Severe Thunderstorm Warning 106, NWS Charleston, SC

Area Forecast Discussion
National Weather Service Charleston SC
107 PM EDT Mon Sep 9 2019

.SYNOPSIS...
A stationary front will linger over or near the area through
Tuesday then dissipate. High pressure is forecasted to build in
from the north midweek. A weak tropical wave should pass to our
south late in the week, bringing an increased chance of rain.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Some chances are forthcoming for the afternoon forecast. The
first is the raising of a short-duration Heat Advisory where dew
points have been pooling near the sea breeze. Although some of
the dew points are 81-82F in spots, which may be a little
suspect, even going with a more conservative 78-79F dew point
yields heat indices as high as 110-113F. This is mainly in the
corridor from Fenwick (Colleton County) to Beaufort,
Hardeeville and Savannah. We have the advisory through 5 pm, but
that'll probably be cancelled early pending the coverage of
convection and the strength of the sea breeze to lower temps.

Secondly, the HREF is showing better4 coverage of showers and
t-storms this afternoon and evening, enough so that we have been
prompted to raise PoP to as high as 40%. The best chances still
look to be near and inland from I-95, but we did raise PoP a
little more closer to the coast. As of early afternoon we are
starting to see isolated activity near the edges of our Georgia
zones, and coverage will increase throughout the next several
hours.

Although there is little shear, the thermodynamics are quite
impressive. Thus the potential for strong storms is even
greater than originally thought, and maybe even a slightly
higher risk for isolated pulse type storms where boundary
interactions occur.

Previous discussion...
The large scale pattern features a continuation of deep layered
ridging aloft, while at the surface a wavering stationary front
remains inland, as a northeast- southwest aligned ridge holds
just offshore.

It'll be another abnormally warm and humid day across the local
region with H85 temps that are 18-19C, and H5 heights are as
great as 5920-5930 meters. These values yield max temps in the
mid and upper 90s near and west of I-95, lower 90s between there
and the intra-coastal, with mid 80s to near 90F closer to the
immediate coast. Where we are showing our hottest temps is where
the dew points will mix out the lowest, while where the dew
points pool, our temps are not as high. Thus we are arriving at
heat indices that reach as high as 102-108F, but not enough for
a Heat Advisory.

We didn't make any major changes to the coverage of showers and
t-storms this afternoon, mainly in the isolated to scattered
range, with initiation around 2 pm when we reach our convective
temps in the lower and middle 90s. The best coverage still looks
to be near and west of I-95, where the proximity to the inland
front, the sea breeze and low level theta-e ridging will
overlap. Based on modified soundings the MUCAPE values are as
great as 3000-4000 J/kg, and DCAPE is 1200-1500 J/kg. This can
support gusty winds and cloud to ground lightning being the
primary hazards. An isolated severe t-storm can not be ruled
out, but would be confined to where mesoscale boundary interactions
occur.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
Tonight: Lingering convection will dissipate by mid-evening, if
not sooner. Dry conditions will prevail through the rest of the
night. Conditions will favor another round of patchy fog/stratus
early Tuesday, mainly across the far interior. Dense fog is not
expected. Lows will range from the lower-mid 70s inland, mid-
upper 70s closer to the coast and upper 70s/near 80 at the
beaches and Downtown Charleston.

Tuesday through Thursday: The mid-levels will consist of high
pressure over the Southeast U.S. The high should slowly weaken
with time, getting nudged slightly to the north on Thursday as a
disturbance approaches from the southeast. At the surface, a
stationary front will meander nearby or over our area Tuesday,
then dissipate Tuesday night. High pressure will then build in
from the north Wednesday and prevail into Thursday. Models show
the most moisture in place on Tuesday with the front. PWATs then
are generally ~1.75". Values then trend down to ~1.25" by
Thursday due to the high. Models still show the potential for
isolated showers across our area Tuesday, so we maintained the
slight chance POPs. Drier conditions are expected over land
Tuesday night. Though, some showers could develop over the
coastal waters late and brush against the beaches, then quickly
dissipate. This shower potential continues into Wednesday. The
coastal showers are pushed further offshore Wednesday night as
drier air associated with the high becomes more dominant. If
there are any showers on Thursday, they should be limited to the
GA coastal counties. The increasing dry air will make it hard
for any thunderstorms to develop. But if they do, it'll probably
be on Tuesday. There is a potential for higher wind gusts if a
stronger storm forms. High and low temperatures will remain a
few degrees above normal.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
Ridging over the Southeast will continue to weaken and get pushed
northwards as a disturbance passes to our south. The surface pattern
generally reflects this with high pressure to our north Thursday
night. A front will try to approach from the north on Friday.
However, it won't make it to our area as a tropical low or wave
passes to our south Friday into Saturday, becoming located near the
central Gulf of Mexico on Sunday. The entire long term could be
unsettled as moisture from this features moves through the region.
Depending on how far north it gets will determine how wet or less
wet our forecast will be. Models seem to show the heaviest
precipitation threat to our south, so we have chance POPs.
Temperatures should be at or below normal due to the clouds and
rainfall potential.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
KCHS: The best chances of SHRA/TSRA looks to stay inland from
the terminal this afternoon and early evening, as does the
better coverage of fog and stratus early Tuesday. Thus we are
showing VFR conditions with the 18Z TAF set.

