Alert archive / Alabama / Mesoscale Discussions in 2021
Mesoscale Discussion 204
The Storm Prediction Center issued this mesoscale discussion at Mar 17, 2021, 1:01 PM CDT for 7 counties in Alabama. It was in force for 89 min.
The area
The outline as issued.
The facts
- Issued
- Mar 17, 2021, 1:01 PM CDT (18:01 UTC)
- Expired
- Mar 17, 2021, 2:30 PM CDT
- In force
- 89 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 29
Counties Autauga County, AL, Chilton County, AL, Coosa County, AL, Elmore County, AL, Lowndes County, AL, Montgomery County, AL, Tallapoosa County, AL
The radar
The Maxwell AFB radar (KMXX), 56 km from the middle of the area, began a volume at 18:00 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, 6.0 hours before the alert went out and 68 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
- 658 J/kg
- Mixed-layer CIN
- -112 J/kg
- Mixed-layer LCL
- 759 m above ground
- 0-6 km bulk shear
- 59 kt
- 0-1 km storm-relative helicity
- 169 m²/s²
- 0-3 km storm-relative helicity
- 301 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 2.1
The text
As transmitted.
383
ACUS11 KWNS 171802
SWOMCD
SPC MCD 171801
ALZ000-171930-
Mesoscale Discussion 0204
NWS Storm Prediction Center Norman OK
0101 PM CDT Wed Mar 17 2021
Areas affected...portions of central Alabama
Concerning...Tornado Watch 29...
Valid 171801Z - 171930Z
The severe weather threat for Tornado Watch 29 continues.
SUMMARY...A local expansion of tornado watch 29 may be needed.
DISCUSSION...A favorable tornadic environment exists across central
Alabama with temperatures in the mid 70s and dewpoints in the upper
60s yielding MLCAPE around 1000 to 1500 J/kg. In addition, this area
is in close proximity to the warm front where low-level winds are
backed and low-level SRH is maximized. A supercell which developed
in Dallas County has taken advantage of this favorable tornadic
environment with radar evidence of a tornado near the Dallas Autauga
county line. There is considerable question regarding the longevity
of the tornado threat with this activity. The warm sector is
advecting northeastward, but this storm may eventually move to the
cool side of the boundary. However, given the potential for this
storm to potentially move out of watch 29 and additional shower
development to it's south and southeast which could deepen and
become tornadic, watch 29 may need to be expanded into eastern
Alabama.
..Bentley/Grams.. 03/17/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BMX...
LAT...LON 32798706 33238651 33308594 33088554 32718535 32368592
32078630 32128689 32358707 32798706SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 17, 10:56 AM CDT | Mesoscale Discussion | SPC | Autauga, Bibb, Chilton, Choctaw, Clarke, Coosa and 17 more | 2 hr |
| Mar 17, 11:36 AM CDT | Tornado Watch | SPC | Autauga, Bibb, Blount, Chilton, Choctaw, Clarke and 25 more | 7 hr |
| Mar 17, 12:02 PM CDT | Mesoscale Discussion | SPC | Choctaw, Clarke, Marengo | 58 min |
| Mar 17, 1:26 PM CDT | Tornado Watch | SPC | Calhoun, Chambers, Cherokee, Cleburne, Elmore, Etowah and 7 more | 5 hr |
| Mar 17, 1:45 PM CDT | Mesoscale Discussion | SPC | Mobile | 90 min |
| Mar 17, 2:24 PM CDT | Mesoscale Discussion | SPC | Bibb, Chilton, Dallas, Hale, Marengo, Perry | 96 min |
| Mar 17, 5:49 PM CDT | Mesoscale Discussion | SPC | Autauga, Bibb, Blount, Bullock, Butler, Calhoun and 32 more | 86 min |
| Mar 17, 6:09 PM CDT | Mesoscale Discussion | SPC | Colbert, Franklin, Lamar, Lauderdale, Lawrence, Marion | 66 min |
| Mar 17, 6:48 PM CDT | Tornado Watch | SPC | Autauga, Baldwin, Barbour, Bibb, Blount, Bullock and 44 more | 8 hr |
Nearby
Mesoscale 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.