Alert archive / Montana / Severe Thunderstorm Warnings in 2002

Severe Thunderstorm Warning 112, NWS Great Falls, MT

August 20, 2002Judith Basin County, Montana

NWS Great Falls, MT issued this severe thunderstorm warning at Aug 20, 2002, 8:02 PM MDT for Judith Basin County, Montana. It was in force for 58 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 20, 2002, 8:02 PM MDT (02:02 UTC)
Expired: Aug 20, 2002, 9:00 PM MDT
In force: 58 min
Issued by: NWS Great Falls, MT
Area: Counties, with a storm outline in the text

County Judith Basin County, MT

The radar

The Great Falls radar (KTFX), 104 km from the middle of the area, began a volume at 02:03 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
Aug 20, 8:43 PM MDT	Hail 1.25	Utica, MT	A severe thunderstorm produced 0.75 inch hail at Utica 2ENE.

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, 2.0 hours before the alert went out and 60 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: 87 J/kg
Mixed-layer CIN: -122 J/kg
Mixed-layer LCL: 2116 m above ground
0-6 km bulk shear: 45 kt
0-1 km storm-relative helicity: 16 m²/s²
0-3 km storm-relative helicity: 200 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.

052 
WUUS55 KTFX 210202
SVRTFX
MTC045-210300-

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE GREAT FALLS MT
801 PM MDT TUE AUG 20 2002

THE NATIONAL WEATHER SERVICE IN GREAT FALLS HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  JUDITH BASIN COUNTY IN CENTRAL MONTANA
  THIS INCLUDES THE CITY OF STANFORD

* UNTIL 900 PM MDT

* AT 758 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM 20 MILES SOUTH OF STANFORD...MOVING NORTHEAST
  AT 20 MPH.

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 4695 11054 4674 11034 4688 11006 4707 10979
          4719 10991 4722 11013

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 20, 3:00 PM MDT, 5 hours 2 minutes earlier.

Area forecast discussion, Aug 20, 3:00 PM MDT, 5 hours 2 minutes before

SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
300 PM MDT TUE AUG 20 2002

.SHORT TERM...WILL HAVE TO DEAL WITH THE UPPER LOW OVER THE PAC NW
THROUGH THE PERIOD. ETA/AVN ARE IN GOOD AGREEMENT THROUGH WED IN
HAVING THE UPPER LOW REMAIN IN THE VICINITY OF NE OREGON. SOLUTIONS
DIFFER THEREAFTER AS THE ETA MOVES THE UPPER LOW INTO NW MT BY THU
WHILE THE AVN CONTINUES WITH THE UPPER LOW OVER NE OREGON. FOR
TONIGHT ETA AND AVN AGREE ON MOVING A MODERATELY STRONG VORTICITY
CENTER FROM SW MT THROUGH N CENTRAL MT. MODEL CROSS SECTIONS SHOW
IMPRESSIVE LIFT. ALTHOUGH THERMODYNAMIC ENVIRONMENT WILL NOT BE ALL
THAT UNSTABLE...IMPRESSIVE DYNAMICS AND DEVELOPING DIFLUENT FLOW
ALOFT SHOULD LEAD TO SOME STRONGER IF NOT SEVERE THUNDERSTORMS. AFTER
TONIGHT ETA/AVN AGREE THAT S TO SW FLOW ALOFT WILL BE OVER THE AREA
BUT DIFFER ON VERTICAL VELOCITY AND MOISTURE FIELDS. THIS WILL MAKE
FORECASTING DIFFICULT. BASICALLY WENT WITH A LOT OF 20 TO 50 PCT POPS
WITH A GENERAL DOWNWARD TREND IN POPS. FOR FRI DID GO DRY IN THE FAR
N AS BOTH THE ETA AND AVN QPF PATTERNS DID NOT SHOW ANY QPF FOR THAT
AREA. BLANK

.EXTENDED...MEDIUM RANGE MODELS VERY INCONSISTENT WITH THEIR
SOLUTIONS. ECMWF A BIT MORE PROGRESSIVE THAN THE MRF AND MOVES
UPPER FEATURES FASTER ALONG THAN THE MRF. UPPER RIDGE OVER THE AREA
SATURDAY WITH RIDGE AXIS SHIFTING EAST SUNDAY. THIS ALLOWS MOISTURE
TO FEED INTO THE AREA AND A CHANCE FOR CONVECTIVE ACTIVITY. AIRMASS
REMAINS UNSETTLED MONDAY AND TUESDAY AND WILL KEEP A CHANCE OF
SHOWERS IN THE FORECAST. TEMPERATURES WILL REMAIN AT OR SLIGHTLY
ABOVE SEASONAL NORMS.

.CCF NUMBERS
GTF WB 053/072 050/078 050 04754
    BBTTT 078/052 086/052 084/052 083/052 082 22211233333
CTB WB 052/067 046/076 048 04662
    BBTTT 076/050 084/050 083/050 082/050 082 11111233333
HLN WB 054/072 049/080 051 04653
    EBTTT 080/052 087/052 088/052 085/052 085 22221233333
BZN EB 046/073 042/080 046 04544
    EBTTT 080/045 083/045 082/045 082/045 082 33221333333
WEY EB 038/068 035/074 039 04344
    EBTTT 074/035 078/035 078/035 076/035 076 33233333333
DLN EB 046/072 042/077 045 04542
    ETTTT 077/044 083/045 084/045 083/045 083 22221233333
HVR WB 057/077 052/083 052 04753
    BBTTT 083/052 089/053 090/053 086/053 086 22111223333
LWT WB 053/072 048/078 048 04744
    BBTTT 078/050 083/050 084/050 083/050 083 32221233333=

.TFX...FLASH FLOOD WATCH CAVE GULCH BURN AREA NEAR HLN LATE
       THIS AFTERNOON AND 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, 8:24 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
Aug 21, 5:43 PM MDT	Severe Thunderstorm Warning	TFX	Madison	47 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.