Alert archive / Montana / Severe Thunderstorm Warnings in 2006

Severe Thunderstorm Warning 1, NWS Great Falls, MT

May 20, 2006Chouteau County, Montana

NWS Great Falls, MT issued this severe thunderstorm warning at May 20, 2006, 2:41 PM MDT for Chouteau County, Montana. It was in force for 64 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued
May 20, 2006, 2:41 PM MDT (20:41 UTC)
Expired
May 20, 2006, 3:45 PM MDT
In force
64 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), 85 km from the middle of the area, began a volume at 20:41 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.

The watch it was issued in

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

IssuedProductOfficeLasted
May 20, 12:24 PM MDTSevere Thunderstorm WatchSPC8 hr

The nearest sounding before it

Great_falls, MT (KTFX), launched 12:00Z, 8.7 hours before the alert went out and 48 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-pSkew-T log-p diagram, Great_falls, MT at 12:00Z on 2006-05-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Great_falls, MT at 12:00Z on 2006-05-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -25 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
2032 m above ground
0-6 km bulk shear
17 kt
0-1 km storm-relative helicity
-25 m²/s²
0-3 km storm-relative helicity
72 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

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 May 20, 12:05 PM MDT, 2 hours 36 minutes earlier.

Area forecast discussion, May 20, 12:05 PM MDT, 2 hours 36 minutes before
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Hazardous weather outlook, May 20, 1:32 PM MDT, 1 hour 9 minutes before
HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE GREAT FALLS MT
132 PM MDT SAT MAY 20 2006

MTZ012>015-046-048>055-211200-
CASCADE-CHOUTEAU-CENTRAL AND SOUTHERN LEWIS AND CLARK-MADISON-
EASTERN PONDERA-SOUTHERN ROCKY MOUNTAIN FRONT-EASTERN TETON-
JUDITH BASIN-FERGUS-JEFFERSON-BROADWATER-MEAGHER-GALLATIN-
132 PM MDT SAT MAY 20 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL
MONTANA...NORTH CENTRAL MONTANA AND SOUTHWEST MONTANA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

THERE IS A RISK OF SEVERE THUNDERSTORMS WITH LARGE HAIL AND
DAMAGING WINDS THIS AFTERNOON AND EARLY THIS EVENING.
THUNDERSTORMS WILL CONTINUE TO DEVELOP OVER THE MOUNTAINS OF
SOUTHWEST MONTANA THEN INTENSIFY AS THEY MOVE INTO CENTRAL
MONTANA. THEREFORE...A SEVERE THUNDERSTORM WATCH HAS BEEN ISSUED FOR
MOST OF SOUTHWEST AND CENTRAL MONTANA...AND IS IN EFFECT UNTIL 8 PM
MDT.

THE THUNDERSTORMS SHOULD MOVE EAST OF THE AREA BY DARK.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

MTZ009>011-044-045-047-211200-
NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER-HILL-TOOLE-LIBERTY-
BLAINE-
132 PM MDT SAT MAY 20 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL
MONTANA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SCATTERED SHOWERS AND THUNDERSTORMS WILL SPREAD NORTHEAST INTO NORTH
CENTRAL MONTANA THIS AFTERNOON AND EARLY THIS EVENING. A FEW
STORMS MAY EVEN BECOME SEVERE WITH STRONG GUSTY WINDS AND HAIL
GREATER THAN ONE HALF INCH IN DIAMETER.

THESE STORMS WILL MOVE EAST OF THE AREA AROUND DARK.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

MTZ008-211200-
BEAVERHEAD-
132 PM MDT SAT MAY 20 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST
MONTANA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE TO DEVELOP OVER
BEAVERHEAD COUNTY THIS AFTERNOON AND SPREAD NORTHEAST. A FEW
STORMS MAY EVEN BECOME SEVERE WITH STRONG GUSTY WINDS AND HAIL
GREATER THAN ONE HALF INCH IN DIAMETER.

THESE STORMS WILL DIMINISH BY DARK.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

In the hours before

Local storm report, May 20, 2:23 PM MDT, 18 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
223 PM MDT SAT MAY 20 2006

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1245 AM     TSTM WND GST     DILLON                  45.22N 112.63W
05/20/2006  M53.00 MPH       BEAVERHEAD         MT   MESONET

            DILLON RAWS LOCATION

1015 AM     TSTM WND GST     8 SW GRANT              44.93N 113.18W
05/20/2006  M54.00 MPH       BEAVERHEAD         MT   MESONET

            BRENNER RAWS LOCATION

0130 PM     HAIL             25 N BOZEMAN            46.04N 111.04W
05/20/2006  E0.25 INCH       GALLATIN           MT   TRAINED SPOTTER

            HEAVY RAIN AND BRIEF HAIL.

0135 PM     HAIL             5 W BOZEMAN             45.68N 111.15W
05/20/2006  E0.25 INCH       GALLATIN           MT   TRAINED SPOTTER

            HEAVY RAIN AND BRIEF HAIL.

0145 PM     HAIL             20 S RINGLING           45.98N 110.81W
05/20/2006  E0.50 INCH       GALLATIN           MT   TRAINED SPOTTER

            OCCURRED NEAR WILSALL WITH GUSTY WINDS.

&&

SAUCIER

The office that day

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

IssuedProductOfficeCountiesLasted
May 20, 3:45 PM MDTSevere Thunderstorm WarningTFXChouteau35 min
May 20, 4:23 PM MDTSevere Thunderstorm WarningTFXFergus67 min
May 20, 5:05 PM MDTSevere Thunderstorm WarningTFXHill25 min

Nearby

Severe Thunderstorm Warnings in Montana, 2006Every severe thunderstorm warning in 2006

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.