Severe Thunderstorm Watch 239

Issued

May 4, 2012, 2:00 PM CDT (19:00 UTC)

In effect from

May 4, 2012, 2:05 PM CDT

Expired

May 4, 2012, 11:00 PM CDT

In force

9 hr

Issued by

the Storm Prediction Center

Largest hail expected

3 in

Strongest gust expected

60 kt

The Sioux Falls radar (KFSD), 55 km from the middle of the area, began a volume at 19:02 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

40%

One or more gusts of 65 knots or more

30%

Ten or more severe hail reports

70%

One or more hailstones of 2 inches or more

70%

Six or more combined severe hail and wind reports

90%

• Mesoscale Discussion 695May 4, 1:50 PM CDT
• Mesoscale Discussion 698May 4, 3:52 PM CDT
• Mesoscale Discussion 700May 4, 5:31 PM CDT
• Mesoscale Discussion 706May 4, 9:54 PM CDT
• Mesoscale Discussion 708May 4, 10:55 PM CDT

359 
WWUS20 KWNS 041904
SEL9
SPC WW 041904
IAZ000-MNZ000-NEZ000-SDZ000-050200-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 239
NWS STORM PREDICTION CENTER NORMAN OK
205 PM CDT FRI MAY 4 2012

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

       NORTHWEST IOWA
       SOUTHWEST AND SOUTH-CENTRAL MINNESOTA
       NORTH-CENTRAL AND NORTHEAST NEBRASKA
       SOUTHEAST SOUTH DAKOTA

EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 205 PM UNTIL 900
PM CDT.

HAIL TO 3 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 65
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 45 MILES WEST OF
ONEILL NEBRASKA TO 35 MILES NORTH NORTHEAST OF MASON CITY IOWA.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU9).

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 238...

DISCUSSION...TSTMS ARE EXPECTED TO INCREASE IN NUMBER AND INTENSITY
THIS AFTERNOON INVOF STATIONARY BOUNDARY STRETCHING FROM SRN SD/NRN
NEB TO ALONG THE MN/IA BORDER.  AIR MASS ALONG/S OF THIS BOUNDARY IS
QUITE MOIST...AND WHEN COUPLED WITH STEEP MIDLEVEL LAPSE RATES AND
DAYTIME HEATING...EXPECT MLCAPE VALUES TO APPROACH 2000-3500 J/KG.
THE STRONGEST DEEP-LAYER SHEAR WILL REMAIN ALONG AND N OF SURFACE
FRONT WITH ENVIRONMENT SUPPORTIVE OF BOTH BOWING AND SUPERCELL
STRUCTURES.  WHILE A TORNADO IS POSSIBLE...VERY LARGE HAIL AND
DAMAGING WINDS WILL BE THE PRIMARY HAZARDS.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 3 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM
MOTION VECTOR 27030.


...MEAD

Severe Thunderstorm Watches in Iowa, 2012Severe Thunderstorm Watches in Nebraska, 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.