Tornado Watch 673

Issued

Sep 20, 2007, 3:45 PM CDT (20:45 UTC)

Expired

Sep 20, 2007, 10:00 PM CDT

In force

6 hr

Issued by

the Storm Prediction Center

Largest hail expected

2 in

Strongest gust expected

60 kt

The Minneapolis radar (KMPX), 87 km from the middle of the area, began a volume at 20:48 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

40%

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 1986Sep 20, 3:16 PM CDT
• Mesoscale Discussion 1990Sep 20, 6:48 PM CDT

000
WWUS20 KWNS 202047
SEL3  
SPC WW 202047
MNZ000-210300-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 673
NWS STORM PREDICTION CENTER NORMAN OK
345 PM CDT THU SEP 20 2007

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

       CENTRAL AND SOUTHERN MINNESOTA

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 345 PM UNTIL
1000 PM 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 40 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 50 MILES NORTHWEST OF
REDWOOD FALLS MINNESOTA TO 25 MILES EAST NORTHEAST OF MINNEAPOLIS
MINNESOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).

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...ELEVATED CONVECTION CONTINUES WELL N OF THE SURFACE
WARM FRONT...WHICH HAS NOW DEVELOPED NWD INTO THE MSP AREA.  THE
BOUNDARY LAYER CONTINUES TO WARM/MOISTEN S OF THE BOUNDARY...AND
CONVECTIVE INHIBITION IS BEGINNING TO WEAKEN FOR SURFACE-BASED
PARCELS ACROSS SW AND S CENTRAL MN.  THE NEWER STORM DEVELOPMENT TO
THE W OF MSP MAY STILL BE SLIGHTLY ELEVATED...BUT IT IS VERY CLOSE
TO SURFACE BOUNDARY.  GIVEN THE STRONG VERTICAL SHEAR PRESENT...ANY
STORMS ROOTED IN THE NEAR-SURFACE LAYER WILL BE CAPABLE OF PRODUCING
TORNADOES.  OTHERWISE...LARGE HAIL AND A FEW DAMAGING GUSTS CAN BE
EXPECTED THROUGH LATE EVENING.

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
500. MEAN STORM MOTION VECTOR 26030.


...THOMPSON

Tornado Watches in Minnesota, 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.