Special Marine Warning 48, NWS Charleston, SC

Area Forecast Discussion
National Weather Service Charleston SC
1212 PM EDT Mon Jun 28 2021

.SYNOPSIS...
A tropical disturbance over the southwest Atlantic could
strengthen to a tropical depression or weak tropical storm
before moving onshore near the South Carolina and Georgia
border this evening. Otherwise, Atlantic high pressure will
prevail with a cold front approaching late week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of noon: A quick update to adjust forecast and headlines for
the Tropical Storm Warning for Charleston and Berkeley Counties.

Previous Discussion:
Today: High pressure across the area early this morning will give
way to low pressure offshore quickly advancing toward the Southeast
Coast. Shear associated with an upper low to the west-southwest of
the low pressure system has prevented it from intensifying with most
showers and thunderstorms displaced west-northwest of it. However,
slight intensification is possible as the system quickly travels
over warmer gulf stream waters off the Southeast Coast this
afternoon. Given the speed of the system, the window of time the
system remains over the gulf stream will be quite small, potentially
limiting the peak strength of the system before reaching the coast.
NHC currently indicates a 70% chance of tropical cyclone formation.
Regardless of whether this system becomes a depression/weak tropical
storm or not, impacts associated with it should come in the form of
localized heavy rainfall, gusty winds, enhanced rip currents, and a
low threat of tornadoes.

Latest guidance suggests the system to make landfall sometime late
afternoon into early evening near the Georgia/South Carolina state
line with the bulk of impacts associated with it occurring across
southeast Georgia. Shower and thunderstorm coverage will likely
increase across land early morning, becoming numerous and/or
widespread across the area late morning and afternoon, especially
across southeast Georgia. The speed of the west-northwest tracking
system could limit a flash flooding threat, but deep tropical
moisture (PWATs 2.00-2.25 inches) should help produce rainfall
totals between 0.25-0.50 inches north to 0.75-1.50 inches with
locally higher amounts possible across southern South Carolina into
southeast Georgia, suggesting at least a potential for minor
flooding concerns during the peak of the event (across coastal
Georgia). The latest Day 1 rainfall outlook from WPC also suggests
this scenario, marking the area with a marginal risk of excessive
rainfall across much of the area. As the center of the system
advances near and eventually onshore, shear and instability across
the area support a low risk of tornadoes, mainly near and north of
the low pressure center across parts of southeast Georgia and
southeast South Carolina this afternoon into early evening. The
system is then expected to shift inland quickly in a weakened state,
producing showers/thunderstorms across inland areas during the
evening.

Overnight, the bulk of heavier precip is expected to come to an end
during late evening hours, but few to scattered showers and/or
thunderstorms could persist across the area during the night,
greatest chances well inland. Atlantic high pressure will spread
back into the area late with precip chances continuing a downward
trend. Some clouds and onshore winds could maintain slightly more
mild temps than the previous night, generally ranging in the low-mid
70s inland to upper 70s along the beaches.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
Forecast confidence: Moderate to high.

Atlantic high pressure will generally prevail, although deep
moisture and the sea breeze will lead to near normal rain chances,
mainly during the daytime. The threat for severe storms is very low
given the limited bulk shear, meaning the best chance will be
associated with mesoscale boundary collisions. Highs will likely
stay below normal while lows will likely be slightly above normal.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Forecast confidence: Moderate to high through Friday, then low to
moderate thereafter.

Atlantic high pressure will generally prevail with near to slightly
higher than normal rain chances until chances increase late week
when a cold front nears the area. The severe storm risk will remain
quite low at least through Friday given the limited deep layer
shear. High temperatures should stay near to below normal while lows
stay a bit above normal.

&&

.AVIATION /16Z MONDAY THROUGH FRIDAY/...
VFR conditions are expected at CHS, JZI, and SAV terminals early
this morning, but conditions are expected to gradually deteriorate
with the approach of a low pressure system late morning into early
afternoon, with all terminals expected to reach prevailing MVFR
conditions with low clouds and showers (potentially thunderstorms)
impacting the terminals. Expect flight restrictions to begin around
15-16Z today. Gusty northeast-east winds up to around 20-22 kt is
also likely at all terminals late morning through the afternoon.
Tempo IFR conditions are possible mid-late afternoon as showers
become widespread, but have not been included in the 12Z TAF
issuance. Conditions should then gradually improve at the terminals
late evening, ending around 02Z Tuesday at CHS and JZI
terminals, but flight restrictions appear likely to persist at
the SAV terminal through about 08Z Tuesday.

Extended Aviation Outlook: High confidence in periodic restrictions
at KCHS/KSAV/KJZI mainly due to morning low clouds and afternoon
showers and storms. The chance for restrictions could rise late week
as a cold front moves closer to the area.

