Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 291943

Area Forecast Discussion
National Weather Service Charleston SC
343 PM EDT Mon May 29 2017

High pressure will persist offshore through tonight. A weak cold front
will gradually move into the area midweek. Atlantic high pressure will
extend west over the region late week into the upcoming weekend.



Late this afternoon: The forecast area remains hot and sunny with
mid level NVA holding on and west winds limiting cumulus formation.
To the west, a strong 850 MB theta-e gradient exists ahead of
mid level impulses ejecting northeast from the lower gulf coast
region. Convection is expected to continue to develop and
spread into Central GA and the CSRA late in the day. The SPC has
issued a new Severe Thunderstorm Watch for east central GA, the
CSRA, and SC Midlands.

Tonight: The main forecast question continues to be the potential
timing, strength, and intensity of the upstream convection as
the cap erodes eastward prior to sunset. High resolution models
continue to show run to run inconsistencies with regards to
both the evolution and translation of multicell convection that
will taking shape over the next few hours. There is a chance for
a cold pool MCS feature in the track of stronger deep layered
wind fields brushing our nw zones and this feature would also
track ne during the early evening hours. The latest HRRR model
paints a squall line which would potentially impact much of the
area to the north of I-16, an outlier solution at this point but
there is concern that strong to severe tstms may brush at least
our nw zones between 7 PM to 11 PM. We continue to mention an
isolated severe risk in our Hazardous Weather Outlook as
convection organizes to the west.

Late tonight, there could be a lingering chance for showers and
a few tstms as weak PVA brushes the region across SC zones but
expect waning instability to occur after midnight. Temps will be
mild overnight will elevated surface dew points and a decent
pressure gradient in the boundary layer.


Tuesday: Models continue to indicate this could be an active day. At
the surface, a weak cold front will be just to our north and slowly
trending southward. Aloft, a shortwave is expected to pass over the
area late in the day. High temperatures around 90 degrees will
combine with dewpoints around 70 degrees to create instability in
the form of BLCAPEs exceeding 1,000 J/kg in the afternoon. LI`s are
decent along with steepening low/mid-level lapse rates. 0-6 km shear
will be 25-30 kt, which is marginal, but could support some storm
organization. DCAPEs initially exceeding 800 J/kg and dry air aloft
should support decent cold pools and a damaging wind potential. The
best severe weather potential looks to be inland, closer to the
better upper level energy.

Wednesday: Models have backed off a bit on the thunderstorm
potential. Despite the cold front moving closer to the area, it will
be weakening/dissipating. Additionally, less instability along with
a stronger cap should limit the overall convection, especially
considering the veering mid-level flow. We lowered POPs a little,
but the general thinking remains that isolated to maybe scattered
storms are possible in the afternoon. The severe weather potential
is low.

Thursday: The cold front appears to dissipate across or just south
of the area. However, this appears to have a limited impact on our
area. If anything, instability might be comparable to Wednesday,
with temperatures maybe 1-2 degrees lower. The amount of moisture is
not overly impressive. With perhaps capping in place the convective
potential appears low, but uncertainty reigns.


Friday through Sunday may feature higher coverage of showers
and tstms mainly in the afternoon and evening as a series of
shortwaves moves through the Southeast and a lee surface trough
exists inland. A more pronounced cold front could affect the
area Sunday or Monday, though the front may not end up making it
this far south.


VFR will prevail at both KCHS and KSAV through 18Z Tuesday.
Thunderstorms could develop late this evening and impact the
area, but confidence in direct impacts at either terminals
remain quite low.

Extended Aviation Outlook: Mainly VFR. Brief flight restrictions are
possible in afternoon/evening showers and tstms.


Southwest to south flow late this afternoon and evening should
average 15 KT with a typically warm air advection surge regime
during this time. Seas will average 2 to 3 FT. Later tonight,
winds will become more offshore. The main risk overnight may be
possible tstms with gusty winds, as an upper level disturbance
passes by. A few of the high resolution models suggest the SC
coastal waters should have a better chance for showers and
tstms late this evening and early in the overnight.

Tuesday through Saturday: A weak cold front will gradually move into
the area midweek. Atlantic high pressure will extend west over the
region late this week into the upcoming weekend. Light winds and
small seas are expected to prevail. The sea breeze will be fairly
weak Tuesday through Thursday, then potentially strengthening a bit
Friday into Saturday as the Atlantic ridge strengthens.


The temperature sensor at KSAV is running high during the
daytime hours. Use this data with caution, especially during
peak heating. The high temperature has been set to missing for
today. Technicians have been notified.




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