KSAV: Scattered SHRA and TSRA will continue to develop near or
inland from the terminal this afternoon and early evening, so
for now we have maintained VCTS. However, pending the trends,
there certainly could be a temporary of MVFR or IFR ceilings
and/or visibilities if there is a direct hit from convection.
For now we feel that the fog and stratus early Tuesday will stay
inland from the airfield, but if enough rainfall occurs then
chances would increase.

Extended Aviation: There is a very low probability of flight
restrictions due to showers/thunderstorms Tuesday afternoon and
then again on Friday. Otherwise, VFR.

&&

.MARINE...
Today and tonight: High pressure centered over and near New
England will stretch across the local waters. The gradient is
slack enough to keep winds less than 10 or 15 kt, mainly from a
southerly component. Seas will hold around 2 ft within 20 nm and
near 3 ft further out.

Monday through Friday: A stationary front will linger over or
near our area Tuesday, then dissipate. High pressure is then
forecasted to build in from the north midweek, followed by a
weak tropical wave passing to our south late in the week. Even
with all of these features, the surface pressure gradient will
generally yield winds of 15 kt or less. Seas will mostly be 5 ft
or less. However, seas are forecasted to build to 6 ft across
the outer GA waters late in the week. Small Craft Advisories may
be needed at that time.

&&

.CLIMATE...
Record high minimums for 9 September:
KCHS: 76/1990 (Low so far today 78F)

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory until 5 PM EDT this afternoon for GAZ118.
SC...Heat Advisory until 5 PM EDT this afternoon for SCZ047>049-051.
MARINE...None.

&&

NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...
CLIMATE...

Hazardous Weather Outlook
National Weather Service Charleston SC
215 PM EDT Mon Sep 9 2019

GAZ087-088-099>101-114>116-137-138-SCZ040-042>045-101815-
Jenkins-Screven-Candler-Bulloch-Effingham-Tattnall-Evans-
Inland Bryan-Long-Inland Liberty-Allendale-Hampton-Inland Colleton-
Dorchester-Inland Berkeley-
215 PM EDT Mon Sep 9 2019

This Hazardous Weather Outlook is for southeast Georgia and
southeast South Carolina.

.DAY ONE...This afternoon and tonight.

Severe thunderstorms: Scattered thunderstorms will continue to
develop this afternoon and persist into the early evening. A few of
the storms could become severe with damaging winds the main weather
hazard. Frequent lightning and small hail are also expected. The
most likely timing of any severe weather is through 8 pm.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Please relay any reports of hazardous weather including, but not
limited to large hail, damaging winds and flooding to the National
Weather Service in Charleston at 1-888-383-2024.

GAZ118-SCZ047-101815-
Inland Chatham-Inland Jasper-
215 PM EDT Mon Sep 9 2019

...HEAT ADVISORY IN EFFECT UNTIL 5 PM EDT THIS AFTERNOON...

This Hazardous Weather Outlook is for southeast Georgia and
southeast South Carolina.

.DAY ONE...This afternoon and tonight.

Severe thunderstorms: Scattered thunderstorms will continue to
develop this afternoon and persist into the early evening. A few of
the storms could become severe with damaging winds the main weather
hazard. Frequent lightning and small hail are also expected. The
most likely timing of any severe weather is through 8 pm.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Heat Advisory.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Please relay any reports of hazardous weather including, but not
limited to large hail, damaging winds and flooding to the National
Weather Service in Charleston at 1-888-383-2024.

AMZ330-350-352-354-374-GAZ117-119-139>141-SCZ050-052-101815-
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 from 20 to 60 NM-
Coastal Bryan-Coastal Chatham-Coastal Liberty-Inland McIntosh-
Coastal McIntosh-Charleston-Tidal Berkeley-
215 PM EDT Mon Sep 9 2019

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

.DAY ONE...This afternoon and tonight.

No hazardous weather is expected at this time.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter assistance is not anticipated at this time.

SCZ048-049-051-101815-
Beaufort-Coastal Colleton-Coastal Jasper-
215 PM EDT Mon Sep 9 2019

...HEAT ADVISORY IN EFFECT UNTIL 5 PM EDT THIS AFTERNOON...

This Hazardous Weather Outlook is for southeast South Carolina.

.DAY ONE...This afternoon and tonight.

Severe thunderstorms: Scattered thunderstorms will continue to
develop this afternoon and persist into the early evening. A few of
the storms could become severe with damaging winds the main weather
hazard. Frequent lightning and small hail are also expected. The
most likely timing of any severe weather is through 8 pm, mainly near
and inland from route 17.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Heat Advisory.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter assistance is not anticipated at this time.

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