Alert archive / Alabama / Mesoscale Discussions in 2021

Mesoscale Discussion 261

March 25, 20216 counties in Alabama

The Storm Prediction Center issued this mesoscale discussion at Mar 25, 2021, 4:45 PM CDT for 6 counties in Alabama. It was in force for 60 min.

The area

The outline as issued.

The facts

Issued: Mar 25, 2021, 4:45 PM CDT (21:45 UTC)
Expired: Mar 25, 2021, 5:45 PM CDT
In force: 60 min
Issued by: the Storm Prediction Center
Concerning: Tornado watch 50

Counties Bibb County, AL, Chilton County, AL, Coosa County, AL, Perry County, AL, Shelby County, AL, Talladega County, AL

The radar

The Birmingham radar (KBMX), 18 km from the middle of the area, began a volume at 21:48 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, 9.8 hours before the alert went out and 19 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.

080 
ACUS11 KWNS 252145
SWOMCD
SPC MCD 252145 
ALZ000-252245-

Mesoscale Discussion 0261
NWS Storm Prediction Center Norman OK
0445 PM CDT Thu Mar 25 2021

Areas affected...central AL

Concerning...Tornado Watch 50...

Valid 252145Z - 252245Z

The severe weather threat for Tornado Watch 50 continues.

SUMMARY...A corridor for a long track intense to potentially violent
tornado is expected to maximize through the next hour across central
AL.

DISCUSSION...An intense tornadic supercell located over Hale County
will likely remain unimpeded as it moves to the east-northeast
across central AL during the next 1-2 hours.  The near-storm
environment is currently primed across central AL with 0-1 km SRH at
600 m2/s2 per observed storm motion according to the KBMX VAD. 
Given the very moist/strongly sheared environment, expecting a
long-track intense (EF3+) and potentially violent tornado to
continue east-northeast and reach the I-65 corridor over the next
hour or so.

..Smith.. 03/25/2021

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

ATTN...WFO...BMX...

LAT...LON   32948754 33488620 33378588 33108586 32938608 32608743
            32948754

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, 3:45 PM CDT	Mesoscale Discussion	SPC	Bibb, Chilton, Choctaw, Dallas, Greene, Hale and 8 more	2 hr
Mar 25, 5:45 PM CDT	Mesoscale Discussion	SPC	Clay, Randolph	60 min

Nearby

Mesoscale Discussions in Alabama, 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.