Mesoscale Discussion 1103

Issued

Jun 25, 2021, 8:34 PM CDT (01:34 UTC)

Expired

Jun 25, 2021, 10:00 PM CDT

In force

86 min

Issued by

the Storm Prediction Center

Concerning

Severe thunderstorm watch 317

The St Louis radar (KLSX), 31 km from the middle of the area, began a volume at 01:36 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.

332 
ACUS11 KWNS 260134
SWOMCD
SPC MCD 260134 
INZ000-ILZ000-MOZ000-260300-

Mesoscale Discussion 1103
NWS Storm Prediction Center Norman OK
0834 PM CDT Fri Jun 25 2021

Areas affected...east-central Missouri into central Illinois

Concerning...Severe Thunderstorm Watch 317...

Valid 260134Z - 260300Z

The severe weather threat for Severe Thunderstorm Watch 317
continues.

SUMMARY...Thunderstorms will continue across the watch through the
evening. The most likely area for severe will be across portions of
Illinois where a threat for strong-to-severe thunderstorm winds and
a couple brief tornadoes will persist for another few hours.

DISCUSSION...Thunderstorms continue across much of the watch this
evening, with several distinct regimes in play.

Across Missouri, outflow dominant thunderstorms continue to slowly
move south as part of the broader southward progression of an MCS
stretching from Kansas into Missouri. Although these thunderstorms
remain in an very unstable atmosphere, they are moving farther away
from the better deep-layer shear. Thus, the overall severe potential
should remain fairly low, with gusty winds being the main severe
threat. Portions of the severe thunderstorm watch here may
eventually be canceled early.

Across west-central Illinois, a small, linear cluster as developed
associated with the leading edge of the original east/northeastward
expansion of the afternoon Kansas MCS. These thunderstorms remain in
a belt of deep-layer shear around 30-40 knots and most-unstable CAPE
in excess of 2000 J/kg. These thunderstorms will continue along the
northwestern edge of the instability axis for the next few hours,
posing a continued risk of strong-to-severe thunderstorm winds.

Farther east, across east-central Illinois, more isolated, discrete
convection has developed along remnant convergent/outflow boundaries
across the area. Although the instability is much less here than
farther southwest, augmented low-level vorticity associated with the
aforementioned boundaries will support a continued threat for brief
tornadoes with any strong updraft that can tap into these vorticity
reservoirs. This threat should diminish quickly as the nocturnal
boundary layer develops and deepens with the loss of diurnal
heating.

..Marsh.. 06/26/2021

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

ATTN...WFO...IND...LOT...ILX...LSX...DVN...SGF...EAX...

LAT...LON   37489362 37849363 37809317 37899306 38729301 38689263
            39289232 40329229 40299042 40729042 40688999 40948989
            40938887 41148878 41108820 41018819 41008748 39488753
            39498798 39368803 39398845 39188849 39238927 39028921
            39008964 38658962 38649012 38419028 38479071 38189075
            38199103 37759110 37709125 37789128 37799176 37609178
            37589226 37489227 37479304 37489362

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