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145
ACUS11 KWNS 100353
SWOMCD
SPC MCD 100353
INZ000-ILZ000-IAZ000-100600-
Mesoscale Discussion 1890
NWS Storm Prediction Center Norman OK
1053 PM CDT Sun Aug 09 2026
Areas affected...northern Illinois
Concerning...Severe Thunderstorm Watch 550...
Valid 100353Z - 100600Z
The severe weather threat for Severe Thunderstorm Watch 550
continues.
SUMMARY...Severe potential continues within WW550.
DISCUSSION...Supercells and supercell hybrid clusters continue
across portions of northern Illinois. As the low-level jet has
strengthened, a few low topped supercells have shown weak rotation.
One supercell in Lee County near the warm front/outflow boundary
across northern Illinois approached 60 kft with more pronounced and
long lived rotation and reports of a tornado. VAD profiles from KLOT
are sampling 0-3 km SRH around 350-400 m2/s2, with weakening flow
above 3 km. Given the favorable low-level shear, transient weak
rotation will likely continue with low topped cells south of the
boundary. Any storm that can anchor to the boundary may have
potential for a tornado in the short term. Mode is becoming more
clustered through time, with increasing damaging wind potential
later into the overnight.
..Thornton.. 08/10/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LOT...ILX...DVN...
LAT...LON 41999078 42238963 42288892 42228818 42088774 41878733
41458738 40908815 40758899 40748977 40889035 41209084
41579095 41999078
MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS11/20260810T0353.txt
606
ACUS11 KWNS 100329
SWOMCD
SPC MCD 100329
KSZ000-NEZ000-COZ000-100530-
Mesoscale Discussion 1889
NWS Storm Prediction Center Norman OK
1029 PM CDT Sun Aug 09 2026
Areas affected...Far northeast Colorado...southwest Nebraska...and
far northwest Kansas
Concerning...Severe Thunderstorm Watch 549...
Valid 100329Z - 100530Z
The severe weather threat for Severe Thunderstorm Watch 549
continues.
SUMMARY...Some threat for severe wind will continue across portions
of far northeast Colorado and southwest Nebraska for the next couple
of hours. There is some potential for a continuation of severe winds
into portions of far northwest Kansas later tonight, but confidence
in this threat is limited.
DISCUSSION...Over the past two hours, convection within a loosely
organized band of storms has largely evolved as expected with the
strongest cores now residing in far northeast CO - largely owing to
the effects of increasing inhibition with eastward extent towards
the North Platte, NE area. Despite this contraction in the band,
latest echo top and GOES IR trends continue to show robust updraft
development within the remaining cluster, suggesting that the
near-storm environment across northeast CO/southwest NE remains
supportive for intense convection. Additionally, KGLD velocity
imagery shows hints of an emerging outflow surge, suggesting that
this cluster will continue to pose a threat for severe wind, and
perhaps transient hail, for the next hour or two as it continues to
migrate across a relatively buoyant environment.
Recent runs of the HRRR and RRFS both suggest that this cluster will
continue to intensify with an expanding wind field through roughly
05-07 UTC as it spreads into southwest NE and far northwest KS.
However, both of these solutions have been depicting broad cold
pools with temperatures in the 65-70 F range. Surface observations
have mostly been reporting cold pool temperatures in the 70-75 F
range, suggesting that the modeled cold pools may be too
deep/intense compared to reality. Consequently, this casts
uncertainty on how widespread and intense the wind threat will be
beyond the next 1-2 hours.
Nonetheless, the downstream environment into northwest KS features
only weak/shallow capping and MLCAPE values of around 2500 J/kg,
which may support at least an isolated severe wind threat beyond WW
549. Convective trends will continue to be monitored, and downstream
watch issuance is possible.
..Moore.. 08/10/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...GID...LBF...GLD...BOU...CYS...
