Alert archive / Mississippi / Mesoscale Discussions in 2021

Mesoscale Discussion 1648

August 30, 202114 counties in Alabama; 16 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Aug 30, 2021, 12:02 PM CDT for 14 counties in Alabama; 16 counties in Mississippi. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 30, 2021, 12:02 PM CDT (17:02 UTC)
Expired: Aug 30, 2021, 2:30 PM CDT
In force: 2 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

All 30 counties

Bibb County, AL, Chilton County, AL, Colbert County, AL, Fayette County, AL, Franklin County, AL, Jefferson County, AL, Lamar County, AL, Marion County, AL, Perry County, AL, Pickens County, AL, Shelby County, AL, Tuscaloosa County, AL, Walker County, AL, Winston County, AL, Alcorn County, MS, Benton County, MS, Calhoun County, MS, Chickasaw County, MS, Clay County, MS, Itawamba County, MS, Lafayette County, MS, Lee County, MS, Lowndes County, MS, Monroe County, MS, Pontotoc County, MS, Prentiss County, MS, Tippah County, MS, Tishomingo County, MS, Union County, MS, Yalobusha County, MS

The radar

The Columbus AFB radar (KGWX), 49 km from the middle of the area, began a volume at 17:01 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 nearest sounding before it

Birmingham, AL (KBMX), launched 12:00Z, 5.0 hours before the alert went out and 115 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: 6 J/kg
Mixed-layer CIN: -242 J/kg
Mixed-layer LCL: 1267 m above ground
0-6 km bulk shear: 29 kt
0-1 km storm-relative helicity: 175 m²/s²
0-3 km storm-relative helicity: 190 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.6

Open this sounding in Storm Lab

The text

As transmitted.

511 
ACUS11 KWNS 301703
SWOMCD
SPC MCD 301702 
ALZ000-MSZ000-301930-

Mesoscale Discussion 1648
NWS Storm Prediction Center Norman OK
1202 PM CDT Mon Aug 30 2021

Areas affected...northern/eastern Mississippi into western Alabama

Concerning...Severe potential...Watch unlikely 

Valid 301702Z - 301930Z

Probability of Watch Issuance...20 percent

SUMMARY...A few strong storms are possible within an outer
convective band from northern Mississippi into western/central
Alabama, but potential currently appears too low for a watch.
Embedded areas of rotation or a brief/weak tornado cannot be ruled
out.

DISCUSSION...Several shallow convective elements are noted on radar
from northwest of Columbus MS to near Centreville AL, with stronger
storms continuing southward into tornado watch 475.

Objective analysis shows the more favorable instability into central
AL where MLCAPE is near 500 J/kg, while values are only near 250
J/kg along the MS/AL border. Low-level shear is currently maximized
over central and eastern MS, with 0-1 km SRH over 300 m2/s2.
Meanwhile, these shear values drop to around 150 m2/s2 over central
AL.

There may be a region of shear/instability overlap from northeast MS
into western AL this afternoon which could support increasing
rotation within the convective line. At this time, the threat is low
for tornadoes, but storm trends will continue to be monitored for
increasing rotation potential.

..Jewell/Grams.. 08/30/2021

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

ATTN...WFO...BMX...HUN...MEG...JAN...

LAT...LON   33378662 32988661 32728675 32618706 32628726 32758751
            33308832 33628889 33788934 33878971 34328988 34898935
            34908825 34778775 34438722 33998680 33378662

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 30, 2:44 AM CDT	Mesoscale Discussion	SPC	Baldwin, Clarke, Conecuh, Escambia, Mobile, Monroe and 1 more	2 hr
Aug 30, 5:48 AM CDT	Tornado Watch	SPC	Baldwin, Butler, Choctaw, Clarke, Conecuh, Covington and 6 more	10 hr
Aug 30, 12:03 PM CDT	Mesoscale Discussion	SPC	Bibb, Chilton, Colbert, Fayette, Franklin, Jefferson and 8 more	4 hr
Aug 30, 3:13 PM CDT	Mesoscale Discussion	SPC	Autauga, Baldwin, Bibb, Butler, Chilton, Choctaw and 17 more	2 hr

Nearby

Mesoscale Discussions in Mississippi, 2021 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.