Source: US National Oceanic and Atmospheric Administration
Note: The expiration time in the watch graphic is amended if the watch is replaced, cancelled or extended.Note: Click for Watch Status Reports.
SEL8
URGENT – IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 518
NWS Storm Prediction Center Norman OK
1235 PM CDT Wed Jul 16 2025
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Northern Illinois
Far Northwest Indiana
Lake Michigan
* Effective this Wednesday afternoon and evening from 1235 PM
until 800 PM CDT.
* Primary threats include…
Scattered damaging wind gusts to 70 mph possible
Isolated large hail events to 1 inch in diameter possible
A tornado or two possible
SUMMARY…Scattered thunderstorms are forecast to develop in a
north-south band and move east across the Watch. A couple of the
stronger thunderstorms may acquire transient supercell
characteristics. Scattered damaging gusts are the primary hazard,
but an isolated risk for large hail will accompany the stronger
storms and a tornado cannot be ruled out.
The severe thunderstorm watch area is approximately along and 75
statute miles east and west of a line from 40 miles east northeast
of Rockford IL to 20 miles south southeast of Marseilles IL. 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.
&&
OTHER WATCH INFORMATION…CONTINUE…WW 517…
AVIATION…A few severe thunderstorms with hail surface and aloft to
1 inch. Extreme turbulence and surface wind gusts to 60 knots. A few
cumulonimbi with maximum tops to 500. Mean storm motion vector
24025.
…Smith
SEL8
URGENT – IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 518
NWS Storm Prediction Center Norman OK
1235 PM CDT Wed Jul 16 2025
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Northern Illinois
Far Northwest Indiana
Lake Michigan
* Effective this Wednesday afternoon and evening from 1235 PM
until 800 PM CDT.
* Primary threats include…
Scattered damaging wind gusts to 70 mph possible
Isolated large hail events to 1 inch in diameter possible
A tornado or two possible
SUMMARY…Scattered thunderstorms are forecast to develop in a
north-south band and move east across the Watch. A couple of the
stronger thunderstorms may acquire transient supercell
characteristics. Scattered damaging gusts are the primary hazard,
but an isolated risk for large hail will accompany the stronger
storms and a tornado cannot be ruled out.
The severe thunderstorm watch area is approximately along and 75
statute miles east and west of a line from 40 miles east northeast
of Rockford IL to 20 miles south southeast of Marseilles IL. 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.
&&
OTHER WATCH INFORMATION…CONTINUE…WW 517…
AVIATION…A few severe thunderstorms with hail surface and aloft to
1 inch. Extreme turbulence and surface wind gusts to 60 knots. A few
cumulonimbi with maximum tops to 500. Mean storm motion vector
24025.
…Smith
Note: The Aviation Watch (SAW) product is an approximation to the watch area. The actual watch is depicted by the shaded areas.
SAW8
WW 518 SEVERE TSTM IL IN LM 161735Z – 170100Z
AXIS..75 STATUTE MILES EAST AND WEST OF LINE..
40ENE RFD/ROCKFORD IL/ – 20SSE MMO/MARSEILLES IL/
..AVIATION COORDS.. 65NM E/W /34NW ORD – 29SSW JOT/
HAIL SURFACE AND ALOFT..1 INCH. WIND GUSTS..60 KNOTS.
MAX TOPS TO 500. MEAN STORM MOTION VECTOR 24025.
LAT…LON 42418691 41098709 41098997 42418985
THIS IS AN APPROXIMATION TO THE WATCH AREA. FOR A
COMPLETE DEPICTION OF THE WATCH SEE WOUS64 KWNS
FOR WOU8.
Watch 518 Status Report Message has not been issued yet.
Note: Click for Complete Product Text.Tornadoes
Probability of 2 or more tornadoes
Low (20%)
Probability of 1 or more strong (EF2-EF5) tornadoes
Low (5%)
Wind
Probability of 10 or more severe wind events
Mod (40%)
Probability of 1 or more wind events > 65 knots
Low (20%)
Hail
Probability of 10 or more severe hail events
Low (20%)
Probability of 1 or more hailstones > 2 inches
Low (10%)
Combined Severe Hail/Wind
Probability of 6 or more combined severe hail/wind events
Mod (60%)
For each watch, probabilities for particular events inside the watch (listed above in each table) are determined by the issuing forecaster. The “Low” category contains probability values ranging from less than 2% to 20% (EF2-EF5 tornadoes), less than 5% to 20% (all other probabilities), “Moderate” from 30% to 60%, and “High” from 70% to greater than 95%. High values are bolded and lighter in color to provide awareness of an increased threat for a particular event.