Alert archive / Montana / Tornado Watches in 2001

Tornado Watch 597

July 20, 20019 counties in Montana; 7 counties in North Dakota; Harding County, Perkins County, South Dakota

The Storm Prediction Center issued this tornado watch at Jul 20, 2001, 4:00 PM MDT for 9 counties in Montana; 7 counties in North Dakota; Harding County, Perkins County, South Dakota. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued: Jul 20, 2001, 4:00 PM MDT (22:00 UTC)
Expired: Jul 20, 2001, 11:00 PM MDT
In force: 7 hr
Issued by: the Storm Prediction Center

Counties Big Horn County, MT, Carter County, MT, Custer County, MT, Fallon County, MT, Powder River County, MT, Prairie County, MT, Rosebud County, MT, Treasure County, MT, Wibaux County, MT, Adams County, ND, Billings County, ND, Bowman County, ND, Golden Valley County, ND, Hettinger County, ND, Slope County, ND, Stark County, ND, Harding County, SD, Perkins County, SD

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
Jul 20, 4:23 PM MDT	Severe Thunderstorm Warning	BYZ	Powder River	67 min
Jul 20, 7:25 PM MDT	Severe Thunderstorm Warning	GGW	Prairie	65 min
Jul 20, 7:30 PM MDT	Severe Thunderstorm Warning	UNR	Harding	45 min
Jul 20, 8:30 PM MDT	Severe Thunderstorm Warning	GGW	Prairie	60 min
Jul 20, 8:35 PM MDT	Flash Flood Warning	GGW	Dawson, Prairie	6 hr
Jul 20, 8:36 PM MDT	Tornado Warning	BIS	Billings, Golden Valley	54 min
Jul 20, 8:43 PM MDT	Tornado Warning	GGW	Wibaux	62 min
Jul 20, 9:32 PM MDT	Severe Thunderstorm Warning	BIS	Billings, Golden Valley	58 min
Jul 20, 10:15 PM MDT	Severe Thunderstorm Warning	GGW	Wibaux	60 min
Jul 20, 10:26 PM MDT	Severe Thunderstorm Warning	BIS	Stark	64 min

The nearest sounding before it

Rapid City, SD (KUNR), launched 12:00Z, 10.0 hours before the alert went out and 270 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: 424 J/kg
Mixed-layer CIN: -500 J/kg
Mixed-layer LCL: 2267 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 69 m²/s²
0-3 km storm-relative helicity: 63 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

232 
WWUS9 KMKC 202150
SEL7  
MKC WW 202141
MTZ000-NDZ000-SDZ000-210500-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 597
STORM PREDICTION CENTER NORMAN OK
341 PM MDT FRI JUL 20 2001

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

   SOUTHEAST MONTANA                            
   SOUTHWEST NORTH DAKOTA                       
   NORTHWEST SOUTH DAKOTA                       

EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 400 PM UNTIL 1100
PM MDT.

TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS ALONG AND 140 STATUTE MILES EAST AND WEST
OF A LINE FROM 70 MILES NORTHEAST OF MILES CITY MONTANA TO 40 MILES
SOUTHEAST OF BROADUS 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.

OTHER WATCH INFORMATION...  CONTINUE...WW 596...

DISCUSSION...THUNDERSTORMS...INCLUDING SUPERCELLS...EXPECTED TO
DEVELOP DOWNWIND OF THE HIGHER TERRAIN OF S CNTRL MT...AND OVER SE
MT INVOF LOW LEVEL VORTEX IN LEE OF THE BIGHORNS.  BOUNDARY LAYER
MOISTURE AND BACKED LOW LEVEL FLOW APPEAR SUFFICIENT TO SUPPORT
THREAT FOR TORNADOES IN ADDITION TO LARGE HAIL/HIGH WINDS.  THE
CONVECTION WILL LIKELY EVOLVE INTO ONE OR TWO BOWS OVER ND LATER
TONIGHT. 

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2 INCHES.  EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 70 KNOTS.  A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. 
MEAN STORM MOTION VECTOR 25025.

...CORFIDI

470,1015 445,1015 445,1074 470,1074

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 19, 7:15 PM MDT	Severe Thunderstorm Watch	SPC	Big Horn, Carbon, Custer, Daniels, Dawson, Garfield and 13 more	4 hr
Jul 20, 12:30 PM MDT	Tornado Watch	SPC	Daniels, Dawson, Garfield, McCone, Richland, Roosevelt and 3 more	6 hr
Jul 20, 5:30 PM MDT	Tornado Watch	SPC	Daniels, Dawson, Garfield, McCone, Richland, Roosevelt and 2 more	6 hr
Jul 19, 10:30 PM MDT	Severe Thunderstorm Watch	SPC	Barnes, Benson, Bottineau, Burke, Burleigh, Cass and 31 more	6 hr
Jul 20, 1:30 AM MDT	Severe Thunderstorm Watch	SPC	Grand Forks, Pembina, Richland, Traill, Walsh	3 hr
Jul 19, 6:00 PM MDT	Tornado Watch	SPC	Beadle, Brown, Buffalo, Campbell, Clark, Codington and 20 more	5 hr

Nearby

Tornado Watches in Montana, 2001 Tornado Watches in North Dakota, 2001 Tornado Watches in South Dakota, 2001 Every tornado watch in 2001

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.