Severe Thunderstorm Warning 20, NWS Charleston, SC

Area Forecast Discussion
National Weather Service Charleston SC
732 PM EDT Tue May 9 2023

.SYNOPSIS...
A cold front will move south through the area tonight, followed
by high pressure through early next week. Another cold front
should then arrive by the middle of next week.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
The temperature at KCHS hit 94F degrees earlier this afternoon,
the hottest it's been since September 7, 2022.

The cold front is drawing closer to the local counties from the
north, and with little to no CINH and MLCAPE values of 2000-2500
J/kg, isolated convection will continue to develop. With time as
the front gets even closer, the coverage of convection will
increase and our forecast closely follows the recent runs of
the HRRR. This produces isolated to scattered coverage, greatest
over the Charleston Quad-County region, mainly between 7 PM and
11 PM. Although CINH increases after sunset, given DCAPE of
1000+ J/kg there remains a risk for a few strong or marginally
severe storms during a similar time frame. It's interesting tat
the SPC meso-analysis shows non-zero values of the Non-Supercell
Tornado parameter. So maybe some funnel clouds can be observed
along the sea breeze boundary inland from US-17 over the
Charleston Tri-County if it collides/merges with the incoming
convection. Wet Bulb Zero is near 10K feet and with 0-6km Bulk
Shear values over 25-30 kt there is also a low end chance of
hail.

Previous discussion... SPC 18Z mesoanalysis reveals between
1000-2000 J/Kg MLCAPE from eastern Georgia into southeast South
Carolina with limited convective inhibition at this juncture.
Scattered Cu field is evident across our CWA. But thus far, not
enough low level kick to get deep moist convection going in our
area...yet. Surface boundary snakes across North Carolina down
across northern Alabama and Georgia and there is some convection
that has developed in northern and western Georgia as well as.
Otherwise, partly to mostly sunny skies persist with very warm
temperatures in the upper 80s to lower 90s (no records thus
far).

Rest of this afternoon and tonight: Upstream boundary will sag
down through the region heading into this evening. Low level
convergence with the boundary as well as interaction with the
pinned sea breeze should fire off showers and thunderstorms
within the next few hours...lingering through a good portion of
the evening hours as the boundary sags on through. Given the
timing of the boundary, it still appears that the highest PoPs
and QPF will reside across the SC counties, diminishing heading
south through the Georgia counties. But given some uncertainty
regarding convection, I will hold with scattered PoPs for now.
PoPs can be adjusted upward as convection unfolds.

Severe weather: Organized severe weather is not anticipated.
But...DCAPE values nearing 1400 J/Kg depicted on SPC 18Z
mesoanalysis is eye-opening. Any convection that develops could
produce strong winds.

Overnight: Boundary will pass on through the region ending the
precip threat for the overnight hours. Cooler and drier air
filters in overnight and there is some indication in model RH
forecasts as well as soundings that there may be some low cloud
development toward morning behind the front that lingers into
Wednesday morning.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Dry high pressure will build from the north on Wednesday,
resulting in temperatures closer to normal in the low to mid
80s. A much drier airmass will preclude precipitation over
southern SC but greater boundary layer moisture and moderate
instability across southeast GA could support isolated
thunderstorms Wednesday afternoon.

A similar pattern will persist into Thursday though temps will
be a degree or two warmer due to increasing upper heights.

The surface high will shift off the coast on Friday while the
upper ridge continues to strengthen. Drier air should move into
the majority of our southeast GA zones by Friday, limiting
convection potential. Highs will be in the mid 80s in most areas
except along the coast.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Hot, dry weather anticipated through the weekend as a deep
layered ridge persists. Saturday highs will be in the mid to
upper 80s while Sunday climbs into the low to mid 90s.

Moisture increases substantially early next week once the
surface high shifts farther off the coast and the upper ridge
begins to weaken. There should be enough instability to support
scattered showers and thunderstorms Monday and Tuesday
afternoon. Highs on Monday will remain quite warm with readings
in the lower 90s. Tuesday should be a few degrees cooler with
highs in the upper 80s due to the upper ridge weakening.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
KCHS and KJZI: A band of convection will impact the airfields
through 04Z, resulting in a 2-3 hour period of TSRA with MVFR or
potentially IFR conditions, along with a short window o gusty
winds.

KSAV: This activity is currently not anticipated to impact KSAV,
but still bears watching just in case.

The cold front will sag down through the region tonight. Behind
the front, about a 3-6 hour period of MVFR or possible IFR
ceilings will occur Wednesday morning, most especially at at CHS
and JZI. VFR returns to all terminals late morning or
afternoon. All sites will also become a little gusty as high
pressure builds in from the north.

Extended Aviation Outlook: VFR conditions should prevail at
CHS/JZI/SAV through Sunday.

&&

.MARINE...
Tonight: High pressure is expected to build north of the waters
later tonight, which will push a backdoor cold front through
from north to south. Winds will veer to northeast and increase
back to 15 to 20 knots across most of the waters later tonight
and into early Wednesday morning. Seas remaining at 3 to 4,
possibly 5 feet. Some wind gusts could reach 25 knots, but not
expecting conditions to reach SCA levels at this time. Storms
coming off land areas will result in Marine Weather Statements
and/or Special Marine Warnings, mainly on the South Carolina
waters through 12-1 AM.

A decent NE gradient will exist Wed through Thu as high pressure
builds from the north. Conditions are currently forecast to
remain just below Small Craft Advisory criteria but wind gusts
along the SC coast could briefly reach 25 kt. Winds will turn to
the E and then SE late week into the weekend and the surface
high shifts offshore.

Rip Currents: Enhanced onshore winds on Wednesday will create a
moderate risk of rip currents along the GA coast.

&&

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

&&

NEAR TERM...
SHORT TERM...JRL
LONG TERM...JRL
AVIATION...
MARINE...

Hazardous Weather Outlook
National Weather Service Charleston SC
343 PM EDT Tue May 9 2023

AMZ330-350-352-354-374-GAZ087-088-099>101-114>116-118-137-138-140-
SCZ040-042>045-047>052-101945-
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-
Jenkins-Screven-Candler-Bulloch-Effingham-Tattnall-Evans-
Inland Bryan-Inland Chatham-Long-Inland Liberty-Inland McIntosh-
Allendale-Hampton-Inland Colleton-Dorchester-Inland Berkeley-
Inland Jasper-Beaufort-Coastal Colleton-Charleston-Coastal Jasper-
Tidal Berkeley-
343 PM EDT Tue May 9 2023

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

.DAY ONE...Tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter assistance is not anticipated at this time.

GAZ117-119-139-141-101945-
Coastal Bryan-Coastal Chatham-Coastal Liberty-Coastal McIntosh-
343 PM EDT Tue May 9 2023

...MODERATE RISK FOR RIP CURRENTS IN EFFECT FROM WEDNESDAY MORNING
THROUGH WEDNESDAY EVENING...

This Hazardous Weather Outlook is for southeast Georgia.

.DAY ONE...Tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

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.

.SPOTTER INFORMATION STATEMENT...

Spotter assistance is not anticipated at this time.

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