Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 241504

Area Forecast Discussion
National Weather Service Raleigh NC
1105 AM EDT Thu May 24 2018

A weak cold front will settle across South Carolina this afternoon,
and remain stationary through Friday. Meanwhile an area of high
pressure will build into central NC from the northeast. This high
will move offshore by the weekend, resulting in a return to a moist
and unsettled weather pattern.


As of 1105 AM Thursday...

A sfc cold front at 15Z had settle into South Carolina. With the
best low level forcing to our south, the cluster of showers with
heavy rain has temporarily ended across the southern counties. Later
this afternoon, the moist air mass will become slightly unstable,
and support the development of scattered convection, primarily along
and south of a Laurinburg to Ansonville line. An area of high
pressure extends aloft over the Carolinas, attributing to a very
light wind flow. Since the steering flow will be less than 10 kts,
the heavier showers and storms will be capable of dumping locally
heavy/excessive rainfall, likely prompting the issuance of a few
flood advisories.

Farther north across the northern counties, northeasterly low level
flow will advect a drier more stable air mass into this region. This
has led to dewpoints in the upper 50s-lower 60s. The arrival of the
stable drier air mass will prohibit the development of convection
through early this evening. Afternoon temperatures will remain warm,
with highs in the low-mid 80s.

Tonight, scattered convection primarily over the southern Piedmont
will diminish with the loss of heating. The presence of the
lingering boundary immediately to our south and available moisture
will maintain a small threat of a shower overnight. Overnight
temperatures generally in the 60-65 degree range with a few upper
50s probable at the normally cooler locations in the northeast.


As of 315 AM Thursday...

The mid level ridge axis extending from NE of the Bahamas into the
Southeast will start to be broken down by both a shortwave trough
moving through the Upper Midwest into the W Great Lakes as well as
by a weak but expansive mid level trough covering the Lower Miss
Valley and Gulf of Mexico. Flow through the low and mid levels will
strengthen from the SSE and S, drawing deepening moisture into S and
W parts of central NC, with less influence over NE sections still
within the scope of influence of the offshore-drifting low-level
ridge. This will result in an increase in clouds, thickest over the
S and W CWA, although precip chances won`t immediately increase
substantially given the light winds through the column and lack of
mechanisms to force ascent, as well as the clouds themselves which
will decrease heating, thus limiting CAPE. Nevertheless, PW is
forecast to rise well over 1.5" over the SW CWA, sufficient to keep
chance pops in this area Fri through Fri night, with lower to no
pops further NE. Expect highs to be similar to today, mostly lower
to mid 80s. With the clouds and rebounding dewpoints, lows Fri night
should respond accordingly, popping back up to above normal readings
in the mid to upper 60s. -GIH


As of 335 AM Thursday...

Much of the long term forecast will be consumed by what could be our
first tropical system of the year coming out of the Gulf of Mexico.
The current tropical weather outlook from the National Hurricane
Center gives the system a 70% chance of formation within the next
five days. Regardless of if that happens or not, the result for
central NC will be the same. That is, a lot more moisture over the
area and rain chances through the long term forecast.

This is the first hint we have seen at longer term deterministic
models coming into better agreement on where the storm might end up.
For Saturday, both simulations put the storm between Western Cuba
and Southwest Florida with the EC solution further west. That is
important because that scenario is mirrored through the forecast
with the GFS bringing the system into the Florida Panhandle and into
GA/AL before dissipating and being caught up in the northern stream
flow. The EC solution stays west and brings the system into
Louisiana on Monday evening before moving it north into Mississippi
and spinning it there for several days. Both of these scenarios
bring a wave of heavy rain through the Carolinas Sunday afternoon
through Monday which could be our wettest period. Chances for rain
and thunder will be present throughout the period but like recent
afternoons, expect some breaks in the rain in time and space and
that could leave some folks dry for periods of time. While rain will
definitely be a concern for central NC given that we have already
had an extended period of wet weather, wind is not expected to be a
problem in this area.

Temperatures through the period will top out in the 80s with lows in
the upper 60s to low 70s making it very humid throughout the long
term forecast.


As of 655 AM Thursday...

MVFR cigs will persist at INT/GSO/FAY through 13z, but these should
lift to VFR by 15z. VFR conditions will hold elsewhere. After 15z,
there is high confidence that VFR conditions will dominate today
through tonight. A surface cold front now dropping southward through
NC will settle just to our south, as high pressure builds in from
the north. This will result in a largely dry day, with the only
shower/storm threat expected to be across the south, perhaps
impacting FAY, during the afternoon through mid evening. In general,
only VFR mid and high clouds are expected across the area, lasting
through the end of the TAF valid period. Surface winds will be less
than 10 kts from the NE for much of the day. VFR conditions are
likely to hold overnight, although FAY may see scattered to broken
clouds based around 2500 to 3500 ft AGL 08z-12z.

Looking beyond 12z Fri, scattered to broken VFR afternoon cumulus is
expected Fri afternoon, with a chance of showers near INT/GSO/FAY
from mid afternoon through Fri night. Sub-VFR conditions are
expected late Fri night through daybreak Sat as moisture returns
across the area. Daily rain chances will resume Sat afternoon into
Mon, mainly affecting INT/GSO, as an upper level trough approaches
from the west. Sub-VFR stratus/fog may impact all central NC
terminals early each morning Sun/Mon. -GIH





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