Alert archive / Mississippi / Mesoscale Discussions in 2021

Mesoscale Discussion 523

May 4, 202110 counties in Alabama; 20 parishes in Louisiana; 37 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at May 4, 2021, 8:33 AM CDT for 10 counties in Alabama; 20 parishes in Louisiana; 37 counties in Mississippi. It was in force for 117 min.

The area

The outline as issued.

The facts

Issued
May 4, 2021, 8:33 AM CDT (13:33 UTC)
Expired
May 4, 2021, 10:30 AM CDT
In force
117 min
Issued by
the Storm Prediction Center
Concerning
Severe potential...watch likely
Chance of a watch
80%
All 67 counties

Choctaw County, AL, Clarke County, AL, Dallas County, AL, Greene County, AL, Hale County, AL, Marengo County, AL, Perry County, AL, Sumter County, AL, Washington County, AL, Wilcox County, AL, Avoyelles Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, East Carroll Parish, LA, East Feliciana Parish, LA, Franklin Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Madison Parish, LA, Pointe Coupee Parish, LA, Rapides Parish, LA, Richland Parish, LA, Saint Helena Parish, LA, Tangipahoa Parish, LA, Tensas Parish, LA, Washington Parish, LA, West Feliciana Parish, LA, Winn Parish, LA, Adams County, MS, Amite County, MS, Claiborne County, MS, Clarke County, MS, Copiah County, MS, Covington County, MS, Forrest County, MS, Franklin County, MS, Greene County, MS, Hinds County, MS, Issaquena County, MS, Jasper County, MS, Jefferson County, MS, Jefferson Davis County, MS, Jones County, MS, Kemper County, MS, Lamar County, MS, Lauderdale County, MS, Lawrence County, MS, Leake County, MS, Lincoln County, MS, Madison County, MS, Marion County, MS, Neshoba County, MS, Newton County, MS, Pearl River County, MS, Perry County, MS, Pike County, MS, Rankin County, MS, Scott County, MS, Simpson County, MS, Smith County, MS, Walthall County, MS, Warren County, MS, Wayne County, MS, Wilkinson County, MS, Yazoo County, MS

The radar

The Jackson/Brandon,MS radar (KDGX), 47 km from the middle of the area, began a volume at 13:35 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

Jackson, MS (KJAN), launched 12:00Z, 1.6 hours before the alert went out and 52 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-pSkew-T log-p diagram, Jackson, MS at 12:00Z on 2021-05-04Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 2428 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Jackson, MS at 12:00Z on 2021-05-04The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 170 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
2428 J/kg
Mixed-layer CIN
-6 J/kg
Mixed-layer LCL
646 m above ground
0-6 km bulk shear
35 kt
0-1 km storm-relative helicity
170 m²/s²
0-3 km storm-relative helicity
235 m²/s²
Significant tornado parameter
2.8
Supercell composite
13.2

Open this sounding in Storm Lab

The text

As transmitted.

535 
ACUS11 KWNS 041334
SWOMCD
SPC MCD 041333 
ALZ000-MSZ000-LAZ000-041530-

Mesoscale Discussion 0523
NWS Storm Prediction Center Norman OK
0833 AM CDT Tue May 04 2021

Areas affected...East Louisiana...Southern Mississippi...and
southwest Alabama

Concerning...Severe potential...Watch likely 

Valid 041333Z - 041530Z

Probability of Watch Issuance...80 percent

SUMMARY...Thunderstorm development is ongoing across portions of the
lower Mississippi river valley region, and will likely continue
through the late morning and early afternoon hours. Strong to severe
storms are expected, and a watch is likely to address this concern.

DISCUSSION...Recent regional radar and satellite trends show
thunderstorm development underway across south-central MS with a
robust supercell noted near the Jackson, MS area. Visible imagery
shows additional agitated cumulus across the region within a broad
warm advection regime. Morning soundings show only minimal capping
in place with MLCAPE values between 2000-2500 J/kg. Additionally,
favorable wind profiles are noted with 30-40 knots of effective bulk
shear and 100-200 m2/s2 0-1 km SRH in regional soundings and VWPs.
These trends and observations suggest that additional thunderstorm
development is likely in the coming hours and should support at
least a few robust severe storms with all severe hazards possible.
(though storm mode and coverage remain somewhat uncertain). A watch
will likely be needed to address this potential.

..Moore/Grams.. 05/04/2021

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

ATTN...WFO...BMX...MOB...JAN...LIX...LCH...SHV...

LAT...LON   31529301 32349264 33029020 33078911 33068787 32818707
            32278705 31498759 31038862 30648982 30589101 30839273
            31529301

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 3, 7:13 PM CDTMesoscale DiscussionSPCAutauga, Bullock, Chambers, Coosa, Elmore, Lee and 4 more62 min
May 4, 5:13 AM CDTSevere Thunderstorm WatchSPCJackson, Lauderdale, Limestone, Madison5 hr
May 4, 7:31 AM CDTMesoscale DiscussionSPCJackson, Lauderdale, Limestone, Madison89 min
May 4, 9:03 AM CDTMesoscale DiscussionSPCBlount, Calhoun, Cherokee, Clay, Cleburne, Cullman and 20 more117 min
May 4, 9:18 AM CDTTornado WatchSPCAutauga, Bibb, Blount, Calhoun, Cherokee, Chilton and 28 more7 hr
May 4, 2:17 PM CDTMesoscale DiscussionSPCChoctaw, Greene, Marengo, Sumter88 min
May 4, 3:03 PM CDTMesoscale DiscussionSPCBibb, Blount, Calhoun, Cherokee, Chilton, Clay and 19 more117 min
May 4, 3:31 PM CDTTornado WatchSPCAutauga, Baldwin, Bibb, Butler, Chilton, Choctaw and 20 more6 hr
May 4, 4:46 PM CDTMesoscale DiscussionSPCAutauga, Baldwin, Bibb, Butler, Chilton, Choctaw and 20 more89 min
May 4, 5:20 PM CDTMesoscale DiscussionSPCBarbour, Bullock, Chambers, Coffee, Covington, Dale and 7 more85 min
May 4, 6:10 PM CDTMesoscale DiscussionSPCAutauga, Coosa, Elmore, Lowndes, Macon, Montgomery and 1 more65 min
May 4, 6:26 PM CDTSevere Thunderstorm WatchSPCBarbour, Bullock, Chambers, Coffee, Covington, Crenshaw and 8 more6 hr
May 3, 9:10 PM CDTSevere Thunderstorm WatchSPCBossier, Caddo, Webster7 hr
May 4, 6:44 AM CDTMesoscale DiscussionSPCBienville, Bossier, Caddo, Claiborne, De Soto, Lincoln and 3 more2 hr
May 4, 10:52 AM CDTTornado WatchSPCAllen, Avoyelles, Beauregard, Bienville, Bossier, Caddo and 31 more7 hr
May 4, 12:16 PM CDTMesoscale DiscussionSPCCaldwell, Catahoula, Concordia, East Carroll, Franklin, Grant and 9 more89 min
May 4, 11:58 AM CDTMesoscale DiscussionSPCAlcorn, Benton, Calhoun, Chickasaw, Coahoma, DeSoto and 13 more2 hr
May 4, 12:18 PM CDTSevere Thunderstorm WatchSPCAlcorn, Benton, Calhoun, Chickasaw, Coahoma, DeSoto and 16 more5 hr

Nearby

Mesoscale Discussions in Mississippi, 2021Mesoscale Discussions in Louisiana, 2021Mesoscale 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.