FXUS62 KRAH 240216

Area Forecast Discussion
National Weather Service Raleigh NC
1016 PM EDT Wed May 23 2018

A cold front will push southward through central North Carolina
tonight. This front will settle across South Carolina Thursday
through Friday, as high pressure builds in from the northeast.


As of 1005 PM Wednesday...

A slow moving cold front is currently pushing southward through the
Mid Atlantic region this evening, and will move through central NC
tonight. Several clusters of showers and storms in advance of the
front remain tonight, with the most notable one across Davidson and
Randolph Counties. This is where the best remaining instability
resides, per the SPC meso page. There will continue to be a threat
of flash flooding across the western Piedmont for the next several
hours along this southward sinking cluster of storms, before
nocturnal stabilization takes hold, resulting in more isolated
convection until the front passes later tonight (similar to the
coverage in the eastern half of the area now). Low temps tonight are
expected to be in the mid to upper 60s.


As of 330 PM Wednesday...

Thursday and Thursday night, the sfc front should stall near or just
southwest of our southern counties. Moisture pooling in vicinity of
this feature should maintain mostly cloudy skies and a small threat
for showers and possibly a thunderstorms, most probable during the
afternoon hours. Otherwise northeast flow will temporarily usher a
drier low level air mass into at least the northeast third of
central NC. Potential for sfc dewpoints to lower into the upper
50s/around 60 from Raleigh north and east, and into the lower 60s in
the NW Piedmont and the central Coastal Plain around GSB. Though
afternoon temperatures will return to the mid 80s, the lower
dewpoints will result in comfortable humidity levels.

Much of the same Thursday night with more clouds SW and fewer NE.
Under clear skies and calm wind regime, some of the cooler spots
across the northern Coastal Plain into the northeast Piedmont should
dip into the upper 50s/around 60 for overnight low temperatures.
Elsewhere, min temps in the low and mid 60s will be common.


As of 330 PM Wednesday...

Within relatively slow, blocked flow aloft across the CONUS during
the medium range, the pattern over cntl NC will be dominated by a
broad, re-loading trough centered over the GOM/Gulf coast states,
and a downstream ridge extending across the top from the swrn N.
Atlantic and cntl/ern Caribbean Sea nwwd across the upr Midwest. The
(generally sly) flow between these two features will direct a plume
of tropical moisture characterized by precipitable water values of
1.75 to 2.5" from the nwrn Caribbean Sea nwwd across the sern U.S.,
especially by early next week.

At the surface, an initially cooler and drier continental air mass,
accompanying modifying surface high pressure off the srn middle
Atlantic coast, will extend wwd into NC on Fri. This ridge will then
drift east of Bermuda through the weekend, with progressively
modifying return flow throughout the sern U.S. through early next
week. (Possibly tropical) low pressure over the GOM this weekend
would likely meander slowly over the nrn GOM and Gulf coast states
through the period owing to the ridge downstream, and over the top.

Some "ring of fire" convection may skirt the wrn and srn Piedmont
late Fri-Fri night, in a developing warm/moist advection regime
directed there, with otherwise continued drier and more stable
conditions in closer proximity to the offshore (deep layer) ridging.
This regime will then likely edge ewd, with an associated good
chance of showers and storms across cntl NC, on Sat. There may be a
relative lull in convective probabilities/coverage, in briefly more
pronounced ridging aloft downstream of the GOM low pressure, on Sun.
It will then become increasingly unsettled, with high chance to
likely probabilities of showers/storms, maximized with diurnal
heating, Memorial Day through the middle of next week.

High temperatures are likely to be near to slightly above normal,
though modulated/hindered by convection/clouds especially early-mid
next week, while low temperatures are likely to be a category or
three above normal for the same reason.


As of 730 PM Wednesday...

Scattered convection continues this afternoon, primarily at
KRWI/KFAY with the bulk of the activity sinking south of KINT/KGSO
before 8pm Wednesday. While no storms pose an immediate threat to
the airport, addition develop may produce instances of sub VFR
ceilings/visibilities. The threat for convection should diminish
rapidly by 02z or so. After 06Z, areas of low stratus will develop
in the NE low level flow behind the departing sfc cold front. Some
uncertainty on timing and coverage of these low CIGS, so have kept
sites VFR with CIGS dropping into the 3,000 - 4,000ft range.
Periodic dips into MVFR CATs may occur on a local basis.

A stable air mass will overspread the majority of the central NC
Thursday and Thursday night, maintaining the VFR conditions. The
only threat for isolated-scattered convection should be across the
southern Piedmont, well south of the Triad, and west of KFAY.The
atmosphere is projected to become increasingly moist and unstable
from Friday and beyond, especially during the later half of the
holiday weekend. This should lead to extended periods of sub VFR
conditions, primarily related to ceilings.





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