Mesoscale Discussion 1091

Issued

Jun 25, 2021, 12:57 PM CDT (17:57 UTC)

Expired

Jun 25, 2021, 3:00 PM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

20%

The Evansville,IN radar (KVWX), 33 km from the middle of the area, began a volume at 18:01 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.

491 
ACUS11 KWNS 251758
SWOMCD
SPC MCD 251757 
INZ000-KYZ000-ILZ000-MOZ000-252000-

Mesoscale Discussion 1091
NWS Storm Prediction Center Norman OK
1257 PM CDT Fri Jun 25 2021

Areas affected...Parts of southeastern Missouri...southern
Illinois....southern Indiana and adjacent portions of Kentucky

Concerning...Severe potential...Watch unlikely 

Valid 251757Z - 252000Z

Probability of Watch Issuance...20 percent

SUMMARY...A developing cluster of thunderstorms may gradually
strengthen and organize this afternoon, eventually posing some risk
for localized potentially damaging wind gusts by 3-5 PM CDT.  Due to
the apparent marginal nature of the severe weather threat, the need
for a watch is not currently anticipated, but trends will be
monitored.

DISCUSSION...A general intensification of thunderstorm development
has been evident along slowly eastward advancing convective outflow,
west of Mount Vernon, IL into areas southwest of Farmington, MO. 
This likely has been aided by inflow of seasonably moist air
characterized by moderately large CAPE in excess of 2000 J/kg,
enhanced by vertical shear near a 30-50 kt westerly mid-level jet
associated with a convectively generated perturbation now migrating
into the Great Lakes region.

Deep-layer mean ambient westerly flow is otherwise modest to weak
(less than 30 kt) across the lower Ohio Valley, and, as the
mid-level jet shifts northeastward this afternoon, it appears that
vertical shear near the developing convection will gradually weaken.
 This may limit/slow potential for substantive further
intensification.  However, with continuing insolation contributing
to downstream destabilization across the lower Ohio Valley vicinity,
the evolution of a small, organizing cluster of storms appears at
least possible.  It might not be out the question that this could
generate a sufficiently strong cold pool to support surface gusts
approaching severe limits.

..Kerr/Guyer.. 06/25/2021

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

ATTN...WFO...LMK...IND...PAH...ILX...LSX...

LAT...LON   39038834 39538669 39238591 38368572 37058928 37419063
            38198898 39038834

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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.