Severe Thunderstorm Watch 423

Issued

Aug 11, 2021, 11:50 AM EDT (15:50 UTC)

Expired

Aug 11, 2021, 3:46 PM EDT

In force

4 hr

Issued by

the Storm Prediction Center

Largest hail expected

1.5 in

Strongest gust expected

65 kt

The Grand Rapids radar (KGRR), 68 km from the middle of the area, began a volume at 15:51 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

20%

One or more EF2 to EF5 tornadoes

5%

Ten or more severe wind reports

70%

One or more gusts of 65 knots or more

60%

Ten or more severe hail reports

30%

One or more hailstones of 2 inches or more

10%

Six or more combined severe hail and wind reports

90%

• Mesoscale Discussion 1476 Severe thunderstorm watch 422Aug 11, 10:52 AM EDT
• Mesoscale Discussion 1480 Severe thunderstorm watch 423Aug 11, 1:26 PM EDT
• Mesoscale Discussion 1482 Severe potential...watch likelyAug 11, 2:12 PM EDT

959 
WWUS20 KWNS 111546
SEL3  
SPC WW 111546
INZ000-MIZ000-OHZ000-LMZ000-112100-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 423
NWS Storm Prediction Center Norman OK
1145 AM EDT Wed Aug 11 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Northern Indiana
  Southwest Lower Michigan
  Extreme northwest Ohio
  Lake Michigan

* Effective this Wednesday morning and afternoon from 1145 AM
  until 500 PM EDT.

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

SUMMARY...A storm cluster with a history of severe gusts across
northeast Illinois is expected to continue moving eastward and
likely expand northward this afternoon across northern Indiana into
southwest Lower Michigan.  Damaging winds up to 75 mph will be the
main threat, though isolated large hail of 1 to 1.5 inch diameter
will be possible with the strongest storms, and a tornado or two may
also occur with embedded circulations.

The severe thunderstorm watch area is approximately along and 70
statute miles east and west of a line from 40 miles north of Grand
Rapids MI to 35 miles southwest of Fort Wayne IN. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU3).

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 422...

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 550. Mean storm motion vector
26040.

...Thompson

Severe Thunderstorm Watches in Indiana, 2021Severe Thunderstorm Watches in Michigan, 2021Severe Thunderstorm Watches in Ohio, 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.