WW 550 SEVERE TSTM IA IL IN LM 100140Z - 100900Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 550
NWS Storm Prediction Center Norman OK
840 PM CDT Sun Aug 9 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Far East-Central Iowa
Northern Illinois
Far Northwest Indiana
Lake Michigan
* Effective this Sunday night and Monday morning from 840 PM
until 400 AM CDT.
* Primary threats include...
Scattered large hail and isolated very large hail events to 2
inches in diameter possible
Scattered damaging wind gusts to 70 mph possible
A tornado or two possible
SUMMARY...Thunderstorm coverage and intensity is expected to
increase over the next few hours from far east-central Iowa into
northern Illinois and eventually far northwest Indiana. Large hail
is the primary risk initially, with an instance or two of very large
hail (i.e. 2" diameter) possible. Upscale growth is possible over
time, with the resulting convective line tracking southeastward.
Additionally, given the residual outflow boundary extending from far
north-central Illinois into central Indiana, a low-probability
tornado risk exists with any storms that can interact with this
boundary.
The severe thunderstorm watch area is approximately along and 60
statute miles north and south of a line from 25 miles west northwest
of Moline IL to 55 miles east of Marseilles IL. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU0).
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.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 548...WW 549...
AVIATION...A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
27025.
...Mosier
WW 549 SEVERE TSTM CO NE 100005Z - 100600Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 549
NWS Storm Prediction Center Norman OK
605 PM MDT Sun Aug 9 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Far Northeast Colorado
Western and Central Nebraska
* Effective this Sunday night from 605 PM until Midnight MDT.
* Primary threats include...
Scattered damaging winds and isolated significant gusts to 75
mph possible
Isolated large hail events to 1.5 inches in diameter possible
SUMMARY...Ongoing severe thunderstorms in the Nebraska Panhandle
have shown a trend towards upscale growth into a convective line.
The airmass downstream is strongly unstable, suggesting that any
line that does develop could maintain its intensity as it continues
into more of western and central Nebraska (and possibly far
northeast Colorado) this evening. Strong to severe gusts (60 to 75
mph) are the primary risk, although isolated instances of hail are
possible as well.
The severe thunderstorm watch area is approximately along and 70
statute miles north and south of a line from 30 miles south
southwest of Alliance NE to 25 miles northeast of North Platte NE.
For a complete depiction of the watch see the associated watch
outline update (WOUS64 KWNS WOU9).
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.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 548...
AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 65 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
31035.
...Mosier
WW 0550 Status Updates
STATUS FOR WATCH 0550 HAS NOT BEEN ISSUED YET
WW 0549 Status Updates
STATUS REPORT ON WW 549
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 E AKO TO
25 ENE SNY TO 40 SW MHN TO 30 NW BBW.
..MOORE..08/10/26
ATTN...WFO...BOU...LBF...CYS...
STATUS REPORT FOR WS 549
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
COC095-115-100340-
CO
. COLORADO COUNTIES INCLUDED ARE
PHILLIPS SEDGWICK
NEC005-029-049-063-085-101-111-113-117-135-100340-
NE
. NEBRASKA COUNTIES INCLUDED ARE
ARTHUR CHASE DEUEL
FRONTIER HAYES KEITH
LINCOLN LOGAN MCPHERSON
PERKINS
THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE
REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL
INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES
CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES.
WW 0548 Status Updates
STATUS REPORT ON WW 548
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 20 NE DAY TO
30 E MFD.
..THORNTON..08/10/26
ATTN...WFO...CLE...ILN...
STATUS REPORT FOR WS 548
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
OHC041-083-089-117-100340-
OH
. OHIO COUNTIES INCLUDED ARE
DELAWARE KNOX LICKING
MORROW
THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE
REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL
INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES
CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES.
MD 1890 CONCERNING SEVERE THUNDERSTORM WATCH 550... FOR NORTHERN ILLINOIS
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
MD 1889 CONCERNING SEVERE THUNDERSTORM WATCH 549... FOR FAR NORTHEAST COLORADO...SOUTHWEST NEBRASKA...AND FAR NORTHWEST KANSAS
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
SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0741 PM CDT Sun Aug 09 2026
Valid 100100Z - 101200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE MIDWEST...
...SUMMARY...
Severe storms are possible this evening into the overnight hours
across portions of the Midwest. Damaging winds will be the main
hazard with this activity. Additional strong to severe storms may
occur from western Nebraska into the Dakotas, and across Arizona.
...Midwest...
A bowing line of storms will continue to move east/southeast across
northern OH the next few hours. Occasional damaging gusts will be
possible with this activity before weakening after 04z as
instability wanes across northeast OH/western PA.
Model guidance continues to indicated additional convection will
develop across portions of eastern IA/northern IL this evening. This
activity may develop along residual outflow and a southward sagging
surface front as a low-level jet increases over the next few hours.
Thunderstorm clusters may grow into one or more MCSs moving east
across northern IL into IN and perhaps southern Lower MI.
...Northern/Central Plains...
Damaging wind and hail will be possible with convection moving
across western NE this evening. As ongoing storms track
east/southeast, they will encounter richer low-level moisture and
increasing instability. While stronger capping persisted with
eastward extent, even elevated storms will pose a severe risk as
they track across WW 0549.
Severe potential is less certain with northward extent across the
Dakotas. Low-level moisture will increase during the evening and
overnight hours, but currently, instability remains weak and capping
is strong. Isolated strong cells over northeast MT will continue to
develop southeast into limited instability but stronger vertical
shear. If storms can be maintained and additional development occurs
later this evening/overnight isolated hail and strong wind gusts
will be possible.
...AZ...
Similar to previous days, easterly midlevel flow will support
convection moving westward off higher terrain and across the lower
deserts within weak to moderate instability and steep low-level
lapse rates. Strong to severe gusts will be possible with this
activity.
..Leitman.. 08/10/2026
| 