&&

.MARINE...
As of noon: A quick update to adjust forecast and headlines for
the Tropical Storm Warnings for the SC waters.

Previous Discussion:
Today and Tonight: Low pressure advancing across the western
Atlantic will approach the region this morning, likely reaching
coastal waters during the afternoon, then shifting onshore late
afternoon into the evening. There is a small potential this
system could intensify to a tropical depression or weak tropical
storm as it approaches local waters this afternoon. Regardless,
the pressure gradient is expected to enhance across local
waters, increasing winds and building seas through the day.
Small Craft Advisories begin across a majority of the waters
this morning, with remaining nearshore Georgia waters this
afternoon. In general, east-northeast winds should peak between
20-25 kt with seas building up to 5-7 ft this afternoon.
Winds/seas could remain elevated into early evening hours, but a
downward trend is anticipated through the night as the low
pressure system advances inland and weakens. Expect conditions
to fall below advisory criteria around midnight.

Rip Currents: A Moderate Risk for rip currents is in place for all
South Carolina and Georgia beaches through this evening as low
pressure advances to the Southeast coast.

Tuesday through Saturday: Moderate to high confidence. Atlantic high
pressure will generally prevail through the period with a cold front
to approach late in the week. Conditions will mostly remain below
Small Craft Advisory levels but could come close, especially in
Charleston Harbor, the Charleston County nearshore waters, and GA
waters beyond 20 nm late in the week.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Tropical Storm Warning for SCZ045-050-052.
MARINE...Tropical Storm Warning for AMZ330-350-352.
     Small Craft Advisory until 11 PM EDT this evening for AMZ354.
     Small Craft Advisory until 2 AM EDT Tuesday for AMZ374.

&&

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

Hazardous Weather Outlook...CORRECTED
National Weather Service Charleston SC
1211 PM EDT Mon Jun 28 2021

GAZ117-119-139-141-SCZ048-049-051-291545-
Coastal Bryan-Coastal Chatham-Coastal Liberty-Coastal McIntosh-
Beaufort-Coastal Colleton-Coastal Jasper-
1211 PM EDT Mon Jun 28 2021

...MODERATE RISK FOR RIP CURRENTS IN EFFECT UNTIL 8 PM EDT THIS
EVENING...

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

.DAY ONE...This afternoon and tonight.

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

   Moderate Risk for Rip Currents.

Flash Flooding: There is a low risk for localized flash flooding,
especially in urbanized areas and coastal locations.

.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.

SCZ050-291545-
Charleston-
1211 PM EDT Mon Jun 28 2021

...MODERATE RISK FOR RIP CURRENTS IN EFFECT UNTIL 8 PM EDT THIS
EVENING...
...TROPICAL STORM WARNING IN EFFECT...

This Hazardous Weather Outlook is for southeast South Carolina.

.DAY ONE...This afternoon and tonight.

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

   Moderate Risk for Rip Currents.
   Tropical Storm Warning.

Flash Flooding: There is a low risk for localized flash flooding,
especially in urbanized areas and coastal locations.

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

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

   Tropical Storm Warning.

.SPOTTER INFORMATION STATEMENT...

Spotter assistance is not anticipated at this time.

GAZ087-088-099>101-114>116-118-137-138-140-SCZ040-042>044-047-291545-
Jenkins-Screven-Candler-Bulloch-Effingham-Tattnall-Evans-
Inland Bryan-Inland Chatham-Long-Inland Liberty-Inland McIntosh-
Allendale-Hampton-Inland Colleton-Dorchester-Inland Jasper-
1211 PM EDT Mon Jun 28 2021

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

.DAY ONE...This afternoon 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.

SCZ045-052-291545-
Inland Berkeley-Tidal Berkeley-
1211 PM EDT Mon Jun 28 2021

...TROPICAL STORM WARNING IN EFFECT...

This Hazardous Weather Outlook is for southeast South Carolina.

.DAY ONE...This afternoon and tonight.

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

   Tropical Storm Warning.

Flash Flooding: There is a low risk for localized flash flooding,
especially in urbanized areas and coastal locations.

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

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

   Tropical Storm Warning.

.SPOTTER INFORMATION STATEMENT...

Spotter assistance is not anticipated at this time.

AMZ330-350-352-291545-
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-
1211 PM EDT Mon Jun 28 2021

...TROPICAL STORM WARNING IN EFFECT...

This Hazardous Weather Outlook is for Atlantic coastal waters.

.DAY ONE...This afternoon and tonight.

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

   Tropical Storm Warning.

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

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

   Tropical Storm Warning.

.SPOTTER INFORMATION STATEMENT...

Spotter assistance is not anticipated at this time.

AMZ354-374-291545-
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-
1211 PM EDT Mon Jun 28 2021

This Hazardous Weather Outlook is for Atlantic coastal waters.

.DAY ONE...This afternoon 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.