Tornado Watch 694

Issued

Jul 27, 2011, 7:43 PM CDT (00:43 UTC)

Expired

Jul 28, 2011, 1:00 AM CDT

In force

5 hr

Issued by

the Storm Prediction Center

Largest hail expected

2 in

Strongest gust expected

60 kt

The Quad Cities radar (KDVN), 100 km from the middle of the area, began a volume at 00:45 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

20%

Ten or more severe wind reports

30%

One or more gusts of 65 knots or more

30%

Ten or more severe hail reports

40%

One or more hailstones of 2 inches or more

30%

Six or more combined severe hail and wind reports

70%

• Mesoscale Discussion 1767Jul 27, 6:54 PM CDT
• Mesoscale Discussion 1769Jul 27, 9:43 PM CDT
• Mesoscale Discussion 1770Jul 28, 12:36 AM CDT

993 
WWUS20 KWNS 280043
SEL4
SPC WW 280043
IAZ000-ILZ000-INZ000-WIZ000-LMZ000-280600-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 694
NWS STORM PREDICTION CENTER NORMAN OK
745 PM CDT WED JUL 27 2011

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

       EAST CENTRAL IOWA
       NORTHERN ILLINOIS
       EXTREME NORTHWEST INDIANA
       EXTREME SOUTHERN WISCONSIN
       LAKE MICHIGAN

EFFECTIVE THIS WEDNESDAY NIGHT AND THURSDAY MORNING FROM 745 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 35 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 40 MILES WEST SOUTHWEST OF
DUBUQUE IOWA TO 30 MILES EAST NORTHEAST OF MEIGS FIELD ILLINOIS.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU4).

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.

DISCUSSION...CLUSTER OF STORMS...SOME WITH EMBEDDED SUPERCELL
STRUCTURES...WILL CONTINUE TO EXPAND ALONG THE SURFACE WARM FRONT
NEAR THE IL/WI BORDER.  STRONG INSTABILITY AND VEERING LOW-LEVEL
SHEAR PROFILES WILL SUPPORT STORM-SCALE ROTATION WITH DEVELOPING
STORMS ON THE BOUNDARY...WITH THE POSSIBILITY OF LARGE HAIL AND A
TORNADO OR TWO IN THE NEXT COUPLE OF HOURS.  UPSCALE GROWTH OF THE
CONVECTION WILL RESULT IN STRONGER COLD POOL GENERATION AND AN
ATTENDANT RISK FOR DAMAGING WINDS.

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
650. MEAN STORM MOTION VECTOR 28020.


...THOMPSON

Tornado Watches in Illinois, 2011Tornado Watches in Iowa, 2011Every tornado watch in 2011

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.