Severe Thunderstorm Warning 58, NWS Charleston, SC

Area Forecast Discussion
National Weather Service Charleston SC
216 PM EDT Mon Aug 13 2018

.SYNOPSIS...
Low pressure will persist over inland areas today before a weak
front drifts into the area and dissipates during the middle of
the week. High pressure will prevail during the second half of
the week before low pressure returns during the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 2 PM: Latest SPC analysis indicated a pool of 4500 J/kg of
CAPE across the CHS area with 4000 J/kg across the rest of the
forecast area. A band of >1000 J/kg is current pushing from the
west. Visible satellite indicates a enhanced area of cumulus
from Jamestown west to Summerville. This line should see
stronger updrafts over the next hour or two. Based on the DCAPE
and instability values, storms with dBZ cores in the 28-29 kft
range could produce damaging wind gusts.

As of 1040 AM: Coastal thunderstorms have started to weaken off
the Charleston County coast. These storms are expected to
continue to dissipate headed into the mid-day hours. The mid-
level water vapor indicates the position of the trough axis,
pushing toward the coast. CAMs indicate that thunderstorms
will develop along and ahead of this feature this afternoon,
especially across the CHS Tri-county area. I will update the
forecast to increase PoPs, QPF, and weather during the
afternoon. There is some potential for training cells to occur
over the Highway 17 corridor, over Downtown Charleston, possibly
resulting in excessive rainfall rates.

Previous Discussion:
Today: The southern flanks of a substantial mid level cut-off
low pressure area will reside over the Carolinas today. A decent
short wave will rotate through the base of the low, impacting
areas to our north from Eastern NC to the Mid Atlc. The forecast
for the local area today is a bit on the tricky side with a
drier deep layered air shifting into our western zones today
while increasing upper difluence is noted along coastal SC zones
during the afternoon hours while sea breeze moisture
convergence becomes maximized. We maintained a good persistence
forecast with highs in the mid 90s well inland to the lower 90s
coast today.

Convection: The flair of the models for several runs now
continues to show similar solutions with much of the
uncertainties riding on the mesoscale subtleties and the
arrival of drier air upstream. Convective initiation looks to
develop earliest across Southeast SC then later in the day
in GA. We have opted to maintain general POP scheme persistence
as chance POPs still in line with overall model trends similar
to previous thinking. The main issue revolves around tstm
intensity today as quite a bit of coastal instability is progged
ahead of a well defined region of much higher DCAPES advecting
east with the drier upper levels later today. The latest CAM
output shows much of the coverage at 18Z-22Z today should be
confined right to the sea breeze along the coastal zones. Some
of these storms could be locally strong/severe if the atmosphere
remains uncontaminated from any earlier convection up to that
point. Late day or evening tstms in the eastern half of
Southeast GA may also be strong with a localized damaging wind
risk but confidence is not good timing uncertainties between
models is rather substantial and mesoscale boundaries the big
players.

Tonight: Convection could linger along coastal GA with mainly
dry weather elsewhere. Lows will be a bit cooler with some near
70 degree readings far inland to the mid 70s coast.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
Conditions will trend drier into mid-week as a mid/upper lvl low
centered north of the region slowly shifts off the Mid-Atlantic and
Northeast coast Tuesday into early Wednesday before a ridge of high
pressure expands over the region from the Atlantic by Thursday.
However, chances of showers and thunderstorms are still possible on
Tuesday, especially closer to the coast as a weak sfc front attempts
to shift into the area before stalling and/or dissipating through
Wednesday. A prevailing west/northwest flow aloft should also help
keep most locations drier well inland and warm sfc temps into the
lower 90s Tuesday, then limit most convection and support slightly
warmer temps into the low/mid 90s on Wednesday. By Thursday, a more
typical summertime pattern will be in place with the Atlantic ridge
expanding aloft and the area remaining between weak low pressure
inland and Atlantic high pressure at the sfc. The pattern should
support another day of warm temps on Thursday with highs peaking in
the low/mid 90s and a slight chance to chance of showers and
thunderstorms, mainly during the afternoon/evening. Overnight lows
should range in the low/mid 70s through mid week.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
A typical summertime pattern should persist into early Friday as
high pressure prevails aloft and a sfc trough of low pressure
remains less pronounced inland. However, greater chances of precip
should return this weekend as a mid/upper lvl trough of low pressure
quickly advances over the Midwest and Northeast states and forces
the Atlantic high to weaken and retreat offshore. Greatest chances
of precip should occur inland and north late weekend into early next
week, closer to a trough axis west of the area and a front
approaching the Mid-Atlantic states to the north. Once the mid/upper
lvl trough of low pressure shifts offshore late Monday, the Atlantic
ridge of high pressure should return aloft. Overall high temps
should peak into the lower 90s, with temps perhaps a degree or two
cooler late weekend into early next week should greater precip
coverage occur. Lows should range in the mid/upper 70s, warmest near
the coast.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
At the onset of the 18Z TAFs, showers and thunderstorms were
developing in the vicinity of both KCHS and KSAV. These
thunderstorms may strengthen quickly during the mid to late
afternoon. I will keep the mention as VCTS at KSAV and TEMPO
TSRA at KCHS between 20Z-23Z. The convection is forecast to
shift offshore around sunset. The remainder of the TAFs will
feature steady SW winds and VFR conditions.

Extended Aviation Outlook: VFR conditions should prevail at CHS and
SAV terminals Tuesday through Thursday. Brief flight restrictions
are possible with afternoon/evening showers and thunderstorms this
weekend.

