Alert archive / Alabama / Mesoscale Discussions in 2021

Mesoscale Discussion 295

March 28, 20214 states

The Storm Prediction Center issued this mesoscale discussion at Mar 28, 2021, 1:57 AM CDT for 4 states. It was in force for 93 min.

The area

The outline as issued.

The facts

Issued
Mar 28, 2021, 1:57 AM CDT (06:57 UTC)
Expired
Mar 28, 2021, 3:30 AM CDT
In force
93 min
Issued by
the Storm Prediction Center
Concerning
Tornado watch 64...65
All 26 counties

Blount County, AL, Colbert County, AL, Cullman County, AL, DeKalb County, AL, Etowah County, AL, Fayette County, AL, Franklin County, AL, Jackson County, AL, Lamar County, AL, Lawrence County, AL, Limestone County, AL, Madison County, AL, Marion County, AL, Marshall County, AL, Morgan County, AL, Walker County, AL, Winston County, AL, Chattooga County, GA, Dade County, GA, Walker County, GA, Itawamba County, MS, Monroe County, MS, Franklin County, TN, Hamilton County, TN, Lincoln County, TN, Marion County, TN

The radar

The Northeast Alabama radar (KHTX), 115 km from the middle of the area, began a volume at 06:57 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 00:00Z, 7.0 hours before the alert went out and 143 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.

Skew-T log-pSkew-T log-p diagram, Birmingham, AL at 00:00Z on 2021-03-28Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 643 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Birmingham, AL at 00:00Z on 2021-03-28The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 126 square meters per square second.1939587897Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
643 J/kg
Mixed-layer CIN
-22 J/kg
Mixed-layer LCL
1359 m above ground
0-6 km bulk shear
52 kt
0-1 km storm-relative helicity
126 m²/s²
0-3 km storm-relative helicity
152 m²/s²
Significant tornado parameter
0.3
Supercell composite
3.7

Open this sounding in Storm Lab

The text

As transmitted.

447 
ACUS11 KWNS 280657
SWOMCD
SPC MCD 280657 
TNZ000-GAZ000-ALZ000-MSZ000-280830-

Mesoscale Discussion 0295
NWS Storm Prediction Center Norman OK
0157 AM CDT Sun Mar 28 2021

Areas affected...Parts of northeastern Mississippi...northern
Alabama...adjacent southern Tennessee and northwestern Georgia

Concerning...Tornado Watch 64...65...

Valid 280657Z - 280830Z

The severe weather threat for Tornado Watch 64, 65 continues.

SUMMARY...A squall line will rapidly overspread the region through
5-6 AM CDT, posing a risk for potentially damaging surface gusts
and/or brief tornadoes.

DISCUSSION...The southern flank of the more intense portion of the
ongoing larger-scale squall line appears likely to rapidly
overspread much of northern Alabama, adjacent southern Tennessee and
northwestern Georgia through 10-11Z.  This convection is embedded
within intensifying southwesterly lower/mid tropospheric wind fields
(including in excess of 50 kt around 850 mb), with associated
strengthening low-level shear contributing to the evolution of a
number of cyclonic mesoscale circulations.  With a relatively warm
and moist boundary layer remaining potentially moderately unstable
across much of northern Alabama, inflow of this air should maintain
renewed vigorous thunderstorm development.

..Kerr.. 03/28/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MRX...FFC...OHX...BMX...HUN...MEG...JAN...

LAT...LON   34208862 34898761 35338622 35188517 34258531 33678714
            33678875 34208862

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Mar 27, 10:45 PM CDTMesoscale DiscussionSPCColbert, Franklin, Lauderdale, Lawrence, Limestone, Madison and 3 more90 min
Mar 27, 11:27 PM CDTTornado WatchSPCBlount, Colbert, Cullman, DeKalb, Fayette, Franklin and 11 more8 hr
Mar 28, 1:25 AM CDTMesoscale DiscussionSPCJackson2 hr
Mar 28, 4:56 AM CDTMesoscale DiscussionSPCBlount, Cullman, DeKalb, Etowah, Marshall, Walker94 min
Mar 28, 5:10 AM CDTSevere Thunderstorm WatchSPCBibb, Blount, Calhoun, Cherokee, Clay, Cleburne and 12 more5 hr
Mar 28, 7:29 AM CDTMesoscale DiscussionSPCCalhoun, Cleburne, Talladega91 min
Mar 28, 9:14 AM CDTMesoscale DiscussionSPCAutauga, Chambers, Chilton, Clay, Coosa, Dallas and 6 more61 min
Mar 28, 11:38 AM CDTMesoscale DiscussionSPCBaldwin, Bibb, Bleckley, Burke, Butts, Columbia and 34 more3 hr
Mar 28, 4:51 PM CDTMesoscale DiscussionSPCAppling, Atkinson, Bacon, Baker, Ben Hill, Berrien and 46 more54 min
Mar 27, 8:42 PM CDTMesoscale DiscussionSPCAlcorn, Benton, Calhoun, Carroll, Chickasaw, Coahoma and 26 more93 min
Mar 27, 9:01 PM CDTTornado WatchSPCAlcorn, Attala, Benton, Bolivar, Calhoun, Carroll and 33 more7 hr
Mar 28, 2:07 AM CDTSevere Thunderstorm WatchSPCAnderson, Bledsoe, Blount, Bradley, Cumberland, Hamilton and 14 more6 hr

Nearby

Mesoscale Discussions in Alabama, 2021Mesoscale Discussions in Tennessee, 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.