SPC Jun 17, 2026 1300 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0759 AM CDT Wed Jun 17 2026

Valid 171300Z - 181200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS ILLINOIS
AND INDIANA...

...SUMMARY...
An outbreak of severe thunderstorms is expected today into tonight,
with the peak threat centered over Illinois and Indiana. Several
intense tornadoes, swaths of damaging gusts over 75 mph and damaging
wind-driven large hail will all be possible.

...Midwest including Illinois/Indiana/Missouri/Ohio...
A very active/potentially dangerous day is expected today into
tonight, although some sub-regional forecast details remain a bit
uncertain. This is largely attributable to an upscale-growing
intense MCS which has been evolving in the predawn hours across
central/eastern Iowa, moving south of the I-80 corridor as of 730am
CDT. Measured significant wind gusts in excess of 80 mph have been
observed before sunrise, including a measured 94 mph measured wind
gust in Marshall County, Iowa.

This intense and increasingly well-organized MCS will continue to be
influenced by an extremely strong southwesterly jet of 70 kt and
robust warm advection/moisture transport, and likely continue
southeastward from southeast Iowa into north-central/west-central
Illinois. This will likely include an increasing potential for
surface-based storms and an appreciable uptick in damaging
wind/tornado potential early today, especially on the
south-southwest flank of the MCS in closer proximity to the
northeastward-shifting warm front.

Ahead of this early activity, a warm front will push
north-northeastward across Indiana/Ohio. New severe storm
development, perhaps MCV-influenced and transitioning out of the
remnant activity and/or forming near the warm front, is possible
across Indiana into Ohio. Shear profiles will be excessive, with
tornado risk only conditional on minimal instability being present.
The result may be a isolated tornadic supercells. The warm frontal
position will need to be monitored northward toward the
Indiana/Michigan border vicinity. Even if instability is elevated
into Michigan, extreme shear and lift may still yield damaging winds
and even a tornado risk.

To the west, rapid air mass recovery is expected on the
west-southwestern flank of the early day MCS from Missouri into
central/possibly parts of northern Illinois, even where appreciable
early day MCS impacts occur early. This recovery will be fueled by
mid-June insolation/moisture content and robust advection, again
attributable to atypically robust (50-65 kt) low/mid-tropospheric
west-southwesterly flow by mid-June/diurnal standards. In the
presence of 65-70 F surface dewpoints, this will likely result in a
corridor of 2000-3500 J/kg MLCAPE.

This will likely set the stage for the development of a broken line
of intense supercells, potentially favoring prior outflow (or
outflow-augmented warm front) and post-MCS recovery zone of
differential heating across Illinois and perhaps eventually into
western Indiana. Given the clearly supercellular shear profiles and
ample venting aloft, linear storm mode is unlikely for most of the
event. Long-tracked supercells producing tornadoes and damaging
large hail are likely. Some strong to potentially intense tornadoes
are plausible given the magnitude of the low/mid-tropospheric flow,
and again potentially heightened in vicinity of the prior
outflow/warm front. Some damaging wind threat will likely also
increase by evening as storms continue across Indiana into Ohio and
potentially southward toward the Ohio River.

...Upper Texas Coast/Middle Gulf Coast...
The NHC forecast shows Potential Tropical Cyclone One moving into
southwest Louisiana by this evening. Wind fields associated with
this system will strengthen out of the south ahead of it, resulting
in areas of strong low-level shear from the upper Texas coast across
southern portions of Louisiana and eventually into southern
Mississippi. Mid to upper 70 F dewpoints will contribute to modest
CAPE values, supporting embedded stronger cells with tornadic
potential.

..Guyer/Broyles.. 06/17/2026


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SPC Jun 17, 2026 0100 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 0100Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0800 PM CDT Tue Jun 16 2026

Valid 170100Z - 171200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF IOWA
AND OVER A SMALL PART OF CENTRAL INDIANA...

