ACUS02 KWNS 130606
SWODY2
SPC AC 130604

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
0104 AM CDT Mon Apr 13 2026

Valid 141200Z - 151200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF IOWA INTO NORTHERN ILLINOIS AND SOUTHERN WISCONSIN...

...SUMMARY...
Isolated to scattered severe thunderstorms are expected on Tuesday
and Tuesday night from the Southern Plains to the Great Lakes. Large
to very large hail, a few tornadoes, and damaging wind gusts will be
possible, particularly across parts of eastern Iowa, northern
Illinois, and southern Wisconsin. Additional strong storms, mainly
producing strong wind gusts, will be possible across parts of the
Northeast.

...Synopsis...

A broad swath of enhanced deep-layer southwesterly flow will
overspread the southern High Plains to the Great Lakes on Tuesday.
An upper shortwave trough over the Great Basin will slowly pivot
east through the period, emerging over the central/southern High
Plains by Wednesday morning. A weak shortwave impulse is also
forecast to move across the northern Plains and Upper Midwest. At
the surface, low pressure will be centered over the Mid-MO Valley
for much of the period, with a warm front extending east/northeast
from north-central IA into southern WI and central Lower MI.
Meanwhile, a dryline will extend southwest across eastern KS into
western TX. Ahead of these boundaries, a seasonally moist airmass
will be in place, with mid-60s dewpoints common. The aforementioned
surface boundaries will become a focus severe thunderstorm
development Tuesday afternoon into the nighttime hours.

...Mid-MS Valley and Great Lakes vicinity...

A severe risk is expected to develop by late afternoon within the
warm frontal zone from Iowa into northern IL/southern WI in a
persistent warm advection regime. While height tendencies are
forecast to remain mostly neutral, low-level convergence along the
boundary and a glancing influence from a weak shortwave impulse
migrating across the northern Plains into northern MN/Upper MI
should provide focused ascent. A southwesterly 850-700 mb jet is
also forecast to increase across the region by late afternoon into
evening. Cool temperatures aloft (around -16 C at 500 mb) and steep
midlevel lapse rates atop a moist boundary layer will support MLCAPE
around 2000-3000 J/kg amid elongated/straight hodographs. As a
result, large to very large hail will be possible with initial
supercell thunderstorms. Storm motion and southwesterly deep-layer
flow may result in convection moving to the cool side of the warm
front. Even so, elevated storms will pose a risk for significant
hail. With time, and as the low-level jet increases during the
evening, convection may consolidate/grow upscale into one or most
bowing segments and progress eastward into Lower MI/IN/OH, posing a
continued risk for hail and an increasing risk for damaging wind gusts.

Any supercells that develop and can be sustained within the warm
sector will also pose a risk for a few tornadoes (some strong), very
large hail and damaging gusts.

...Southern Plains into eastern KS/western MO...

Moderate destabilization is forecast along the surface dryline by
afternoon. Strong heating along/just west of the dryline will
promote mixing, while low-level confluence and subtle height falls
(by 21-00z) provide sufficient forcing for ascent for isolated
thunderstorm development. Supercell wind profiles will be present
amid steep midlevel lapse rates and elongated hodographs. Large to
very large hail, locally strong wind gusts and a couple of tornadoes
will be possible. Storms should develop northward during the evening
into eastern KS and western MO as the low-level jet increases.

...Northeast...

Rounds of thunderstorms are expected during the afternoon and
evening within a warm advection regime. MLCAPE should increase to
around 1000 J/kg within a moistening low-level airmass. Strong
deep-layer westerly flow and steepening low-level lapse rates will
support isolated strong wind gusts across the region.

..Leitman.. 04/13/2026

$$
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* Origin: Project Scorpio TEST (618:250/6)