Alert archive / Louisiana / Mesoscale Discussions in 2021
Mesoscale Discussion 860
The Storm Prediction Center issued this mesoscale discussion at Jun 6, 2021, 9:56 AM CDT for Baldwin County, Mobile County, Washington County, Alabama; 29 parishes in Louisiana; 21 counties in Mississippi. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Jun 6, 2021, 9:56 AM CDT (14:56 UTC)
- Expired
- Jun 6, 2021, 12:30 PM CDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 53 counties
Baldwin County, AL, Mobile County, AL, Washington County, AL, Acadia Parish, LA, Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Parish, LA, Lafayette Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Pointe Coupee Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Vermilion Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Amite County, MS, Covington County, MS, Forrest County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Jefferson Davis County, MS, Jones County, MS, Lamar County, MS, Lawrence County, MS, Lincoln County, MS, Marion County, MS, Pearl River County, MS, Perry County, MS, Pike County, MS, Stone County, MS, Walthall County, MS, Wayne County, MS, Wilkinson County, MS
The nearest sounding before it
Slidell Radar S, LA (KSIL), launched 12:00Z, 2.9 hours before the alert went out and 97 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
- 1791 J/kg
- Mixed-layer CIN
- -3 J/kg
- Mixed-layer LCL
- 571 m above ground
- 0-6 km bulk shear
- 20 kt
- 0-1 km storm-relative helicity
- 181 m²/s²
- 0-3 km storm-relative helicity
- 240 m²/s²
- Significant tornado parameter
- 1.4
- Supercell composite
- 9.7
The text
As transmitted.
560
ACUS11 KWNS 061456
SWOMCD
SPC MCD 061456
ALZ000-FLZ000-MSZ000-LAZ000-061730-
Mesoscale Discussion 0860
NWS Storm Prediction Center Norman OK
0956 AM CDT Sun Jun 06 2021
Areas affected...southern Louisiana...southern Mississippi...and
southwestern Alabama
Concerning...Severe potential...Watch possible
Valid 061456Z - 061730Z
Probability of Watch Issuance...40 percent
SUMMARY...Potential for short-lived, low-end tornadoes is evident
across a broad portion of the lower Mississippi Valley/central Gulf
Coast area. WW is not anticipated in the short term, but the area
is being monitored.
DISCUSSION...Latest surface observations reveal a very moist
low-level airmass across the central Gulf Coast/lower Mississippi
Valley area, with dewpoints ranging from the low 70s inland, to the
upper 70s in some coastal areas. The moist airmass is contributing
to 1000 to 2000 J/kg mixed-layer CAPE across the area -- which
combined with broad ascent within the warm conveyor east of the
upper low now centered over the Arklatex region is resulting in
widespread shower/thunderstorm development.
As daytime heating allows gradual additional destabilization to
occur, convective coverage will likely expand, along with
occasional/local enhancement of updrafts. While deep-layer flow
remains somewhat muted, ample veering/increasing of the flow field
in the lowest couple of km will continue to support some updraft
rotation. Correspondingly, occasional/largely brief tornadic
spin-ups are expected, which -- dependent upon convective evolution
-- could eventually require WW consideration.
..Goss/Guyer.. 06/06/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MOB...JAN...LIX...LCH...
LAT...LON 29669331 30379269 31209150 31669021 31838871 31638760
30888758 28838883 28429081 29119319 29669331Nearby
Mesoscale Discussions in Louisiana, 2021Mesoscale Discussions in Mississippi, 2021Mesoscale 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.