Alert archive / Montana / Severe Thunderstorm Warnings in 2002

Severe Thunderstorm Warning 71, NWS Great Falls, MT

July 23, 2002Lewis and Clark County, Montana

NWS Great Falls, MT issued this severe thunderstorm warning at Jul 23, 2002, 4:44 PM MDT for Lewis and Clark County, Montana. It was in force for 61 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Jul 23, 2002, 4:44 PM MDT (22:44 UTC)
Expired: Jul 23, 2002, 5:45 PM MDT
In force: 61 min
Issued by: NWS Great Falls, MT
Area: Counties, with a storm outline in the text

County Lewis and Clark County, MT

The radar

The Great Falls radar (KTFX), 96 km from the middle of the area, began a volume at 22:48 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.

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 watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Jul 23, 2:30 PM MDT	Severe Thunderstorm Watch	SPC	7 hr

The nearest sounding before it

Great_falls, MT (KTFX), launched 12:00Z, 10.7 hours before the alert went out and 155 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1658 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 13 m²/s²
0-3 km storm-relative helicity: 86 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

Open this sounding in Storm Lab

The text

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

546 
WUUS55 KTFX 232244
SVRTFX
MTC049-232345-

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE GREAT FALLS MT
441 PM MDT TUE JUL 23 2002

THE NATIONAL WEATHER SERVICE IN GREAT FALLS HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  CENTRAL LEWIS AND CLARK COUNTY IN WEST CENTRAL MONTANA

* UNTIL 545 PM MDT

* AT 439 PM...A SEVERE THUNDERSTORM WAS REPORTED OVER NORTH          
  CENTRAL POWELL COUNTY...OR ABOUT 49 MILES NORTH OF DRUMMOND...     
  MOVING EAST AT 20 MPH.

* THE SEVERE THUNDERSTORM WILL MOVE THROUGH...
  RURAL NORTHERN LEWIS AND CLARK COUNTY THROUGH 515 PM AND BE NEAR
  AUGUSTA BY 530 PM. 

ONE INCH DIAMETER HAIL...WIND GUSTS TO 60 MPH AND HEAVY RAIN WILL 
ACCOMPANY THIS THUNDERSTORM. 

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

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 900 PM MDT
TUESDAY EVENING FOR SOUTHWESTERN MONTANA.

LAT...LON 4760 11303 4720 11298 4725 11215 4747 11213
          4748 11261

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 23, 3:00 PM MDT, 1 hour 44 minutes earlier.

Area forecast discussion, Jul 23, 3:00 PM MDT, 1 hour 44 minutes before

SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
300 PM MDT TUE JUL 23 2002

.SHORT TERM...THUNDERSTORMS FIRING OVER SOUTHWEST MONTANA THIS
AFTERNOON WILL SPREAD NORTHEAST INTO CENTRAL MONTANA BY THIS
EVENING. SOME STORMS MAY BE SEVERE...WITH SUFFICIENT INSTABILITY
(CAPE VALUES OF 1500-2500 J/KG) AND VERTICAL WIND SHEAR (30-40 KTS
OF 0-6 KM SHEAR) TO PRODUCE DAMAGING WIND AND LARGE HAIL. HEAVY
RAINFALL AMOUNTS ARE LIKELY AS WELL...WITH PRECIPITABLE WATER
VALUES AROUND 1 INCH. STORMS SHOULD MOVE INTO EASTERN ZONES LATE
THIS EVENING...AND EXIT THE AREA AROUND MIDNIGHT. WEDNESDAY...AN
UPPER LEVEL RIDGE BUILDS OVER THE PACIFIC NORTHWEST...WITH NORTHWEST
FLOW ALOFT AND DOWNSLOPE WIND OVER CENTRAL MONTANA. EVEN WITH A FEW
WEAK DISTURBANCES MOVING THROUGH...THERE WILL BE LESS INSTABILITY AND
MOISTURE...SO AM NOT EXPECTING MUCH IN THE WAY OF THUNDERSTORM
DEVELOPMENT TOMORROW. WILL JUST MENTION ISOLATED MOUNTAIN
THUNDERSTORMS. THURSDAY...THE WESTERN RIDGE FLATTENS OUT...AS A
TROUGH OVER THE EASTERN PACIFIC MOVES ON SHORE. THE FLOW ALOFT BEGINS
TO BACK AS WELL...WITH A FEW DISTURBANCES EMBEDDED IN THE SOUTHWEST
FLOW. WILL MENTION ISOLATED POPS FOR NOW. DRY AIR AND DOWNSLOPE WIND
WILL DOMINATE THE WEATHER ON FRIDAY...AS A LARGE UPPER LEVEL TROUGH
LURKS OVER SOUTHERN CANADA. TEMPS WILL WARM SLIGHTLY WEDNESDAY AND
THURSDAY...WITH A SLIGHT COOL-DOWN FRIDAY. VILLANI

