Alert archive / Montana / Severe Thunderstorm Warnings in 2002

Severe Thunderstorm Warning 121, NWS Great Falls, MT

August 21, 2002Madison County, Montana

NWS Great Falls, MT issued this severe thunderstorm warning at Aug 21, 2002, 5:43 PM MDT for Madison County, Montana. It was in force for 47 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: Aug 21, 2002, 5:43 PM MDT (23:43 UTC)
Expired: Aug 21, 2002, 6:30 PM MDT
In force: 47 min
Issued by: NWS Great Falls, MT
Area: Counties, with a storm outline in the text

County Madison County, MT

What was reported inside it

Time	Report	Where	Remark
Aug 21, 6:00 PM MDT	Thunderstorm Wind 65 E	Sheridan, MT	A severe thunderstorm produced severe winds, damaging several homes and trailers.

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 12:00Z, 11.7 hours before the alert went out and 255 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: 850 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 66 m²/s²
0-3 km storm-relative helicity: 83 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.

062 
WUUS55 KTFX 212343
SVRTFX
MTC057-220030-

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE GREAT FALLS MT
542 PM MDT WED AUG 21 2002

THE NATIONAL WEATHER SERVICE IN GREAT FALLS HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  WEST CENTRAL MADISON COUNTY IN SOUTHWEST MONTANA
  THIS INCLUDES THE CITY OF SHERIDAN

* UNTIL 630 PM MDT

* AT 541 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM 16 MILES SOUTHWEST OF SHERIDAN...OR ABOUT 11
  MILES NORTHEAST OF DILLON...MOVING NORTH AT 25 MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
  SHERIDAN AT 610 PM MDT...OVER TWIN BRIDGES AT 615 PM MDT...AND
  NEAR SILVER STAR AT 630 PM MDT.

NICKEL-SIZED HAIL WAS REPORTED WITH THIS STORM IN SOUTHEAST DILLON.

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 4543 11251 4520 11238 4559 11200 4571 11218
          4569 11248

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 Aug 21, 3:00 PM MDT, 2 hours 43 minutes earlier.

Area forecast discussion, Aug 21, 3:00 PM MDT, 2 hours 43 minutes before

SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
300 PM MDT WED AUG 21 2002

.SHORT TERM...UNSETTLED WEATHER PATTERN TO CONTINUE INTO THIS
WEEKEND. UPPER LOW WILL MEANDER AROUND OVER THE PAC NW THROUGH FRI.
ON SAT AVN OPENS THE CLOSED LOW AND MOVES A VERY NEGATIVELY TILTED
UPPER TROUGH THROUGH THE FORECAST AREA. PRESSURE GRADIENTS WILL
CONTINUE TO BE WEAK THROUGH THE PERIOD SO EXPECT WINDS TO BE FOR THE
MOST PART LESS THAN 10 MPH. FOR TONIGHT MODELS HAVE A SHORTWAVE
MOVING N THROUGH THE AREA. AS MENTIONED IN THE MORNING DISCUSSION...
INGREDIENTS ARE IN PLACE FOR THE POTENTIAL OF ISOLATED SEVERE STORMS
INTO THIS EVENING FROM CENTRAL MT S. FOR THU AIRMASS IS FORECAST TO
BE GENERALLY LESS UNSTABLE OVER THE AREA. SHORTWAVES...IF THERE ARE
ANY...SHOULD ONLY AFFECT THE FAR ERN ZONES. WILL GO DRY WEST AND
MENTION SLIGHT CHANCE TO CHANCE POPS FARTHER E WHERE MODELS FORECAST
BETTER INSTABILITY. ON FRI MODELS INDICATE MORE SHORTWAVE ACTIVITY
AND HAVE AIRMASS MORE UNSTABLE. WILL THEREFORE GO WITH SLIGHT CHANCE
TO CHANCE POPS FOR THE ENTIRE AREA. ON SAT WITH AIRMASS AGAIN
FORECAST TO BE UNSTABLE AND THE POSSIBILITY OF AN UPPER TROUGH MOVING
INTO THE AREA CONTINUED THE FORECAST OF SLIGHT CHANCE TO CHANCE POPS.
WITH NO MAJOR CHANGE IN AIRMASS FORESEEN WILL CHANGE HIGHS AND LOWS
LITTLE FROM THU THROUGH SAT. BLANK

.EXTENDED...MRF AND ECMWF IN A LITTLE BETTER AGREEMENT TODAY THOUGH
THE ECMWF REMAINS PROGRESSIVE WITH THE PATTERN. UPPER TROF REMAINS
ACROSS THE PACIFIC NORTHWEST SUNDAY WITH MOIST AND UNSTABLE
SOUTHWEST FLOW ALOFT OVER THE AREA. TROF AXIS MOVES ACROSS THE AREA
MONDAY FOR CONTINUED UNSETTLED CONDITIONS. UPPER RIDGE BEGINS TO
BUILD OVER THE PACIFIC NORTHWEST TUESDAY WITH NORTHWEST FLOW ALOFT.
WILL MENTION LOW POPS FOR INSTABILITY SHOWERS. RIDGE BUILDS OVER
THE AREA WEDNESDAY FOR DRY AND WARMER CONDITIONS. TEMPERATURES
SHOULD REMAIN AT OR SLIGHTLY ABOVE SEASONAL NORMS.

.CCF NUMBERS
GTF BB 050/078 052/078 052 04512
    ETTTB 080/052 084/052 082/052 083/052 085 33333332221
CTB BE 050/075 048/075 050 04511
    ETTTB 077/050 083/050 082/050 083/050 084 22223322221
HLN BE 047/079 051/079 052 04611
    BTTTB 078/052 086/052 085/052 085/052 086 33223333321
BZN BE 042/079 046/079 046 04323
    BTTTB 078/045 084/045 082/045 082/045 084 33323333321
WEY BE 035/072 039/072 037 04223
    BTTTB 072/035 078/035 076/035 076/035 077 33323333321
DLN BE 042/077 045/077 044 04411
    BTTTB 077/045 084/045 083/045 083/045 084 23223222221
HVR BB 052/083 055/084 055 04212
    ETTTB 085/053 090/053 086/053 086/053 087 23323222221
LWT BB 048/078 052/078 050 04424
    ETTTB 079/050 084/050 083/050 083/050 084 33423333321=

.TFX...FLASH FLOOD WATCH FOR THE CAVE GULCH BURN AREA FROM 3 PM
       UNTIL 9 PM THIS EVENING.

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 20, 6:55 PM MDT	Severe Thunderstorm Warning	TFX	Broadwater, Meagher	50 min
Aug 20, 8:02 PM MDT	Severe Thunderstorm Warning	TFX	Judith Basin	58 min
Aug 20, 8:24 PM MDT	Severe Thunderstorm Warning	TFX	Judith Basin	36 min
Aug 20, 8:58 PM MDT	Severe Thunderstorm Warning	TFX	Fergus, Judith Basin	62 min
Aug 21, 3:04 PM MDT	Severe Thunderstorm Warning	TFX	Jefferson, Madison	56 min
Aug 21, 4:21 PM MDT	Severe Thunderstorm Warning	TFX	Judith Basin	39 min
Aug 21, 4:46 PM MDT	Severe Thunderstorm Warning	TFX	Fergus	44 min
Aug 21, 5:13 PM MDT	Severe Thunderstorm Warning	TFX	Beaverhead	47 min
Aug 21, 5:15 PM MDT	Severe Thunderstorm Warning	TFX	Beaverhead	45 min
Aug 21, 5:30 PM MDT	Severe Thunderstorm Warning	TFX	Fergus	60 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.