Mesoscale Discussion 1442

Issued

Aug 8, 2021, 11:40 AM CDT (16:40 UTC)

Expired

Aug 8, 2021, 2:15 PM CDT

In force

3 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

60%

The St Louis radar (KLSX), 72 km from the middle of the area, began a volume at 16:45 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.

• Severe Thunderstorm Watch 415Aug 8, 12:45 PM CDT

790 
ACUS11 KWNS 081640
SWOMCD
SPC MCD 081640 
ILZ000-MOZ000-081915-

Mesoscale Discussion 1442
NWS Storm Prediction Center Norman OK
1140 AM CDT Sun Aug 08 2021

Areas affected...Portions of central/eastern MO and western/southern
IL

Concerning...Severe potential...Watch possible 

Valid 081640Z - 081915Z

Probability of Watch Issuance...60 percent

SUMMARY...A threat for scattered damaging winds and severe hail
should increase this afternoon. Watch issuance is possible.

DISCUSSION...Widespread cloudiness is present across much of western
MO this morning, which has limited heating across this area so far.
Less cloud cover over central/eastern MO into IL has allowed surface
temperatures to generally warm into the 80s as of 1630Z. A very
moist low-level airmass depicted on the 12Z SGF sounding and
evidenced by low to mid 70s surface dewpoints from various
observations sites is present across this region. Continued diurnal
heating will likely allow 2000-3000 J/kg of MLCAPE to develop by
peak afternoon heating. A shortwave trough evident in water vapor
satellite imagery will move eastward from the central Plains towards
the mid MS Valley through the rest of the day. Large-scale ascent
preceding this feature will likely encourage the development of
scattered to numerous thunderstorms this afternoon across much of
central/eastern MO and eventually into western IL.

Initial storms will probably focus along a differential heating zone
and remnant outflow boundary present across south-central MO as
small-scale perturbations embedded within the shortwave trough
overspread this area. Mid-level flow is not expected to be overly
strong, but marginal deep layer shear around 25-30 kt should be
enough to support some storm organization. Convection will probably
tend to form into multiple clusters with time. As low-level lapse
rates continue to steepen, damaging downdraft wind gusts should
become the primary threat. But, isolated severe hail may also occur
with initially more discrete development. Trends will be monitored
for signs of increasing convective coverage and intensity, with
watch issuance possible early this afternoon.

..Gleason/Thompson.. 08/08/2021

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

ATTN...WFO...PAH...ILX...LSX...DVN...SGF...EAX...

LAT...LON   36619340 37619318 39129271 39869181 40409039 40298930
            39398900 38528928 37778965 36599101 36549261 36619340

Mesoscale Discussions in Missouri, 2021Mesoscale Discussions in Illinois, 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.