Alert archive / Montana / Severe Thunderstorm Warnings in 2002

Severe Thunderstorm Warning 68, NWS Great Falls, MT

July 17, 2002Chouteau County, Montana

NWS Great Falls, MT issued this severe thunderstorm warning at Jul 17, 2002, 6:54 PM MDT for Chouteau County, Montana. It was in force for 36 min. 1 report came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Jul 17, 2002, 6:54 PM MDT (00:54 UTC)
Expired: Jul 17, 2002, 7:30 PM MDT
In force: 36 min
Issued by: NWS Great Falls, MT
Area: Counties, with a storm outline in the text

County Chouteau County, MT

The radar

The Great Falls radar (KTFX), 51 km from the middle of the area, began a volume at 00:56 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.

What was reported inside it

Time	Report	Where	Remark
Jul 17, 7:00 PM MDT	Hail 0.75	Carter, MT	A severe thunderstorm produced 0.75 inch hail at Carter 8NW.

NCEI Storm Data entries that began inside the alert's area while it was in force. Before 2003 the local storm report archive is thin, so this is the record of what happened rather than what was phoned in.

Did it verify

Not verified. The Iowa Environmental Mesonet's Cow found no qualifying storm report inside this severe thunderstorm warning while it was in force. That is not proof nothing happened: reports are thin where few people live.

Cow counts a report within 15 km of the polygon while the warning was in force: a tornado for a tornado warning; hail of 1 inch or more, a gust of 58 mph or more or wind damage for a severe thunderstorm warning; a flash flood report for a flash flood warning.

The nearest sounding before it

Great_falls, MT (KTFX), launched 00:00Z, 0.9 hours before the alert went out and 55 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: 182 J/kg
Mixed-layer CIN: -30 J/kg
Mixed-layer LCL: 3158 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 22 m²/s²
0-3 km storm-relative helicity: 6 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.1

Open this sounding in Storm Lab

The text

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

658 
WUUS55 KTFX 180054
SVRTFX
MTC015-180130-

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE GREAT FALLS MT
653 PM MDT WED JUL 17 2002

THE NATIONAL WEATHER SERVICE IN GREAT FALLS HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  WEST CENTRAL CHOUTEAU COUNTY IN NORTH CENTRAL MONTANA

* UNTIL 730 PM MDT

* AT 646 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM 6 MILES NORTHWEST OF CARTER...OR ABOUT 19 MILES
  WEST OF FORT BENTON...MOVING NORTHEAST AT 25 MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
RURAL WESTERN CHOUTEAU COUNTY AT 710 PM MDT
RURAL CENTRAL CHOUTEAU COUNTY AT 720 PM MDT

REPORT SEVERE WEATHER TO THE NEAREST LAW ENFORCEMENT AGENCY. THEY
WILL RELAY YOUR REPORT TO THE NATIONAL WEATHER SERVICE FORECAST
OFFICE IN GREAT FALLS.

LAT...LON 4780 11128 4768 11109 4792 11067 4808 11091

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Great Falls, MT wrote its last area forecast discussion before this severe thunderstorm warning went out at Jul 17, 2:40 PM MDT, 4 hours 14 minutes earlier.

Area forecast discussion, Jul 17, 2:40 PM MDT, 4 hours 14 minutes before

SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
240 PM MDT WED JUL 17 2002

