Hazard Report Provided By forecast.weather.gov

Flood Watch
National Weather Service Boise ID
1230 PM PDT Tue Aug 26 2025

.A surge of deep monsoonal moisture combined with a slow-moving
upper trough will bring periods of heavy showers and thunderstorms
across the region. This airmass contains anomalously high moisture
content, supporting the potential for excessive rainfall. Flash
flooding will be possible, especially in steep terrain, narrow
canyons, and near recent burn scars where soils are less able to
absorb rainfall. The greatest risk will be Tuesday afternoon through
Wednesday evening as repeated rounds of storms move through.

IDZ011>016-028>030-033-ORZ062>064-272000-
/O.CON.KBOI.FF.A.0005.000000T0000Z-250828T0600Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
West Central Mountains-Lower Treasure Valley-Boise Mountains-
Upper Treasure Valley-Southwest Highlands-Western Magic Valley-
Camas Prairie-Owyhee Mountains-Southern Twin  Falls County-Upper
Weiser River-Baker County-Malheur County-Oregon Lower Treasure
Valley-
Including the cities of Silver City, McCall, Big Creek,
Hollister, Glendale, Ontario, Mesa, Cuprum, Nyssa, Caldwell,
Soldier, Ola, Murphy Hot Springs, Hill City, Fruitvale,
Fairfield, Grasmere, Nampa, Cambridge, Riddle, Council, Warm
Lake, Baker, Malheur City, Rogerson, Prairie, Indian Valley,
Anderson Dam, Selby, Goodrich, Reynolds, Blaine, Corral, Bear,
Three Creek, Cascade, Twin Falls, Boise, and Pine
130 PM MDT Tue Aug 26 2025 /1230 PM PDT Tue Aug 26 2025/

...FLASH FLOOD WATCH REMAINS IN EFFECT THROUGH WEDNESDAY EVENING...

* WHAT...Flash flooding caused by excessive rainfall continues to be
  possible.

* WHERE...Portions of Idaho, including the following areas, Boise
  Mountains, Camas Prairie, Lower Treasure Valley, Owyhee Mountains,
  Southern Twin  Falls County, Southwest Highlands, Upper Treasure
  Valley, Upper Weiser River, West Central Mountains and Western
  Magic Valley and Oregon, including the following areas, Baker
  County, Malheur County and Oregon Lower Treasure Valley.

* WHEN...Through Wednesday evening.

* IMPACTS...Heavy rainfall could trigger flash flooding or debris
  flows, especially in and near recent wildfire burn scars.

* ADDITIONAL DETAILS...
  - https://www.weather.gov/safety/flood

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action
should Flash Flood Warnings be issued.

&&

$$

TL

Flash Flood Statement
National Weather Service Boise ID
725 PM MDT Tue Aug 26 2025

IDC001-015-039-270330-
/O.CON.KBOI.FF.W.0009.000000T0000Z-250827T0330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Ada ID-Boise ID-Elmore ID-
725 PM MDT Tue Aug 26 2025

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 930 PM MDT THIS
EVENING FOR NORTHEASTERN ADA, SOUTHWESTERN BOISE AND NORTHWESTERN
ELMORE COUNTIES...

At 725 PM MDT, Doppler radar indicated thunderstorms producing heavy
rain across the warned area. Between 2 and 3.5 inches of rain have
fallen. The estimated rainfall rate is 1 to 2 inches in 1 hour.
Additional rainfall amounts of 1 to 1.5 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...
  Lucky Peak Spring Shores Marina, Lucky Peak Reservoir, Arrowrock
  Dam, Lucky Peak Dam, Arrowrock Reservoir, and the Valley Fire Burn
  Scar.

Heaviest rain so far (up to 3.25 inches) has occurred between Lucky
Peak Dam and Arrowrock Reservoir.  Movement of the thunderstorms has
been northward around 10 mph.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don`t drown when encountering flooded roads. Most flood
deaths occur in vehicles.

Be especially cautious at night when it is harder to recognize the
dangers of flooding.

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

Avoid areas below steep hillsides where rocks and mud may fall.

In hilly terrain there are hundreds of low water crossings which are
potentially dangerous in heavy rain. Do not attempt to cross flooded
roads. Find an alternate route.

&&

LAT...LON 4367 11590 4354 11589 4348 11597 4350 11605
      4357 11607 4363 11605 4369 11599

FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL RATE...1-2 INCHES IN 1 HOUR

$$

LC

Flash Flood Warning
IDC015-270300-
/O.NEW.KBOI.FF.W.0008.250827T0005Z-250827T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Boise ID
605 PM MDT Tue Aug 26 2025

The National Weather Service in Boise has issued a

* Flash Flood Warning for...
  East Central Boise County in southwestern Idaho...

* Until 900 PM MDT.

* At 605 PM MDT, Boise County law enforcement reported numerous 911
  calls about rock slides and standing water on Idaho State Highway
  21 between Lowman and Grandjean. Flash flooding is ongoing.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Law enforcement reported.

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

Rock slides were reported on Idaho State Highway 21 at mileposts 72
and 76-77.  Three feet of water was reported on the road at milepost
80.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Stay away or be swept away. River banks and culverts can become
unstable and unsafe.

In hilly terrain there are hundreds of low water crossings which are
potentially dangerous in heavy rain. Do not attempt to cross flooded
roads. Find an alternate route.

&&

LAT...LON 4415 11528 4411 11535 4410 11545 4406 11551
      4407 11559 4406 11562 4409 11563 4408 11556
      4410 11548 4413 11542 4414 11533 4419 11526
      4418 11525 4418 11524

FLASH FLOOD...OBSERVED

$$

LC

Flash Flood Warning
IDC015-270245-
/O.NEW.KBOI.FF.W.0007.250826T2345Z-250827T0245Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Boise ID
545 PM MDT Tue Aug 26 2025

The National Weather Service in Boise has issued a

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

* Until 845 PM MDT.

* At 545 PM MDT, Doppler radar indicated thunderstorms producing
  heavy rain across the warned area. Flash flooding is ongoing or
  expected to begin shortly.

Excessive rainfall over the burn scar will result in debris flow
moving through the Wapiti Burn Scar. The debris flow can consist of
rock, mud, vegetation and other loose materials.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

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

* Locations that will experience flash flooding include...
  mainly rural areas of Northeastern Boise County along Idaho
  state    Highway 21.

A landslide has closed Idaho State Highway 21 between Grandjean and
the Custer County line.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Move away from recently burned areas. Life-threatening flooding of
creeks, roads and normally dry washes is likely. The heavy rains
will likely trigger rockslides, mudslides and debris flows in steep
terrain, especially in and around these areas.

&&

LAT...LON 4429 11524 4430 11524 4431 11523 4425 11520
      4422 11521 4420 11524 4418 11524 4418 11526
      4422 11525 4425 11522

FLASH FLOOD...RADAR INDICATED

$$

LC

Hazard Report Provided By forecast.weather.gov