Severe Thunderstorm Watch 421

Issued

Aug 10, 2021, 8:38 PM EDT (00:38 UTC)

Expired

Aug 11, 2021, 1:32 AM EDT

In force

5 hr

Issued by

the Storm Prediction Center

Largest hail expected

1.5 in

Strongest gust expected

65 kt

The Grand Rapids radar (KGRR), 64 km from the middle of the area, began a volume at 00:40 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

50%

One or more gusts of 65 knots or more

30%

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

80%

• Mesoscale Discussion 1468 Severe potential...watch likelyAug 10, 8:12 PM EDT
• Mesoscale Discussion 1469 Severe thunderstorm watch 421Aug 10, 10:57 PM EDT

733 
WWUS20 KWNS 110036
SEL1  
SPC WW 110036
ILZ000-INZ000-MIZ000-OHZ000-LMZ000-110700-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 421
NWS Storm Prediction Center Norman OK
840 PM EDT Tue Aug 10 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Northeastern Illinois
  Northern Indiana
  Western and central Lower Michigan
  Extreme northwestern Ohio
  Lake Michigan

* Effective this Tuesday night and Wednesday morning from 840 PM
  until 300 AM EDT.

* 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...An organized complex of thunderstorms, with a history of
measured severe gusts in IL and WI, will continue to pose a
damaging-wind threat across Lake Michigan and into parts of MI and
northern IN before weakening tonight.

The severe thunderstorm watch area is approximately along and 70
statute miles east and west of a line from 30 miles south southeast
of South Bend IN to 15 miles west northwest of Traverse City MI. For
a complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU1).

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...WW 420...

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
27035.

...Edwards

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