Alert archive / Alabama / Mesoscale Discussions in 2021
Mesoscale Discussion 2020
The Storm Prediction Center issued this mesoscale discussion at Dec 11, 2021, 7:34 AM CST for 14 counties in Alabama; 9 counties in Georgia. It was in force for 86 min.
The area
The outline as issued.
The facts
- Issued
- Dec 11, 2021, 7:34 AM CST (13:34 UTC)
- Expired
- Dec 11, 2021, 9:00 AM CST
- In force
- 86 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 5%
All 23 counties
Bibb County, AL, Blount County, AL, Calhoun County, AL, Cherokee County, AL, Clay County, AL, Cleburne County, AL, DeKalb County, AL, Etowah County, AL, Jefferson County, AL, Pickens County, AL, Shelby County, AL, St. Clair County, AL, Talladega County, AL, Tuscaloosa County, AL, Bartow County, GA, Catoosa County, GA, Chattooga County, GA, Floyd County, GA, Gordon County, GA, Haralson County, GA, Polk County, GA, Walker County, GA, Whitfield County, GA
The radar
The Birmingham radar (KBMX), 79 km from the middle of the area, began a volume at 13:34 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 12:00Z, 1.6 hours before the alert went out and 79 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
- 245 J/kg
- Mixed-layer CIN
- -11 J/kg
- Mixed-layer LCL
- 703 m above ground
- 0-6 km bulk shear
- 63 kt
- 0-1 km storm-relative helicity
- 325 m²/s²
- 0-3 km storm-relative helicity
- 371 m²/s²
- Significant tornado parameter
- 0.4
- Supercell composite
- 3.8
The text
As transmitted.
837
ACUS11 KWNS 111335
SWOMCD
SPC MCD 111334
GAZ000-ALZ000-111500-
Mesoscale Discussion 2020
NWS Storm Prediction Center Norman OK
0734 AM CST Sat Dec 11 2021
Areas affected...portions of north-central AL into northwest GA
Concerning...Severe potential...Watch unlikely
Valid 111334Z - 111500Z
Probability of Watch Issuance...5 percent
SUMMARY...Locally gusty winds may accompany thunderstorms across
parts of central AL into northwest GA this morning. However, severe
thunderstorm potential is expected to remain limited.
DISCUSSION...A line of strong storms extends from north-central AL
into east-central MS this morning ahead of an eastward-advancing
cold front. WW 562 is in effect for portions of northern AL,
however, severe potential appears low to the south and east of the
watch across parts of central AL and northwest GA. Strong deep-layer
southwesterly flow will continue to support fast moving cells within
the line of convection amid weak instability. This could allow for
locally gusty winds to move across the MCD area over the next few
hours. However, the 12z BMX RAOB and experimental RAOBs from the
University of Alabama - Huntsville indicate a somewhat hostile
midlevel thermodynamic environment with weak capping between 850-700
mb. Additionally, midlevel lapse rates remain poor across the
region. This will largely limit more intense convection and a new
watch is not expected at this time.
..Leitman.. 12/11/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FFC...BMX...HUN...
LAT...LON 33268830 33568752 34238607 34618566 34928538 34968516
34918493 34748472 34558473 34158487 33858507 33278568
33078607 32968664 32898728 32868776 32898812 32988825
33268830SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Dec 11, 2:00 AM CST | Mesoscale Discussion | SPC | Colbert, Franklin, Lauderdale, Lawrence, Limestone, Madison and 2 more | 90 min |
| Dec 11, 3:15 AM CST | Mesoscale Discussion | SPC | Colbert, Franklin, Lauderdale, Marion | 90 min |
| Dec 11, 3:41 AM CST | Tornado Watch | SPC | Colbert, Cullman, DeKalb, Fayette, Franklin, Jackson and 10 more | 6 hr |
| Dec 11, 6:15 AM CST | Mesoscale Discussion | SPC | Cullman, Fayette, Franklin, Jackson, Lamar, Lawrence and 6 more | 90 min |
| Dec 11, 10:47 AM CST | Mesoscale Discussion | SPC | Autauga, Bullock, Butler, Chambers, Clarke, Clay and 15 more | 118 min |
| Dec 11, 4:32 PM CST | Mesoscale Discussion | SPC | Bleckley, Burke, Columbia, Emanuel, Glascock, Houston and 10 more | 88 min |
Nearby
Mesoscale Discussions in Alabama, 2021Mesoscale Discussions in Georgia, 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.