LAT...LON 40760281 41040275 41190247 41290206 41030157 40650089
40349971 40109956 39869953 39649978 39530006 39480050
39450109 39550165 39680207 39930233 40190262 40500275
40760281
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS11/20260810T0329.txt
435
ACUS11 KWNS 100208
SWOMCD
SPC MCD 100207
MOZ000-IAZ000-KSZ000-NEZ000-100400-
Mesoscale Discussion 1888
NWS Storm Prediction Center Norman OK
0907 PM CDT Sun Aug 09 2026
Areas affected...Southeast Nebraska into northeast
Kansas...northwest Missouri...and southwest Iowa
Concerning...Severe potential...Watch unlikely
Valid 100207Z - 100400Z
Probability of Watch Issuance...5 percent
SUMMARY...A localized corridor of severe hail and wind potential may
emerge over the next few hours across southeast Nebraska, northeast
Kansas, and into adjacent portions of northwest Missouri and
southwest Iowa. However, this threat will likely remain sufficiently
isolated to preclude watch issuance.
DISCUSSION...Convective trends have been monitored over the past
hour as an isolated thunderstorm developed across far southeast NE
and crossed the MO River. More recently, additional attempts at deep
convection are noted in radar and GOES IR imagery, and appear to be
driven by strengthening isentropic ascent across a warm frontal zone
as the nocturnal jet begins to slowly intensify (0-2 km winds have
been increasing to 30-40 knots in upstream VWPs over the past 30-45
minutes). Despite a somewhat focused zone for initiation, the
placement of this zone within the upper-level ridge axis suggests
synoptic-scale forcing for ascent and deep-layer wind shear is
limited for storm maintenance and/or intensification. The relatively
short lifespan and recent demise of the initial cell crossing the MO
River reflects these mitigating factors, despite an otherwise highly
favorable thermodynamic environment (MUCAPE analyzed upwards of
4000-5000 J/kg).
Over the next few hours, the expectation is for additional
development of isolated cells and perhaps a few clusters to the
north of the surface warm front. Very strong instability will favor
robust updraft development that may pose a threat for isolated large
hail and perhaps strong to severe downbursts. However, given the
buoyancy-driven nature of this convection within a modestly sheared
environment, storm organization and longevity may be limited.
Furthermore, this activity should primarily reside within an MUCIN
minimum co-located with the strongest isentropic ascent. Storm
maintenance out of this corridor seems unlikely, and should
spatially confine the severe threat. Given these limitations, watch
issuance is not anticipated.
..Moore/Mosier.. 08/10/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DMX...EAX...OAX...TOP...GID...
LAT...LON 41009548 40999452 40759396 40509375 40049369 39769384
39439415 39369496 39069709 39079756 39539796 39979789
41009548
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS11/20260810T0208.txt
047
ACUS11 KWNS 100152
SWOMCD
SPC MCD 100151
OHZ000-100345-
Mesoscale Discussion 1887
NWS Storm Prediction Center Norman OK
0851 PM CDT Sun Aug 09 2026
Areas affected...northern Ohio
Concerning...Severe Thunderstorm Watch 548...
Valid 100151Z - 100345Z
The severe weather threat for Severe Thunderstorm Watch 548
continues.
SUMMARY...Damaging wind potential continues within WW548.
DISCUSSION...The line of thunderstorms across northern OH has
weakened over the last hour. Instability decreases across eastern OH
into far western PA. Further weakening is anticipated as the storms
move toward this less favorable air mass. Damaging wind potential
continues across the far northern portion of the line and with some
redevelopment along the outflow across the southern portion of the
line. A more favorably unstable air mass remains ahead of the new
development near the southern portion of the line, though deep layer
shear decreases with southward extent. Overall, damaging wind
potential is expected to continue over the next couple of hours
before gradual weakening occurs. A downstream watch is not currently
anticipated but trends will be monitored.
..Thornton.. 08/10/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PBZ...RLX...CLE...ILN...
