Severe Thunderstorm Watch 420

Issued

Aug 10, 2021, 3:47 PM CDT (20:47 UTC)

Expired

Aug 10, 2021, 9:18 PM CDT

In force

6 hr

Issued by

the Storm Prediction Center

Largest hail expected

1.5 in

Strongest gust expected

65 kt

The Milwaukee radar (KMKX), 22 km from the middle of the area, began a volume at 20:47 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

10%

One or more EF2 to EF5 tornadoes

2%

Ten or more severe wind reports

70%

One or more gusts of 65 knots or more

60%

Ten or more severe hail reports

40%

One or more hailstones of 2 inches or more

20%

Six or more combined severe hail and wind reports

90%

• Mesoscale Discussion 1465 Severe potential...watch likelyAug 10, 3:10 PM CDT
• Mesoscale Discussion 1467 Severe thunderstorm watch 419...420Aug 10, 5:51 PM CDT
• Mesoscale Discussion 1468 Severe potential...watch likelyAug 10, 7:12 PM CDT

203 
WWUS20 KWNS 102045
SEL0  
SPC WW 102045
ILZ000-WIZ000-LMZ000-110300-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 420
NWS Storm Prediction Center Norman OK
345 PM CDT Tue Aug 10 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Northern Illinois
  Southeastern Wisconsin
  Lake Michigan

* Effective this Tuesday afternoon and evening from 345 PM until
  1000 PM CDT.

* Primary threats include...
  Scattered damaging winds and isolated significant gusts to 75
    mph likely
  Scattered large hail events to 1.5 inches in diameter possible

SUMMARY...Thunderstorms across eastern Iowa will continue to expand
while spreading eastward and northeastward into Wisconsin and
Illinois through late evening.  The storm environment favors storm
clusters capable of producing damaging winds (some significant up to
75 mph) and occasional large hail.

The severe thunderstorm watch area is approximately along and 70
statute miles east and west of a line from 35 miles north northwest
of Oshkosh WI to 25 miles west southwest 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 419...

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 600. Mean storm motion vector
27025.

...Thompson

Severe Thunderstorm Watches in Wisconsin, 2021Severe Thunderstorm Watches in Illinois, 2021Every severe thunderstorm 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.