Alert archive / Alabama / Mesoscale Discussions in 2021

Mesoscale Discussion 259

March 25, 202114 counties in Alabama; 9 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Mar 25, 2021, 3:45 PM CDT for 14 counties in Alabama; 9 counties in Mississippi. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Mar 25, 2021, 3:45 PM CDT (20:45 UTC)
Expired: Mar 25, 2021, 5:45 PM CDT
In force: 2 hr
Issued by: the Storm Prediction Center
Concerning: Tornado watch 50

All 23 counties

Bibb County, AL, Chilton County, AL, Choctaw County, AL, Dallas County, AL, Greene County, AL, Hale County, AL, Jefferson County, AL, Marengo County, AL, Perry County, AL, Shelby County, AL, St. Clair County, AL, Sumter County, AL, Tuscaloosa County, AL, Walker County, AL, Clarke County, MS, Covington County, MS, Forrest County, MS, Jasper County, MS, Jones County, MS, Lamar County, MS, Lauderdale County, MS, Marion County, MS, Wayne County, MS

The radar

The Birmingham radar (KBMX), 114 km from the middle of the area, began a volume at 20:50 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.

Tornado Watch 53Mar 25, 7:45 PM CDT

The nearest sounding before it

Birmingham, AL (KBMX), launched 12:00Z, 8.8 hours before the alert went out and 114 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 54 J/kg
Mixed-layer CIN: -239 J/kg
Mixed-layer LCL: 507 m above ground
0-6 km bulk shear: 65 kt
0-1 km storm-relative helicity: 613 m²/s²
0-3 km storm-relative helicity: 713 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 5.6

Open this sounding in Storm Lab

The text

As transmitted.

074 
ACUS11 KWNS 252045
SWOMCD
SPC MCD 252045 
ALZ000-MSZ000-252245-

Mesoscale Discussion 0259
NWS Storm Prediction Center Norman OK
0345 PM CDT Thu Mar 25 2021

Areas affected...east-central Mississippi into central Alabama

Concerning...Tornado Watch 50...

Valid 252045Z - 252245Z

The severe weather threat for Tornado Watch 50 continues.

SUMMARY...Conditions remain favorable for tornadic supercells
through this afternoon.

DISCUSSION...The air mass remains unstable ahead of a broken line of
cells from east-central MS into north-central AL, with southerly
surface winds and warmer temperatures over southern AL aiding
destabilization. Although these storms are aligned roughly parallel
to the strong southwesterlies aloft, low-level winds remain
sufficiently backed to maintain favorable low-level SRH for
supercells and tornadoes. Effective SRH from objective analysis and
from area VWPs exceeds 300 m2/s2, with values over 400 m2/s2 for a
right-moving cell.

Additional cells have recently intensified over southern MS, and
these may become better organized as they proceed east into the
stronger low-level shear environment.

..Jewell.. 03/25/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...BMX...HUN...MOB...JAN...

LAT...LON   33158622 32668664 31878743 31128926 31118982 31379004
            31868936 32148905 32768850 33238802 33908743 34078681
            33938648 33698620 33158622

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Mar 24, 9:25 PM CDT	Mesoscale Discussion	SPC	Baldwin, Mobile, Washington	65 min
Mar 25, 9:02 AM CDT	Mesoscale Discussion	SPC	Blount, Calhoun, Cherokee, Cleburne, Colbert, Cullman and 21 more	118 min
Mar 25, 10:12 AM CDT	Mesoscale Discussion	SPC	Bibb, Blount, Colbert, Cullman, DeKalb, Etowah and 22 more	3 hr
Mar 25, 10:58 AM CDT	Mesoscale Discussion	SPC	Colbert, Fayette, Franklin, Lamar, Lawrence, Marion and 2 more	3 hr
Mar 25, 11:26 AM CDT	Tornado Watch PDS	SPC	Autauga, Bibb, Blount, Calhoun, Chambers, Cherokee and 39 more	9 hr
Mar 25, 12:28 PM CDT	Mesoscale Discussion	SPC	Bibb, Calhoun, Clay, Cleburne, Shelby, Talladega	2 hr
Mar 25, 1:24 PM CDT	Mesoscale Discussion	SPC	Colbert, Fayette, Franklin, Greene, Lamar, Lawrence and 4 more	2 hr
Mar 25, 4:45 PM CDT	Mesoscale Discussion	SPC	Bibb, Chilton, Coosa, Perry, Shelby, Talladega	60 min
Mar 25, 5:45 PM CDT	Mesoscale Discussion	SPC	Clay, Randolph	60 min
Mar 25, 11:00 AM CDT	Mesoscale Discussion	SPC	Hancock, Harrison, Pearl River, Stone	2 hr
Mar 25, 2:29 PM CDT	Mesoscale Discussion	SPC	Alcorn	2 hr
Mar 25, 3:48 PM CDT	Tornado Watch	SPC	Alcorn	7 hr

Nearby

Mesoscale Discussions in Alabama, 2021 Mesoscale Discussions in Mississippi, 2021 Every 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.