Alert archive / Montana / Tornado Watches in 2002

Tornado Watch 580

August 6, 200211 counties in Montana

The Storm Prediction Center issued this tornado watch at Aug 6, 2002, 2:40 PM MDT for 11 counties in Montana. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Aug 6, 2002, 2:40 PM MDT (20:40 UTC)
Expired: Aug 6, 2002, 9:00 PM MDT
In force: 6 hr
Issued by: the Storm Prediction Center

Counties Blaine County, MT, Daniels County, MT, Fergus County, MT, Garfield County, MT, Judith Basin County, MT, McCone County, MT, Petroleum County, MT, Phillips County, MT, Roosevelt County, MT, Sheridan County, MT, Valley County, MT

Warnings issued inside it

7 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
Aug 6, 4:57 PM MDT	Severe Thunderstorm Warning	TFX	Fergus	63 min
Aug 6, 5:11 PM MDT	Tornado Warning	TFX	Fergus	64 min
Aug 6, 5:45 PM MDT	Tornado Warning	GGW	Petroleum	60 min
Aug 6, 6:14 PM MDT	Tornado Warning	TFX	Fergus	61 min
Aug 6, 6:44 PM MDT	Tornado Warning	GGW	Petroleum, Phillips	61 min
Aug 6, 8:09 PM MDT	Severe Thunderstorm Warning	GGW	Garfield	66 min
Aug 6, 8:38 PM MDT	Tornado Warning	GGW	McCone	67 min

The nearest sounding before it

Glasgow Intl Airport, MT (KGGW), launched 12:00Z, 8.7 hours before the alert went out and 136 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 1041 J/kg
Mixed-layer CIN: -138 J/kg
Mixed-layer LCL: 676 m above ground
0-6 km bulk shear: 45 kt
0-1 km storm-relative helicity: 110 m²/s²
0-3 km storm-relative helicity: 140 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.9

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

000 
WWUS20 KWNS 062048
SEL0  
SPC WW 062040
MTZ000-070300-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 580
STORM PREDICTION CENTER NORMAN OK
240 PM MDT TUE AUG 6 2002

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

   CENTRAL AND NORTHERN MONTANA                            

EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 240 PM UNTIL 900
PM MDT.

TORNADOES...HAIL TO 4 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS ALONG AND 125 STATUTE MILES EAST AND WEST
OF A LINE FROM 55 MILES EAST SOUTHEAST OF LEWISTOWN MONTANA TO 55
MILES NORTH OF GLASGOW MONTANA.

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...SUPERCELLS EXPECTED TO DEVELOP IN THE NEXT FEW HOURS
IN WW AREA...DOWNWIND FROM HIGHER TERRAIN INITIATION ZONE IN SW
PART OF STATE.  CELLS SHOULD MOVE ALONG BOTH SYNOPTIC COLD FRONT
EDGING SLOWLY E FROM NEAR GTF...AND ALONG NE/SW ORIENTED OUTFLOW
BOUNDARY FROM OVERNIGHT CONVECTION N CNTRL/NE PART OF STATE.  LONG
HODOGRAPHS AND RICH BOUNDARY LAYER MOISTURE...ESPECIALLY INVOF
OUTFLOW BOUNDARY...LOOK FAVORABLE FOR LONG-LIVED SUPERCELLS WITH
VERY LARGE HAIL/BOWING SEGMENTS/ISOLATED TORNADOES.  ACTIVITY
SHOULD EVOLVE INTO A NE/SW LINEAR MCS LATER THIS EVENING.   

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 4 INCHES.  EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 60 KNOTS.  A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. 
MEAN STORM MOTION VECTOR 23035.

...CORFIDI

464,1110 485,1092 485,1035 464,1054

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 6, 4:15 PM MDT	Severe Thunderstorm Watch	SPC	Big Horn, Carter, Custer, Fallon, Powder River, Rosebud and 1 more	6 hr

Nearby

Tornado Watches in Montana, 2002 Every tornado watch in 2002

Sources

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.