...SUMMARY...
Severe storms producing hail remain possible from southern Kansas
into northwest Oklahoma this evening. Isolated severe hail or wind
will persist across the northern Plains and into Iowa by Wednesday
morning. Isolated severe storms may persist from Indiana into
western Ohio this evening.

...IN/OH/MI...
00Z DTX and ILN soundings show modest instability but favorable
shear profiles to sustain cellular storm mode this evening. However,
storms across this region are beginning to decrease in coverage and
intensity, though isolated strong to severe storms may persist with
marginal hail or brief tornado risk before the upper trough moves
out of the area and the air mass stabilizes.

...KS/OK/TX Panhandle...
A mixed boundary layer, increasing low-level jet and northwest flow
aloft is aiding a few cells over southwest KS into northwest OK.
Periodic large damaging hail remain possible, and a cell or two may
persist this evening, perhaps toward the eastern TX Panhandle as
moisture returns northwestward. However, the cooling boundary layer
will eventually result in decreasing coverage.

...From MT to IA...
Scattered storms exist from MT into ND, beneath cool temperatures
aloft with the developing upper trough. Locally severe gusts may
occur with any of this activity as a relatively dry/mixed sub cloud
layer exists on 00Z soundings.

Later tonight, as the low-level jet increases into the central
Plains, a plume of mid 60s F dewpoints will reach eastern NE into
IA, and may fuel cells initially producing hail following a possible
MCS.

..Jewell.. 06/17/2026


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SPC Jun 16, 2026 2000 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 2000Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0255 PM CDT Tue Jun 16 2026

Valid 162000Z - 171200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
EASTERN ILLINOIS...INDIANA AND LOWER MICHIGAN THROUGH THIS EVENING
AND IOWA TONIGHT...

...SUMMARY...
Severe thunderstorms remain possible this afternoon and tonight
across multiple parts of the Midwest, as well as on a more isolated
basis across the Gulf Coast, south-central Plains and northern
Plains.

...20z Update Wisconsin and Michigan to Illinois and Indiana...
Beneath the cold core of the clipper, steep mid-level lapse rates
and weak buoyancy are supporting scattered thunderstorms. While
available MUCAPE is somewhat limited (500-750 J/kg) 500 mb temps
near -20C are supportive of marginally severe hail with the stronger
cores. This threat should end by evening as buoyancy declines with
the loss of diurnal heating. Have expanded the 5% hail across Lake
Michigan into the UP and eastern WI shores.

Southern portions of the Level 2 Slight risk were also expanded into
eastern IL where robust convection is expected along the cold front
this afternoon and evening. Hail, damaging gusts and a couple of
tornadoes remain possible.

...MT and northern Plains into the Midwest tonight...
Ahead of the strong belt of mid-level flow ahead of the upper trough
moving out of Canada, afternoon model guidance remains bullish on
several rounds of strong and occasionally severe storms late tonight
into early Wed. However, CAPE will be rather weak, which should
limit overall convective organization. Isolated severe gusts remain
possible.

The upstream convection will eventually intersect with a rapidly
moistening air mass across parts of IA and the Midwest. This will
likely result in a cluster of more robust severe storms near
daybreak across SD, IA and MN at the nose of a 50+ kt 850 mb jet.
Increasingly strong vertical shear from the upstream trough/jet will
support supercells or elevated bowing segments capable of hail and
severe wind gusts by 12z Wed. Have connected the MRGL areas over the
northern Plains into the Midwest.

...Southern and central Plains...
Strong heating along the stalled front initially over the southern
and central Plains could result in isolated to widely scattered
thunderstorms late this afternoon and early evening. Increasing
vertical shear and low-level moisture advection could favor some
risk for hail with supercells. However, warm temperatures aloft and
only modest large-scale forcing for ascent casts considerable
uncertainty on storm development/maintenance this evening. Should a
supercell or two become established, large hail and damaging gusts
would be possible before ending overnight.

