with the warmest readings in the
northwest including the Triad where there will be the most sun
with the coolest conditions in the southeast with the more
persistent cloud cover and scattered showers. Highs will range
from the mid 80s northwest to lower 80s southeast.

Skies will continue to clear this evening with the loss of heating
and the arrival of drier air. With little forcing for ascent, no
rain is expected overnight. Some clouds may persist across the
southeast before areas of fog and perhaps some low stratus appear
increasingly likely, most widespread from the northern Coastal
Plain southwest across the remainder of the Coastal Plain into the
Sandhills and eastern Piedmont. Lows tonight will range in the
mid 60s northwest to near 780 southeast. -Blaes


As of 255 AM Friday...

Dry and very warm weather expected. Mid level ridging aloft
continues to build in from the west, while at the surface, the weak
trough drifts further offshore as weak high pressure moves in from
the west, although lee troughing does form in the afternoon over the
western Piedmont. With low PW and a fairly stable column, will keep
pops under 15%, with mostly sunny skies. Thicknesses and statistical
guidance indicate highs in the mid-upper 80s, around 6-10 degrees
above normal. The anticipated backdoor front moving toward NC from
the NNE is poised to move into the NE CWA Sat night into early Sun
morning, driven by energy rotating around a large vortex centered
near the Newfoundland/Quebec border. But this low does not appear to
dig markedly down the East Coast, hinting that the front may not
work very far into NC despite being propelled by a cool dense
surface high to our north. The ECMWF tends to hold the front just
north of the VA/NC border through daybreak Sunday, while the NAM/GFS
dip the front into northern NC. Will lean toward the ECMWF solution
and hold onto mild temps overnight, with lows Sat night in the mid-
upper 60s and a minimal drop in dewpoints over the NE. Regardless of
frontal progression, we are likely to see increasing clouds from NNE
to SSW Sat night. While a few models generate shower activity ahead
of or along the front over north central and NE NC Sat night, the
presence of features to force ascent is uncertain, and will opt for
dry weather for now and monitor trends. -GIH


As of 320 AM Friday...

Confidence in the long term forecast is still fairly low but nothing
like it was yesterday morning as model solutions are slowly starting
to come up with somewhat of a common solution. The big difference
maker, which was the blocking pattern in the GFS solution is not
showing up as much as in previous runs and has allowed high pressure
over to come southward out of Quebec on Sunday to become more
transitory and move into New England on Monday and out to sea on
Tuesday. This allows a cold front to drop into the Carolinas on
Wednesday, hang up over the area on Thursday before exiting to the
south Thursday night into Friday. During this time period the best
chances for thunderstorms would be on Tuesday and Wednesday ahead of
and with the cold front. Otherwise some slight chances for rain
throughout the period, mostly in the form of diurnal showers are
possible. Temperatures will generally stay in the upper 70s to low
80s before the cold front with some hints at some highs in the mid
70s for the end of the week.


As of 650 AM Friday...

Widespread IFR to LIFR conditions will linger through 12-13z this
morning across all of central NC, a result of light winds along with
stable and very moist air in the low levels. Cigs are expected to
rise to MVFR between 14z and 16z, and then to VFR between 16z and
18z west (INT/GSO), 18z-20z central (RDU), and 19z-21z east
(RWI/FAY). Rain chances today are low west (INT/GSO) trending higher
east (RDU and especially RWI/FAY), with the highest coverage near
FAY, which could see a few hours of showers, and perhaps a storm or
two, with MVFR vsbys and cigs this afternoon. Conditions will trend
toward VFR everywhere after sunset tonight, as weak high pressure
starts to build in from the west with drier air moving in.

Looking beyond 12z Sat morning, VFR conditions will dominate into
Sat evening, with the risk of sub-VFR stratus and fog returning late
Sat night/Sun morning as a backdoor front approaches from the north.
MVFR cigs may linger through much of Sunday and Sunday night,
although confidence is not high, as there is uncertainty regarding
the southward pace of the backdoor front through NC. After mostly
dry weather Sat, the chance for sub-VFR showers and storms returns
for Sunday along the backdoor front. Shower/storm chances will
increase further late Mon into Tue as an upper level low pressure
trough approaches from the NW. There may be a risk for low level
wind shear early Tue morning. -GIH




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