.SHORT TERM...SOUTHWEST FLOW ALOFT IS CONTINUING OVER THE CWA THIS
AFTERNOON. THE SURFACE AIRMASS REMAINS MOIST AND UNSTABLE...AND
CONVECTION IS ALREADY FIRING OVER THE SOUTHWEST MOUNTAINS AND ALONG
THE ROCKY MOUNTAIN FRONT. EXPECT ISOLATED TO SCATTERED THUNDERSTORMS
THIS EVENING AND THURSDAY EVENING. SEVERE WEATHER SHOULD BE LIMITED
DUE TO WEAK SHEAR AND LACK OF UPPER LEVEL DYNAMICS. SLOW MOVING CELLS
COULD TRIGGER LOCALLY HEAVY RAINS WITH ATTENDANT FLASH FLOOD OR MUD
SLIDE DANGER NEAR BURN AREAS. ON FRIDAY THE MODELS ARE IN GOOD
AGREEMENT...PUSHING A SURFACE COLD FRONT INTO CENTRAL MT FROM THE
WEST...ACCOMPANIED BY AN UPPER LEVEL SHORTWAVE. MODEL LIFTED INDICES
AND CAPE INDICATE THAT THE AIRMASS BECOMES RELATIVELY STABLE AS THE
COLD FRONT PUSHES INTO CENTRAL MT FRIDAY AFTERNOON. ETA/MESO-ETA
MODEL QPF IS FAIRLY IMPRESSIVE...THOUGH LIKELY OVERDONE. TIMING OF
THE UPPER DISTURBANCE VARIES BETWEEN THE ETA/MESO-ETA AND AVN
MODELS...BUT EXPECT SCATTERED SHOWERS AND THUNDERSTORMS TO DEVELOP
AHEAD OF THE FRONT AS IT MOVES INTO THE REGION. ISOLATED
THUNDERSTORMS REDEVELOP OVER THE SOUTHWEST MOUNTAINS AGAIN ON
SATURDAY...BUT DOWNSLOPE WINDS SHOULD KEEP THE PLAINS DRY. MPJ

.EXTENDED...LIKE YESTERDAY AVN AND ECMWF HAVE SIGNIFICANT
DIFFERENCES BETWEEN THEM. 00Z WED AVN HAS NW FLOW ALOFT OVER THE AREA
EARLY NEXT WEEK WITH UPPER RIDGE AXIS NEAR 120W. 12Z TUE ECMWF HAS
THE UPPER RIDGE AXIS OVER THE WRN U.S. 12Z WED RUN OF THE UKMET
LOOKS MORE LIKE THE AVN THAN THE ECMWF. WILL LEAN TOWARDS THE 00Z
WED AVN RUN FOR THIS FORECAST. IT KEEPS WARM TEMPERATURES THROUGH
TUE WITH COOLING FOR WED. 12Z WED RUN OF THE AVN IS A LOT DIFFERENT
THAN ITS 00Z RUN IN THAT IT HAS MUCH MORE TROUGHINESS OVER WRN CAN
AND THE NW U.S. SUN AND MON. FEEL THIS TROUGHINESS IS OVERDONE BUT
IF IT PANS OUT WILL SEE COOLING AS EARLY AS MON. BLANK

.CCF NUMBERS
GTF BW 062/095 062/090 057 14212
    BBBBB 086/054 085/054 085/054 085/052 082 43111111222
CTB BW 059/092 058/086 055 14212
    BBBBB 083/052 082/052 082/052 082/050 078 43111111222
HLN BW 059/093 060/088 058 14314
    BBBBB 088/055 087/055 087/055 087/054 084 53111111222
BZN BW 054/088 056/085 052 14423
    BBBBB 086/052 085/052 085/052 085/052 083 53211111222
WEY BW 052/083 050/079 047 14334
    BBBBB 078/043 080/043 080/043 080/043 078 53211111222
DLN BW 053/086 054/082 052 14335
    BBBBB 083/051 084/051 084/051 084/051 083 52211111222
HVR BW 058/097 062/095 060 14212
    BBBBB 088/055 087/055 087/055 087/054 083 33211111222
LWT BW 056/090 058/089 056 14312
    BBBBB 084/053 085/053 085/053 085/052 080 34211111222=

.TFX...NONE

The office that day

Everything else NWS Great Falls, MT issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 17, 7:50 PM MDT	Severe Thunderstorm Warning	TFX	Cascade	40 min

Nearby

Severe Thunderstorm Warnings in Montana, 2002 Every severe thunderstorm warning 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; verification from NCEI's Storm Data; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.