Alert archive / Alabama / Mesoscale Discussions in 2021
Mesoscale Discussion 534
The Storm Prediction Center issued this mesoscale discussion at May 4, 2021, 3:03 PM CDT for 25 counties in Alabama; 11 counties in Mississippi. It was in force for 117 min.
The area
The outline as issued.
The facts
- Issued
- May 4, 2021, 3:03 PM CDT (20:03 UTC)
- Expired
- May 4, 2021, 5:00 PM CDT
- In force
- 117 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 144
All 36 counties
Bibb County, AL, Blount County, AL, Calhoun County, AL, Cherokee County, AL, Chilton County, AL, Clay County, AL, Coosa County, AL, Cullman County, AL, Etowah County, AL, Fayette County, AL, Franklin County, AL, Greene County, AL, Hale County, AL, Jefferson County, AL, Lamar County, AL, Marion County, AL, Marshall County, AL, Morgan County, AL, Pickens County, AL, Shelby County, AL, St. Clair County, AL, Talladega County, AL, Tuscaloosa County, AL, Walker County, AL, Winston County, AL, Chickasaw County, MS, Choctaw County, MS, Clay County, MS, Itawamba County, MS, Kemper County, MS, Lowndes County, MS, Monroe County, MS, Noxubee County, MS, Oktibbeha County, MS, Webster County, MS, Winston County, MS
The radar
The Columbus AFB radar (KGWX), 74 km from the middle of the area, began a volume at 20:05 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, 8.1 hours before the alert went out and 92 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.
376
ACUS11 KWNS 042004
SWOMCD
SPC MCD 042003
ALZ000-MSZ000-042200-
Mesoscale Discussion 0534
NWS Storm Prediction Center Norman OK
0303 PM CDT Tue May 04 2021
Areas affected...Northeast MS...Central AL
Concerning...Tornado Watch 144...
Valid 042003Z - 042200Z
The severe weather threat for Tornado Watch 144 continues.
SUMMARY...Complex convective evolution is anticipated from
west-central MS through northern/central AL over the next few hours.
Strong winds appear most likely from east-central MS into
west-central AL
DISCUSSION...Strongest part of the ongoing convective line appears
to be progressing through central MS currently. However, radar and
surface observations reveal a remnant outflow boundary draped from
northeast MS across central AL and through west-central GA. Western
and central portions of this outflow boundary have stalled, with the
western portion appearing to now move back northward as an effective
warm front. Thunderstorms are ongoing north of the boundary across
much of AL, which could impede any northward motion.
Given these mesoscale complexities, the overall convective evolution
as the line begins to interact with this boundary is uncertain.
Dewpoints are in the mid 60s across east-central MS and west-central
AL, decreasing to closer to 60 over east-central AL and west-central
GA. This is resulting is decreasing buoyancy from west to east,
introducing additional uncertainty with how far north and east
severe will occur with this convective line. Most probable area for
strong wind gusts is from east-central MS into west-central AL where
buoyancy remains strong. Elsewhere, convective trends will be
monitored closely, with at least some potential for a watch over
northern AL.
..Mosier.. 05/04/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BMX...HUN...MEG...JAN...
LAT...LON 33298967 34568841 34418565 33338552 32778636 32738867
33298967SPC 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, 2:17 PM CDT | Mesoscale Discussion | SPC | Choctaw, Greene, Marengo, Sumter | 88 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 Alabama, 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.