Alert archive / Mississippi / Mesoscale Discussions in 2021

Mesoscale Discussion 485

May 3, 20215 counties in Mississippi; 5 counties in Tennessee

The Storm Prediction Center issued this mesoscale discussion at May 3, 2021, 1:56 AM CDT for 5 counties in Mississippi; 5 counties in Tennessee. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: May 3, 2021, 1:56 AM CDT (06:56 UTC)
Expired: May 3, 2021, 4:30 AM CDT
In force: 3 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch possible
Chance of a watch: 40%

Counties Alcorn County, MS, Benton County, MS, DeSoto County, MS, Marshall County, MS, Tippah County, MS, Fayette County, TN, Hardeman County, TN, Hardin County, TN, McNairy County, TN, Wayne County, TN

The radar

The Memphis radar (KNQA), 97 km from the middle of the area, began a volume at 06:57 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

Little Rock, AR (KLZK), launched 00:00Z, 6.9 hours before the alert went out and 99 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: 36 J/kg
Mixed-layer CIN: -39 J/kg
Mixed-layer LCL: 777 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 59 m²/s²
0-3 km storm-relative helicity: 120 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.5

Open this sounding in Storm Lab

The text

As transmitted.

209 
ACUS11 KWNS 030657
SWOMCD
SPC MCD 030656 
TNZ000-ALZ000-MSZ000-030930-

Mesoscale Discussion 0485
NWS Storm Prediction Center Norman OK
0156 AM CDT Mon May 03 2021

Areas affected...far northern Mississippi into southwestern
Tennessee

Concerning...Severe potential...Watch possible 

Valid 030656Z - 030930Z

Probability of Watch Issuance...40 percent

SUMMARY...A corridor of severe risk, including damaging gusts or a
brief tornado, may develop along the Mississippi/Tennessee border.
It is uncertain whether coverage of severe will warrant a watch.

DISCUSSION...Scattered showers and storms currently extend eastward
along the MS/TN border, with a recent uptick in intensity and
organization just south of Memphis TN. While winds just off the
surface have veered on the immediate back side of the upper trough,
shear remains strong and instability remains sufficient to sustain
severe storms. VWPs still indicate 200-300 m2/s2 0-1 SRH, along with
40 kt effective shear.

The northwest MS cluster is ingesting upper 60s F dewpoints, and
south/southwest low-level mean winds will aid advection of moisture,
eventually into TN. This will result in MLCAPE on the order of
750-1000 J/kg. Thus, given current radar trends, a narrow zone of
severe wind/QLCS tornado threat may extend east of the developing
line of storms. Trends will continue to be monitored for any upscale
growth.

..Jewell/Edwards.. 05/03/2021

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

ATTN...WFO...OHX...HUN...MEG...

LAT...LON   35149000 35538803 35478764 35268749 34978756 34898780
            34808855 34688941 34678994 34779014 34899011 35149000

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 2, 11:45 PM CDT	Mesoscale Discussion	SPC	Alcorn, Benton, Calhoun, Chickasaw, Clay, Coahoma and 17 more	2 hr
May 3, 11:47 AM CDT	Severe Thunderstorm Watch	SPC	Attala, Choctaw, Clarke, Clay, Jasper, Kemper and 13 more	10 hr
May 3, 4:00 PM CDT	Mesoscale Discussion	SPC	Clarke, Kemper, Lauderdale, Wayne	90 min
May 3, 6:50 AM CDT	Mesoscale Discussion	SPC	Bedford, Bledsoe, Cannon, Coffee, Cumberland, DeKalb and 23 more	115 min

Nearby

Mesoscale Discussions in Mississippi, 2021 Mesoscale Discussions in Tennessee, 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.