LAT...LON 41528265 40868313 40198347 39998357 39858300 39828259
39918218 40478187 40958178 41498192 41588207 41528265
MOST PROBABLE PEAK WIND GUST...55-70 MPH
File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS11/20260810T0152.txt
205
ACUS11 KWNS 100114
SWOMCD
SPC MCD 100114
INZ000-ILZ000-WIZ000-IAZ000-100315-
Mesoscale Discussion 1886
NWS Storm Prediction Center Norman OK
0814 PM CDT Sun Aug 09 2026
Areas affected...eastern Iowa into northern Illinois
Concerning...Severe potential...Severe Thunderstorm Watch likely
Valid 100114Z - 100315Z
Probability of Watch Issuance...80 percent
SUMMARY...Supercells are likely to develop across eastern Iowa into
northern Illinois this evening. Primary threat will be for large
hail and damaging wind.
DISCUSSION...A southwesterly low-level jet (LLJ) around 30-35 kts
will move into portions of northern Illinois this evening. A surface
boundary extends across northern Illinois. Near the boundary and
the nose of the LLJ, there is good run to run agreement in CAM
guidance that storms will develop across some portion of far eastern
Iowa into northern Illinois within the warm advection regime this
evening. Some radar returns and cloud cooling have been noted in the
last 30 minutes across this area. The environment across this region
is strongly unstable, with MLCAPE around 2000-4000 J/kg sampled by
00z RAOBs from DVN and ILX. Deep layer shear around 35-40 kts will
increase with the LLJ later this evening. This regime will support
supercells with the primary threat of large hail and damaging wind.
For any supercell that can remain rooted in the surface, a tornado
will be possible. A watch will likely be needed to cover this
potential in the next couple of hours.
..Thornton/Mosier.. 08/10/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LOT...ILX...MKX...DVN...
LAT...LON 40499156 41529139 42199070 42478996 42538906 42528832
42258779 41988732 41768725 41238754 40598858 40408979
40479114 40499156
MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS11/20260810T0114.txt
786
ACUS11 KWNS 100101
SWOMCD
SPC MCD 100100
NEZ000-KSZ000-COZ000-100300-
Mesoscale Discussion 1885
NWS Storm Prediction Center Norman OK
0800 PM CDT Sun Aug 09 2026
Areas affected...Western Nebraska
Concerning...Severe Thunderstorm Watch 549...
Valid 100100Z - 100300Z
The severe weather threat for Severe Thunderstorm Watch 549
continues.
SUMMARY...The potential for severe winds will continue for the next
2-3 hours across much of WW 549 in western Nebraska. However, the
most likely corridor for severe winds may emerge from the southern
Nebraska Panhandle into far northeast Colorado and far southwest
Nebraska.
DISCUSSION...Recent echo top trends show deepening convective towers
as a broken band of convection continues to push east into a
reservoir of increasing MLCAPE. Downstream from this activity, the
recent 00 UTC LBF sounding sampled very steep (8.7 C/km) mid-level
lapse rates that are conducive for robust updrafts. However, warm
temperatures between 850-700 mb are also yielding MLCIN on the order
of -300 to -350 J/kg. Mixed-layer LFCs were estimated to be around 4
km, suggesting that a substantially deep cold pool will likely be
needed to continue lifting parcels through the stable layer and
maintain intensity of the line.
Based on regional velocity/reflectivity data, it appears that such a
cold pool is in the process of being established, but may not yet be
sufficiently deep to maintain all portions of the line. Based on
recent mesoanalysis estimates, MLCIN increases with eastward extent
into central NE, but remains somewhat more modest across southwest
NE, suggesting that the southern flank of the line may be favored
for maintenance and/or further intensification over the next few
hours. Given that this band has already produced measured gusts on
the order of 55-65 mph, similar wind speeds appear possible for the
short term (next hour or so), and may persist for the next few hours
across southwest NE and far northeast CO.
..Moore.. 08/10/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LBF...GLD...BOU...CYS...
LAT...LON 41080359 41890303 42310271 42350234 41920027 41490018
41100019 40680056 40190115 40010166 39980210 40110259
40920347 41080359
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS11/20260810T0101.txt
930
ACUS11 KWNS 092323
SWOMCD
SPC MCD 092322
OHZ000-INZ000-100045-
Mesoscale Discussion 1884
NWS Storm Prediction Center Norman OK
0622 PM CDT Sun Aug 09 2026
Areas affected...northern Indiana into northeastern Ohio
Concerning...Severe Thunderstorm Watch 547...548...
