Mesoscale Discussion 652

Issued

May 17, 2021, 2:55 PM CDT (19:55 UTC)

Expired

May 17, 2021, 5:00 PM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

40%

Counties Acadia Parish, LA, Cameron Parish, LA, Iberia Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, Saint Martin Parish, LA, St. Mary Parish, LA, Vermilion Parish, LA

The Lake Charles radar (KLCH), 80 km from the middle of the area, began a volume at 19:58 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.

156 
ACUS11 KWNS 171955
SWOMCD
SPC MCD 171955 
LAZ000-172200-

Mesoscale Discussion 0652
NWS Storm Prediction Center Norman OK
0255 PM CDT Mon May 17 2021

Areas affected...southwest and south-central Louisiana

Concerning...Severe potential...Watch possible 

Valid 171955Z - 172200Z

Probability of Watch Issuance...40 percent

SUMMARY...Brief tornadoes will be possible across southwest and
south-central Louisiana this afternoon.

DISCUSSION...A very moist airmass remains in place across southwest
and south-central Louisiana this afternoon. Within this environment
exists a large, slowly eastward moving mesoscale convective system
(MCS). At the core of this MCS is a mesoscale convective vortex
(MCV), currently located over Lake Charles. To the south and east of
this MCV, near-surface wind profiles remain relatively enlarged as
compared to the surrounding environment, with 0-1 kilometer shear
values around 30 knots and storm-relative helicity values around 225
m2/s2 per KLCH VAD. This kinematic and thermodynamic environment has
resulted in a very favorable environment for minisupercell
thunderstorms, and a corresponding increase for brief, transient
tornadoes, especially to the east of the larger MCV. This MCV will
continue to slowly move east through the afternoon, resulting in an
increase in tornado potential across south-central Louisiana.

Current expectation at this time is that the tornado potential
should remain sufficiently brief and transient in nature at any one
location to preclude a watch. However, severe weather outlook
probabilities will be increased to 5-percent with the next outlook
issuance (approximately 20UTC/3PM CDT) to account for this
increasing potential. Convective trends will be monitored through
the afternoon.

..Marsh/Guyer.. 05/17/2021

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

ATTN...WFO...LIX...LCH...

LAT...LON   30129338 30399316 30349195 30209148 29839116 29469131
            29339185 29439261 29189291 29159341 29699337 30129338

Mesoscale Discussions in Louisiana, 2021Every mesoscale discussion in 2021

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.