Alert archive / Alabama / Mesoscale Discussions in 2021
Mesoscale Discussion 216
The Storm Prediction Center issued this mesoscale discussion at Mar 17, 2021, 9:16 PM CDT for 7 counties in Alabama. It was in force for 89 min.
The area
The outline as issued.
The facts
- Issued
- Mar 17, 2021, 9:16 PM CDT (02:16 UTC)
- Expired
- Mar 17, 2021, 10:45 PM CDT
- In force
- 89 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 37
Counties Cullman County, AL, DeKalb County, AL, Jackson County, AL, Limestone County, AL, Madison County, AL, Marshall County, AL, Morgan County, AL
The radar
The Northeast Alabama radar (KHTX), 57 km from the middle of the area, began a volume at 02:16 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
Birmingham, AL (KBMX), launched 00:00Z, 2.3 hours before the alert went out and 151 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
- 188 J/kg
- Mixed-layer CIN
- -25 J/kg
- Mixed-layer LCL
- 669 m above ground
- 0-6 km bulk shear
- 63 kt
- 0-1 km storm-relative helicity
- 336 m²/s²
- 0-3 km storm-relative helicity
- 465 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.6
The text
As transmitted.
514
ACUS11 KWNS 180217
SWOMCD
SPC MCD 180216
ALZ000-180345-
Mesoscale Discussion 0216
NWS Storm Prediction Center Norman OK
0916 PM CDT Wed Mar 17 2021
Areas affected...Northeastern Alabama
Concerning...Tornado Watch 37...
Valid 180216Z - 180345Z
The severe weather threat for Tornado Watch 37 continues.
SUMMARY...Severe wind gusts and perhaps a tornado will remain
possible with storms moving across northeast Alabama.
DISCUSSION...Widespread strong to severe storms are ongoing across
much of northern Alabama. Storms have transitioned to a
predominately linear mode over the last two hours, suggesting a
shift toward a damaging wind threat. However, strong low-level shear
(0-1km SRH 400 m2s2) as sampled from the HTX radar and university
soundings remains in place across northern Alabama and southern
Tennessee. As storms move east into more marginal buoyancy, (250-500
J/kg MUCAPE) along and northeast of the diffuse frontal zone
tonight, there remains a chance for a tornado along with the threat
of damaging wind gusts. The threat will likely begin to decrease
after 03 to 04Z as storms move into an increasingly unfavorable
environment for severe weather.
..Lyons/Guyer.. 03/18/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BMX...HUN...
LAT...LON 34098699 34828723 34938703 34978612 34828581 34498578
34218587 34158609 34098699SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 17, 7:07 PM CDT | Tornado Watch | SPC | Colbert, Cullman, Franklin, Lauderdale, Lawrence, Limestone and 3 more | 3 hr |
| Mar 17, 10:15 PM CDT | Mesoscale Discussion | SPC | Baldwin, Barbour, Bullock, Calhoun, Chambers, Cherokee and 18 more | 90 min |
| Mar 17, 11:02 PM CDT | Tornado Watch | SPC | Coffee, Covington, Dale, Geneva, Henry, Houston | 9 hr |
| Mar 18, 1:52 AM CDT | Mesoscale Discussion | SPC | Barbour, Coffee, Covington, Dale, Geneva, Henry and 2 more | 83 min |
| Mar 18, 4:28 AM CDT | Mesoscale Discussion | SPC | Coffee, Dale, Geneva, Henry, Houston | 92 min |
Nearby
Mesoscale 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.