219 
ACUS03 KWNS 151932
SWODY3
SPC AC 151931

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0231 PM CDT Mon Jun 15 2026

Valid 171200Z - 181200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE MID-MISSISSIPPI VALLEY INTO INDIANA AND WESTERN OHIO....

...SUMMARY...
An all-hazards severe thunderstorm event is expected across portions
of the Middle Mississippi Valley into Indiana on Wednesday. Intense
thunderstorms may produce swaths of damaging wind, as well as strong
tornadoes and very large hail.

...Synopsis...
A strong mid-level jet will extend from the Northwest to the Ohio
Valley. An embedded 75 to 85 knot mid-level shortwave trough will
extend from Nebraska into Iowa by Wednesday afternoon. A strong
surface cyclone will move from eastern South Dakota to southern
Ontario during the period. 

...Midwest...
Elevated supercells will likely be ongoing at the beginning of the
period across central/eastern Iowa at the nose of the low-level jet.
This cluster will continue to move east-southeast along/north of the
warm front through the day. This activity will likely have some hail
threat through the day with at least some tornado threat on the
southern periphery if any storms can latch onto the warm front.
Strong lower tropospheric flow should result in rapid
recovery/destabilization in the wake of these morning storms across
central/northern Illinois. A very favorable kinematic environment
will be in place with 70 knots of mid-level flow and 100+ knots of
upper-level flow with a 60+ knot low-level jet. Therefore, any
storms which develop within this zone could have a threat for very
large hail, and strong tornadoes. Due to this morning convection,
there is considerable uncertainty exactly where this most favorable
environment may set up and how broad of a region it will be.
Notably, strong isentropic ascent is forecast along the frontal zone
through the entire period which could result in continued
development along the warm frontal zone (more widespread than
currently depicted by guidance) and a limited window for recovery in
the wake of the morning storms. 

Despite these uncertainties, have upgraded severe probabilities to
45% in the region where multiple rounds of severe weather appear
most likely. Conceptually, the 12Z RRFS solution matches a
reasonable solution with a morning cluster of supercells including a
severe supercell on the southern extent. Additional supercells
developing along the trailing outflow/warm front during the
afternoon, followed by supercells developing along the cold front by
late afternoon. Even if storm development north of the warm front is
quite extensive during the day, forecast soundings show a Bunkers
storm motion parallel to the expected front/outflow orientation.
This points toward a favorable environment for one or more
supercells to move along the boundary in a favorable tornadic
environment. 

Widespread storm development is expected along the cold front by
late afternoon from southeast Iowa to far eastern Kansas. Very
strong instability and moderate to strong shear will support
supercells capable of large to very large hail. In addition, strong
low-level shear will support the potential for strong tornadoes.
There is some question regarding storm mode along the front. Strong
forcing would favor more storm interaction and upscale growth, but
fast storm motions (40-50 knots) and a Bunkers RM motion nearly
perpendicular to the front may support maintenance of supercell mode
at least within some areas along the front. This would support a
greater tornado threat during the evening from north-central
Missouri to central Illinois. If storms do grow more upscale early
in the lifecycle, the tornado/hail threat would be reduced, but the
threat for significant wind gusts would increase substantially. 

...Gulf Coast...
A Marginal Risk has been added along the Gulf as a tropical airmass
moves inland with a strengthening wind field associated with the
tropical disturbance identified by the NHC.

..Bentley.. 06/15/2026

$$


File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS03/20260615T1932.txt



307 
ACUS03 KWNS 150728
SWODY3
SPC AC 150727

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0227 AM CDT Mon Jun 15 2026

Valid 171200Z - 181200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE MID-MISSISSIPPI VALLEY INTO INDIANA...

...SUMMARY...
An all-hazards severe thunderstorm episode is expected across
portions of the Middle Mississippi Valley into Indiana on Wednesday.
Intense thunderstorms may produce swaths of damaging wind, as well
as strong tornadoes and large hail.

...Midwest...

A midlevel shortwave trough is forecast to move from the northern
Plains through the Upper Midwest and Great Lakes region on
Wednesday. As this occurs, very strong deep-layer flow, especially
for this time of year, will move across portions of the Mid-MS
Valley into the Ohio Valley. A westerly 500 mb jet streak
characterized by at least 70-80 kt will overspread parts of
IA/MO/IL/IN in the afternoon and evening. Meanwhile, a 50+ kt
southwesterly 850 mb low-level jet will spread across the same area
during the afternoon/evening, just ahead of an
east/southeast-advancing surface cold front. These strong wind
fields, in conjunction with a surface low moving eastward across MN
and the Upper Great Lakes, will aid in northward transport of rich
boundary layer moisture (upper 60s to near 70 F surface dewpoints).
Cooling aloft will steepen midlevel lapse rates, and moderate to
strong destabilization is expected across the warm sector. Overall,
this pattern should support numerous severe storms. While convective
evolution remains uncertain, it is likely that at least some initial
supercell risk will unfold during the afternoon and early evening
(particularly across MO/IL), with potential for one or more bowing
MCSs developing with time. This environment will support a risk for
all severe hazards, and particularly swaths of damaging winds, and
strong tornadoes.

Some uncertainty remains regarding the northward extent of the
severe risk. Most medium range guidance indicates a lead shortwave
impulse may move across IA/IL early in the day. Coupled with strong
warm advection across the region, morning thunderstorm develop
near/north of a warm front oriented from southeast MN into northeast
IL at midday could suppress northward development of the warm front.
Likewise, the southwest extent of the risk area into portions of
KS/OK may be limited by capping concerns, and weaker forcing for
ascent. Meanwhile, the southward extent of the severe risk across
the Ohio Valley will be modulated by the stronger westerly component
of mid/upper flow overnight and slow southward movement of the
surface cold front. The risk area may shift some in coming days as
surface boundaries and other mesoscale details become better
resolved.

..Leitman.. 06/15/2026

$$


File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS03/20260615T0728.txt