Alert archive / Alabama / Mesoscale Discussions in 2021
Mesoscale Discussion 202
The Storm Prediction Center issued this mesoscale discussion at Mar 17, 2021, 12:02 PM CDT for Choctaw County, Clarke County, Marengo County, Alabama; Clarke County, Jones County, Wayne County, Mississippi. It was in force for 58 min.
The area
The outline as issued.
The facts
- Issued
- Mar 17, 2021, 12:02 PM CDT (17:02 UTC)
- Expired
- Mar 17, 2021, 1:00 PM CDT
- In force
- 58 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 29
Counties Choctaw County, AL, Clarke County, AL, Marengo County, AL, Clarke County, MS, Jones County, MS, Wayne County, MS
The radar
The Mobile radar (KMOB), 133 km from the middle of the area, began a volume at 17:05 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
Jackson, MS (KJAN), launched 12:00Z, 5.0 hours before the alert went out and 168 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.
569
ACUS11 KWNS 171702
SWOMCD
SPC MCD 171702
ALZ000-MSZ000-171800-
Mesoscale Discussion 0202
NWS Storm Prediction Center Norman OK
1202 PM CDT Wed Mar 17 2021
Areas affected...Portions of southeast Mississippi and southwest
Alabama
Concerning...Tornado Watch 29...
Valid 171702Z - 171800Z
The severe weather threat for Tornado Watch 29 continues.
SUMMARY...A strong tornado threat will increase from Wayne county,
Mississippi to Marengo and Wilcox counties in Alabama over the next
1-2 hours.
DISCUSSION...Shower activity through the morning has continued to
deepen and a strong storm has developed in Jones County, MS. This
storm has quickly exhibited low-level rotation which is indicative
of the favorable low-level shear profile in this region. SPC
mesoanalysis shows an area of 300 to 400 m2/s2 of 0-3km SRH in this
region which is a result of southeasterly surface winds in local
observations in this area and a 50 knot south-southwesterly
low-level jet around 1.5km to 2km sampled by the KMOB and KDGX VWP.
The ongoing storm in this region in addition to any subsequent
development could pose a significant tornado threat given the
aforementioned favorable low-level shear profile and STP values
around 2 to 3.
..Bentley/Grams.. 03/17/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BMX...MOB...JAN...
LAT...LON 31808915 32228864 32538795 32418740 32128729 31668749
31588799 31458874 31478910 31538924 31808915SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 17, 10:56 AM CDT | Mesoscale Discussion | SPC | Autauga, Bibb, Chilton, Choctaw, Clarke, Coosa and 17 more | 2 hr |
| Mar 17, 11:36 AM CDT | Tornado Watch | SPC | Autauga, Bibb, Blount, Chilton, Choctaw, Clarke and 25 more | 7 hr |
| Mar 17, 1:01 PM CDT | Mesoscale Discussion | SPC | Autauga, Chilton, Coosa, Elmore, Lowndes, Montgomery and 1 more | 89 min |
| Mar 17, 1:26 PM CDT | Tornado Watch | SPC | Calhoun, Chambers, Cherokee, Cleburne, Elmore, Etowah and 7 more | 5 hr |
| Mar 17, 1:45 PM CDT | Mesoscale Discussion | SPC | Mobile | 90 min |
| Mar 17, 2:24 PM CDT | Mesoscale Discussion | SPC | Bibb, Chilton, Dallas, Hale, Marengo, Perry | 96 min |
| Mar 17, 5:49 PM CDT | Mesoscale Discussion | SPC | Autauga, Bibb, Blount, Bullock, Butler, Calhoun and 32 more | 86 min |
| Mar 17, 6:09 PM CDT | Mesoscale Discussion | SPC | Colbert, Franklin, Lamar, Lauderdale, Lawrence, Marion | 66 min |
| Mar 17, 6:48 PM CDT | Tornado Watch | SPC | Autauga, Baldwin, Barbour, Bibb, Blount, Bullock and 44 more | 8 hr |
| Mar 17, 5:34 AM CDT | Mesoscale Discussion | SPC | Alcorn, Benton, Bolivar, Calhoun, Coahoma, DeSoto and 15 more | 86 min |
| Mar 17, 5:53 AM CDT | Tornado Watch | SPC | Alcorn, Benton, Bolivar, Calhoun, Chickasaw, Coahoma and 20 more | 7 hr |
| Mar 17, 7:38 AM CDT | Mesoscale Discussion | SPC | Alcorn, Benton, Coahoma, DeSoto, Itawamba, Lafayette and 11 more | 67 min |
| Mar 17, 12:15 PM CDT | Mesoscale Discussion | SPC | Bolivar, Calhoun, Carroll, Claiborne, Coahoma, Grenada and 22 more | 90 min |
| Mar 17, 12:57 PM CDT | Tornado Watch | SPC | Adams, Alcorn, Benton, Bolivar, Calhoun, Carroll and 32 more | 6 hr |
| Mar 17, 1:19 PM CDT | Mesoscale Discussion | SPC | Jefferson Davis, Lawrence, Lincoln, Simpson, Smith | 86 min |
| Mar 17, 2:38 PM CDT | Tornado Watch | SPC | Amite, Hancock, Harrison, Jackson, Pearl River, Pike and 2 more | 8 hr |
| Mar 17, 2:56 PM CDT | Mesoscale Discussion | SPC | Adams, Attala, Bolivar, Calhoun, Carroll, Chickasaw and 41 more | 94 min |
Nearby
Mesoscale Discussions in Alabama, 2021Mesoscale Discussions in Mississippi, 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.