Alert archive / Montana / Flash Flood Warnings in 2012

Flash Flood Warning 1, NWS Great Falls, MT

July 20, 2012Lewis and Clark County, Montana

NWS Great Falls, MT issued this flash flood warning at Jul 20, 2012, 4:23 PM MDT for Lewis and Clark County, Montana. It was in force for 3 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: Jul 20, 2012, 4:23 PM MDT (22:23 UTC)
Expired: Jul 20, 2012, 7:15 PM MDT
In force: 3 hr
Issued by: NWS Great Falls, MT
Area: Storm-based polygon
Flood severity: None

County Lewis and Clark County, MT

The nearest sounding before it

Great_falls, MT (KTFX), launched 12:00Z, 10.4 hours before the alert went out and 141 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: 92 J/kg
Mixed-layer CIN: -463 J/kg
Mixed-layer LCL: 2595 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 37 m²/s²
0-3 km storm-relative helicity: 78 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.

313 
WGUS55 KTFX 202223
FFWTFX
MTC049-210115-
/O.NEW.KTFX.FF.W.0001.120720T2223Z-120721T0115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE GREAT FALLS MT
423 PM MDT FRI JUL 20 2012

THE NATIONAL WEATHER SERVICE IN GREAT FALLS HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  THE SCRATCH GRAVEL HILLS OF SOUTH CENTRAL LEWIS AND CLARK COUNTY   
  IN WEST CENTRAL MONTANA...

* UNTIL 715 PM MDT

* AT 400 PM MDT...FLASH FLOODING WAS REPORTED FROM A THUNDERSTORM    
  OVER THE SCRATCH GRAVEL HILLS.

* THE THUNDERSTORM THAT PRODUCED THE FLASH FLOODING HAS DISSIPATED   
  HOWEVER MORE SHOWERS AND THUNDERSTORMS ARE EXPECTED THROUGH THE    
  REST OF THIS AFTERNOON. ADDITIONAL RAINFALL TOTALS SHOULD BE LESS  
  THAN A QUARTER OF AN INCH. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLASH FLOOD WARNING MEANS THAT FLOODING...MUD AND DEBRIS FLOWS ARE
IMMINENT OR ALREADY OCCURRING. MOVE TO HIGHER GROUND. RESIDENTS
LIVING ALONG STREAMS AND CREEKS SHOULD TAKE IMMEDIATE PRECAUTIONS TO
PROTECT LIFE AND PROPERTY.

&&


LAT...LON 4677 11218 4677 11201 4662 11198 4663 11216

$$

1 follow-up statement

046 
WGUS75 KTFX 210114
FFSTFX

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE GREAT FALLS MT
714 PM MDT FRI JUL 20 2012

MTC049-210122-
/O.EXP.KTFX.FF.W.0001.000000T0000Z-120721T0115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
LEWIS AND CLARK MT-
714 PM MDT FRI JUL 20 2012

...THE FLASH FLOOD WARNING WILL EXPIRE AT 715 PM MDT FOR THE SCRATCH 
GRAVEL HILLS OF SOUTH CENTRAL LEWIS AND CLARK COUNTY...

THE THREAT OF ADDITIONAL HEAVY RAIN HAS ENDED SO THE WARNING WILL BE
ALLOWED TO EXPIRE.

LAT...LON 4677 11218 4677 11201 4662 11198 4663 11216

$$

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 20, 3:30 PM MDT	Special Weather Statement	TFX	Silver Bow	60 min
Jul 20, 4:02 PM MDT	Special Weather Statement	TFX	Lewis and Clark	43 min
Jul 20, 4:32 PM MDT	Special Weather Statement	TFX	Lewis and Clark	88 min
Jul 20, 5:32 PM MDT	Special Weather Statement	TFX	Glacier, Teton	58 min
Jul 20, 5:56 PM MDT	Special Weather Statement	TFX	Chouteau, Liberty, Pondera, Toole	64 min

Nearby

Flash Flood Warnings in Montana, 2012 Every flash flood warning in 2012

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.