Severe Thunderstorm Watch 507

Issued

Sep 20, 2021, 2:07 PM CDT (19:07 UTC)

Expired

Sep 20, 2021, 8:41 PM CDT

In force

7 hr

Issued by

the Storm Prediction Center

Largest hail expected

1.5 in

Strongest gust expected

60 kt

The La Crosse radar (KARX), 73 km from the middle of the area, began a volume at 19:09 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

2%

Ten or more severe wind reports

70%

One or more gusts of 65 knots or more

20%

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 1768 Severe potential...watch likelySep 20, 12:38 PM CDT
• Mesoscale Discussion 1770 Severe thunderstorm watch 507Sep 20, 3:55 PM CDT
• Mesoscale Discussion 1771 Severe thunderstorm watch 507...509Sep 20, 5:52 PM CDT

839 
WWUS20 KWNS 201906
SEL7  
SPC WW 201906
IAZ000-MNZ000-WIZ000-210300-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 507
NWS Storm Prediction Center Norman OK
210 PM CDT Mon Sep 20 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Central and Eastern Iowa
  Southeast Minnesota
  Western Wisconsin

* Effective this Monday afternoon and evening from 210 PM until
  1000 PM CDT.

* Primary threats include...
  Scattered damaging wind gusts to 70 mph likely
  Scattered large hail events to 1.5 inches in diameter possible
  A tornado or two possible

SUMMARY...Thunderstorms are expected to develop rapidly this
afternoon along a cold front moving into southeast Minnesota and
central Iowa.  These storms will track quickly eastward across the
watch area, posing a risk of damaging winds and hail.  An isolated
tornado or two is also possible over western Wisconsin later this
afternoon.

The severe thunderstorm watch area is approximately along and 70
statute miles east and west of a line from 40 miles north of Eau
Claire WI to 25 miles east of Lamoni IA. For a complete depiction of
the watch see the associated watch outline update (WOUS64 KWNS
WOU7).

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.

&&

AVIATION...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 450. Mean storm motion vector
24035.

...Hart

Severe Thunderstorm Watches in Iowa, 2021Severe Thunderstorm Watches in Wisconsin, 2021Severe Thunderstorm Watches in Minnesota, 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.