Alert archive / Mississippi / Mesoscale Discussions in 2021
Mesoscale Discussion 531
The Storm Prediction Center issued this mesoscale discussion at May 4, 2021, 2:17 PM CDT for 4 counties in Alabama; 32 counties in Mississippi. It was in force for 88 min.
The area
The outline as issued.
The facts
- Issued
- May 4, 2021, 2:17 PM CDT (19:17 UTC)
- Expired
- May 4, 2021, 3:45 PM CDT
- In force
- 88 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 144...146
All 36 counties
Choctaw County, AL, Greene County, AL, Marengo County, AL, Sumter County, AL, Attala County, MS, Choctaw County, MS, Claiborne County, MS, Clarke County, MS, Copiah County, MS, Covington County, MS, Franklin County, MS, Hinds County, MS, Holmes County, MS, Jasper County, MS, Jefferson County, MS, Jefferson Davis County, MS, Jones County, MS, Kemper County, MS, Lauderdale County, MS, Lawrence County, MS, Leake County, MS, Lincoln County, MS, Madison County, MS, Montgomery County, MS, Neshoba County, MS, Newton County, MS, Noxubee County, MS, Oktibbeha County, MS, Rankin County, MS, Scott County, MS, Simpson County, MS, Smith County, MS, Warren County, MS, Webster County, MS, Winston County, MS, Yazoo County, MS
The radar
The Jackson/Brandon,MS radar (KDGX), 54 km from the middle of the area, began a volume at 19:19 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
Jackson, MS (KJAN), launched 12:00Z, 7.3 hours before the alert went out and 57 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
- 2428 J/kg
- Mixed-layer CIN
- -6 J/kg
- Mixed-layer LCL
- 646 m above ground
- 0-6 km bulk shear
- 35 kt
- 0-1 km storm-relative helicity
- 170 m²/s²
- 0-3 km storm-relative helicity
- 235 m²/s²
- Significant tornado parameter
- 2.8
- Supercell composite
- 13.2
The text
As transmitted.
737 ACUS11 KWNS 041918 SWOMCD SPC MCD 041917 ALZ000-MSZ000-LAZ000-042045- Mesoscale Discussion 0531 NWS Storm Prediction Center Norman OK 0217 PM CDT Tue May 04 2021 Areas affected...Far Eastern LA...Central MS...West-Central AL Concerning...Tornado Watch 144...146... Valid 041917Z - 042045Z The severe weather threat for Tornado Watch 144, 146 continues. SUMMARY...Threat for strong damaging wind gusts, some over 70 mph, and embedded QLCS tornadoes will continue for the next several hours. DISCUSSION...Recent radar imagery depicts a now well-organized convective line extending from north-central MS southwestward into eastern LA moving eastward at 45-50 kt. VAD profile from SHV sampled the rear-inflow jet well and the latest imagery from DGX is also sampling strong winds within this system. Potential exists for gusts over 70 mph at the surface. Downstream air mass is very moist, with recent mesoanalysis estimating 100-mb mean mixing ratios over 16 g/kg and surface dewpoints in the low 70s. Earlier storms have reduced the mid-level lapse rates a bit, but forecast soundings and mesoanalysis still show steep lapse rates in the 800 to 600 mb layer. As such, overall buoyancy remains strong and there are no indications within the observations or environment of the line weakening. Some potential for embedded QLCS tornadoes exist, particularly if the rear-inflow continues to mature and descend into the low-levels. ..Mosier.. 05/04/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BMX...MOB...JAN...LIX... LAT...LON 33039060 33668937 33168780 31808778 31169148 33039060
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 3, 7:13 PM CDT | Mesoscale Discussion | SPC | Autauga, Bullock, Chambers, Coosa, Elmore, Lee and 4 more | 62 min |
| May 4, 5:13 AM CDT | Severe Thunderstorm Watch | SPC | Jackson, Lauderdale, Limestone, Madison | 5 hr |
| May 4, 7:31 AM CDT | Mesoscale Discussion | SPC | Jackson, Lauderdale, Limestone, Madison | 89 min |
| May 4, 8:33 AM CDT | Mesoscale Discussion | SPC | Choctaw, Clarke, Dallas, Greene, Hale, Marengo and 4 more | 117 min |
| May 4, 9:03 AM CDT | Mesoscale Discussion | SPC | Blount, Calhoun, Cherokee, Clay, Cleburne, Cullman and 20 more | 117 min |
| May 4, 9:18 AM CDT | Tornado Watch | SPC | Autauga, Bibb, Blount, Calhoun, Cherokee, Chilton and 28 more | 7 hr |
| May 4, 3:03 PM CDT | Mesoscale Discussion | SPC | Bibb, Blount, Calhoun, Cherokee, Chilton, Clay and 19 more | 117 min |
| May 4, 3:31 PM CDT | Tornado Watch | SPC | Autauga, Baldwin, Bibb, Butler, Chilton, Choctaw and 20 more | 6 hr |
| May 4, 4:46 PM CDT | Mesoscale Discussion | SPC | Autauga, Baldwin, Bibb, Butler, Chilton, Choctaw and 20 more | 89 min |
| May 4, 5:20 PM CDT | Mesoscale Discussion | SPC | Barbour, Bullock, Chambers, Coffee, Covington, Dale and 7 more | 85 min |
| May 4, 6:10 PM CDT | Mesoscale Discussion | SPC | Autauga, Coosa, Elmore, Lowndes, Macon, Montgomery and 1 more | 65 min |
| May 4, 6:26 PM CDT | Severe Thunderstorm Watch | SPC | Barbour, Bullock, Chambers, Coffee, Covington, Crenshaw and 8 more | 6 hr |
| May 4, 10:52 AM CDT | Tornado Watch | SPC | Adams, Amite, Bolivar, Claiborne, Franklin, Grenada and 9 more | 7 hr |
| May 4, 11:58 AM CDT | Mesoscale Discussion | SPC | Alcorn, Benton, Calhoun, Chickasaw, Coahoma, DeSoto and 13 more | 2 hr |
| May 4, 12:16 PM CDT | Mesoscale Discussion | SPC | Adams, Claiborne, Copiah, Franklin, Hinds, Issaquena and 4 more | 89 min |
| May 4, 12:18 PM CDT | Severe Thunderstorm Watch | SPC | Alcorn, Benton, Calhoun, Chickasaw, Coahoma, DeSoto and 16 more | 5 hr |
Nearby
Mesoscale Discussions in Mississippi, 2021Mesoscale Discussions in Alabama, 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.