Alert archive / Montana / Severe Thunderstorm Warnings in 2007

Severe Thunderstorm Warning 104, NWS Great Falls, MT

July 20, 2007Hill County, Montana

NWS Great Falls, MT issued this severe thunderstorm warning at Jul 20, 2007, 10:20 PM MDT for Hill County, Montana. It was in force for 40 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
Jul 20, 2007, 10:20 PM MDT (04:20 UTC)
Expired
Jul 20, 2007, 11:00 PM MDT
In force
40 min
Issued by
NWS Great Falls, MT
Area
Counties, with a storm outline in the text

County Hill County, MT

The radar

The Great Falls radar (KTFX), 161 km from the middle of the area, began a volume at 04:23 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 nearest sounding before it

Great_falls, MT (KTFX), launched 00:00Z, 4.3 hours before the alert went out and 135 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 00:00Z on 2007-07-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 481 joules per kilogram.LCLLFCEL10008507005003002001001 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 00:00Z on 2007-07-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 66 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
481 J/kg
Mixed-layer CIN
-116 J/kg
Mixed-layer LCL
2969 m above ground
0-6 km bulk shear
45 kt
0-1 km storm-relative helicity
66 m²/s²
0-3 km storm-relative helicity
226 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.7

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 Jul 20, 9:38 PM MDT, 42 minutes earlier.

Area forecast discussion, Jul 20, 9:38 PM MDT, 42 minutes before
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Hazardous weather outlook, Jul 20, 2:57 PM MDT, 7 hours 23 minutes before
HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE GREAT FALLS MT
257 PM MDT FRI JUL 20 2007

MTZ008-014-015-052-053-055-211200-
BEAVERHEAD-CENTRAL AND SOUTHERN LEWIS AND CLARK-MADISON-JEFFERSON-
BROADWATER-GALLATIN-
257 PM MDT FRI JUL 20 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST
MONTANA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

A RED FLAG WARNING REMAINS IN EFFECT FOR MUCH OF SOUTHWEST
MONTANA THROUGH EARLY THIS EVENING. HOT TEMPERATURES...COMBINED
WITH LOW HUMIDITIES AND INCREASING WINDS WILL ALLOW FOR CRITICAL
FIRE WEATHER CONDITIONS TO EXIST. ADDITIONALLY...ISOLATED
THUNDERSTORMS MAY ALSO DEVELOP DURING THIS TIME. SOME OF THE
STRONGER THUNDERSTORMS WILL PRODUCE GUSTY ERRATIC WINDS.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

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.

MTZ009-010-044>046-211200-
NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER-TOOLE-LIBERTY-
EASTERN PONDERA-
257 PM MDT FRI JUL 20 2007

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

ISOLATED THUNDERSTORMS ARE POSSIBLE OVER NORTH CENTRAL AND
CENTRAL MONTANA THROUGH THIS EVENING. AN ISOLATED STRONG
THUNDERSTORM IS POSSIBLE...WITH THE MAIN THREAT BEING A DAMAGING
WIND GUST...BUT A WIDESPREAD SEVERE WEATHER EVENT IS NOT EXPECTED
AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

BREEZY WESTERLY WINDS WILL DEVELOP ON SATURDAY ALONG THE NORTHERN
ROCKY MOUNTAIN FRONT AND ACROSS THE ADJACENT PLAINS. HOT AND DRY
CONDITIONS WILL ALSO CONTINUE ACROSS THIS AREA...WITH RELATIVE
HUMIDITIES IN SOME AREAS FALLING TO NEAR OR BELOW 20 PERCENT.
BECAUSE OF THIS EXPECTED COMBINATION OF DRY AND BREEZY
CONDITIONS...A FIRE WEATHER WATCH HAS BEEN ISSUED FOR THIS AREA
FOR SATURDAY AFTERNOON INTO EARLY SATURDAY EVENING.

.SPOTTER INFORMATION STATEMENT...

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

MTZ011>013-047>051-054-211200-
HILL-CASCADE-CHOUTEAU-BLAINE-SOUTHERN ROCKY MOUNTAIN FRONT-
EASTERN TETON-JUDITH BASIN-FERGUS-MEAGHER-
257 PM MDT FRI JUL 20 2007

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

ISOLATED THUNDERSTORMS ARE POSSIBLE OVER NORTH CENTRAL AND
CENTRAL MONTANA THROUGH THIS EVENING. AN ISOLATED STRONG
THUNDERSTORM IS POSSIBLE...WITH THE MAIN THREAT BEING A DAMAGING
WIND GUST...BUT A WIDESPREAD SEVERE WEATHER EVENT IS NOT EXPECTED
AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

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.

COULSTON/BRUSDA

In the hours before

Local storm report, Jul 20, 9:13 PM MDT, 1 hour 7 minutes before
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The office that day

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

IssuedProductOfficeCountiesLasted
Jul 20, 7:33 PM MDTSevere Thunderstorm WarningTFXChouteau42 min
Jul 20, 8:13 PM MDTSevere Thunderstorm WarningTFXChouteau47 min
Jul 20, 8:44 PM MDTSevere Thunderstorm WarningTFXBlaine46 min
Jul 20, 9:00 PM MDTSevere Thunderstorm WarningTFXChouteau45 min
Jul 20, 9:26 PM MDTSevere Thunderstorm WarningTFXBlaine49 min
Jul 20, 11:19 PM MDTSevere Thunderstorm WarningTFXHill41 min
Jul 21, 4:07 AM MDTRed Flag WarningTFXBlaine, Broadwater, Cascade, Chouteau, Fergus, Gallatin and 12 more21 days
Jul 21, 4:46 AM MDTRed Flag WarningTFXGlacier, Liberty, Pondera, Toole16 hr

Nearby

Severe Thunderstorm Warnings in Montana, 2007Every severe thunderstorm warning in 2007

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.