RSS Mesoscale Discussions from Storm Prediction Center
WW 338 SEVERE TSTM IL IN MI OH LM 162010Z - 170300Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 338
NWS Storm Prediction Center Norman OK
410 PM EDT Tue Jun 16 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
East Central Illinois
Northern and Central Indiana
Southern Lower Michigan
Northwest Ohio
Lake Michigan
* Effective this Tuesday afternoon and evening from 410 PM until
1100 PM EDT.
* Primary threats include...
Scattered damaging wind gusts to 70 mph possible
Scattered large hail events to 1.5 inches in diameter possible
A tornado or two possible
SUMMARY...Thunderstorms will form this afternoon along a cold front
and sweep eastward across the watch area. The strongest storms will
be capable of damaging winds and large hail. A tornado or two is
also possible.
The severe thunderstorm watch area is approximately along and 55
statute miles east and west of a line from 30 miles south of Terre
Haute IN to 30 miles east northeast of Grand Rapids MI. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU8).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.
&&
AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
24030.
...Hart
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WW 0338 Status Updates
STATUS FOR WATCH 0338 HAS NOT BEEN ISSUED YET
Read more
MD 1157 CONCERNING SEVERE THUNDERSTORM WATCH 338... FOR PARTS OF SOUTHWESTERN LOWER MICHIGAN AND NORTHERN INDIANA
Mesoscale Discussion 1157
NWS Storm Prediction Center Norman OK
0453 PM CDT Tue Jun 16 2026
Areas affected...Parts of southwestern lower Michigan and northern
Indiana
Concerning...Severe Thunderstorm Watch 338...
Valid 162153Z - 162330Z
The severe weather threat for Severe Thunderstorm Watch 338
continues.
SUMMARY...Risk of damaging winds and isolated severe hail should
increase over the next few hours -- within Severe Thunderstorm Watch
#338.
DISCUSSION...Ahead of a compact midlevel shortwave trough advancing
eastward across the Midwest, isolated cells are developing across
southern Lake Michigan. As this activity spreads/develops eastward
over the next few hours, a pocket of cold midlevel temperatures
(around -20C at 500mb) and resultant steep lapse rates should
promote some increase in updraft intensity. Despite modest buoyancy,
the steepening midlevel lapse rates combined with strengthening
low/midlevel flow preceding the trough (around 30-40 kt in the
lowest 3 km AGL per nearby VWP) should promote damaging gusts and
isolated severe hail with a mix of cells and small clusters.
..Weinman.. 06/16/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...IWX...GRR...
LAT...LON 41508678 41818676 42698635 42938598 42888564 42668523
42148501 41628520 41288554 41238606 41328652 41508678
MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
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MD 1156 CONCERNING SEVERE THUNDERSTORM WATCH 338... FOR CENTRAL IL INTO WEST-CENTRAL AND NORTH-CENTRAL IN
Mesoscale Discussion 1156
NWS Storm Prediction Center Norman OK
0450 PM CDT Tue Jun 16 2026
Areas affected...central IL into west-central and north-central IN
Concerning...Severe Thunderstorm Watch 338...
Valid 162150Z - 162315Z
The severe weather threat for Severe Thunderstorm Watch 338
continues.
SUMMARY...Several supercells will potentially be capable of a threat
for mainly large hail (1 to 1.75 inches in diameter). Localized
severe gusts (55-65 mph) are possible with the stronger cores. A
brief tornado is also possible.
DISCUSSION...Water-vapor imagery shows a potent upper shortwave
trough moving east across the central Great Lakes. Surface analysis
places a cold front from the mid MS Valley arching
east-northeastward into east-central IL and northeastward into the
southern Lake Michigan vicinity. This boundary is serving as the
primary low-level forcing mechanism for storm development late this
afternoon from central IL northeastward towards Lafayette, IN.
Ahead of these storms---which contain a few supercell left-right
splits---surface conditions of lower 70s deg F temperatures and mid
50s dewpoints are observed.
RAP forecast soundings show cold 500-mb temperatures (-16 to -18 deg
C) and gradually veering and strengthening flow with height beneath
80-kt 300 mb westerly flow. As a result, sufficient buoyancy/shear
will continue to support supercells for the next several hours.
Large hail appears to be the primary severe hazard, but localized
severe gusts and perhaps a brief tornado are also possible.
..Smith.. 06/16/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...IWX...IND...LOT...ILX...
LAT...LON 40268572 39618691 39368841 39438886 39638888 39788878
39888806 40098748 40568702 41018674 41158592 41018550
40778538 40268572
MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
Read more
MD 1155 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF THE CENTRAL/SOUTHERN GREAT PLAINS INTO THE OZARKS
Mesoscale Discussion 1155
NWS Storm Prediction Center Norman OK
0348 PM CDT Tue Jun 16 2026
Areas affected...portions of the central/southern Great Plains into
the Ozarks
Concerning...Severe potential...Watch possible
Valid 162048Z - 162245Z
Probability of Watch Issuance...40 percent
SUMMARY...Isolated thunderstorm development is expected from the
eastern Texas Panhandle into northern Oklahoma/southern Kansas and
the Ozarks over the next 1-2 hours. Large hail will be the primary
risk, with localized damaging wind gusts also possible.
DISCUSSION...Latest GOES visible satellite imagery depicts
developing cumulus across portions of the central/southern Great
Plains ahead of a slow-moving surface cold front. Surface dewpoints
range from the low-60s F across the eastern Texas Panhandle and
northwest Oklahoma to the mid/upper 60s in northeastern Oklahoma.
