Alert archive / Alabama / Mesoscale Discussions in 2021

Mesoscale Discussion 1969

December 6, 20214 states

The Storm Prediction Center issued this mesoscale discussion at Dec 6, 2021, 1:08 PM CST for 4 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Dec 6, 2021, 1:08 PM CST (19:08 UTC)
Expired: Dec 6, 2021, 3:15 PM CST
In force: 2 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

All 36 counties

Baldwin County, AL, Barbour County, AL, Bullock County, AL, Butler County, AL, Clarke County, AL, Coffee County, AL, Conecuh County, AL, Covington County, AL, Crenshaw County, AL, Dale County, AL, Escambia County, AL, Geneva County, AL, Henry County, AL, Houston County, AL, Lowndes County, AL, Macon County, AL, Mobile County, AL, Monroe County, AL, Montgomery County, AL, Pike County, AL, Russell County, AL, Washington County, AL, Wilcox County, AL, Chattahoochee County, GA, Clay County, GA, Harris County, GA, Muscogee County, GA, Quitman County, GA, Stewart County, GA, Talbot County, GA, Washington Parish, LA, George County, MS, Greene County, MS, Pearl River County, MS, Perry County, MS, Stone County, MS

The radar

The Mobile radar (KMOB), 145 km from the middle of the area, began a volume at 19:08 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 nearest sounding before it

Birmingham, AL (KBMX), launched 12:00Z, 7.1 hours before the alert went out and 173 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: 219 J/kg
Mixed-layer CIN: -10 J/kg
Mixed-layer LCL: 484 m above ground
0-6 km bulk shear: 51 kt
0-1 km storm-relative helicity: 223 m²/s²
0-3 km storm-relative helicity: 204 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 1.3

Open this sounding in Storm Lab

The text

As transmitted.

006 
ACUS11 KWNS 061908
SWOMCD
SPC MCD 061908 
GAZ000-FLZ000-ALZ000-MSZ000-LAZ000-062115-

Mesoscale Discussion 1969
NWS Storm Prediction Center Norman OK
0108 PM CST Mon Dec 06 2021

Areas affected...Parts of southwestern Georgia...southern
Alabama...southeastern Mississippi

Concerning...Severe potential...Watch unlikely 

Valid 061908Z - 062115Z

Probability of Watch Issuance...20 percent

SUMMARY...Some intensification of thunderstorm development is still
possible late this afternoon, particularly across parts of south
central through southeastern Alabama by 3-4 PM CST.  While this may
be accompanied by the risk of a few strong wind gusts and/or,
perhaps, a tornado, it still seems unlikely that a severe weather
watch will be needed.  Trends, however, will continue to be
monitored.

DISCUSSION...There has been some weak boundary-layer destabilization
ahead of the line of more vigorous thunderstorm development, which
continues to advance southward near/just ahead of the cold front. 
Convection along the line appears to have been periodically enhanced
by subtle mid-level perturbations/speed maximum within the weak
branch of westerlies emanating from the subtropical Pacific. 
However, the primary mid-level short wave impulse, within the
mid-latitude westerlies, is passing well to the northeast of the
region, and deep-layer mean wind fields are generally maintaining
modest strength or slowly weakening across the Gulf Coast vicinity.

Still, a lingering belt 30-40 kt west-southwesterly to westerly flow
in the 850-700 mb layer, coincident with the line of storms, may be
sufficient to maintain continuing risk for a few strong surface
gusts and/or an isolated tornado through the remainder of the
afternoon.  With further boundary-layer destabilization still
possible, there might be some intensification of ongoing storms,
particularly across parts of south central through southeastern
Alabama by 21-22Z.

..Kerr/Hart.. 12/06/2021

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

ATTN...WFO...FFC...TAE...BMX...MOB...JAN...LIX...

LAT...LON   31008966 31448840 32238777 32348648 32478537 32858477
            32728434 31018525 30608760 30769048 31008966

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 6, 5:06 AM CST	Mesoscale Discussion	SPC	Colbert, Lauderdale	114 min
Dec 6, 10:06 AM CST	Mesoscale Discussion	SPC	Autauga, Bibb, Calhoun, Chambers, Chilton, Choctaw and 21 more	114 min
Dec 6, 7:17 AM CST	Mesoscale Discussion	SPC	Avoyelles, Beauregard, Caldwell, Catahoula, Concordia, East Carroll and 14 more	118 min

Nearby

Mesoscale Discussions in Alabama, 2021 Mesoscale Discussions in Georgia, 2021 Mesoscale Discussions in Mississippi, 2021 Every 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.