ACUS11 KWNS 171648
SWOMCD
SPC MCD 171648=20
WIZ000-ILZ000-IAZ000-MNZ000-171915-

Mesoscale Discussion 0473
NWS Storm Prediction Center Norman OK
1148 AM CDT Fri Apr 17 2026

Areas affected...northeastern Iowa...southeastern
Minnesota...southern/western Wisconsin

Concerning...Severe potential...Tornado Watch likely=20

Valid 171648Z - 171915Z

Probability of Watch Issuance...80 percent

SUMMARY...Increasing potential for supercells capable of all
hazards.

DISCUSSION...Visible satellite trends show two areas of cumulus
increasing near the cold front/dry line in north-central
Iowa/southern Minnesota and further east in a confluence band in
northeastern Iowa. A few attempts are note on radar near the front
over the last 30 minutes. Across the open warm sector in
central/eastern Iowa into southern WI/northern Illinois, strong warm
air advection within the 40-45 kt southerly LLJ is ongoing with
moderate to strong MLCAPE and strong deep layer shear profiles
supportive of supercells. Uncertainty remains in what the exact
evolution of storms will be. Two scenarios are possible: initial
supercell development in eastern Iowa ahead of the front and
supercell development along the cold front.=20

Confidence is highest that there will be development further west
along the cold front, which will initially be supercelluar given,
the favorable profiles. The time period for more discrete supercells
may be cut short across this region as the cold front undercuts
convection. Nonetheless, initially large to very large hail will be
possible with an increasing tornado threat as convection matures. As
more clustering/upscale growth occurs, threat to damaging winds will
increase with a line embedded tornado threat continuing through the afternoon/evening.

Further east, isolated supercells may develop within the open warm
sector across northeastern Iowa nearer to the warm front. These
would also be capable of large to very large hail. Should they
persist, there would also be enhanced potential for strong tornadoes
given the SRH rich environment.

A Tornado watch will likely be needed in the next 1-2 hours.

..Thornton/Mosier.. 04/17/2026

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!-223PoAKnl0ZqIkbP6qVzph8Et3ifoVkwrWUiOuUaYj_52YJafdCFVgPJAwu_7UXIir1uvC6-= unV0UvqwqRMKjZ_6kw$ for graphic product...

ATTN...WFO...GRB...LOT...MKX...DVN...ARX...MPX...DMX...

LAT...LON 44529149 44128969 44028899 43828843 43318829 42138908
42058925 41818999 42049121 42329258 42619354 43299446
43999375 44629338 45079327 45179313 44919236 44529149=20

MOST PROBABLE PEAK TORNADO INTENSITY...140-170 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...2.75-4.25 IN


=3D =3D =3D
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