Mesoscale Discussion 0762
NWS Storm Prediction Center Norman OK
0740 PM CDT Sun May 17 2026
Areas affected...portions of central and southern Iowa
Concerning...Severe potential...Tornado Watch likely
Valid 180040Z - 180145Z
Probability of Watch Issuance...80 percent
SUMMARY...A severe threat will accompany an approaching QLCS. Severe
wind and hail will be the most predominant threats, but isolated
line-embedded tornadoes may also occur. A Tornado Watch will be
needed soon to address the impending threat.
DISCUSSION...An elongated persistent convective system with a
history of severe wind and hail is approaching the NE/IA border, and
is poised to exit the ongoing Tornado Watches in the next few hours
as the line advances further into IA. Across IA, which resides south
of the warm front and ahead of a surface trough, a highly buoyant
and sheared warm sector exists. Roughly 80 F/70 F surface
temperatures/dewpoints overspread by 8+ C/km mid-level lapse rates
is contributing up to 3000 J/kg MLCAPE per 00Z mesoanalysis.
Meanwhile, mesoanalysis also shows a LLJ increasing to 40 kts over
IA. These analyses roughly matches the 00Z OAX observed sounding,
which shows near 8 C/km mid-level lapse rates and nearly 3000 J/kg
MLCAPE, as well as a curved low-level hodograph with over 300 m2/s2
effective SRH.
Given the aforementioned environment, the current thinking is that a
QLCS will progress across central IA, accompanied by a severe
wind/hail threat. Isolated QLCS tornadoes are possible with any
mesovortices that materialize, and focused corridors of severe wind
will accompany any bowing segments. A couple of gusts over 75 mph
cannot be ruled out. A Tornado Watch will be needed in the next
couple of hours.
..Squitieri/Smith.. 05/18/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DMX...OAX...
LAT...LON 40629324 40659508 40949540 41659531 42429520 42639418
42689354 42539274 42169243 41579252 40879275 40679299
40629324
MOST PROBABLE PEAK TORNADO INTENSITY...100-125 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
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