Severe Thunderstorm Watch 615

Issued

Sep 4, 2012, 7:45 PM CDT (00:45 UTC)

Expired

Sep 5, 2012, 2:00 AM CDT

In force

6 hr

Issued by

the Storm Prediction Center

Largest hail expected

2 in

Strongest gust expected

60 kt

The Sioux Falls radar (KFSD), 7 km from the middle of the area, began a volume at 00:48 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

30%

One or more gusts of 65 knots or more

20%

Ten or more severe hail reports

30%

One or more hailstones of 2 inches or more

20%

Six or more combined severe hail and wind reports

70%

• Mesoscale Discussion 1882Sep 4, 5:08 PM CDT
• Mesoscale Discussion 1884Sep 4, 7:27 PM CDT
• Mesoscale Discussion 1886Sep 4, 9:51 PM CDT
• Mesoscale Discussion 1887Sep 5, 1:14 AM CDT

039 
WWUS20 KWNS 050047
SEL5
SPC WW 050047
IAZ000-MNZ000-NEZ000-SDZ000-050700-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 615
NWS STORM PREDICTION CENTER NORMAN OK
745 PM CDT TUE SEP 4 2012

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

       NORTHWEST IOWA
       SOUTHWEST MINNESOTA
       NORTHEAST NEBRASKA
       SOUTHEAST SOUTH DAKOTA

EFFECTIVE THIS TUESDAY NIGHT AND WEDNESDAY MORNING FROM 745 PM
UNTIL 200 AM CDT.

HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 60
STATUTE MILES EAST AND WEST OF A LINE FROM 15 MILES NORTH OF
BROOKINGS SOUTH DAKOTA TO 15 MILES EAST SOUTHEAST OF SIOUX CITY
IOWA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED
WATCH OUTLINE UPDATE (WOUS64 KWNS WOU5).

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 614...

DISCUSSION...BAND OF CONVECTION OVER NE NEB/SE SD IS EXPECTED TO
PERSIST OVERNIGHT AS LOW-LEVEL FLOW/WAA STRENGTHEN IN RESPONSE TO A
SHORTWAVE TROUGH MOVING EWD OVER THE DAKOTAS.  THE 00Z OAX SOUNDING
AND SURFACE OBSERVATIONS CONFIRM A FEED OF INSTABILITY FROM THE S
INTO THIS AREA...THUS THE RISK FOR LARGE HAIL/DAMAGING WINDS SHOULD
PERSIST FOR THE NEXT FEW HOURS WITH MAINLY ELEVATED STORMS INTO NW
IA/SW MN.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 27025.


...THOMPSON

Severe Thunderstorm Watches in South Dakota, 2012Severe Thunderstorm Watches in Iowa, 2012Severe Thunderstorm Watches in Minnesota, 2012Every severe thunderstorm watch in 2012

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.