..Lyons.. 06/16/2026

.PREV DISCUSSION... /ISSUED 1113 AM CDT Tue Jun 16 2026/

...IN/Lower MI...
Morning water vapor loop shows a strong and progressive Clipper
system tracking southeastward across MN/WI. A band of clouds and
isolated thunderstorms precedes this system, extending from southern
Lower MI into central IL. While a few strong storms are possible to
develop in this band, the greater risk for severe storms appears to
be associated with a period of heating in the wake of these clouds.
Steep lapse rates and cold temperatures aloft will combine with
dewpoints around 60F to result in sufficient afternoon/evening CAPE
for widely scattered strong/severe storm development. Large hail
will be the initial main concern, along with some risk of a tornado
or two. By early evening, damaging winds will be the main concern.

...IA Overnight...
The next in a series of fast-moving upper-level features will move
across the Dakotas tonight, with large-scale forcing for ascent
spreading into parts of MN/IA before 12z. This ascent will begin
interacting with a plume of returning moisture, leading to scattered
thunderstorm development in the pre-dawn hours. Elevated supercells
capable of large hail will be the main risk through 12z.

...MT/ND...
The aforementioned upper feature will affect northeast MT and the
Dakotas this afternoon and evening. A deeply-mixed boundary layer
will develop over this area with temperatures in the 80s and 35-45F
t-td spreads. CAPE will be rather weak, which should limit overall
convective organization. Nevertheless, fast-moving high-based
showers and thunderstorms capable of gusty and occasionally severe
wind gusts are expected.

...Gulf Coast...
The tropical system (PTC 1) along the south TX coast is expected to
slowly organize today, with widespread showers and thunderstorms
from east TX into the central Gulf coast. Low-level winds are not
particularly strong and forecast hodographs are only marginally
favorable for updraft rotation. Nevertheless with such a broad area
of risk, a tornado or two is certainly possible this afternoon
through tonight.


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SPC Jun 16, 2026 1630 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1630Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1113 AM CDT Tue Jun 16 2026

Valid 161630Z - 171200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND
EVENING ACROSS PARTS OF INDIANA AND LOWER MICHIGAN...AND TONIGHT
OVER PARTS OF IOWA....

...SUMMARY...
Severe thunderstorms are possible this afternoon and tonight across
multiple parts of the Midwest, as well as on a more isolated basis
across the Gulf Coast, south-central Plains and northern Plains.

...IN/Lower MI...
Morning water vapor loop shows a strong and progressive Clipper
system tracking southeastward across MN/WI. A band of clouds and
isolated thunderstorms precedes this system, extending from southern
Lower MI into central IL. While a few strong storms are possible to
develop in this band, the greater risk for severe storms appears to
be associated with a period of heating in the wake of these clouds.
Steep lapse rates and cold temperatures aloft will combine with
dewpoints around 60F to result in sufficient afternoon/evening CAPE
for widely scattered strong/severe storm development. Large hail
will be the initial main concern, along with some risk of a tornado
or two. By early evening, damaging winds will be the main concern.

...IA Overnight...
The next in a series of fast-moving upper-level features will move
across the Dakotas tonight, with large-scale forcing for ascent
spreading into parts of MN/IA before 12z. This ascent will begin
interacting with a plume of returning moisture, leading to scattered
thunderstorm development in the pre-dawn hours. Elevated supercells
capable of large hail will be the main risk through 12z.

...MT/ND...
The aforementioned upper feature will affect northeast MT and the
Dakotas this afternoon and evening. A deeply-mixed boundary layer
will develop over this area with temperatures in the 80s and 35-45F
t-td spreads. CAPE will be rather weak, which should limit overall
convective organization. Nevertheless, fast-moving high-based
showers and thunderstorms capable of gusty and occasionally severe
wind gusts are expected.

...Gulf Coast...
The tropical system (PTC 1) along the south TX coast is expected to
slowly organize today, with widespread showers and thunderstorms
from east TX into the central Gulf coast. Low-level winds are not
particularly strong and forecast hodographs are only marginally
favorable for updraft rotation. Nevertheless with such a broad area
of risk, a tornado or two is certainly possible this afternoon
through tonight.

..Hart/Lyons.. 06/16/2026


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