Coupled with diurnal heating, this is contributing to the
development of 1000-2000+ J/kg MLCAPE. While some uncertainty
remains regarding thunderstorm development owing to relatively
neutral mid-level height falls, weak surface convergence along the
front and erosion of remaining inhibition by surface heating may
support isolated strong to severe thunderstorm development through
early evening.
Should storms develop, strong northwesterly mid-level flow and
40-50+ kts of effective shear will promote supercell development,
with the primary risk being large hail. Warming mid-level
temperatures and weakening mid-level lapse rates may tend to temper
storm longevity/maintenance, but an instance or two of large hail to
around golf-ball size (1.75") may be possible pending the
development of a sustained supercell, with the greatest potential
across northeast Oklahoma/southeast Kansas.
Farther west, more isolated thunderstorm development may occur
across the eastern TX/OK Panhandles. Continued heating/mixing will
yield a deepening boundary layer through the afternoon, with steep
low-level lapse rates and LCLs rising to 2-2.5 km. Isolated large
hail and damaging/severe wind gusts may accompany any storms that do
develop in this environment.
..Chalmers/Hart.. 06/16/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...SGF...TSA...ICT...OUN...DDC...AMA...
LAT...LON 36129652 35849769 35649853 34970026 34810082 34800117
34870150 35150170 35570175 36210147 36880103 37380061
37640019 37879967 38009927 38089852 38059720 37989591
37939513 37859463 37739438 37489416 37019395 36609398
36369430 36249467 36219530 36129652
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
Read more
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.
Read more
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
Read more
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
Read more
SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0131 PM CDT Tue Jun 16 2026
Valid 171200Z - 181200Z
...Afternoon Update...
Only minimal changes were made to the risk areas based on updated
guidance. Hot, dry and breezy conditions may permit the potential
emergence of lightning holdovers from dry thunderstorms several days
ago throughout northern New Mexico/Arizona and southern
Utah/Colorado. In addition, new/ongoing fire starts across these
regions could be further exacerbated as fire weather conditions
persist over the Great Basin through the end of this week.
Otherwise, the forecast remains on track. See the previous
discussion for more information.
..Elizalde-Garcia.. 06/16/2026
.PREV DISCUSSION... /ISSUED 0201 AM CDT Tue Jun 16 2026/
...Synopsis...
Within the base of a broad/amplifying large-scale trough
encompassing the northern CONUS, a belt of 60-70-kt midlevel
northwesterly flow will overspread the northern/central Rockies and
adjacent Plains on Wednesday. To the south, diurnal heating of a dry
antecedent air mass will result in an expansive area of 10-15
percent afternoon RH across much of the Intermountain West/Great
Basin into the central/southern Rockies.
As moderate-strong deep-layer flow peripheral the primary jet stream
overspreads this deeply mixed air mass, widespread 15-20 mph
sustained west-northwesterly surface winds are expected. The
combination of warm/dry conditions and these breezy/gusty winds will
favor a large area of elevated to locally critical fire-weather
conditions. A Critical area was considered in parts of eastern UT
into western CO, where 20 mph sustained west-northwesterly surface
winds should overlap 15-20 percent RH amid dry fuels, though this
favorable overlap appeared a bit localized for the upgrade at this
time.
...Please see www.spc.noaa.gov/fire for graphic product...
Read more
SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0450 PM CDT Tue Jun 16 2026
Valid 181200Z - 241200Z
...Synopsis...
On Day 3/Thursday, an upper low will slowly slide eastward over
southern Quebec as a belt of strong mid-level flow expands across
the Ohio Valley into the Northeast. Simultaneously, an upper ridge
will break down across the West owing to an approaching upper
trough. Some isolated dry thunderstorm potential alongside dry and
breezy conditions with above normal temperatures (and resultant dry
fuels) will support expansive fire concerns through Day 5/Saturday.
The trough will lose its amplitude as it traverses the Great Plains,
transitioning western CONUS to temporary zonal flow aloft. While
predictability is low, extended guidance exhibits increasing
potential for ridging to build back across the Pacific Northwest,
bringing warm and dry conditions back into the region early next
week.
...Day 3-5/Thursday-Saturday - Parts of the Pacific Northwest and
Great Basin...
As upper-level troughing moves onshore the West Coast, surging
mid-level moisture and synoptic scale lift will bring increasing
chances for thunderstorms. Given preceding days of warm and dry
conditions and coincident curing fuels, the isolated nature of
thunderstorm development could pose a threat for lightning ignitions
across a very dry environment -- possibly as early as Day 3/Thursday
evening. The potential for thunderstorm development on Day
3/Thursday will be reevaluated on the approaching Day 2 outlook
cycle as higher resolution guidance becomes available. Fast storm
motions, high cloud bases, and locally breezy conditions support 10%
Dry Thunderstorm probabilities on Day 4/Friday, and again on Day
5/Saturday as the trough shifts eastward. Spatial extent of the
aforementioned risk areas may fluctuate as guidance is better
resolved in future outlook cycles.
Increasing southerly to westerly flow across the Southwest will
transport very dry air and breezy conditions amid recently receptive
fuels, promoting continued fire concerns in the Great Basin through
the weekend. 40% Critical probabilities have been maintained on Days
4-5/Friday-Saturday to account for this threat.
..Elizalde-Garcia.. 06/16/2026
...Please see www.spc.noaa.gov/fire for graphic product...
Read more
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