ACUS11 KWNS 181259
SWOMCD
SPC MCD 181259=20
ILZ000-KYZ000-TNZ000-MOZ000-ARZ000-181500-

Mesoscale Discussion 1343
NWS Storm Prediction Center Norman OK
0759 AM CDT Wed Jun 18 2025

Areas affected...parts of central and southern Illinois...east
central and southeastern MO...parts of northeastern
Arkansas...adjacent western Kentucky and Tennessee

Concerning...Severe potential...Watch possible=20

Valid 181259Z - 181500Z

Probability of Watch Issuance...40 percent

SUMMARY...Strong thunderstorm development may begin to initiate and
pose increasing risk for damaging wind gusts and perhaps a couple of
tornadoes as early as 10-11 AM CDT. Trends are being monitored for
the possibility of a severe weather watch.

DISCUSSION...A significant mesoscale convective vortex, generated by
a now largely dissipated overnight thunderstorm cluster, is
migrating northeastward across central Missouri, with an associated
surface low progressing across the Columbia vicinity. This appears
likely to continue a northeastward movement to the northwest of the
Greater St. Louis area through mid to late morning, with a belt of
enhanced southerly to southwesterly flow (including 40-50 Kt in the
850-500 mb layer) to its south and east overspreading the middle
Mississippi Valley/Mid South vicinity.=20=20

This will overspread a seasonably moist boundary layer, including
surface dew points above 70F, with sufficient breaks in cloud cover
to allow for destabilization and weakening inhibition. The Rapid
Refresh indicates that this may include CAPE increasing to 1000-2000
J/kg toward midday. At least some convection allowing guidance
suggests that this could support the initiation of intensifying
thunderstorm development as early as 15-16Z.=20=20

Given the strength of the wind fields and deep-layer shear,
organizing thunderstorm development posing a risk for strong to
severe wind gusts may commence. This may include a couple of
supercell structures, with low-level hodographs posing at least some
risk for tornadoes, and perhaps some small to marginally severe
hail.

..Kerr/Gleason.. 06/18/2025

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!_AlL1Mrh1-nXsa-bF3AKW30KxHqTGd5fgy0FU_LorcbOMV0vf64fgVBkt5t535T99ixOS_tPi= xG9Zpb5hVH9p6qOTrc$ for graphic product...

ATTN...WFO...PAH...ILX...MEG...LSX...LZK...SGF...

LAT...LON 39479005 40148957 40068815 39188803 38128831 37398866
36038956 35369089 35629215 37449097 38289045 39479005=20

MOST PROBABLE PEAK TORNADO INTENSITY...85-115 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN


=3D =3D =3D
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