Mesoscale Discussion 1421

Issued

Jul 8, 2022, 4:42 PM CDT (21:42 UTC)

Expired

Jul 8, 2022, 6:45 PM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

20%

The St Louis radar (KLSX), 102 km from the middle of the area, began a volume at 21:44 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.

639 
ACUS11 KWNS 082143
SWOMCD
SPC MCD 082142 
KYZ000-INZ000-ILZ000-MOZ000-082345-

Mesoscale Discussion 1421
NWS Storm Prediction Center Norman OK
0442 PM CDT Fri Jul 08 2022

Areas affected...Southeast Missouri southern Illinois...and far
western Kentucky

Concerning...Severe potential...Watch unlikely 

Valid 082142Z - 082345Z

Probability of Watch Issuance...20 percent

SUMMARY...A strong to severe thunderstorm or two may develop across
southeast Missouri, the southern half of Illinois, and far western
Kentucky through the evening hours. This threat will likely remain
fairly isolated, and a watch is not anticipated.

DISCUSSION...Robust thunderstorm initiation is noted across eastern
MO over the past hour per regional reflectivity/echo top data as
well as GOES IR cloud-top temperature trends. This activity is
developing along a cool front and in the vicinity of a weak surface
low where forcing for ascent is maximized within an unstable air
mass (upwards of 1500-2500 J/kg MLCAPE per latest mesoanalysis
estimates). Additional convection across central IL has been ongoing
for several hours, but has shown some signs of additional
development within the past 30-60 minutes. 

Although the downstream region was previously overturned by morning
convection, clearing skies and theta-e advection from the southwest
has allowed for sufficient air mass recovery for storm maintenance.
Regional VWPs are also sampling 30-40 knot winds between 4-6 km,
which, combined with the weak low-level flow, is supporting 30-35
knots of effective bulk shear. Consequently, a couple of strong to
severe storms are possible through the evening hours with
hail/severe wind as the primary hazards. This threat will likely be
bounded by the cool front as well as the residual outflow boundary
across IL that denotes the northeastward extent of the better
instability. Convective coverage is uncertain given the weak forcing
for ascent. Trends will continue to be monitored, but a watch is not
currently anticipated.

..Moore/Hart.. 07/08/2022

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

ATTN...WFO...IND...PAH...ILX...LSX...SGF...

LAT...LON   37929184 38529104 39289071 40299041 40649039 40959007
            40588895 40108824 39478769 38868745 38378734 37678732
            37108773 36708848 36558933 36669006 36929079 37359149
            37929184

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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.