Alert archive / Montana / Tornado Watches in 2001

Tornado Watch 596

July 20, 20019 counties in Montana; 8 counties in North Dakota

The Storm Prediction Center issued this tornado watch at Jul 20, 2001, 12:30 PM MDT for 9 counties in Montana; 8 counties in North Dakota. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Jul 20, 2001, 12:30 PM MDT (18:30 UTC)
Expired: Jul 20, 2001, 6:00 PM MDT
In force: 6 hr
Issued by: the Storm Prediction Center

Counties Daniels County, MT, Dawson County, MT, Garfield County, MT, McCone County, MT, Richland County, MT, Roosevelt County, MT, Sheridan County, MT, Valley County, MT, Wibaux County, MT, Billings County, ND, Burke County, ND, Divide County, ND, Dunn County, ND, McKenzie County, ND, Mercer County, ND, Mountrail County, ND, Williams County, ND

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
Jul 20, 12:53 PM MDT	Severe Thunderstorm Warning	GGW	Daniels, Roosevelt	52 min
Jul 20, 1:14 PM MDT	Severe Thunderstorm Warning	GGW	Sheridan	61 min
Jul 20, 1:15 PM MDT	Severe Thunderstorm Warning	GGW	Valley	60 min
Jul 20, 2:06 PM MDT	Severe Thunderstorm Warning	BIS	Divide	59 min
Jul 20, 3:10 PM MDT	Severe Thunderstorm Warning	BIS	Divide	60 min
Jul 20, 3:25 PM MDT	Tornado Warning	GGW	Valley	65 min
Jul 20, 3:35 PM MDT	Severe Thunderstorm Warning	BIS	Burke	55 min
Jul 20, 3:55 PM MDT	Tornado Warning	BIS	Burke	35 min
Jul 20, 4:30 PM MDT	Tornado Warning	GGW	Garfield, Valley	60 min
Jul 20, 5:16 PM MDT	Tornado Warning	GGW	McCone	59 min
Jul 20, 5:27 PM MDT	Tornado Warning	GGW	Daniels	63 min
Jul 20, 5:30 PM MDT	Tornado Warning	GGW	Garfield	60 min

The nearest sounding before it

Glasgow Intl Airport, MT (KGGW), launched 12:00Z, 6.5 hours before the alert went out and 124 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: 28 J/kg
Mixed-layer CIN: -349 J/kg
Mixed-layer LCL: 2123 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: 11 m²/s²
0-3 km storm-relative helicity: 133 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.

231 
WWUS9 KMKC 201804
SEL6  
MKC WW 201800
MTZ000-NDZ000-210000-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 596
STORM PREDICTION CENTER NORMAN OK
1200 PM MDT FRI JUL 20 2001

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

   NORTHEAST  MONTANA                            
   WESTERN NORTH DAKOTA                       

EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 1230 PM UNTIL 600
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 70 STATUTE MILES NORTH AND
SOUTH OF A LINE FROM 25 MILES SOUTHWEST OF GLASGOW MONTANA TO 15
MILES NORTH OF ROSEGLEN NORTH DAKOTA.

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...THUNDERSTORMS WILL RAPIDLY INTENSIFY NERN MT AS AIR
MASS CONTINUES TO DESTABILIZE AND DEEP LAYER SHEAR PROFILES ARE
FAVORABLE FOR SUPERCELLS.  CAPES HAVE RISEN TO NEAR 3000 J/KG WHICH
COUPLED WITH STEEP LAPSE RATES FAVORS INTENSE UPDRAFTS AND STORM
ROTATION.


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 24035.


...HALES

485,1070 485,1014 465,1014 465,1070

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, 4:00 PM MDT	Tornado Watch	SPC	Big Horn, Carter, Custer, Fallon, Powder River, Prairie and 3 more	7 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

Nearby

Tornado Watches in Montana, 2001 Tornado Watches in North 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.