Alert archive / North Carolina / Mesoscale Discussions in 2021
Mesoscale Discussion 535
The Storm Prediction Center issued this mesoscale discussion at May 4, 2021, 4:16 PM EDT for 41 counties in North Carolina; 35 counties in South Carolina. It was in force for 119 min.
The area
The outline as issued.
The facts
- Issued
- May 4, 2021, 4:16 PM EDT (20:16 UTC)
- Expired
- May 4, 2021, 6:15 PM EDT
- In force
- 119 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 76 counties
Alamance County, NC, Anson County, NC, Bladen County, NC, Cabarrus County, NC, Caswell County, NC, Chatham County, NC, Columbus County, NC, Cumberland County, NC, Davidson County, NC, Duplin County, NC, Durham County, NC, Edgecombe County, NC, Franklin County, NC, Granville County, NC, Greene County, NC, Guilford County, NC, Harnett County, NC, Hoke County, NC, Johnston County, NC, Lee County, NC, Lenoir County, NC, Mecklenburg County, NC, Montgomery County, NC, Moore County, NC, Nash County, NC, Orange County, NC, Pender County, NC, Person County, NC, Pitt County, NC, Randolph County, NC, Richmond County, NC, Robeson County, NC, Sampson County, NC, Scotland County, NC, Stanly County, NC, Union County, NC, Vance County, NC, Wake County, NC, Warren County, NC, Wayne County, NC, Wilson County, NC, Abbeville County, SC, Aiken County, SC, Bamberg County, SC, Barnwell County, SC, Berkeley County, SC, Calhoun County, SC, Chester County, SC, Chesterfield County, SC, Clarendon County, SC, Colleton County, SC, Darlington County, SC, Dillon County, SC, Dorchester County, SC, Edgefield County, SC, Fairfield County, SC, Florence County, SC, Georgetown County, SC, Greenwood County, SC, Horry County, SC, Kershaw County, SC, Lancaster County, SC, Laurens County, SC, Lee County, SC, Lexington County, SC, Marion County, SC, Marlboro County, SC, McCormick County, SC, Newberry County, SC, Orangeburg County, SC, Richland County, SC, Saluda County, SC, Sumter County, SC, Union County, SC, Williamsburg County, SC, York County, SC
The radar
The Columbia radar (KCAE), 123 km from the middle of the area, began a volume at 20:16 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 watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Greensboro/Hi Pt, NC (KGSO), launched 12:00Z, 8.3 hours before the alert went out and 165 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
- 463 J/kg
- Mixed-layer CIN
- -235 J/kg
- Mixed-layer LCL
- 935 m above ground
- 0-6 km bulk shear
- 30 kt
- 0-1 km storm-relative helicity
- 72 m²/s²
- 0-3 km storm-relative helicity
- 87 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
432
ACUS11 KWNS 042017
SWOMCD
SPC MCD 042016
NCZ000-SCZ000-VAZ000-042215-
Mesoscale Discussion 0535
NWS Storm Prediction Center Norman OK
0316 PM CDT Tue May 04 2021
Areas affected...Central North and South Carolina
Concerning...Severe potential...Watch possible
Valid 042016Z - 042215Z
Probability of Watch Issuance...40 percent
SUMMARY...Isolated to scattered wind damage and severe hail are
possible across central North and South Carolina over the next few
hours. This threat is expected to be fairly localized and short in
duration, but a watch is possible.
DISCUSSION...Scattered thunderstorms have begun to develop along an
outflow boundary from prior convection over TN/KY/GA. MRMS
vertically integrated ice and echo top trends over the past 30-60
minutes show that this activity has been largely transient with
individual cells exhibiting short lifespans in the absence of
stronger forcing for ascent and weak vertical wind shear.
Nonetheless, strong boundary-layer heating is noted across the
Carolinas where skies have been mostly clear through the day and
temperatures have warmed into the upper 80s and low 90s amid
dewpoints in the upper 60s and low 70s. This is supporting MLCAPE
values on the order of 1000-2000 J/kg along with steep low-level
lapse rates (near 8 C/km per RAP mesoanalysis). This environment is
supportive of at least a few instances of severe hail and damaging
winds with any stronger updraft pulses. The severe threat may be
slightly higher across central/southern SC where deep-layer shear is
somewhat stronger (near 30 knots of effective bulk shear). Overall,
the coverage and duration of this threat is expected to remain low,
but trends will be monitored and a watch is possible if confidence
in coverage and intensity increases.
..Moore/Grams.. 05/04/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MHX...RAH...ILM...RNK...CHS...CAE...GSP...
LAT...LON 34168261 34808170 35168111 35688040 36377971 36547895
36357780 35967727 35357737 34477761 33767886 33087968
32808040 32798092 33188159 33678212 34168261SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 4, 9:37 AM EDT | Severe Thunderstorm Watch | SPC | Cherokee, Clay, Graham, Macon, Swain | 3 hr |
| May 4, 1:04 PM EDT | Mesoscale Discussion | SPC | Caswell, Northampton, Person, Rockingham, Stokes, Surry and 2 more | 56 min |
| May 4, 1:21 PM EDT | Mesoscale Discussion | SPC | Clay, Macon | 114 min |
| May 4, 4:56 PM EDT | Severe Thunderstorm Watch | SPC | Anson, Bladen, Cumberland, Harnett, Hoke, Lee and 7 more | 3 hr |
| May 4, 7:59 PM EDT | Mesoscale Discussion | SPC | Berkeley, Clarendon, Dorchester, Marion, Williamsburg | 61 min |
Nearby
Mesoscale Discussions in North Carolina, 2021Mesoscale 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.