Valid 092322Z - 100045Z
The severe weather threat for Severe Thunderstorm Watch 547, 548
continues.
SUMMARY...Damaging wind potential continues within WW547.
DISCUSSION...A bowing segment continues eastward across northern
Indiana, with recent wind gusts to 67 mph reported near Fort Wayne,
IN. KIWX radar continues to sample winds around 60 kts around 2 kft.
Initial outflow has rushed out ahead of the main line, with
additional thunderstorm development ongoing ahead of the line near
the outflow. Storms have become better oriented with the mean
flow/deep layer shear, which may help aid downstream organization.
The greater buoyancy is located across southern/central Ohio. It
seems most likely that the southern portion of the line will
continue to evolve along this gradient into portions of Ohio with
continued damaging wind gusts 60-70 mph downstream for the next
couple of hours before outrunning better buoyancy.
..Thornton.. 08/09/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...CLE...ILN...IWX...
LAT...LON 41688397 41678477 41278487 41108493 40888521 40708521
40618475 40488392 40358263 40618200 41268171 41708266
41688397
MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS11/20260809T2323.txt
636
ACUS11 KWNS 092241
SWOMCD
SPC MCD 092241
NEZ000-SDZ000-COZ000-WYZ000-100045-
Mesoscale Discussion 1883
NWS Storm Prediction Center Norman OK
0541 PM CDT Sun Aug 09 2026
Areas affected...eastern Wyoming into portions of western and
central Nebraska
Concerning...Severe potential...Watch possible
Valid 092241Z - 100045Z
Probability of Watch Issuance...40 percent
SUMMARY...Thunderstorms to increase in coverage and spread westward
this evening with potential for damaging winds.
DISCUSSION...Thunderstorm development is increasing across potions
of eastern Wyoming into western Nebraska over the last hour. The 18z
RAOB from LBF shows stout MLCIN in place, which is still depicted by
SPC mesoanalysis. However, with daytime heating CIN has weakened
across the Nebraska Panhandle where temperatures are in the mid to
upper 90s. Dew points in the 40s-50s F are contributing to large
temperature/dew point spreads across the Nebraska Panhandle. Steep
low to mid-level lapse rates are also noted across the region.
Guidance is inconsistent with the evolution of storms out of
Wyoming, with some favoring a more organized cluster with damaging
wind potential and others favoring a weakening cluster with eastward
propagation. This leads to low confidence in evolution and watch
potential at this time. Should a cluster evolve, damaging wind
potential (perhaps 75+ mph) would increase downstream. Trends will
be monitored and a watch may be possible.
..Thornton/Mosier.. 08/09/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...GID...LBF...UNR...BOU...CYS...
LAT...LON 42779982 42950040 43080193 43070392 42970403 42440434
41940433 41340358 40400182 40400060 40959974 41979952
42729973 42779982
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS11/20260809T2241.txt
316
ACUS11 KWNS 092148
SWOMCD
SPC MCD 092147
AZZ000-092345-
Mesoscale Discussion 1882
NWS Storm Prediction Center Norman OK
0447 PM CDT Sun Aug 09 2026
Areas affected...Southern Arizona
Concerning...Severe potential...Watch unlikely
Valid 092147Z - 092345Z
Probability of Watch Issuance...20 percent
SUMMARY...Isolated to widely scattered thunderstorms will likely
spread across southern Arizona through the late afternoon/evening
hours. Watch issuance is not anticipated given the fairly modest
kinematic environment, though a few severe downbursts appear
possible.
DISCUSSION...Latest GOES imagery and lightning data show the onset
of deep convection both along the Mogollon Rim and within the higher
terrain of southern/southeast AZ. Although this activity has been
slow to move off the terrain so far, modest easterly flow through
much of the column, combined with cold-pool propagation, should
promote thunderstorms spreading westward over the next several
hours. As this occurs, convection will begin to impinge on a very
deeply mixed, but buoyant, air mass characterized by MLCAPE values
of around 500-1000 J/kg and 40-45 F dewpoint depressions (which
suggest LCL heights are around 3 to 3.5 km). This thermodynamic
profile is very conducive for accelerating downdrafts capable of
producing swaths of strong to severe winds (possibly as high as
55-70 mph) within the more intense downbursts.
