RSS Mesoscale Discussions from Storm Prediction Center
Public Severe Weather Outlook
PUBLIC SEVERE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0114 AM CDT WED JUN 17 2026
...Severe thunderstorms expected over parts of the Midwest today and
tonight...
* LOCATIONS...
Northern Indiana
Northern and Central Illinois
* HAZARDS...
Several tornadoes, a couple intense
Scattered damaging winds, some hurricane force
Scattered large hail, some baseball size
* SUMMARY...
An outbreak of severe thunderstorms is expected today, with
primary threat centered over Illinois and Indiana. Several
intense tornadoes, swaths of damaging gusts over 75 mph and
damaging wind-driven hail will all be possible.
Preparedness actions...
Review your severe weather safety procedures for the possibility
of dangerous weather today. Stay tuned to NOAA Weather Radio,
weather.gov, or other media for watches and warnings. A tornado
watch means that conditions are favorable for tornadoes to form
during the next several hours. If a tornado warning is issued for
your area, move to a place of safety, ideally in a basement or
interior room on the lowest floor of a sturdy building.
&&
..Guyer.. 06/17/2026
$$
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SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1256 AM CDT Wed Jun 17 2026
Valid 171200Z - 181200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS OVER ILLINOIS
AND INDIANA...
...SUMMARY...
An outbreak of severe thunderstorms is expected today, with primary
threat centered over Illinois and Indiana. Several intense
tornadoes, swaths of damaging gusts over 75 mph and damaging
wind-driven hail will all be possible.
...IL...IN...MO...OH...
An intense mid and upper level jet will nose southeastward across
the Midwest today, with a prominent leading disturbance moving out
of IA and into IL through midday. Severe storms are likely to be
associated with this early wave as a southwesterly low-level jet
increases to 60 kt and rapidly bring instability into the area. This
initial activity will bring damaging winds to eastern IA and
northern/central IL. This system is expected to weaken later in the
afternoon, but some remnants will move across IN.
Ahead of this early activity, a warm front will push north across IN
and OH. New severe storm development, perhaps transitioning out of
the remnant activity and/or forming near the warm front, is possible
across northern IN into northwest OH. Shear profiles will be
excessive, with tornado risk only conditional on minimal instability
being present. The result may be a isolated tornadic supercells.
To the west, the air mass across northern MO, IL, and into central
IN will easily recover and rapidly destabilize due to strong
southwest winds. A 60+ kt low-level jet is forecast, with notably
strong winds around 700 mb as well (surface to 3 km shear values may
exceed 60 kt). A plume of 65-70 F dewpoints will likely extend from
central MO into IL and western IN in the 21-00Z time frame,
contributing to 2000-3000 J/kg MLCAPE.
A broken line of supercells is likely to develop and mature roughly
from northern IN into central IL and MO around 21Z and spreading
east/southeast through early evening. Given the clearly
supercellular shear profiles, linear storm mode is unlikely for most
of the event. Long-tracked supercells producing tornadoes and
damaging hail are likely.
Finally, the warm frontal position will need to be monitored near
the IN/MI border. Even if instability is elevated into MI, extreme
shear and lift may still yield damaging winds and even a tornado
risk. As such, probabilities have been increased into far southern
Lower MI.
...Upper TX Coast into the northern Gulf Coast...
The NHC forecast shows Potential TC One moving into southwest LA by
00Z. Wind fields associated with this system will strengthen out of
the south ahead of it, resulting in areas of strong low-level shear
from TX into southern LA, and possibly into MS. Mid to upper 70 F
dewpoints will contribute to modest CAPE values, supporting embedded
stronger cells with tornado potential.
..Jewell/Weinman.. 06/17/2026
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SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1225 AM CDT Wed Jun 17 2026
Valid 181200Z - 191200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM KENTUCKY INTO
THE MID-ATLANTIC AND NORTHEAST...
...SUMMARY...
Isolated to scattered severe thunderstorms will be possible from
Kentucky to the Mid-Atlantic, and across parts of the Northeast.
Damaging wind gusts will be the main hazard with this activity.
...Synopsis...
An upper shortwave trough over the Lower Great Lakes/Upper Ohio
Valley Thursday morning will pivot northeast across the Northeast
through evening. Strong deep layer southwesterly flow associated
with this feature will already be in place at the beginning of the
period, with 500 mb flow from 60-80 kt stretching across portions of
the Northeast. Meanwhile, an intense 850 mb low-level jet will lift
northeast across the central Appalachians, the Mid-Atlantic, and the
Northeast. A surface low over southern Ontario will pivot northeast
into Quebec, while a trailing cold front stretches from the Lower
Great Lakes west/southwest toward the Mid-MS Valley and the OK/TX
Panhandles Thursday morning. The northern extent of this boundary
will spread east across the Northeast while the western extent
across the Ohio Valley into the Plains slowly sags southward.
