RSS Mesoscale Discussions from Storm Prediction Center
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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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 1730Z Day 2 Outlook
Day 2 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
0127 PM CDT Tue Jun 16 2026
Valid 171200Z - 181200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
CENTRAL ILLINOIS INTO NORTHWEST INDIANA...
CORRECTED FOR TORNADO PROBABILITIES
...SUMMARY...
An outbreak of severe thunderstorms is expected across portions of
Illinois and Indiana on Wednesday. Intense tornadoes, swaths of
damaging gusts to 80 mph and hail to 2.5 inch diameter are expected.
...Synopsis...
A strong mid-level jet streak will overspread parts of the Midwest
and lower Great Lakes on Wednesday. A deep surface low initially
within the Upper Midwest is forecast to evolve across the lower
Great Lakes and southern Ontario/Quebec. A strong low-level jet will
advect rich surface moisture ahead of a cold front through the
period. A warm front, likely reinforced by morning convection is
expected to lift northward into parts of central/northern Illinois
and northern Indiana/Ohio. Potent wind fields for this point in June
will support a threat for scattered to numerous severe storms
capable of all severe hazards -- including strong to intense
tornadoes, very-large hail, and 75+ mph winds.
...Mid-Mississippi Valley into northern Indiana/far western Ohio...
A majority of the CAMs as well as regional/global guidance suggest
convection will be ongoing in parts of eastern Iowa early Wednesday
morning. This activity will shift through northern/central Illinois
into Indiana. Some risk for damaging winds will probably accompany
this activity. The degree to which this cluster of convection can
intensify through mid/late morning is not clear. The environment
with eastward extent will begin drier and less unstable. The most
probable outcome is that this convection shifts east-southeast
relatively quickly and weakens with time.
The more substantial severe threat is expected to develop perhaps by
early/mid afternoon and depend strongly upon how morning convection
evolves spatially. Given the strong moisture advection into the
region, it is reasonable to expect an area of relatively rapid
airmass recovery from the Quad Cities vicinity into parts of central
Illinois. Storms that form in this environment near the surface
low/warm front will likely be discrete and take advantage of strong
low-level shear. Large to very-large hail, significant wind gusts,
and strong/intense tornadoes will all be possible. As convection
continues eastward into Indiana, the low-level moisture will be
improving with time.
...Southeast Kansas into Missouri...
Along the cold front, scattered storms are expected to develop by
mid/late afternoon. With mid-level height falls not being overly
strong and effective shear vectors have a large orthogonal component
across the front, storms will likely be supercellular for a few
hours. Steep mid-level and low-level lapse rates will promote a risk
of large/very-large hail as well as potentially 75+ mph wind gusts.
Despite being west of the low-level jet core, low-level wind fields
will still support a risk of tornadoes, some of which could be
strong.
...Central Gulf Coast...
Potential Tropical Cyclone 1 is forecast to move northeastward with
time. The marginally enhanced low-level wind fields will support
weak supercell structures that may produce brief, weak tornadoes.
Given the poor thermodynamic environment and the main timing of the
threat being during the evening/overnight, the overall threat should
remain marginal.
..Wendt.. 06/16/2026
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SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0232 PM CDT Tue Jun 16 2026
Valid 181200Z - 191200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM KENTUCKY AND
NORTHERN TENNESSEE INTO THE MID-ATLANTIC...
...SUMMARY...
Isolated to scattered severe thunderstorms will be possible from
Kentucky to the Mid-Atlantic. Damaging wind gusts will be the main
hazard with this activity.
...Synopsis...
An upper trough will move across southern Quebec on Thursday. A
trailing cold front from the Northeast into the southern Plains will
serve as a focus for convection. A remnant tropical system will also
promote scattered thunderstorms in the Southeast.
...Ohio Valley into the Northeast/Mid-Atlantic...
As the upper trough slowly moves through southern Quebec, a belt of
strong mid-level winds will be present across these regions.
Mid-level flow will rapidly diminish from south of the mid/lower
Ohio Valley latitude, however. Precipitation is expected to be
ongoing along at least parts of the cold front early in the day.
This will act to limit surface heating/destabilization into the
afternoon. Even with that limitation, the very moist airmass ahead
of the front will promote moderate (Mid-Atlantic/parts of Northeast)
to strong (mid/lower Ohio Valley) buoyancy. Given the strong
low/mid-level winds, potential exists for scattered damaging winds.
...Southern Plains into Mid-South...
Strong instability is forecast south of a sagging cold front. Though
these regions will be removed from the stronger mid-level winds,
sufficient effective shear will be in place to promote potential for
damaging downburst winds with the stronger storms/clusters that
develop during the afternoon.
...Southeast...
The remnants of Potential Tropical Cyclone 1 will continue to move
through the northern Gulf into the Southeast on Thursday. With 70+
dewpoints likely to be ahead of this feature, even muted surface
heating will promote moderate instability will develop. With locally
enhanced shear near the remnant low, isolated strong wind gusts and
perhaps a tornado or two will be possible. Should greater
destabilization occur, higher probabilities could be warranted.
..Wendt.. 06/16/2026
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