.EXTENDED...MODELS ARE COMING INTO BETTER AGREEMENT WITH UPPER LEVEL
FEATURES PROGGED TO AFFECT THE REGION THIS WEEKEND. TROUGH NOW
APPEARS TO BE BROADER AND APPEARS TO MOVE INTO THE STATE A BIT
FASTER THAN PREVIOUSLY PROGGED. ECMWF PROGRESSES THE TROUGH THROUGH
THE STATE BY MONDAY...WHILE THE MRF/AVN KEEPS THE TROUGH LINGERING
OVER CNTRL MT THROUGH MONDAY EVENING. STABILITY INDICES LOOK RATHER
UNIMPRESSIVE IN THE MEDIUM RANGE MODELS...AND FLOW OVER THE STATE
MAY NOT BE MOIST ENOUGH FOR MUCH CONVECTION. STILL...WITH THE TROUGH
APPROACHING THE AREA WOULD EXPECT SOME SHOWERS...AND WILL KEEP A
SLIGHT CHANCE THROUGH THE WEEKEND. MONDAY AND TUESDAY SHOULD BE DRIER
AS THE FLOW BECOMES MORE NORTHWESTERLY. TEMPERATURES WILL BE A BIT
COOLER OVER THE WEEKEND AS THE TROUGH LOWERS THICKNESSES. MPJ

.CCF NUMBERS
GTF BB 058/088 058/088 055 16411
    BBBUU 084/052 079/051 080/052 083/050 080 12122221100
CTB BB 056/085 056/085 053 16111
    BBBUU 079/051 075/050 076/051 079/049 077 12122221100
HLN BB 060/090 060/090 057 16511
    BBBBB 087/054 081/052 082/051 085/055 082 22222221111
BZN BB 053/088 053/088 052 16511
    BBBBB 084/051 080/050 081/051 084/049 081 22222222111
WEY BB 046/082 043/082 044 16311
    BBBBB 079/042 074/041 075/042 077/041 074 22222222111
DLN BB 052/088 052/088 051 16311
    BBBBB 085/052 080/049 081/050 083/051 080 22222222111
HVR BB 058/088 058/088 055 16211
    BBBUU 085/053 079/051 081/052 085/051 082 12122221100
LWT BB 056/086 055/086 054 16511
    BBBUU 083/051 078/049 079/050 082/050 079 12122221100=

.TFX...NONE

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 23, 4:20 PM MDT	Severe Thunderstorm Warning	TFX	Beaverhead	40 min
Jul 23, 5:04 PM MDT	Severe Thunderstorm Warning	TFX	Teton	56 min
Jul 23, 5:46 PM MDT	Severe Thunderstorm Warning	TFX	Lewis and Clark	29 min
Jul 23, 5:50 PM MDT	Severe Thunderstorm Warning	TFX	Cascade	55 min
Jul 23, 5:56 PM MDT	Severe Thunderstorm Warning	TFX	Pondera	49 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.