Alert archive / Alabama / Mesoscale Discussions in 2021

Mesoscale Discussion 508

May 3, 202110 counties in Alabama

The Storm Prediction Center issued this mesoscale discussion at May 3, 2021, 7:13 PM CDT for 10 counties in Alabama. It was in force for 62 min.

The area

The outline as issued.

The facts

Issued
May 3, 2021, 7:13 PM CDT (00:13 UTC)
Expired
May 3, 2021, 8:15 PM CDT
In force
62 min
Issued by
the Storm Prediction Center
Concerning
Severe thunderstorm watch 128

Counties Autauga County, AL, Bullock County, AL, Chambers County, AL, Coosa County, AL, Elmore County, AL, Lee County, AL, Macon County, AL, Montgomery County, AL, Russell County, AL, Tallapoosa County, AL

The radar

The Maxwell AFB radar (KMXX), 11 km from the middle of the area, began a volume at 00:15 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, 0.2 hours before the alert went out and 124 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 2021-05-04Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1119 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 2021-05-04The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 202 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
1119 J/kg
Mixed-layer CIN
-125 J/kg
Mixed-layer LCL
1247 m above ground
0-6 km bulk shear
37 kt
0-1 km storm-relative helicity
202 m²/s²
0-3 km storm-relative helicity
215 m²/s²
Significant tornado parameter
0.3
Supercell composite
4.4

Open this sounding in Storm Lab

The text

As transmitted.

031 
ACUS11 KWNS 040014
SWOMCD
SPC MCD 040013 
ALZ000-040115-

Mesoscale Discussion 0508
NWS Storm Prediction Center Norman OK
0713 PM CDT Mon May 03 2021

Areas affected...east-central Alabama

Concerning...Severe Thunderstorm Watch 128...

Valid 040013Z - 040115Z

The severe weather threat for Severe Thunderstorm Watch 128
continues.

SUMMARY...Ongoing severe storms may pose a risk for isolated
damaging wind gusts and severe hail after the 0100z watch expiration
of WW128. A local extension maybe needed.

DISCUSSION...A cluster of severe storms across east-central Alabama
in the vicinity of Montgomery has shown occasional organization and
severe characteristics over the last hour. These storms are ongoing
in a partially modified unstable airmass with surface temperatures
in the upper 70s and dewpoints in the upper 60s F. SPC mesoanalysis
indicates between 2000-2500 J/kg of MLCAPE with 30-40 kts of
effective shear. The loss of diurnal heating should result in only
marginal boundary-layer cooling suggesting that storms may retain
intensity beyond 0100z. Given the favorable parameter space and
occasional updraft rotation noted, isolated damaging wind gusts and
severe hail will remain possible. A local extension of WW128 may be
needed to account for the threat past 0100z.

..Lyons.. 05/04/2021

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

ATTN...WFO...BMX...

LAT...LON   32068532 32008545 31978590 32018616 32148638 32388678
            32628694 32898669 32968628 33008561 32978524 32768516
            32558507 32408507 32268515 32068532

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 4, 5:13 AM CDTSevere Thunderstorm WatchSPCJackson, Lauderdale, Limestone, Madison5 hr
May 4, 7:31 AM CDTMesoscale DiscussionSPCJackson, Lauderdale, Limestone, Madison89 min
May 4, 8:33 AM CDTMesoscale DiscussionSPCChoctaw, Clarke, Dallas, Greene, Hale, Marengo and 4 more117 min
May 4, 9:03 AM CDTMesoscale DiscussionSPCBlount, Calhoun, Cherokee, Clay, Cleburne, Cullman and 20 more117 min
May 4, 9:18 AM CDTTornado WatchSPCAutauga, Bibb, Blount, Calhoun, Cherokee, Chilton and 28 more7 hr
May 4, 2:17 PM CDTMesoscale DiscussionSPCChoctaw, Greene, Marengo, Sumter88 min
May 4, 3:03 PM CDTMesoscale DiscussionSPCBibb, Blount, Calhoun, Cherokee, Chilton, Clay and 19 more117 min
May 4, 3:31 PM CDTTornado WatchSPCAutauga, Baldwin, Bibb, Butler, Chilton, Choctaw and 20 more6 hr
May 4, 4:46 PM CDTMesoscale DiscussionSPCAutauga, Baldwin, Bibb, Butler, Chilton, Choctaw and 20 more89 min
May 4, 5:20 PM CDTMesoscale DiscussionSPCBarbour, Bullock, Chambers, Coffee, Covington, Dale and 7 more85 min
May 4, 6:10 PM CDTMesoscale DiscussionSPCAutauga, Coosa, Elmore, Lowndes, Macon, Montgomery and 1 more65 min
May 4, 6:26 PM CDTSevere Thunderstorm WatchSPCBarbour, Bullock, Chambers, Coffee, Covington, Crenshaw and 8 more6 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.