Although a favorable thermodynamic environment is in place, the
observed wind profiles from regional VWPs show meager deep-layer
wind shear with 0-6 km BWD values of around 15 knots - somewhat
weaker than the 20-25 knots depicted by RAP mesoanalyses and recent
HRRR solutions. Consequently, the expectation is for sporadic strong
to severe downburst winds within poorly organized cells and clusters
through at least early evening. This activity should remain
sufficiently transient and isolated to preclude the need for a
watch.
..Moore/Mosier.. 08/09/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...TWC...FGZ...PSR...
LAT...LON 34221182 33871089 33631037 33330996 33110976 32580974
32000993 31681014 31421048 31351074 31371107 31471155
31721234 32001296 32251317 32641331 33131330 33801302
33991290 34171273 34271225 34221182
MOST PROBABLE PEAK WIND GUST...55-70 MPH
File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS11/20260809T2148.txt
511
ACUS11 KWNS 092049
SWOMCD
SPC MCD 092049
INZ000-MIZ000-ILZ000-092215-
Mesoscale Discussion 1881
NWS Storm Prediction Center Norman OK
0349 PM CDT Sun Aug 09 2026
Areas affected...Northwest Indiana
Concerning...Severe Thunderstorm Watch 546...547...
Valid 092049Z - 092215Z
The severe weather threat for Severe Thunderstorm Watch 546, 547
continues.
SUMMARY...A locally greater wind threat is evident in northwest
Indiana.
DISCUSSION...KLOT and TMDW/TORD radar velocity data suggest a
locally greater wind threat developing in northwest Indiana. Two
small bowing segments are evident with around 50 kt outbound
velocities. Given the strong heating and large buoyancy ahead of
these storms, they will likely pose a locally greater severe wind
threat over the next 1-3 hours. Depending on the persistence of
these storms, additional extensions of WW 547 may become necessary.
..Wendt.. 08/09/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...IWX...LOT...
LAT...LON 40898601 41158705 41288738 41488761 41898689 41528585
41268572 40918591 40898601
MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS11/20260809T2049.txt
169
ACUS11 KWNS 092040
SWOMCD
SPC MCD 092039
OHZ000-MIZ000-INZ000-092245-
Mesoscale Discussion 1880
NWS Storm Prediction Center Norman OK
0339 PM CDT Sun Aug 09 2026
Areas affected...Southeast Lower Michigan into northwest Ohio
Concerning...Severe potential...Watch possible
Valid 092039Z - 092245Z
Probability of Watch Issuance...40 percent
SUMMARY...The threat for wind damage will eventually spread eastward
into parts of western Ohio and southeast Lower Michigan. A watch is
possible for parts of these areas later this afternoon.
DISCUSSION...Airmass destabilization continues in portions of
northwest Ohio into southeast Lower Michigan. An upstream line of
convection may impact portions of these areas later this afternoon
into the evening. Cloud cover ahead of the convection has slowed the
northward progress of the more favorable airmass and the northern
portion of the convection has trended downward in the last hour. It
is possible that the strongest activity may track farther south
where buoyancy is much larger. The greatest risk for damaging winds
will probably exist where dewpoints are 70+ F. However, at least
isolated wind damage will remain possible along the instability
gradient into the evening. A watch is possible for portions of these
areas later this afternoon.
..Wendt/Hart.. 08/09/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...CLE...ILN...DTX...IWX...GRR...
LAT...LON 42358410 42178321 41648237 41058253 40488321 40428390
40548457 40608470 41198482 42358410
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS11/20260809T2040.txt
320
ACUS11 KWNS 091857
SWOMCD
SPC MCD 091857
MIZ000-INZ000-ILZ000-092030-
Mesoscale Discussion 1879
NWS Storm Prediction Center Norman OK
0157 PM CDT Sun Aug 09 2026
Areas affected...Southwestern Lower Michigan into far northern
Indiana
Concerning...Severe Thunderstorm Watch 546...547...
