Alert archive / Montana / Flash Flood Warnings in 2021

Flash Flood Warning 1, NWS Missoula, MT

August 1, 2021Ravalli County, Montana

NWS Missoula, MT issued this flash flood warning at Aug 1, 2021, 5:42 PM MDT for Ravalli 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
Aug 1, 2021, 5:42 PM MDT (23:42 UTC)
Expired
Aug 1, 2021, 8:15 PM MDT
In force
3 hr
Issued by
NWS Missoula, MT
Area
Storm-based polygon
Flood severity
None

County Ravalli County, MT

The radar

The Missoula radar (KMSX), 65 km from the middle of the area, began a volume at 23:45 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

Spokane, WA (KOTX), launched 12:00Z, 11.7 hours before the alert went out and 211 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, Spokane, WA at 12:00Z on 2021-08-01Temperature 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, Spokane, WA at 12:00Z on 2021-08-01The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 39 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
2118 m above ground
0-6 km bulk shear
16 kt
0-1 km storm-relative helicity
39 m²/s²
0-3 km storm-relative helicity
51 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

245 
WGUS55 KMSO 012342
FFWMSO
MTC081-020215-
/O.NEW.KMSO.FF.W.0001.210801T2342Z-210802T0215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Missoula MT
542 PM MDT Sun Aug 1 2021

The National Weather Service in Missoula has issued a

* Flash Flood Warning for...
  Northern Ravalli County in west central Montana...

* Until 815 PM MDT.

* At 542 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain in Big Creek. Between 1.5 and 2 inches of rain have 
  fallen. Flash flooding is ongoing or expected to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  IMPACT...Flash flooding of small creeks and streams, and other
           poor drainage and low-lying areas.

* Big Creek

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood 
deaths occur in vehicles.

Flooding is occurring or is imminent. It is important to know where 
you are relative to streams, rivers, or creeks which can become 
killers in heavy rains. Campers and hikers should avoid streams or 
creeks.

Please report observed flooding to local emergency services or law 
enforcement and request they pass this information to the National 
Weather Service when you can do so safely.

&&

LAT...LON 4652 11430 4652 11427 4649 11420 4647 11418
      4646 11417 4645 11418 4645 11430 4646 11433
      4650 11432

FLASH FLOOD...RADAR INDICATED

$$

JK
1 follow-up statement
974 
WGUS75 KMSO 020206
FFSMSO

Flash Flood Statement
National Weather Service Missoula MT
806 PM MDT Sun Aug 1 2021

MTC081-020216-
/O.EXP.KMSO.FF.W.0001.000000T0000Z-210802T0215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Ravalli MT-
806 PM MDT Sun Aug 1 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 815 PM MDT THIS EVENING FOR 
NORTHERN RAVALLI COUNTY...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Please continue to heed remaining road closures.

A Flash Flood Watch remains in effect until 900 PM MDT for portions 
of northwest Montana and west central Montana.

LAT...LON 4652 11430 4652 11427 4649 11420 4647 11418
      4646 11417 4645 11418 4645 11430 4646 11433
      4650 11432

$$

JK

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 1, 8:16 AM MDTWind AdvisoryMSOFlathead, Lake, Lincoln, Mineral, Missoula, Sanders15 hr
Aug 1, 11:33 AM MDTFlash Flood WatchMSODeer Lodge, Granite, Powell, Silver Bow22 hr
Aug 1, 2:45 PM MDTAreal Flood AdvisoryMSOMissoula3 hr
Aug 1, 3:25 PM MDTAreal Flood AdvisoryMSOMineral3 hr
Aug 1, 3:38 PM MDTSpecial Weather StatementMSOMineral67 min
Aug 1, 3:48 PM MDTSpecial Weather StatementMSOMissoula42 min
Aug 1, 4:04 PM MDTSpecial Weather StatementMSOMineral41 min
Aug 1, 4:23 PM MDTSpecial Weather StatementMSOLake52 min
Aug 1, 4:41 PM MDTAreal Flood AdvisoryMSOMineral3 hr
Aug 1, 4:45 PM MDTAreal Flood AdvisoryMSOLake3 hr
Aug 1, 5:00 PM MDTSpecial Weather StatementMSOMissoula30 min
Aug 1, 5:06 PM MDTSpecial Weather StatementMSORavalli39 min
Aug 1, 5:29 PM MDTAreal Flood AdvisoryMSORavalli3 hr
Aug 1, 5:30 PM MDTSpecial Weather StatementMSOLake45 min
Aug 1, 5:35 PM MDTSpecial Weather StatementMSOLake40 min

Nearby

Flash Flood Warnings in Montana, 2021Every flash flood warning in 2021

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.