Alert archive / South Carolina / Mesoscale Discussions in 2021
Mesoscale Discussion 540
The Storm Prediction Center issued this mesoscale discussion at May 4, 2021, 7:59 PM EDT for 5 counties in South Carolina. It was in force for 61 min.
The area
The outline as issued.
The facts
- Issued
- May 4, 2021, 7:59 PM EDT (23:59 UTC)
- Expired
- May 4, 2021, 9:00 PM EDT
- In force
- 61 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 150
Counties Berkeley County, SC, Clarendon County, SC, Dorchester County, SC, Marion County, SC, Williamsburg County, SC
The radar
The Wilmington radar (KLTX), 128 km from the middle of the area, began a volume at 00:04 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
The nearest sounding before it
Charleston AFB, SC (KCHS), launched 12:00Z, 12.0 hours before the alert went out and 77 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 573 J/kg
- Mixed-layer CIN
- -149 J/kg
- Mixed-layer LCL
- 1000 m above ground
- 0-6 km bulk shear
- 37 kt
- 0-1 km storm-relative helicity
- 68 m²/s²
- 0-3 km storm-relative helicity
- 48 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 1.0
The text
As transmitted.
832
ACUS11 KWNS 050000
SWOMCD
SPC MCD 042359
SCZ000-050100-
Mesoscale Discussion 0540
NWS Storm Prediction Center Norman OK
0659 PM CDT Tue May 04 2021
Areas affected...portions of eastern South Carolina
Concerning...Severe Thunderstorm Watch 150...
Valid 042359Z - 050100Z
The severe weather threat for Severe Thunderstorm Watch 150
continues.
SUMMARY...Ongoing storms along the I-95 corridor of eastern South
Carolina will pose a risk for isolated damaging winds and marginally
severe hail over the next hour. A general weakening trend is
expected to continue.
DISCUSSION...As of 2335 UTC, radar and satellite trends across the
Carolinas have shown a general weakening of ongoing convection. A
couple of severe storms remain east of I-95 in South Carolina.
Recent storm reports confirm these storms are still capable of
producing mainly severe wind gusts as they move off to the
northeast. SPC mesoanalysis shows mixed-layer inhibition of -100 to
-150 J/kg slowly increasing across the area with the loss of diurnal
heating and convective overturning from previous bands of storms.
Hi-res guidance also agrees with the observed weakening trend,
supporting moderate to high confidence that the severe weather risk
will continue to gradually decay early this evening and after
sunset. Until then, storms will remain capable of producing isolated
damaging wind gusts given an unstable (1500-2000 J/kg of MLCAPE) and
weakly sheared environment.
..Lyons/Thompson.. 05/04/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ILM...CHS...CAE...
LAT...LON 33607921 33267952 32897995 32968059 33288070 33728028
34147942 34107917 33947904 33607921SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 4, 1:21 PM EDT | Mesoscale Discussion | SPC | Abbeville, Anderson, Oconee, Pickens | 114 min |
| May 4, 4:16 PM EDT | Mesoscale Discussion | SPC | Abbeville, Aiken, Bamberg, Barnwell, Berkeley, Calhoun and 29 more | 119 min |
| May 4, 4:56 PM EDT | Severe Thunderstorm Watch | SPC | Aiken, Bamberg, Barnwell, Calhoun, Chesterfield, Clarendon and 13 more | 3 hr |
Nearby
Mesoscale Discussions in South Carolina, 2021Every mesoscale discussion in 2021
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.