Tornado Watch 671

Issued

Jul 22, 2011, 1:25 PM MDT (19:25 UTC)

Expired

Jul 22, 2011, 9:00 PM MDT

In force

8 hr

Issued by

the Storm Prediction Center

Largest hail expected

4 in

Strongest gust expected

70 kt

Counties Carter County, MT, Custer County, MT, Daniels County, MT, Dawson County, MT, Fallon County, MT, Garfield County, MT, McCone County, MT, Phillips County, MT, Powder River County, MT, Prairie County, MT, Richland County, MT, Roosevelt County, MT, Rosebud County, MT, Sheridan County, MT, Treasure County, MT, Valley County, MT, Wibaux County, MT

The Glasgow radar (KGGW), 86 km from the middle of the area, began a volume at 19:26 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

50%

One or more gusts of 65 knots or more

40%

Ten or more severe hail reports

40%

One or more hailstones of 2 inches or more

40%

Six or more combined severe hail and wind reports

90%

• Mesoscale Discussion 1686Jul 22, 10:05 AM MDT
• Mesoscale Discussion 1688Jul 22, 1:06 PM MDT
• Mesoscale Discussion 1694Jul 22, 4:17 PM MDT

956 
WWUS20 KWNS 221923
SEL1
SPC WW 221923
MTZ000-230300-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 671
NWS STORM PREDICTION CENTER NORMAN OK
125 PM MDT FRI JUL 22 2011

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

       EASTERN MONTANA

EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 125 PM UNTIL 900
PM MDT.

TORNADOES...HAIL TO 4 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 90 STATUTE
MILES EAST AND WEST OF A LINE FROM 60 MILES NORTH NORTHEAST OF
GLASGOW MONTANA TO 35 MILES SOUTHWEST OF BROADUS MONTANA.  FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU1).

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 670...

DISCUSSION...POTENT UPPER TROUGH AND UNSTABLE AIRMASS WILL
CONTRIBUTE TO AN INCREASE IN SEVERE THUNDERSTORMS ACROSS ERN MT THIS
AFTERNOON. DEEP SHEAR WILL INITIALLY SUPPORT SUPERCELLS WITH THE
POTENTIAL FOR VERY LARGE HAIL. TORNADO THREAT WILL ALSO EXIST
ALTHOUGH MIXING OF DRIER AIR THROUGH DEEP HEATED BOUNDARY LAYER MAY
KEEP THIS POTENTIAL FOCUSED MOSTLY NEAR THE LOW/TROUGH AND ALONG THE
FRONTAL ZONE EXTENDING FROM THE LEE LOW/TROUGH SEWD ACROSS ECNTRL
MT. GGW VWP INDICATIVE OF STRONG DIRECTIONAL SHEAR SUPPORTIVE OF
INTENSE LOW LEVEL UPDRAFT ROTATION. EXPECT A TRANSITION TO MORE
LINEAR/WIND DAMAGE STORM MODE LATER THIS AFTERNOON AS FORCING WITH
THE UPPER TROUGH AND COLD FRONT MOVE INTO STRONG INSTABILITY...
CELLS AND STORMS MERGE/CONGEAL...AND CONVECTIVE COLD POOLS
MATURE...ALL IN THE PRESENCE OF INCREASINGLY STRONG DEEP LAYER FLOW
AND FORCING.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 4 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
450. MEAN STORM MOTION VECTOR 24030.


...CARBIN

Tornado Watches in Montana, 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.