Alert archive / Alabama / Mesoscale Discussions in 2018

Mesoscale Discussion 921

June 28, 20184 states

The Storm Prediction Center issued this mesoscale discussion at Jun 28, 2018, 1:07 PM CDT for 4 states. It was in force for 113 min.

The area

The outline as issued.

The facts

Issued: Jun 28, 2018, 1:07 PM CDT (18:07 UTC)
Expired: Jun 28, 2018, 3:00 PM CDT
In force: 113 min
Issued by: the Storm Prediction Center

All 83 counties

Autauga County, AL, Barbour County, AL, Bibb County, AL, Blount County, AL, Bullock County, AL, Butler County, AL, Calhoun County, AL, Chambers County, AL, Cherokee County, AL, Chilton County, AL, Clay County, AL, Cleburne County, AL, Colbert County, AL, Coosa County, AL, Crenshaw County, AL, Cullman County, AL, Dallas County, AL, DeKalb County, AL, Elmore County, AL, Etowah County, AL, Fayette County, AL, Franklin County, AL, Greene County, AL, Hale County, AL, Jackson County, AL, Jefferson County, AL, Lamar County, AL, Lauderdale County, AL, Lawrence County, AL, Lee County, AL, Limestone County, AL, Lowndes County, AL, Macon County, AL, Madison County, AL, Marion County, AL, Marshall County, AL, Montgomery County, AL, Morgan County, AL, Perry County, AL, Pike County, AL, Randolph County, AL, Russell County, AL, Shelby County, AL, St. Clair County, AL, Talladega County, AL, Tallapoosa County, AL, Tuscaloosa County, AL, Walker County, AL, Wilcox County, AL, Winston County, AL, Carroll County, GA, Chattahoochee County, GA, Coweta County, GA, Crawford County, GA, Crisp County, GA, Dooly County, GA, Haralson County, GA, Harris County, GA, Heard County, GA, Houston County, GA, Lee County, GA, Macon County, GA, Marion County, GA, Meriwether County, GA, Muscogee County, GA, Peach County, GA, Quitman County, GA, Randolph County, GA, Schley County, GA, Stewart County, GA, Sumter County, GA, Talbot County, GA, Taylor County, GA, Terrell County, GA, Troup County, GA, Upson County, GA, Webster County, GA, Tishomingo County, MS, Giles County, TN, Lawrence County, TN, Lewis County, TN, Lincoln County, TN, Wayne County, TN

The radar

The Birmingham radar (KBMX), 72 km from the middle of the area, began a volume at 18:08 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.

Severe Thunderstorm Watch 236Jun 28, 5:00 PM CDT

The nearest sounding before it

Birmingham, AL (KBMX), launched 12:00Z, 6.1 hours before the alert went out and 72 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 1996 J/kg
Mixed-layer CIN: -52 J/kg
Mixed-layer LCL: 830 m above ground
0-6 km bulk shear: 17 kt
0-1 km storm-relative helicity: 0 m²/s²
0-3 km storm-relative helicity: 72 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.1

Open this sounding in Storm Lab

The text

As transmitted.

789 
ACUS11 KWNS 281808
SWOMCD
SPC MCD 281807 
GAZ000-ALZ000-TNZ000-MSZ000-282000-

Mesoscale Discussion 0921
NWS Storm Prediction Center Norman OK
0107 PM CDT Thu Jun 28 2018

Areas affected...Southern Tennessee...Alabama...Western Georgia

Concerning...Severe Thunderstorm Watch 231...

Valid 281807Z - 282000Z

The severe weather threat for Severe Thunderstorm Watch 231
continues.

SUMMARY...Wind damage and hail will be possible across parts of
middle Tennessee, Alabama and western Georgia over the next few
hours. Weather watch issuance may be needed to the south of the
current watch later this afternoon.

DISCUSSION...The latest surface analysis shows a very moist airmass
in place across much of the Southeast with surface dewpoints in the
mid to upper 70s F. As a result, moderate instability is analyzed by
the RAP across much of southwestern Tennessee, Alabama and
southwestern Georgia with MLCAPE values estimating in the 2000 to
3500 J/kg range. In addition, 0-3 km lapse rates have increased
markedly over the last few hours with the RAP showing the steepest
lapse rates in central Alabama. This would be the most likely area
for a continued severe threat later this afternoon. Wind damage will
still be possible as the linear MCS moves southward across the
southern and western part of WW 231. As the line approaches the area
of maximized low-level lapse rates in Alabama, a new weather watch
or watch extension will need to be considered.

..Broyles/Hart.. 06/28/2018

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

ATTN...WFO...FFC...TAE...OHX...BMX...HUN...MOB...MEG...

LAT...LON   35428809 35608759 35428683 34928610 34588561 33948521
            33058451 32558368 32008356 31758386 31658534 31578682
            32268778 32978803 34798834 35428809

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 28, 10:22 AM CDT	Mesoscale Discussion	SPC	Calhoun, Cherokee, Cleburne, DeKalb, Etowah, Jackson and 6 more	113 min
Jun 28, 10:46 AM CDT	Severe Thunderstorm Watch	SPC	Autauga, Barbour, Blount, Bullock, Calhoun, Chambers and 32 more	8 hr
Jun 28, 4:34 PM CDT	Mesoscale Discussion	SPC	Autauga, Baldwin, Butler, Choctaw, Clarke, Coffee and 21 more	86 min
Jun 28, 4:59 PM CDT	Severe Thunderstorm Watch	SPC	Baldwin, Butler, Choctaw, Clarke, Coffee, Conecuh and 18 more	7 hr
Jun 28, 6:22 PM CDT	Mesoscale Discussion	SPC	Brooks, Camden, Charlton, Clinch, Decatur, Echols and 5 more	83 min
Jun 28, 2:00 AM CDT	Mesoscale Discussion	SPC	Cheatham, Clay, Davidson, Henry, Houston, Jackson and 10 more	3 hr
Jun 28, 5:33 PM CDT	Severe Thunderstorm Watch	SPC	Dyer, Gibson, Henry, Lake, Lauderdale, Obion and 1 more	7 hr

Nearby

Mesoscale Discussions in Alabama, 2018 Mesoscale Discussions in Georgia, 2018 Mesoscale Discussions in Tennessee, 2018 Every mesoscale discussion in 2018

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.