Alert archive / Mississippi / Mesoscale Discussions in 2021
Mesoscale Discussion 576
The Storm Prediction Center issued this mesoscale discussion at May 9, 2021, 6:40 PM CDT for 9 counties in Mississippi. It was in force for 65 min.
The area
The outline as issued.
The facts
- Issued
- May 9, 2021, 6:40 PM CDT (23:40 UTC)
- Expired
- May 9, 2021, 7:45 PM CDT
- In force
- 65 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 158
Counties Calhoun County, MS, Chickasaw County, MS, Itawamba County, MS, Lafayette County, MS, Lee County, MS, Monroe County, MS, Pontotoc County, MS, Prentiss County, MS, Union County, MS
The radar
The Columbus AFB radar (KGWX), 79 km from the middle of the area, began a volume at 23:40 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
Little Rock, AR (KLZK), launched 12:00Z, 11.7 hours before the alert went out and 105 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
- 203 J/kg
- Mixed-layer CIN
- -439 J/kg
- Mixed-layer LCL
- 759 m above ground
- 0-6 km bulk shear
- 26 kt
- 0-1 km storm-relative helicity
- 446 m²/s²
- 0-3 km storm-relative helicity
- 571 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
030
ACUS11 KWNS 092340
SWOMCD
SPC MCD 092340
ALZ000-MSZ000-100045-
Mesoscale Discussion 0576
NWS Storm Prediction Center Norman OK
0640 PM CDT Sun May 09 2021
Areas affected...Northern Mississippi and far Northwest Alabama
Concerning...Severe Thunderstorm Watch 158...
Valid 092340Z - 100045Z
The severe weather threat for Severe Thunderstorm Watch 158
continues.
SUMMARY...Potential bowing segment and corridor of wind damage
developing the next 1-2 hours. A downstream watch may be considered.
DISCUSSION...A long-lived semi-discrete supercell has crossed the
Mississippi River, and is beginning to show early indications of
upscale convective growth and cold-pool organization, per KNQA and
KGWX radar observations. Should this convective trend continue, a
corridor of wind damage potential may materialize in the next 1-2
hours across northern portions of Mississippi. This trend is
supported by SPC Mesoanalysis, indicating 1500-2000 J/kg of MLCAPE
amid 40-50 of effective bulk shear. Additionally, short-term
convection allowing models are suggestive of a bowing convective
segment tracking across this region. It remains uncertain how far
east the threat will persist, given the weaker
thermodynamic/kinematic environment over northwest Alabama
currently. However, should a bowing segment develop, a downstream
watch may be needed across this area.
..Karstens.. 05/09/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BMX...MEG...JAN...
LAT...LON 33858925 34168991 34568999 34748955 34628834 34048806
33648858 33858925SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 9, 12:14 PM CDT | Mesoscale Discussion | SPC | Alcorn, Benton, Bolivar, Calhoun, Carroll, Coahoma and 22 more | 91 min |
| May 9, 1:14 PM CDT | Severe Thunderstorm Watch | SPC | Bolivar, Humphreys, Issaquena, Leflore, Sharkey, Sunflower and 1 more | 8 hr |
| May 9, 2:27 PM CDT | Severe Thunderstorm Watch | SPC | Alcorn, Benton, Calhoun, Chickasaw, Coahoma, DeSoto and 16 more | 7 hr |
| May 9, 3:42 PM CDT | Mesoscale Discussion | SPC | Alcorn, Benton, Bolivar, Calhoun, Chickasaw, Coahoma and 14 more | 93 min |
| May 9, 3:53 PM CDT | Mesoscale Discussion | SPC | Claiborne, Copiah, Covington, Hinds, Jasper, Jefferson and 10 more | 2 hr |
| May 9, 5:41 PM CDT | Mesoscale Discussion | SPC | Bolivar, Coahoma, Humphreys, Issaquena, Sharkey, Sunflower and 1 more | 2 hr |
| May 9, 5:48 PM CDT | Mesoscale Discussion | SPC | Alcorn, Benton, Coahoma, DeSoto, Itawamba, Lafayette and 11 more | 87 min |
Nearby
Mesoscale Discussions in Mississippi, 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.