Alert archive / Alabama / Mesoscale Discussions in 2021
Mesoscale Discussion 524
The Storm Prediction Center issued this mesoscale discussion at May 4, 2021, 9:03 AM CDT for 26 counties in Alabama; 14 counties in Georgia; 4 counties in Mississippi. It was in force for 117 min.
The area
The outline as issued.
The facts
- Issued
- May 4, 2021, 9:03 AM CDT (14:03 UTC)
- Expired
- May 4, 2021, 11:00 AM CDT
- In force
- 117 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch likely
- Chance of a watch
- 80%
All 44 counties
Blount County, AL, Calhoun County, AL, Cherokee County, AL, Clay County, AL, Cleburne County, AL, Cullman County, AL, DeKalb County, AL, Etowah County, AL, Fayette County, AL, Franklin County, AL, Jackson County, AL, Jefferson County, AL, Lamar County, AL, Lawrence County, AL, Madison County, AL, Marion County, AL, Marshall County, AL, Morgan County, AL, Pickens County, AL, Randolph County, AL, Shelby County, AL, St. Clair County, AL, Talladega County, AL, Tuscaloosa County, AL, Walker County, AL, Winston County, AL, Bartow County, GA, Carroll County, GA, Chattooga County, GA, Cherokee County, GA, Cobb County, GA, Douglas County, GA, Floyd County, GA, Gilmer County, GA, Gordon County, GA, Haralson County, GA, Paulding County, GA, Pickens County, GA, Polk County, GA, Walker County, GA, Clay County, MS, Lowndes County, MS, Monroe County, MS, Oktibbeha County, MS
The radar
The Birmingham radar (KBMX), 84 km from the middle of the area, began a volume at 14:07 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
Birmingham, AL (KBMX), launched 12:00Z, 2.1 hours before the alert went out and 84 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
- 2158 J/kg
- Mixed-layer CIN
- -5 J/kg
- Mixed-layer LCL
- 569 m above ground
- 0-6 km bulk shear
- 28 kt
- 0-1 km storm-relative helicity
- 145 m²/s²
- 0-3 km storm-relative helicity
- 195 m²/s²
- Significant tornado parameter
- 1.4
- Supercell composite
- 7.3
The text
As transmitted.
766
ACUS11 KWNS 041404
SWOMCD
SPC MCD 041403
GAZ000-ALZ000-MSZ000-041600-
Mesoscale Discussion 0524
NWS Storm Prediction Center Norman OK
0903 AM CDT Tue May 04 2021
Areas affected...Far Northeast/East-Central MS...Northern/Central
AL...Northwest GA
Concerning...Severe potential...Watch likely
Valid 041403Z - 041600Z
Probability of Watch Issuance...80 percent
SUMMARY...Ongoing storm cluster may evolve into a more organized
linear system capable of damaging wind gusts and isolated hail.
Trends are being monitored for likely watch issuance.
DISCUSSION...Western edge of the ongoing cluster of thunderstorms
from northeast MS across northern AL is beginning to show more
forward propagation, suggestive that a cold pool may becoming more
established/organized. This increased forward motion may also be
tied to the ascent associated with the shortwave trough moving into
AR. In either case, the downstream environment supports continued
development. 12Z BMX sounding sampled a deep, moist boundary layer
and 100-mb mean mixing ratio over 15 g/kg. Ongoing storms have
likely reduced the maximum lapse rate between 2-6 km, which was over
7 deg C per km on the sounding, but the moist low-levels still
result moderate buoyancy (i.e. MLCAPE around 1500 J/kg).
Whether or not this ongoing cluster is able to evolve into a linear
MCS remains uncertain, but trends are indicating this potential is
increasing. Additionally, interaction between the more
eastward-moving storms on the western edge of the cluster with
leading storms could result in localized updraft intensification.
This intensification would likely promote strong downdrafts and
occasional hail. Convective trends are being monitored closely for
watch issuance.
..Mosier/Grams.. 05/04/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FFC...BMX...HUN...MEG...JAN...
LAT...LON 33838443 32948601 33118831 33518935 34388810 34808689
34758445 33838443SPC 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, 9:18 AM CDT | Tornado Watch | SPC | Autauga, Bibb, Blount, Calhoun, Cherokee, Chilton and 28 more | 7 hr |
| May 4, 2:17 PM CDT | Mesoscale Discussion | SPC | Choctaw, Greene, Marengo, Sumter | 88 min |
| 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, 9:48 AM CDT | Severe Thunderstorm Watch | SPC | Banks, Barrow, Bartow, Butts, Carroll, Catoosa and 43 more | 6 hr |
| May 4, 12:21 PM CDT | Mesoscale Discussion | SPC | Banks, Barrow, Bartow, Carroll, Cherokee, Clarke and 34 more | 114 min |
| May 4, 2:07 PM CDT | Mesoscale Discussion | SPC | Banks, Barrow, Bartow, Butts, Carroll, Cherokee and 35 more | 113 min |
| May 4, 3:56 PM CDT | Severe Thunderstorm Watch | SPC | Burke, Columbia, McDuffie, Richmond | 3 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 Alabama, 2021Mesoscale Discussions in Georgia, 2021Mesoscale 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.