&&

.MARINE...
Today through Saturday: Conditions are expected to remain below
Small Craft Advisory levels through late week. However, a somewhat
tightened pressure gradient between low pressure inland and high
pressure offshore will support southwest/south winds up to 15-20
kt at times through at least Tuesday. Strong thunderstorms are
possible later today into tonight with a risk for localized
strong wind gusts near shore, very heavy rainfall and deadly
lightning strikes.

High pressure building over the coastal waters should lead to a
more relaxed gradient and south/southwest winds topping out
near 15 kt Wednesday and Thursday, before the gradient tightens
once again this weekend and results in wind speeds up to 15-20
kt between low pressure inland and high pressure over the
western Atlantic. Seas will generally range between 2-4 ft into
Tuesday, then slowly subside to 1-3 ft Wednesday into Thursday,
before building back to 2-4 ft by this weekend.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.

&&

NEAR TERM...NED
SHORT TERM...DPB
LONG TERM...DPB
AVIATION...NED
MARINE...

Hazardous Weather Outlook
National Weather Service Charleston SC
433 AM EDT Mon Aug 13 2018

AMZ330-350-352-354-374-GAZ087-088-099>101-114>119-137>141-SCZ040-
042>045-047>052-140845-
Charleston Harbor-
Waters from South Santee River to Edisto Beach SC out 20 NM-
Waters from Edisto Beach SC to Savannah GA out 20 NM-
Waters from Savannah GA to Altamaha Sound GA out 20 NM, including
Grays Reef National Marine Sanctuary-
Waters from Savannah GA to Altamaha Sound GA extending from 20 to
60 NM-Jenkins-Screven-Candler-Bulloch-Effingham-Tattnall-Evans-
Inland Bryan-Coastal Bryan-Inland Chatham-Coastal Chatham-Long-
Inland Liberty-Coastal Liberty-Inland McIntosh-Coastal McIntosh-
Allendale-Hampton-Inland Colleton-Dorchester-Inland Berkeley-
Inland Jasper-Beaufort-Coastal Colleton-Charleston-Coastal Jasper-
Tidal Berkeley-
433 AM EDT Mon Aug 13 2018

This Hazardous Weather Outlook is for Atlantic coastal waters,
southeast Georgia and southeast South Carolina.

.DAY ONE...Today and tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotter assistance is not anticipated at this time.

Special Weather Statement
National Weather Service Charleston SC
153 PM EDT MON AUG 13 2018

GAZ116>119-138-131830-
Inland Liberty-Coastal Chatham-Inland Chatham-Inland Bryan-Coastal
Bryan-
153 PM EDT MON AUG 13 2018

...STRONG THUNDERSTORMS WILL IMPACT PORTIONS OF BRYAN...LIBERTY AND
CHATHAM COUNTIES...

At 153 PM EDT, National Weather Service doppler radar indicated a
strong thunderstorm near Richmond Hill, moving northeast at 20 mph.

  HAZARD...strong winds 45 to 55 mph, up to penny sized hail and
           excessive cloud to ground lightning.

  IMPACT...Expect minor damage to tree limbs and blowing around of
           light, unsecured objects. Minor hail damage to plants,
           trees and crops is possible. Damage to windshields is
           unlikely. All outdoor activities should cease. Move
           indoors immediately.

Some locations in the path of this storm include...
Savannah, Pooler, Richmond Hill, Wilmington Island, Montgomery,
Garden City, Thunderbolt and Vernonburg.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm and may lead to
flooding of low lying and poor drainage areas. Do not drive your
vehicle through flooded roadways.

Report damage directly to the Charleston National Weather Service at
1-888-383-2024 when it is safe to do so. You can also email your
report to nws.charlestonsc@noaa.gov.

&&

LAT...LON 3194 8149 3213 8114 3203 8095 3188 8122
      3189 8122 3188 8123 3178 8140
TIME...MOT...LOC 1753Z 245DEG 16KT 3190 8137

NED

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHARLESTON SC
313 PM EDT MON AUG 13 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0204 PM     TSTM WND DMG     1 NNW RICHMOND HILL     31.95N  81.32W
08/13/2018                   BRYAN              GA   911 CALL CENTER

            TWO TREES DOWN REPORTED IN RICHMOND HILL. ONE SMALL
            TREE FELL ON CAR IN RICHMOND HILL LIBRARY PARKING LOT.
            NO ONE WAS IN THE CAR. THE SECOND TREE WAS UPROOTED IN
            THE WHITE OAK VILLAGE SUBDIVISION.

&&

EVENT NUMBER CHS1800745

ETM

Special Weather Statement
National Weather Service Charleston SC
319 PM EDT MON AUG 13 2018

GAZ116-117-138-139-132000-
Coastal Liberty-Inland Liberty-Inland Bryan-Coastal Bryan-
319 PM EDT MON AUG 13 2018

...STRONG THUNDERSTORMS WILL IMPACT PORTIONS OF BRYAN AND LIBERTY
COUNTIES...

At 319 PM EDT, National Weather Service doppler radar indicated
strong thunderstorms along a line extending from near Belfast to
Sunbury, and moving east at 15 mph.

  HAZARD...strong winds 45 to 55 mph and excessive cloud to ground
           lightning.

  IMPACT...Expect minor damage to tree limbs and blowing around of
           light, unsecured objects. All outdoor activities should
           cease. Move indoors immediately.

Some locations in the path of these storms include...
Sunbury and Belfast.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms and may lead
to flooding of low lying and poor drainage areas. Do not drive your
vehicle through flooded roadways.

Excessive cloud to ground lightning is occurring with these storms.
Lightning can strike 15 miles away from a thunderstorm. Seek safe
shelter inside a building or vehicle.

&&

LAT...LON 3179 8142 3183 8144 3183 8126 3177 8117
      3175 8117 3171 8127
TIME...MOT...LOC 1919Z 267DEG 14KT 3182 8137 3178 8128