Across the Gulf Coast states, the remnants of current Potential
Tropical Cyclone One will migrate eastward across the region. This
feature could locally enhance deep layer shear amid a very moist and
modestly airmass.
...Kentucky to the Mid-Atlantic/Northeast Vicinity...
Convection will be ongoing Thursday morning in the vicinity of the
surface cold front. Ahead of the front, a seasonally moist airmass
will be in place. Instability will likely be muted from PA/NY into
New England due to cloud cover, poor lapse rates and a narrow/modest
warm sector. Nevertheless, intense deep-layer flow will overspread
the Northeast and fast moving storms could produce damaging wind
gusts.
Stronger instability is expected in a corridor from KY into the
Mid-Atlantic where richer boundary layer moisture will be in place.
This corridor also may see stronger heating. The strong 850 mb
low-level jet will gradually weaken through the day as it lifts
northeast, but strong deep-layer flow will persist atop this
moist/unstable airmass. Scattered storms are expected during the
afternoon into evening, posing mainly a risk of damaging gusts.
...Gulf Coast/Southeast...
The remnants of current Potential Tropical Cyclone One will migrate
east/northeast across the region on Thursday. A very moist airmass
will be in place, and where stronger heating can occur, moderate
destabilization is expected. Furthermore, the remnant low will
locally enhance vertical shear. Isolated strong storms capable of
producing gusty winds and a tornado or two will be possible.
...Southern Plains to Mid-South...
Severe thunderstorm potential is a bit more uncertain from
OK/northwest TX into the Ozarks vicinity. A very moist and unstable
airmass will be in place ahead of the southward sagging cold front.
However, large-scale ascent will be weak and capping could limit
storm coverage. If storms can develop ahead of the front, some risk
for strong wind and hail will be possible.
..Leitman.. 06/17/2026
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SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0139 AM CDT Wed Jun 17 2026
Valid 191200Z - 201200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE SOUTHEAST...
...SUMMARY...
Isolated strong thunderstorms may produce damaging wind gusts across
portions of the Gulf Coast states/Southeast on Friday.
...Southeast...
A series of mid/upper shortwave impulses will migrate across the
Gulf Coast states/Southeast on Friday. Forecast guidance depicts
fairly strong 850 mb flow across the region early in the day, and
lifting shifting offshore from the Carolinas by late afternoon.
While 850-700 mb flow will be enhanced, vertical shear will be
modest. Nevertheless, convection will develop within a very moist
airmass amid moderate to strong instability ahead of a southward
sagging front. Isolated strong/damaging gusts will be possible with
this activity.
..Leitman.. 06/17/2026
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Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0221 AM CDT Wed Jun 17 2026
Valid 201200Z - 251200Z
...DISCUSSION...
...Day 4/Saturday - Central Plains...
A mid/upper trough ejecting across the central Rockies into the
Plains will break down the upper ridge centered over the Plains on
Saturday. This will result in some enhancement of mid/upper level
west/northwesterly flow. Surface lee troughing will extend from
eastern WY through eastern CO, and increasing south/southeasterly
low-level flow will transport 60s F dewpoints northward into NE and
far southwest SD. Increasing boundary layer moisture and steepening
midlevel lapse rates will support moderate destabilization by late
afternoon and evening. Thunderstorms are expected to develop by
21-00z and migrate southeast, posing a severe risk across portions
of the central Plains.
...Day 5/Sunday - OK/KS into the Mid-MS Valley...
Medium range guidance varies considerably regarding evolution of a
modest midlevel shortwave trough and associated surface low and cold
front on Sunday. It is possible that an MCS related to Day
4/Saturday convection could be ongoing Sunday morning somewhere near
the Mid-MO Valley. Depending on how surface feature evolve, a severe
risk could develop across parts of eastern OK/KS into the Mid-MS
Valley given a seasonally moist/unstable airmass and at least some
enhancement of deep-layer flow from the mid/upper shortwave trough.
However, placement of the surface low Sunday morning varies by a few
hundred miles between the ECMWF and GFS deterministic members. The
AIGFS is more similar to the ECMWF, but details remain quite
different. This precludes a 15 percent delineation at this time, but
probabilities may be needed at some point somewhere from OK/KS into
the Mid-MS Valley/Mid-South regions.
...Days 6-8/Monday-Wednesday...
A more June-like pattern appears to evolve through mid-week with
weaker deep-layer flow expected amid weak troughing in the East and
upper ridging across the West. Some severe thunderstorm potential
could develop across the Plains as low-level moisture spreads
northward beneath modest northwesterly flow aloft. However,
predictability is low given a lack of stronger large-scale ascent.
Daily thunderstorm chances will be driven by mesoscale processes not
well resolved at longer time scale.
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