Alert archive / Idaho / Flash Flood Warnings in 2021

Flash Flood Warning 4, NWS Boise, ID

July 31, 2021Ada County, Boise County, Idaho

NWS Boise, ID issued this flash flood warning at Jul 31, 2021, 10:12 PM MDT for Ada County, Boise County, Idaho. It was in force for 3 hr. 6 reports 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
Jul 31, 2021, 10:12 PM MDT (04:12 UTC)
Expired
Aug 1, 2021, 1:00 AM MDT
In force
3 hr
Issued by
NWS Boise, ID
Area
Storm-based polygon
Flood severity
None

Counties Ada County, ID, Boise County, ID

The radar

The Boise radar (KCBX), 26 km from the middle of the area, began a volume at 04:13 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

TimeReportWhereRemark
Jul 31, 10:40 PM MDTFLASH FLOOD3 Se Boise, IDPARKCENTER HAD 1 TO 2 FEET OF STANDING WATER. NWS EMPLOYEE HAD TO TURN AROUND AND GO A DIFFERENT ROUTE.
Jul 31, 11:19 PM MDTFLASH FLOOD1 Ese Boise, IDSTREET FLOODING ON EAST BANNOCK STREET. WATER OVER THE CURBS AND ABOUT ANKLE DEEP IN YARDS.
Aug 1, 12:00 AM MDTHEAVY RAIN 0.9911 Ne Garden City, IDMESONET STATION BR 11.6 NE BOISE (DCEW).
Aug 1, 12:15 AM MDTHEAVY RAIN 1.165 Ne Garden City, IDMESONET STATION LW 5.5 NE BOISE (DCEW).
Aug 1, 12:25 AM MDTFLASH FLOOD4 Se Boise, IDMULTIPLE SMALL ROCK SLIDES AND FLOODING ALONG STARVIEW DR ON WARM SPRINGS.
Aug 1, 1:00 AM MDTHEAVY RAIN 1.352 Ese Boise, IDMESONET STATION BOII 1.7 SE BOISE (AGRIMET).

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 00:00Z, 4.2 hours before the alert went out and 16 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, Boise Airport, ID at 00:00Z on 2021-08-01Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 166 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, Boise Airport, ID at 00:00Z on 2021-08-01The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 17 square meters per square second.1939Sfc1 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
166 J/kg
Mixed-layer CIN
-45 J/kg
Mixed-layer LCL
2597 m above ground
0-6 km bulk shear
19 kt
0-1 km storm-relative helicity
17 m²/s²
0-3 km storm-relative helicity
39 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.1

Open this sounding in Storm Lab

The text

As transmitted.

408 
WGUS55 KBOI 010412
FFWBOI
IDC001-015-010545-
/O.NEW.KBOI.FF.W.0004.210801T0412Z-210801T0545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Boise ID
1012 PM MDT Sat Jul 31 2021

The National Weather Service in Boise has issued a

* Flash Flood Warning for...
  Northeastern Ada County in southwestern Idaho...
  Southwestern Boise County in southwestern Idaho...

* Until 1145 PM MDT.

* At 1012 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain moving across the warned area. Between 1 and 2 inches 
  of rain is expected. 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...
  Northeastern Boise, Eagle, Garden City, Aldape Summit, Hidden 
  Springs, and Lucky Peak Reservoir.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be aware of your surroundings and do not drive on flooded roads.

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 4379 11626 4383 11620 4370 11598 4349 11599
      4370 11639

FLASH FLOOD...RADAR INDICATED

$$

BOI
2 follow-up statements
810 
WGUS55 KBOI 010532
FFWBOI
IDC001-015-010700-
/O.EXT.KBOI.FF.W.0004.000000T0000Z-210801T0700Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Boise ID
1132 PM MDT Sat Jul 31 2021

The National Weather Service in Boise has extended the

* Flash Flood Warning for...
  Northeastern Ada County in southwestern Idaho...
  Southwestern Boise County in southwestern Idaho...

* Until 100 AM MDT.

* At 1132 PM MDT, Doppler radar and automated rain gauges indicated 
  thunderstorms producing heavy rain across the warned area. Between 
  1 and 2 inches of rain have fallen. Moderate rain will continue to 
  fall across the warned area. Flash flooding is ongoing or expected 
  to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar and automated gauges.

  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...
  Northeastern Boise, Eagle, Garden City, Aldape Summit, Bogus Basin 
  Ski Area, Hidden Springs and Lucky Peak Reservoir.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be aware of your surroundings and do not drive on flooded roads.

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 4379 11626 4383 11620 4370 11598 4349 11599
      4370 11639

FLASH FLOOD...RADAR AND GAUGE INDICATED

$$

BOI
689 
WGUS75 KBOI 010658
FFSBOI

Flash Flood Statement
National Weather Service Boise ID
1258 AM MDT Sun Aug 1 2021

IDC001-015-010708-
/O.EXP.KBOI.FF.W.0004.000000T0000Z-210801T0700Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Ada ID-Boise ID-
1258 AM MDT Sun Aug 1 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 1 AM MDT EARLY THIS MORNING 
FOR NORTHEASTERN ADA AND SOUTHWESTERN BOISE COUNTIES...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. However, areas of ponding of water on roadways may persist. 
Please continue to heed remaining road closures.

A Flash Flood Watch remains in effect until 600 PM MDT Monday for 
portions of Idaho and Oregon.

LAT...LON 4379 11626 4383 11620 4370 11598 4349 11599
      4370 11639

$$

ST

The office that day

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

IssuedProductOfficeCountiesLasted
Jul 31, 6:40 PM MDTSpecial Weather StatementBOITwin Falls35 min
Jul 31, 7:06 PM MDTFlash Flood WarningBOIOwyhee, Twin Falls3 hr
Jul 31, 7:39 PM MDTFlash Flood WarningBOITwin Falls3 hr
Jul 31, 9:32 PM MDTSpecial Weather StatementBOIAda28 min
Jul 31, 9:33 PM MDTAreal Flood AdvisoryBOIElmore, Owyhee117 min
Jul 31, 11:58 PM MDTFlash Flood WarningBOICanyon, Gem, Owyhee, Payette2 hr
Aug 1, 12:43 AM MDTAreal Flood AdvisoryBOIPayette, Washington2 hr
Aug 1, 1:47 AM MDTAreal Flood AdvisoryBOICamas103 min
Aug 1, 1:11 PM MDTSpecial Weather StatementBOITwin Falls49 min
Aug 1, 1:25 PM MDTAreal Flood AdvisoryBOITwin Falls3 hr
Aug 1, 2:15 PM MDTSpecial Weather StatementBOIJerome60 min
Aug 1, 2:39 PM MDTFlash Flood WarningBOIElmore5 hr
Aug 1, 3:21 PM MDTAreal Flood AdvisoryBOIJerome, Twin Falls3 hr
Aug 1, 3:39 PM MDTFlash Flood WarningBOICamas, Elmore3 hr
Aug 1, 4:01 PM MDTFlash Flood WarningBOIOwyhee3 hr
Aug 1, 4:49 PM MDTAreal Flood AdvisoryBOIElmore3 hr
Aug 1, 5:32 PM MDTFlash Flood WarningBOIElmore3 hr
Aug 1, 5:39 PM MDTAreal Flood AdvisoryBOIOwyhee2 hr

Nearby

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