Tornado Watch 615

Issued

Aug 18, 2007, 6:17 PM CDT (23:17 UTC)

Expired

Aug 19, 2007, 12:00 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), 41 km from the middle of the area, began a volume at 23:17 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

30%

One or more EF2 to EF5 tornadoes

10%

Ten or more severe wind reports

30%

One or more gusts of 65 knots or more

10%

Ten or more severe hail reports

40%

One or more hailstones of 2 inches or more

10%

Six or more combined severe hail and wind reports

80%

• Mesoscale Discussion 1793Aug 18, 3:56 PM CDT
• Mesoscale Discussion 1795Aug 18, 8:03 PM CDT
• Mesoscale Discussion 1797Aug 18, 11:10 PM CDT

000
WWUS20 KWNS 182321
SEL5  
SPC WW 182321
IAZ000-MNZ000-NEZ000-SDZ000-190600-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 615
NWS STORM PREDICTION CENTER NORMAN OK
615 PM CDT SAT AUG 18 2007

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

       NORTHERN IOWA
       SOUTHWEST MINNESOTA
       NORTHERN NEBRASKA
       SOUTHEAST SOUTH DAKOTA

EFFECTIVE THIS SATURDAY NIGHT AND SUNDAY MORNING FROM 615 PM
UNTIL 100 AM CDT.

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

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 55 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 40 MILES SOUTH OF
CHAMBERLAIN SOUTH DAKOTA TO 20 MILES SOUTH SOUTHEAST OF MASON
CITY IOWA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU5).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND 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.

OTHER WATCH INFORMATION...CONTINUE...WW 614...

DISCUSSION...POTENTIAL SHOULD INCREASE FOR TSTMS/SUPERCELLS TO
DEVELOP ALONG STALLED SFC BOUNDARIES IN SE SD/N CNTRL NEB IN THE
NEXT COUPLE OF HOURS IN RESPONSE TO SUSTAINED HEATING/CONVERGENCE. 
OTHER STORMS MAY FORM LATER THIS EVENING ALONG WARM FRONT EXTENDING
ESE INTO NRN IA AS LLJ VEERS AND STRENGTHENS.  WHILE MID LVL
TEMPERATURES ARE RATHER WARM...AND SHORTWAVE FORCING FOR ASCENT
APPEARS WEAK... BOUNDARY LAYER IS VERY WARM/MOIST.  CONSIDERABLE LOW
LVL DIRECTIONAL SHEAR IS ALSO PRESENT INVOF WARM FRONT. 
THUS...POTENTIAL WILL EXIST FOR POSSIBLE TORNADOES IN ADDITION TO
SVR HAIL/WIND WITH DISCRETE STORMS THAT DO INDEED FORM.  ACTIVITY
SHOULD MERGE INTO AN MCS TONIGHT...WITH A DIMINISHING THREAT FOR
TORNADOES...BUT A LINGERING THREAT FOR HAIL/WIND.

AVIATION...TORNADOES AND 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
550. MEAN STORM MOTION VECTOR 28015.


...CORFIDI

Tornado Watches in Iowa, 2007Tornado Watches in South Dakota, 2007Tornado Watches in Nebraska, 2007Every tornado watch in 2007

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.