Tornado Watch 417

Issued

Aug 9, 2021, 2:43 PM CDT (19:43 UTC)

Expired

Aug 10, 2021, 12:00 AM CDT

In force

9 hr

Issued by

the Storm Prediction Center

Largest hail expected

1.5 in

Strongest gust expected

60 kt

The Chicago radar (KLOT), 43 km from the middle of the area, began a volume at 19:43 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

Two or more tornadoes

40%

One or more EF2 to EF5 tornadoes

20%

Ten or more severe wind reports

40%

One or more gusts of 65 knots or more

20%

Ten or more severe hail reports

20%

One or more hailstones of 2 inches or more

10%

Six or more combined severe hail and wind reports

60%

• Mesoscale Discussion 1450 Severe potential...watch possibleAug 9, 12:18 PM CDT
• Mesoscale Discussion 1453 Tornado watch 417Aug 9, 5:53 PM CDT
• Mesoscale Discussion 1455 Tornado watch 417Aug 9, 8:33 PM CDT

717 
WWUS20 KWNS 091938
SEL7  
SPC WW 091938
ILZ000-INZ000-LMZ000-100300-

URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 417
NWS Storm Prediction Center Norman OK
240 PM CDT Mon Aug 9 2021

The NWS Storm Prediction Center has issued a

* Tornado Watch for portions of 
  Northern Illinois
  Extreme northwestern Indiana
  Lake Michigan

* Effective this Monday afternoon and evening from 240 PM until
  1000 PM CDT.

* Primary threats include...
  A couple tornadoes possible
  Scattered damaging wind gusts to 70 mph possible
  Isolated large hail events to 1.5 inches in diameter possible

SUMMARY...Severe storms are expected to develop in clusters or short
bands across northern Illinois this afternoon, and storms will
spread east-southeastward through late evening.  The storm
environment favors a mix of clusters and embedded supercells capable
of producing a couple of tornadoes, damaging winds of 60 to 70 mph,
and isolated large hail of 1 to 1.5 inch diameter.

The tornado watch area is approximately along and 45 statute miles
north and south of a line from 30 miles southwest of Rockford IL to
85 miles east of Marseilles IL. For a complete depiction of the
watch see the associated watch outline update (WOUS64 KWNS WOU7).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Tornado Watch means conditions are favorable for
tornadoes and 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.

&&

AVIATION...Tornadoes and 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 550. Mean
storm motion vector 30025.

...Thompson

Tornado Watches in Illinois, 2021Tornado Watches in Indiana, 2021Every tornado watch in 2021

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.