909 

ACUS11 KWNS 131857
SWOMCD
SPC MCD 131857
WIZ000-IAZ000-MNZ000-132030-

Mesoscale Discussion 0396
NWS Storm Prediction Center Norman OK
0157 PM CDT Mon Apr 13 2026

Areas affected...portions of far southeastern Minnesota into central
Wisconsin...and extreme northeastern Iowa

Concerning...Severe potential...Tornado Watch likely

Valid 131857Z - 132030Z

Probability of Watch Issuance...80 percent

SUMMARY...The severe threat is expected to gradually increase over
the next few hours. Severe wind and hail are likely, accompanied by
a tornado risk, especially with storms that can anchor on the warm
front.

DISCUSSION...A surface low continues to meander eastward over
eastern NE, with a warm front extending from FSD to MKX ahead of the
low. Visible satellite depicts lingering cloud cover along the warm
front. Nonetheless, diurnal heating has allowed surface temperatures
to warm into the 70s F along the warm front. Given mid 60s F surface
dewpoints beneath 7.5 C/km mid-level lapse rates (per 18Z GRB
observed sounding), surface-based instability is already in place,
with over 1500 J/kg MLCAPE being common (per 18Z mesoanalysis). The
aforementioned sounding shows an elongated, straight hodograph in
place, with over 30 kts of effective bulk shear. The buoyancy/shear
parameter space already supports supercell structures. With erosion
of the cloud deck, along with an increase in a southwesterly LLJ
later this afternoon, supercells are expected to develop along the
warm front, as shown by high-resolution/ensemble guidance consensus.


At the very least, a large hail threat should accompany the
supercells, regardless of whether they sustain immediately north or
south of the warm front. A few instances of 2+ inch diameter hail
are possible. Should any supercells, or upscale growing line
segments with mesovortices anchor to the warm front, then locally
enhanced SRH with these storms may also support a tornado threat. A
tornado watch will likely be needed in the next few hours.

..Squitieri/Hart.. 04/13/2026

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

ATTN...WFO...GRB...MKX...ARX...MPX...

LAT...LON   44419293 44549289 44769235 44919093 44998985 44868893
            44598822 44118778 43738779 43488790 43298810 43058934
            43109030 43169118 43329201 43479250 43539259 43629262
            44419293

MOST PROBABLE PEAK TORNADO INTENSITY...120-150 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN