Alert archive / Mississippi / Mesoscale Discussions in 2021
Mesoscale Discussion 203
The Storm Prediction Center issued this mesoscale discussion at Mar 17, 2021, 12:15 PM CDT for 5 counties in Arkansas; 15 parishes in Louisiana; 28 counties in Mississippi. It was in force for 90 min.
The area
The outline as issued.
The facts
- Issued
- Mar 17, 2021, 12:15 PM CDT (17:15 UTC)
- Expired
- Mar 17, 2021, 1:45 PM CDT
- In force
- 90 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...tornado watch likely
- Chance of a watch
- 95%
All 48 counties
Ashley County, AR, Chicot County, AR, Desha County, AR, Drew County, AR, Phillips County, AR, Caldwell Parish, LA, Catahoula Parish, LA, East Carroll Parish, LA, Franklin Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Madison Parish, LA, Morehouse Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Richland Parish, LA, Tensas Parish, LA, Union Parish, LA, West Carroll Parish, LA, Winn Parish, LA, Bolivar County, MS, Calhoun County, MS, Carroll County, MS, Claiborne County, MS, Coahoma County, MS, Grenada County, MS, Hinds County, MS, Holmes County, MS, Humphreys County, MS, Issaquena County, MS, Jefferson County, MS, Lafayette County, MS, Leflore County, MS, Madison County, MS, Marshall County, MS, Montgomery County, MS, Panola County, MS, Pontotoc County, MS, Quitman County, MS, Sharkey County, MS, Sunflower County, MS, Tallahatchie County, MS, Tate County, MS, Tunica County, MS, Warren County, MS, Washington County, MS, Yalobusha County, MS, Yazoo County, MS
The radar
The Jackson/Brandon,MS radar (KDGX), 159 km from the middle of the area, began a volume at 17:15 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, 5.3 hours before the alert went out and 150 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.
- Mixed-layer CAPE
- 687 J/kg
- Mixed-layer CIN
- -86 J/kg
- Mixed-layer LCL
- 713 m above ground
- 0-6 km bulk shear
- 61 kt
- 0-1 km storm-relative helicity
- 218 m²/s²
- 0-3 km storm-relative helicity
- 178 m²/s²
- Significant tornado parameter
- 0.6
- Supercell composite
- 4.9
The text
As transmitted.
765
ACUS11 KWNS 171715
SWOMCD
SPC MCD 171715
MSZ000-ARZ000-LAZ000-171845-
Mesoscale Discussion 0203
NWS Storm Prediction Center Norman OK
1215 PM CDT Wed Mar 17 2021
Areas affected...Far southeast AR...Northern/West-Central
MS...Northeast LA
Concerning...Severe potential...Tornado Watch likely
Valid 171715Z - 171845Z
Probability of Watch Issuance...95 percent
SUMMARY...The environment will remain favorable for tornadic
supercells throughout the afternoon and into the evening. A new PDS
Tornado Watch will be issued before 18Z to cover this threat.
DISCUSSION...Recent radar imagery shows a well-defined pre-frontal
convective line from northwest AR into southeast TX. Expectation is
for this line to continue gradually eastward throughout the day and
into the evening. Forward motion within the line has slowed over the
past hour or so but continued the approach of the shortwave and
downstream destabilization is expected to result in a reinvigoration
of the line this afternoon.
Currently, KPOE VAD wind profile shows strong low-level flow (50-55
kt at 2 km) beneath deep and robust southwesterly flow aloft. This
kinematic profile supports strong deep-layer vertical shear.
Low-level shear is also expected to become more favorable over time
as the low-level winds strengthen further. Additionally, filtered
diurnal heating has also be noted, with recent surface observations
showing temperatures have increased in the mid to upper 70s.
Mesoanalysis now shows MLCAPE around 1500 J/kg throughout this
entire region.
The overall environment will remain favorable for supercells through
the afternoon and into the evening. There is potential for both
supercells within the convective line as well as ahead of it within
the open warm sector. These supercells will be capable of all severe
hazards, including intense tornadoes, and a new PDS Tornado Watch
will be issued by 18Z.
..Mosier/Grams.. 03/17/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MEG...JAN...LZK...SHV...
LAT...LON 33459195 34809068 34878953 34308889 31579069 31619324
33459195SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 17, 12:45 AM CDT | Mesoscale Discussion | SPC | Benton, Washington | 90 min |
| Mar 17, 1:32 AM CDT | Mesoscale Discussion | SPC | Ashley, Bradley, Calhoun, Clark, Cleveland, Columbia and 27 more | 118 min |
| Mar 17, 4:04 AM CDT | Mesoscale Discussion | SPC | Columbia, Hempstead, Lafayette, Little River, Miller, Sevier | 86 min |
| Mar 17, 4:37 AM CDT | Severe Thunderstorm Watch | SPC | Hempstead, Howard, Lafayette, Little River, Miller, Nevada and 1 more | 5 hr |
| Mar 17, 5:34 AM CDT | Mesoscale Discussion | SPC | Arkansas, Crittenden, Cross, Desha, Lee, Lincoln and 3 more | 86 min |
| Mar 17, 5:53 AM CDT | Tornado Watch | SPC | Arkansas, Bradley, Cleveland, Crittenden, Desha, Drew and 8 more | 7 hr |
| Mar 17, 6:40 AM CDT | Mesoscale Discussion | SPC | Calhoun, Clark, Columbia, Crawford, Dallas, Franklin and 19 more | 95 min |
| Mar 17, 7:38 AM CDT | Mesoscale Discussion | SPC | Crittenden, Lee, Monroe, Phillips, St. Francis | 67 min |
| Mar 17, 7:47 AM CDT | Tornado Watch | SPC | Calhoun, Clark, Conway, Dallas, Faulkner, Garland and 15 more | 5 hr |
| Mar 17, 8:43 AM CDT | Tornado Watch | SPC | Columbia, Union | 4 hr |
| Mar 17, 12:57 PM CDT | Tornado Watch | SPC | Ashley, Chicot, Lee, Phillips | 6 hr |
| Mar 17, 1:18 PM CDT | Mesoscale Discussion | SPC | Benton, Boone, Carroll, Clark, Crawford, Franklin and 22 more | 57 min |
| Mar 17, 2:00 PM CDT | Tornado Watch | SPC | Benton, Boone, Carroll, Crawford, Franklin, Johnson and 12 more | 7 hr |
| Mar 17, 2:56 PM CDT | Mesoscale Discussion | SPC | Ashley, Chicot, Desha, Drew | 94 min |
| Mar 17, 3:37 PM CDT | Mesoscale Discussion | SPC | Baxter, Benton, Boone, Carroll, Crawford, Franklin and 5 more | 83 min |
| Mar 17, 6:09 PM CDT | Mesoscale Discussion | SPC | Crittenden, Cross | 66 min |
| Mar 17, 11:35 AM CDT | Mesoscale Discussion | SPC | Allen, Beauregard, Bienville, Calcasieu, Cameron, De Soto and 8 more | 85 min |
| Mar 17, 11:53 AM CDT | Tornado Watch | SPC | Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 7 more | 6 hr |
| Mar 17, 1:45 PM CDT | Mesoscale Discussion | SPC | Ascension, Assumption, East Baton Rouge, East Feliciana, Iberia, Iberville and 18 more | 90 min |
| Mar 17, 2:38 PM CDT | Tornado Watch | SPC | Ascension, Assumption, East Baton Rouge, East Feliciana, Iberia, Iberville and 19 more | 8 hr |
| Mar 17, 10:56 AM CDT | Mesoscale Discussion | SPC | Attala, Choctaw, Clarke, Clay, Copiah, Covington and 26 more | 2 hr |
| Mar 17, 11:36 AM CDT | Tornado Watch | SPC | Attala, Choctaw, Clarke, Clay, Copiah, Covington and 28 more | 7 hr |
| Mar 17, 12:02 PM CDT | Mesoscale Discussion | SPC | Clarke, Jones, Wayne | 58 min |
| Mar 17, 1:19 PM CDT | Mesoscale Discussion | SPC | Jefferson Davis, Lawrence, Lincoln, Simpson, Smith | 86 min |
| Mar 17, 5:49 PM CDT | Mesoscale Discussion | SPC | Clarke, Covington, Forrest, George, Greene, Jasper and 13 more | 86 min |
| Mar 17, 6:48 PM CDT | Tornado Watch | SPC | Attala, Choctaw, Clarke, Clay, Covington, Forrest and 20 more | 8 hr |
Nearby
Mesoscale Discussions in Mississippi, 2021Mesoscale Discussions in Louisiana, 2021Mesoscale Discussions in Arkansas, 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.