Valid 091857Z - 092030Z
The severe weather threat for Severe Thunderstorm Watch 546, 547
continues.
SUMMARY...Wind damage potential will increase along the
southern/eastern Lake Michigan shore over the next 1-2 hours.
DISCUSSION...A linear segment is nearing the eastern Lake Michigan
shoreline. The most prominent feature within this line is a small
mesovortex west of Ottawa County Michigan. While this feature may
locally enhance wind damage potential, the airmass ahead of it has
struggled to destabilize this afternoon owing to cloud cover.
Temperatures far southwest Lower Michigan and northern Indiana are
warmer. These locations should have a locally greater wind damage
threat given the steeper low-level lapse rates and larger overall
buoyancy. Further extensions in area/time of WW 546 may be needed
into northwest Indiana given current convective trends.
..Wendt.. 08/09/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...IWX...GRR...LOT...
LAT...LON 41468706 41548807 41838839 42188763 42248736 42708680
42978659 42888558 42198559 41698592 41498643 41468706
MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS11/20260809T1857.txt
346
ACUS11 KWNS 091624
SWOMCD
SPC MCD 091624
MIZ000-INZ000-091800-
Mesoscale Discussion 1878
NWS Storm Prediction Center Norman OK
1124 AM CDT Sun Aug 09 2026
Areas affected...Southwestern Lower Michigan into far northern
Indiana
Concerning...Severe potential...Watch possible
Valid 091624Z - 091800Z
Probability of Watch Issuance...60 percent
SUMMARY...Risk for damaging winds will increase in northern Indiana
and southern Lower Michigan as a bowing segment moves
south-southeast into the afternoon. A watch is possible for portions
of these areas.
DISCUSSION...Dewpoints continue to increase ahead of a small bowing
cluster currently near Milwaukee. By the time this cluster crosses
southern Lake Michigan, temperatures in southeastern Lower
Michigan/far northern Indiana will be in the 80s F. Sufficient shear
and modest lift from a convectively enhanced perturbation should
allow this activity to move along the lifting theta-e gradient. Some
risk for damaging winds will likely accompany this bowing segment
into the afternoon. A watch is possible for portions of Lower
Michigan and northern Indiana.
..Wendt/Hart.. 08/09/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...IWX...GRR...LOT...
LAT...LON 42278777 42948765 43318744 43008613 42678541 42138528
41648549 41448619 41678702 42278777
MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS11/20260809T1624.txt
595
ACUS11 KWNS 091421
SWOMCD
SPC MCD 091420
WIZ000-ILZ000-091545-
Mesoscale Discussion 1877
NWS Storm Prediction Center Norman OK
0920 AM CDT Sun Aug 09 2026
Areas affected...Portions of southern Wisconsin into far northern
Illinois
Concerning...Severe potential...Watch possible
Valid 091420Z - 091545Z
Probability of Watch Issuance...40 percent
SUMMARY...An organized bowing structure, likely elevated at present
time, could become near surface based as it moves into southeastern
Wisconsin and adjacent northern Illinois. Wind damage would be the
main threat. A watch is possible should observational trends
warrant.
DISCUSSION...A small bowing cluster has been moving southeastward
this morning. This activity has remained elevated thus far, but the
airmass ahead of it is slowly destabilizing. Dewpoints in northern
Illinois/southern Wisconsin have increased over the past couple of
hours. The main limiter in terms of destabilization has been the
cloud cover/smoke that has reduced insolation. Based on forecast
soundings, if temperatures can reach the mid 70s F the storms will
be at least near surface based. Given the current organization of
ongoing convection, there may be an increase in damaging wind
potential over the next couple of hours. The need for a watch is
uncertain and will depend on observation trends.
..Wendt/Hart.. 08/09/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LOT...MKX...ARX...
