146 

ACUS11 KWNS 131603
SWOMCD
SPC MCD 131603
ILZ000-IAZ000-131730-

Mesoscale Discussion 0395
NWS Storm Prediction Center Norman OK
1103 AM CDT Mon Apr 13 2026

Areas affected...portions of extreme eastern Iowa into
western...central...and northern Illinois

Concerning...Severe potential...Watch possible

Valid 131603Z - 131730Z

Probability of Watch Issuance...40 percent

SUMMARY...Some hail (possibly over 1 inch in diameter) may occur
with gradually intensifying storms over the next few hours. It is
unclear if these storms will pose the greatest severe risk this
afternoon, or if the greater risk will occur with later storms.

DISCUSSION...850 mb troughing is underway across the Plains states
into the Midwest, with 15Z mesoanalysis showing the northeasterly
terminus of a LLJ currently positioned along the IA/IL/MO border.
Here, an 850 mb Td gradient exists, with modest WAA likely
supporting the gradual intensification of elevated convection within
this regime. The 12Z ILX observed sounding and 15Z mesoanalysis
depicts 700-500 mb lapse rates in the 8-8.5 C/km range, contributing
to MUCAPE approaching 2000 J/kg. These storms are encroaching on a
region of stronger 500 mb southwesterly flow, driven by a departing
upper trough over the eastern U.S., which is resulting in 30-40 kt
of effective bulk shear ahead of the storms. If storms continue to
intensify, it is plausible that at a hail threat may materialize
over the next few hours, with some stones potentially exceeding 1
inch in diameter.

Short-range high resolution ensemble guidance is providing mixed
signals regarding the evolution of this convection. Some
deterministic CAMS show that the ongoing storms eventually
consolidate and develop into stronger supercell structures in
northern IL by afternoon. Other guidance members depict the ongoing
storms oscillating in intensity, while stronger storms develop
later. As such, there is an appreciable degree of uncertainty as to
the evolution of the longer term severe threat with these WAA
storms. All this being said, convective trends will continue to be
monitored for the need of a WW issuance.

..Squitieri/Guyer.. 04/13/2026

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

ATTN...WFO...LOT...ILX...LSX...DVN...

LAT...LON   40829153 41349115 41809076 42269021 42318942 42178872
            41918839 41478835 41028850 40608866 40238895 40058932
            39988999 40039043 40249121 40829153

MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN