Alert archive / Mississippi / Mesoscale Discussions in 2021
Mesoscale Discussion 198
The Storm Prediction Center issued this mesoscale discussion at Mar 17, 2021, 7:38 AM CDT for 5 counties in Arkansas; 17 counties in Mississippi; 4 counties in Tennessee. It was in force for 67 min.
The area
The outline as issued.
The facts
- Issued
- Mar 17, 2021, 7:38 AM CDT (12:38 UTC)
- Expired
- Mar 17, 2021, 8:45 AM CDT
- In force
- 67 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 26
All 26 counties
Crittenden County, AR, Lee County, AR, Monroe County, AR, Phillips County, AR, St. Francis County, AR, Alcorn County, MS, Benton County, MS, Coahoma County, MS, DeSoto County, MS, Itawamba County, MS, Lafayette County, MS, Lee County, MS, Marshall County, MS, Panola County, MS, Pontotoc County, MS, Prentiss County, MS, Quitman County, MS, Tate County, MS, Tippah County, MS, Tishomingo County, MS, Tunica County, MS, Union County, MS, Fayette County, TN, Hardeman County, TN, McNairy County, TN, Shelby County, TN
The radar
The Memphis radar (KNQA), 79 km from the middle of the area, began a volume at 12:39 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 12:00Z, 0.6 hours before the alert went out and 23 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
- 18 J/kg
- Mixed-layer CIN
- -262 J/kg
- Mixed-layer LCL
- 1466 m above ground
- 0-6 km bulk shear
- 65 kt
- 0-1 km storm-relative helicity
- 217 m²/s²
- 0-3 km storm-relative helicity
- 186 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.5
The text
As transmitted.
552
ACUS11 KWNS 171238
SWOMCD
SPC MCD 171238
TNZ000-MSZ000-ARZ000-171345-
Mesoscale Discussion 0198
NWS Storm Prediction Center Norman OK
0738 AM CDT Wed Mar 17 2021
Areas affected...Portions of eastern AR...northern MS...and far
southwestern TN
Concerning...Tornado Watch 26...
Valid 171238Z - 171345Z
The severe weather threat for Tornado Watch 26 continues.
SUMMARY...All severe hazards, including a few tornadoes, remain
possible in the short term.
DISCUSSION...Primary severe risk at the moment across Tornado Watch
26 remains focused over northern MS with an ongoing supercell. The
12Z sounding from JAN indicated a favorable low-level wind profile
for updraft rotation, but instability remains a somewhat limiting
factor. Low-level southerly flow should continue to gradually
increase over the next couple of hours, and storms that can interact
with the warm front may pose a tornado threat given effective SRH of
200-250 m2/s2. Any semi-discrete supercells may also have an
isolated large hail and damaging wind threat. The overall severe
threat this morning should remain fairly isolated, with a much more
substantial risk for all hazards, including strong tornadoes, likely
to develop later this afternoon.
..Gleason.. 03/17/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MEG...LZK...
LAT...LON 34439174 34899142 35369007 35348868 34888821 34208826
34118965 34179070 34439174SPC 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, 7:47 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.