Alert archive / Alabama / Mesoscale Discussions in 2021
Mesoscale Discussion 477
The Storm Prediction Center issued this mesoscale discussion at May 2, 2021, 4:41 PM CDT for 9 counties in Alabama. It was in force for 64 min.
The area
The outline as issued.
The facts
- Issued
- May 2, 2021, 4:41 PM CDT (21:41 UTC)
- Expired
- May 2, 2021, 5:45 PM CDT
- In force
- 64 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...tornado watch likely
- Chance of a watch
- 95%
Counties Fayette County, AL, Greene County, AL, Hale County, AL, Lamar County, AL, Marengo County, AL, Pickens County, AL, Sumter County, AL, Tuscaloosa County, AL, Wilcox County, AL
The radar
The Birmingham radar (KBMX), 106 km from the middle of the area, began a volume at 21:41 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
Birmingham, AL (KBMX), launched 12:00Z, 9.7 hours before the alert went out and 105 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
- 2107 m above ground
- 0-6 km bulk shear
- 39 kt
- 0-1 km storm-relative helicity
- 101 m²/s²
- 0-3 km storm-relative helicity
- 120 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
383
ACUS11 KWNS 022142
SWOMCD
SPC MCD 022141
ALZ000-022245-
Mesoscale Discussion 0477
NWS Storm Prediction Center Norman OK
0441 PM CDT Sun May 02 2021
Areas affected...western Alabama.
Concerning...Severe potential...Tornado Watch likely
Valid 022141Z - 022245Z
Probability of Watch Issuance...95 percent
SUMMARY...Small supercells with a history of producing tornadoes may
continue to pose a risk for brief tornadoes over the next couple of
hours as a warm front lifts northeastward.
DISCUSSION...21z surface analysis showed a diffuse warm front across
western Alabama and eastern Mississippi. Several small supercells
have developed over the last within the deep surface moisture to the
southwest of the warm front. Weak destabilization, MLCAPE around 500
J/kg, will likely continue to support weak convection for at least a
couple of hours. Backed low-level winds along the front are
enhancing low-level shear with 0-1km SRH of 150-200 m2/s2. Hi-res
guidance and observational trends suggest a corridor of tornado
potential will likely exists for at least a couple of hours as
storms move to the northeast along the front. Coverage is expected
to remain low, but a few tornadoes will be possible. Portions of
west-central Alabama will be included in a Tornado Watch being
coordinated across Mississippi.
..Lyons/Gleason.. 05/02/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BMX...MOB...
LAT...LON 33838781 33418738 32428730 31968730 31668742 31628766
31728790 32218819 32868830 33458824 33558823 33908808
33838781SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 2, 4:46 PM CDT | Tornado Watch | SPC | Bibb, Dallas, Fayette, Greene, Hale, Lamar and 5 more | 5 hr |
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.