LAT...LON 42338865 42578899 43008959 43609043 43968955 43808901
43158779 42748767 42538767 42418772 42278830 42338865
MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS11/20260809T1421.txt
719
ACUS11 KWNS 090939
SWOMCD
SPC MCD 090938
MNZ000-IAZ000-091245-
Mesoscale Discussion 1876
NWS Storm Prediction Center Norman OK
0438 AM CDT Sun Aug 09 2026
Areas affected...parts of southern Minnesota...northern Iowa
Concerning...Severe potential...Watch unlikely
Valid 090938Z - 091245Z
Probability of Watch Issuance...20 percent
SUMMARY...Increasing, intensifying thunderstorm development appears
probable near and north of the Minnesota/Iowa border vicinity
through 6-8 AM CDT. This may be accompanied by a period of
increasing potential for severe hail, then, perhaps, increasing
potential for strong to severe surface gusts. It is possible that
this could eventually require a severe weather watch, though it is
not yet clear that this will be needed in the near term.
DISCUSSION...Downstream of stronger lingering convection developing
southeastward near/northeast of the Huron SD vicinity, models have
been suggesting that forcing for ascent associated with the subtle
digging short wave perturbation may increasingly couple with lift
driven by warm advection/convergence on the nose of a lingering
30-40 kt nocturnally strengthened southerly low-level jet. By
11-13Z, it appears this will become focused near/north of the
Minnesota/Iowa border vicinity, where a corridor of increasing
moisture return above at least a shallow stable boundary-layer is
likely to contribute to increasingly sizable CAPE, in the presence
of strengthening cloud-bearing layer shear.
As this occurs, a more notable increase and intensification of
thunderstorm activity appears possible, perhaps accompanied by at
least a period of increasing potential for severe hail. Subsequent
upscale growth might eventually organize and become accompanied by
increasing risk for damaging wind gusts, though if/how soon this
occurs after daybreak remains unclear.
..Kerr/Smith.. 08/09/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ARX...MPX...DMX...FSD...
LAT...LON 44119609 44689403 43679158 42849301 43069395 43299587
44119609
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS11/20260809T0939.txt
926
ACUS11 KWNS 090727
SWOMCD
SPC MCD 090727
MNZ000-SDZ000-090930-
Mesoscale Discussion 1875
NWS Storm Prediction Center Norman OK
0227 AM CDT Sun Aug 09 2026
Areas affected...northeastern South Dakota and adjacent portions of
Minnesota
Concerning...Severe Thunderstorm Watch 545...
Valid 090727Z - 090930Z
The severe weather threat for Severe Thunderstorm Watch 545
continues.
SUMMARY...Storms could gradually evolve into an organizing cluster,
with some continuing risk for severe hail and, perhaps, increasing
potential to produce strong to severe wind gusts through 3-5 AM CDT.
DISCUSSION...Strong thunderstorm development has been focused within
a narrow corridor east of Mobridge, aided by lift associated with
low-level warm advection/frontogenesis, to the north/northeast of a
weak surface low over central South Dakota. Forcing associated with
a subtle short wave impulse digging within seasonably strong
west-northwesterly mid/upper flow may also be providing support. As
this perturbation progresses southeastward during the next few
hours, the surface low is forecast to weaken with a gradual
southward advancement of the near-surface frontal zone.
Although storms are likely elevated above at least a shallow stable
surface-based layer, they have been maintained by inflow of
seasonably high moisture content supportive of large CAPE, beneath
steep mid-level lapse rates associated with a plume of warm elevated
mixed-layer air. This moisture, still largely concentrated over
central/eastern South Dakota and Nebraska, is forecast to advect
eastward in an evolving plume along the frontal zone across southern
Minnesota/northern Iowa through 9-11Z.
As it does, as least some convection allowing-guidance suggests
potential for continuing upscale growth into an organizing cluster,
which may eventually pose increasing potential to produce strong to
severe surface gusts.
..Kerr.. 08/09/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MPX...FSD...ABR...
LAT...LON 45709909 45509774 44779624 44039656 43909765 44649925
45150006 45590027 45709909
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN
File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS11/20260809T0727.txt
