Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1128 AM CDT Wed Jun 17 2026
Valid 171630Z - 181200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
ILLINOIS AND INDIANA...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TONIGHT OVER
SOUTHEAST LOUISIANA AND SOUTHERN MISSISSIPPI...
...SUMMARY...
Numerous severe thunderstorms are expected this afternoon into
tonight, with the peak threat centered over Illinois and Indiana.
Intense tornadoes, swaths of damaging gusts over 75 mph and damaging
wind-driven large hail will all be possible.
...MO/IL/IN...
An intense and fast-moving shortwave trough continues to approach
the Midwest today, with an associated 90+ knot mid level jet
streaking across the region. A very strong southerly low-level jet
precedes this trough, and has resulted in widespread thunderstorms
over central IL. The effects of this early convection will be
important to the mesoscale details of where the main risk of severe
storms will develop later today.
The primary outflow boundary from ongoing storms currently extends
from extreme northeast MO into south-central IL, and continues to
sag southward. Strong heating is occurring to the south of the
boundary, and given the intense low-level flow, some northward
return is expected. However, it appears unlikely to substantially
destabilize as far north as earlier forecasts. The zone in vicinity
of the boundary will become very unstable by mid-late afternoon,
with forecast soundings continuing to show impressive shear values
and hodograph structures suggestive of tornadic supercell potential.
Very large hail and damaging winds will also be possible with this
activity as it tracks quickly eastward into central IN. Strong
tornadoes are possible.
By mid-evening, a line of severe storms will likely extend from
central MO into southern IN, with damaging winds becoming the
primary threat.
...Southeast MN...
A small area of heating/destabilization has developed near the
surface low over southern MN. Cold temperatures aloft and strong
deep-layer shear suggests a threat of a few severe storms capable of
hail and gusty/damaging winds this afternoon.
...LA/MS...
Tropical Storm Arthur will track northward and affect LA and
southern MS tonight. A zone of strong southerly low-level winds to
the east of the circulation will result in some concern for
overnight and pre-dawn tornadoes across southeast LA into far
southern MS.
...Southern AZ/NM...
Scattered afternoon and evening thunderstorms are expected across
southeast AZ and southwest NM. Strong heating and ample instability
will pose a risk of damaging wind gusts in the strongest cells.
..Hart/Chalmers.. 06/17/2026
