SPC MD 768
MD 0768 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR EASTERN MISSOURI...FAR SOUTHEAST IOWA...AND WEST-CENTRAL ILLINOIS

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

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https://www.spc.noaa.gov/products/md/md0768.html