Alert archive / Mississippi / Mesoscale Discussions in 2021
Mesoscale Discussion 196
The Storm Prediction Center issued this mesoscale discussion at Mar 17, 2021, 5:34 AM CDT for 9 counties in Arkansas; 21 counties in Mississippi; 6 counties in Tennessee. It was in force for 86 min.
The area
The outline as issued.
The facts
- Issued
- Mar 17, 2021, 5:34 AM CDT (10:34 UTC)
- Expired
- Mar 17, 2021, 7:00 AM CDT
- In force
- 86 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch likely
- Chance of a watch
- 80%
All 36 counties
Arkansas County, AR, Crittenden County, AR, Cross County, AR, Desha County, AR, Lee County, AR, Lincoln County, AR, Monroe County, AR, Phillips County, AR, St. Francis County, AR, Alcorn County, MS, Benton County, MS, Bolivar County, MS, Calhoun County, MS, Coahoma County, MS, DeSoto County, MS, Grenada County, MS, Lafayette County, MS, Lee County, MS, Marshall County, MS, Panola County, MS, Pontotoc County, MS, Prentiss County, MS, Quitman County, MS, Sunflower County, MS, Tallahatchie County, MS, Tate County, MS, Tippah County, MS, Tunica County, MS, Union County, MS, Yalobusha County, MS, Fayette County, TN, Hardeman County, TN, Haywood County, TN, McNairy County, TN, Shelby County, TN, Tipton County, TN
The radar
The Memphis radar (KNQA), 100 km from the middle of the area, began a volume at 10:35 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
Little Rock, AR (KLZK), launched 00:00Z, 10.6 hours before the alert went out and 42 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 2044 m above ground
- 0-6 km bulk shear
- 63 kt
- 0-1 km storm-relative helicity
- 200 m²/s²
- 0-3 km storm-relative helicity
- 260 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -0.0
The text
As transmitted.
643
ACUS11 KWNS 171034
SWOMCD
SPC MCD 171034
MSZ000-TNZ000-ARZ000-171200-
Mesoscale Discussion 0196
NWS Storm Prediction Center Norman OK
0534 AM CDT Wed Mar 17 2021
Areas affected...Portions of eastern AR...northern MS...and
southwestern TN
Concerning...Severe potential...Watch likely
Valid 171034Z - 171200Z
Probability of Watch Issuance...80 percent
SUMMARY...An increasing severe threat, including the potential for a
few tornadoes, may develop this morning. Watch issuance is likely.
DISCUSSION...A supercell has recently strengthened over southeastern
AR to the south of a warm front. A broad zone of low-level warm
advection persists over the lower MS Valley vicinity this morning,
and current expectations are for the low-level wind field to
gradually strengthen from west to east over the next few hours as an
upper low ejects over the southern Plains. The low-level profile
will be quite favorable for updraft rotation, and a few tornadoes
will be possible with any storms that can form along or south of the
northward-moving warm front. MLCAPE of 1000-1500 J/kg should be
sufficient in tandem with 45-55 kt of effective bulk shear to
support large hail with any supercells. Isolated damaging wind gusts
may also occur. Given the possibility of additional supercells
developing this morning across southeastern AR into northern MS and
southwestern TN, watch issuance will likely be needed.
..Gleason/Thompson.. 03/17/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MEG...JAN...LZK...
LAT...LON 33559057 33619170 34029197 35349077 35649024 35618927
35218849 34668824 34118871 33718953 33559057SPC 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, 5:53 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, 12:15 PM CDT | Mesoscale Discussion | SPC | Ashley, Chicot, Desha, Drew, Phillips | 90 min |
| 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, 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, 1:45 PM CDT | Mesoscale Discussion | SPC | Amite, Forrest, George, Greene, Hancock, Harrison and 9 more | 90 min |
| Mar 17, 2:38 PM CDT | Tornado Watch | SPC | Amite, Hancock, Harrison, Jackson, Pearl River, Pike and 2 more | 8 hr |
| 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 |
| Mar 17, 12:59 PM CDT | Tornado Watch | SPC | Benton, Carroll, Chester, Crockett, Decatur, Dyer and 13 more | 6 hr |
| Mar 17, 2:16 PM CDT | Mesoscale Discussion | SPC | Bedford, Benton, Cannon, Coffee, Davidson, Decatur and 18 more | 59 min |
Nearby
Mesoscale Discussions in Mississippi, 2021Mesoscale Discussions in Arkansas, 2021Mesoscale Discussions in Tennessee, 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.