Tornado Watch 73

Issued

Mar 12, 2012, 4:22 PM EDT (20:22 UTC)

Expired

Mar 12, 2012, 11:00 PM EDT

In force

7 hr

Issued by

the Storm Prediction Center

Largest hail expected

1 in

Strongest gust expected

60 kt

The Grand Rapids radar (KGRR), 61 km from the middle of the area, began a volume at 20:24 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

20%

One or more hailstones of 2 inches or more

10%

Six or more combined severe hail and wind reports

70%

• Mesoscale Discussion 250Mar 12, 6:29 PM EDT
• Mesoscale Discussion 251Mar 12, 8:43 PM EDT

309 
WWUS20 KWNS 122023
SEL3
SPC WW 122023
INZ000-MIZ000-OHZ000-LMZ000-130300-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 73
NWS STORM PREDICTION CENTER NORMAN OK
425 PM EDT MON MAR 12 2012

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

       NORTHERN INDIANA
       CENTRAL AND SOUTHWEST LOWER MICHIGAN
       EXTREME NORTHWEST OHIO
       LAKE MICHIGAN

EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 425 PM UNTIL
1100 PM EDT.

TORNADOES...HAIL TO 1 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 65 STATUTE
MILES EAST AND WEST OF A LINE FROM 30 MILES SOUTH SOUTHEAST OF
SOUTH BEND INDIANA TO 35 MILES NORTHEAST OF ROBEN HOOD MICHIGAN.
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...A PRONOUNCED MIDLEVEL TROUGH IS EJECTING NEWD OVER
WI...WITH STRONG FLOW ALOFT EXTENDING SEWD OVER NRN IL/INDIANA TO
LOWER MI.  CLOUD BREAKS AND MOISTURE ADVECTION HAVE RESULTED IN SOME
DESTABILIZATION NEWD INTO LOWER MI...AND CONVECTION APPEARS TO BE
INCREASING IN COVERAGE/INTENSITY SINCE 1945Z.  GIVEN THE MODEST
INSTABILITY /MUCAPE OF 500-1000 J PER KG/ AND STRONG DEEP-LAYER
SHEAR...THE ENVIRONMENT WILL SUPPORT A RISK FOR DAMAGING WINDS WITH
BOTH SUPERCELLS AND LINE SEGMENTS.  LOW-LEVEL SHEAR AND MOISTURE
WILL ALSO BE AT LEAST MARGINALLY FAVORABLE FOR A TORNADO OR
TWO...ESPECIALLY WITH ANY DISCRETE SUPERCELLS WITHIN THE CORRIDOR OF
STRONGER INSTABILITY.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 400.
MEAN STORM MOTION VECTOR 24045.


...THOMPSON

Tornado Watches in Michigan, 2012Tornado Watches in Indiana, 2012Every tornado 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.