Alert archive / Idaho / Flash Flood Warnings in 2021

Flash Flood Warning 6, NWS Boise, ID

August 1, 2021Elmore County, Idaho

NWS Boise, ID issued this flash flood warning at Aug 1, 2021, 2:39 PM MDT for Elmore County, Idaho. It was in force for 5 hr. 1 report came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Aug 1, 2021, 2:39 PM MDT (20:39 UTC)
Expired: Aug 1, 2021, 8:00 PM MDT
In force: 5 hr
Issued by: NWS Boise, ID
Area: Storm-based polygon
Flood severity: None

County Elmore County, ID

The radar

The Boise radar (KCBX), 75 km from the middle of the area, began a volume at 20:39 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.

What was reported inside it

Time	Report	Where	Remark
Aug 1, 4:00 PM MDT	FLASH FLOOD	7 Wnw Pine, ID	BOISE NATIONAL FOREST OFFICIALS REPORTED THAT TRINITY RIDGE ROAD 129 IS IMPASSABLE AT BURNT CREEK DUE TO A WASHOUT WHICH OCCURRED ON SUNDAY. THERE WERE ALSO OTHER SMALLER WASHOUTS BETWEEN BEAR HOLE AND BURNT CREEK. PHOTOS INDICATED THAT LOGS AND OTHER DEBRIS W

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Boise Airport, ID (KBOI), launched 12:00Z, 8.7 hours before the alert went out and 69 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: 4 J/kg
Mixed-layer CIN: -186 J/kg
Mixed-layer LCL: 1142 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: 78 m²/s²
0-3 km storm-relative helicity: 92 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

640 
WGUS55 KBOI 012039
FFWBOI
IDC039-012330-
/O.NEW.KBOI.FF.W.0006.210801T2039Z-210801T2330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Boise ID
239 PM MDT Sun Aug 1 2021

The National Weather Service in Boise has issued a

* Flash Flood Warning for...
  Northeastern Elmore County in southwestern Idaho...

* Until 530 PM MDT.

* At 239 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 1.5 inches of 
  rain have fallen. The expected rainfall rate is 1.5 inches in 1 
  hour. Additional rainfall amounts of 1 to 2 inches are possible in 
  the warned area. 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, urban
           areas, highways, streets and underpasses as well as
           other poor drainage and low-lying areas.

* Some locations that will experience flash flooding include...
  Atlanta, Rocky Bar, Dutch Creek Guard Station, Trinity Lakes and 
  Featherville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4350 11538 4364 11566 4366 11569 4368 11565
      4378 11555 4383 11550 4386 11546 4390 11536
      4395 11525 4396 11517 4384 11511 4382 11509
      4360 11517 4354 11520 4350 11522 4349 11530

FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL...1-1.5 INCHES IN 1 HOUR

$$

JPB

2 follow-up statements

835 
WGUS55 KBOI 012323
FFWBOI
IDC039-020200-
/O.EXT.KBOI.FF.W.0006.000000T0000Z-210802T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Boise ID
523 PM MDT Sun Aug 1 2021

The National Weather Service in Boise has extended the

* Flash Flood Warning for...
  Northeastern Elmore County in southwestern Idaho...

* Until 800 PM MDT.

* At 523 PM MDT, Doppler radar continued to indicate thunderstorms 
  producing heavy rain across the warned area. Between 1 and 2 
  inches of rain have fallen. Additional rainfall amounts of 0.5 to 
  1 inch are possible in the warned area. 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, urban
           areas, highways, streets and underpasses as well as
           other poor drainage and low-lying areas.

* Some locations that will experience flash flooding include...
  Trinity Lakes, Rocky Bar and Featherville.

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 4350 11538 4364 11566 4366 11569 4368 11565
      4381 11552 4374 11532 4362 11525

FLASH FLOOD...RADAR INDICATED

$$

ST

385 
WGUS75 KBOI 020153
FFSBOI

Flash Flood Statement
National Weather Service Boise ID
753 PM MDT Sun Aug 1 2021

IDC039-020203-
/O.EXP.KBOI.FF.W.0006.000000T0000Z-210802T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Elmore ID-
753 PM MDT Sun Aug 1 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 8 PM MDT THIS EVENING FOR 
NORTHEASTERN ELMORE 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 1200 AM MDT for portions 
of south central Idaho, southwest Idaho and west central Idaho.

LAT...LON 4350 11538 4364 11566 4366 11569 4368 11565
      4381 11552 4374 11532 4362 11525

$$

ST

The office that day

Everything else NWS Boise, ID issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 31, 6:40 PM MDT	Special Weather Statement	BOI	Twin Falls	35 min
Jul 31, 7:06 PM MDT	Flash Flood Warning	BOI	Owyhee, Twin Falls	3 hr
Jul 31, 7:39 PM MDT	Flash Flood Warning	BOI	Twin Falls	3 hr
Jul 31, 9:32 PM MDT	Special Weather Statement	BOI	Ada	28 min
Jul 31, 9:33 PM MDT	Areal Flood Advisory	BOI	Elmore, Owyhee	117 min
Jul 31, 10:12 PM MDT	Flash Flood Warning	BOI	Ada, Boise	3 hr
Jul 31, 11:58 PM MDT	Flash Flood Warning	BOI	Canyon, Gem, Owyhee, Payette	2 hr
Aug 1, 12:43 AM MDT	Areal Flood Advisory	BOI	Payette, Washington	2 hr
Aug 1, 1:47 AM MDT	Areal Flood Advisory	BOI	Camas	103 min
Aug 1, 1:11 PM MDT	Special Weather Statement	BOI	Twin Falls	49 min
Aug 1, 1:25 PM MDT	Areal Flood Advisory	BOI	Twin Falls	3 hr
Aug 1, 2:15 PM MDT	Special Weather Statement	BOI	Jerome	60 min
Aug 1, 3:21 PM MDT	Areal Flood Advisory	BOI	Jerome, Twin Falls	3 hr
Aug 1, 3:39 PM MDT	Flash Flood Warning	BOI	Camas, Elmore	3 hr
Aug 1, 4:01 PM MDT	Flash Flood Warning	BOI	Owyhee	3 hr
Aug 1, 4:49 PM MDT	Areal Flood Advisory	BOI	Elmore	3 hr
Aug 1, 5:32 PM MDT	Flash Flood Warning	BOI	Elmore	3 hr
Aug 1, 5:39 PM MDT	Areal Flood Advisory	BOI	Owyhee	2 hr

Nearby

Flash Flood Warnings in Idaho, 2021 Every 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.