Alert archive / Montana / Flash Flood Warnings in 2002

Flash Flood Warning 12, NWS Glasgow, MT

August 21, 2002Valley County, Montana

NWS Glasgow, MT issued this flash flood warning at Aug 21, 2002, 10:20 AM MDT for Valley County, Montana. It was in force for 6 hr. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Aug 21, 2002, 10:20 AM MDT (16:20 UTC)
Expired: Aug 21, 2002, 4:15 PM MDT
In force: 6 hr
Issued by: NWS Glasgow, MT
Area: Counties, with a storm outline in the text

County Valley County, MT

The radar

The Glasgow radar (KGGW), 27 km from the middle of the area, began a volume at 16:21 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 flash flood 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

Glasgow Intl Airport, MT (KGGW), launched 12:00Z, 4.3 hours before the alert went out and 29 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: 10 J/kg
Mixed-layer CIN: -496 J/kg
Mixed-layer LCL: 983 m above ground
0-6 km bulk shear: 25 kt
0-1 km storm-relative helicity: -50 m²/s²
0-3 km storm-relative helicity: -10 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.

000 
WGUS55 KGGW 211620
FFWGGW
MTC105-212215-

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE GLASGOW MT
1020 AM MDT WED AUG 21 2002

THE NATIONAL WEATHER SERVICE IN GLASGOW HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  SOUTHERN VALLEY COUNTY IN NORTHEAST MONTANA

* UNTIL 415 PM MDT

* HEAVY RAIN IN EXCESS OF 5 INCHES OCCURED OVERNIGHT IN SOUTHERN  
  VALLEY COUNTY. RUNOFF FROM FIELDS BETWEEN DUCK CREEK AND THE 
  BENTONITE PLANT HAS CAUSED THE WATER LEVEL ON WILLOW CREEK TO RISE 
  TO BANKFUL. WATER WAS FLOWING OVER PORTIONS OF WILLOW CREEK ROAD.

DO NOT DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE
ROADWAY. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO CROSS
SAFELY. VEHICLES CAUGHT IN RISING WATER SHOULD BE ABANDONED QUICKLY.
MOVE TO HIGHER GROUND.

LAT...LON 4794 10711 4780 10677 4809 10639 4827 10680

.END
90

What forecasters said that day

The local office's own words before this flash flood warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Glasgow, MT wrote its last area forecast discussion before this flash flood warning went out at Aug 21, 9:30 AM MDT, 50 minutes earlier.

Area forecast discussion, Aug 21, 9:30 AM MDT, 50 minutes before

NORTHEAST MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
930 AM MDT WED AUG 21 2002

UPDATE PLANNED

.SHORT TERM...
THUNDERSTORMS OVER SOUTHEAST GARFIELD/NORTHERN ROSEBUD COUNTIES
MOVING VERY SLOWLY NORTHEAST. THUNDERSTORMS ASSOCIATED WITH WEAK
SHORTWAVE MOVING THROUGH SOUTHWEST FLOW AND WEAK SURFACE BOUNDARY.
AREA OF HIGHEST INSTABLITY REMAINS OVER SOUTHEAST ZONES THROUGHOUT
THE DAY WITH SOME STABLIZING OF AIRMASS OVER NORTHWEST ZONES. WILL
MAKE SOME MINOR CHANGES TO ZONES WITH REGARD TO TIMING ON NEXT ROUND
OF STORMS. EXPECT NEXT ROUND OF STORMS NOW FORMING OFF THE SOUTHWEST
MOUNTAINS TO TAKE SEVERAL HOURS TO REACH NORTHEAST MONTANA. EBERT

.LONG TERM...
MRF AND ECMWF IN AGREEMENT WITH UPPER LOW THAT IS NEARLY STATIONARY OVER
THE PACIFIC NW FINALLY PULLS OUT EARLY NEXT WEEK. CONFIDENCE IS LOW
THAT SATURDAY WILL REMAIN DRY WHILE A CHANCE OF THUNDERSTORMS FROM
SUNDAY THROUGH TUESDAY LOOKS GOOD AT THE MOMENT.

KGGW TBB /075 055/082 058/081 7643222
     BBBB 051/081 050/084 051/081 052/083 052/ 76223333333
KGDV TBB /082 058/084 058/084 7643222
     BBBB 052/082 050/083 050/082 051/084 051/ 76223333333

.GGW...NONE.

In the hours before

Special weather statement, Aug 21, 5:38 AM MDT, 4 hours 42 minutes before

MTZ016>027-059>062-221200-

SEVERE WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GLASGOW MT
538 AM MDT WED AUG 21 2002

...SEVERE THUNDERSTORMS POSSIBLE TODAY AND TONIGHT...

MOIST UNSTABLE AIR WILL REMAIN OVER NORTHEAST MONTANA TODAY.
MEANWHILE... SOUTHWEST FLOW WILL BRING UPPER LEVEL DISTURBANCES WILL
ACROSS NORTHEAST MONTANA TODAY AND TONIGHT. EXPECT SCATTERED
THUNDERSTORMS ACROSS THE REGION. SOME OF THESE STORMS WILL CONTAIN
LARGE HAIL...VERY HEAVY RAIN AND WINDS GUSTS IN EXCESS OF 60 MPH.
THE BEST CHANCE OF SEVERE THUNDERSTORMS WILL BE ALONG AND SOUTH OF
U.S. HIGHWAY 2.

STAY TUNED TO NOAA WEATHER RADIO AND OTHER LOCAL MEDIA FOR FURTHER
DETAILS OR UPDATES.

Special weather statement, Aug 21, 5:38 AM MDT, 4 hours 42 minutes before

MTZ016>027-059>062-221200-

SEVERE WEATHER OUTLOOK...CORRECTION
NATIONAL WEATHER SERVICE GLASGOW MT
538 AM MDT WED AUG 21 2002

...SEVERE THUNDERSTORMS POSSIBLE TODAY AND TONIGHT...

MOIST UNSTABLE AIR WILL REMAIN OVER NORTHEAST MONTANA TODAY.
MEANWHILE... SOUTHWEST FLOW WILL BRING UPPER LEVEL DISTURBANCES
ACROSS NORTHEAST MONTANA TODAY AND TONIGHT. EXPECT SCATTERED
THUNDERSTORMS ACROSS THE REGION. SOME OF THESE STORMS WILL CONTAIN
LARGE HAIL...VERY HEAVY RAIN AND WINDS GUSTS IN EXCESS OF 60 MPH.
THE BEST CHANCE OF SEVERE THUNDERSTORMS WILL BE ALONG AND SOUTH OF
U.S. HIGHWAY 2.

STAY TUNED TO NOAA WEATHER RADIO AND OTHER LOCAL MEDIA FOR FURTHER
DETAILS OR UPDATES.

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 20, 11:23 PM MDT	Severe Thunderstorm Warning	GGW	Valley	52 min
Aug 21, 12:18 AM MDT	Severe Thunderstorm Warning	GGW	Valley	57 min
Aug 21, 12:35 AM MDT	Flash Flood Warning	GGW	Valley	6 hr
Aug 21, 1:19 AM MDT	Severe Thunderstorm Warning	GGW	Valley	56 min
Aug 21, 2:19 AM MDT	Severe Thunderstorm Warning	GGW	McCone, Valley	56 min
Aug 21, 2:44 AM MDT	Flash Flood Warning	GGW	McCone	6 hr
Aug 21, 4:53 AM MDT	Severe Thunderstorm Warning	GGW	McCone	67 min

Nearby

Flash Flood Warnings in Montana, 2002 Every flash flood 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.