146 

ACUS11 KWNS 181151

SWOMCD

SPC MCD 181151 

ILZ000-MOZ000-IAZ000-181315-



Mesoscale Discussion 0768

NWS Storm Prediction Center Norman OK

0651 AM CDT Mon May 18 2026



Areas affected...eastern Missouri...far southeast Iowa...and

west-central Illinois



Concerning...Severe potential...Watch unlikely 



Valid 181151Z - 181315Z



Probability of Watch Issuance...20 percent



SUMMARY...A long lived thunderstorm cluster has shown signs of

renewed updraft intensity. An isolated large hail or damaging wind

gust to two will be possible this morning. A watch is currently not

expected.



DISCUSSION...A long lived MCS continues to move east across northern

and central Missouri this morning. Recent satellite observations

have shown a renewed cooling trend of cloud tops indicated of

increasingly robust updrafts. This correlated to an increase in the

number of taller, stronger updraft cores evident in MRMS CAPPI

imagery.



The renewed vigor of some of these updrafts appears tied to a

slightly better environment across eastern Missouri than farther

west. MUCAPE values are between 1500-2000 J/kg and objectively

analyzed effective-layer shear has improved to between 30 and 40

knots. Additionally, KLSX VAD winds show strong 0-1 kilometer

veering flow, with around 40-knots of shear. Upper-tropospheric

winds have also improved as the area is on the northern periphery of

a 60-knot 300-mb subtropical jet streak lifting northeast across

Arkansas and Missouri.



All this will result in the potential for some severe hail and wind

this morning along the main convective edge of the MCS. Given the

strength of the low-level flow, a brief tornado cannot be ruled out,

especially where this MCS intersects the outflow of an earlier MCS.



There is uncertainty as to the longevity of this threat. Latest CAM

guidance suggests that as the low-level jet weakens later this

morning, the overall severity of the MCS will weaken as well.

However, given the overall character of the environment, the

potential for isolated severe hail and wind will be possible over

the next couple of hours.



Given the sporadic nature and uncertainty regarding the longevity of

the threat, a watch appears unlikely at this time, but trends are

being monitored.



..Marsh/Gleason.. 05/18/2026



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



ATTN...WFO...ILX...LSX...DVN...SGF...



LAT...LON   38389268 38909226 39539180 40379160 41129155 41219082

            41089013 40568959 39768942 39108959 38648979 38159035

            38019113 38129222 38389268 



MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH

MOST PROBABLE PEAK WIND GUST...55-70 MPH

MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN