Name: Flooding in Idaho, May 1 to 15, 2012
Start: 2012-05-01T00:00
End: 2012-05-15T14:45
Location: Idaho

Where it happened

Every event with a place to put it. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 2

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS BOI wrote it up.

Snow melt of the high elevation snowpack in the Boise River basin prompted water managers to clear more reservoir storage space and continued the discharge from Lucky Peak Dam with the associated minor flooding along the river in Ada and Canyon counties.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Boise, ID wrote its last area forecast discussion before the first event at Apr 30, 7:33 PM MST, 4 hours 27 minutes earlier.

Area forecast discussion, Apr 30, 7:33 PM MST, 4 hours 27 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
833 MDT MON APR 30 2012

.DISCUSSION...FORECAST WAS UPDATED EARLIER TO ACCOUNT FOR ISOLATED
THUNDERSTORMS ACROSS SECTIONS OF SOUTHEAST OREGON/SOUTHWEST IDAHO
NORTH OF THE TREASURE VALLEY. LATEST RADAR DATA WAS SHOWING A
DIMINISHING TREND IN THE STRENGTH AND COVERAGE OF THE
THUNDERSTORMS...WHICH IS TO BE EXPECTED AS WE APPROACH SUNSET. A FEW
STORMS REMAIN IN THE BOISE MOUNTAINS...BUT THOSE TOO SHOULD
DISSIPATE IN THE NEXT HOUR. THE SHOWER AND THUNDERSTORM ACTIVITY WAS
ASSOCIATED WITH INSTABILITY ALONG AN UPPER TROUGH AS IT TRANSVERSES
THE REGION. WINDS AND SHOWERS WILL DIMINISH OVERNIGHT WITH MOSTLY
CLEAR SKIES PREVAILING BY TUESDAY MORNING. SHOWERS WILL LINGER IN
THE BOISE/WEST CENTRAL MOUNTAINS...OTHERWISE DRIER CONDITIONS AND
SLIGHTLY COOLER TEMPS ARE ON TAP FOR TUESDAY.

&&

.AVIATION...GENERALLY VFR...EXCEPT LOW VFR IN SHOWERS NEAR KTWF/KJER
TILL 03Z...AND OCCASIONAL MVFR IN NORTHERN MOUNTAIN VALLEYS IN
SHOWERS OR ISOLATED THUNDERSTORMS OBSCURING HIGHER TERRAIN TIL 04Z.
SNOW LEVEL NEAR 7500 WILL DROP TO NEAR 5500 FT BY TUESDAY
MORNING...ISOLATED SNOW SHOWER NORTHERN MOUNTAINS POSSIBLE THROUGH
10Z.  SURFACE WINDS WESTERLY 10-20 KTS.  WINDS ALOFT WEST 35 KTS AT
10K FEET MSL.

&&

.HYDROLOGY...MANAGED FLOWS ON THE BOISE RIVER THROUGH BOISE REMAIN
ABOVE FLOOD LEVEL. DISCHARGE FROM LUCKY PEAK RESERVOIR WAS INCREASED
200 CFS EARLIER TODAY WHICH UPPED FLOWS AT THE GLENWOOD BRIDGE RIVER
GAGE IN BOISE TO AROUND 7500 CFS. MORE INCREASES ARE PLANNED...WITH
AN ADDITIONAL 300 CFS TUESDAY AND ANOTHER 200 CFS ON
WEDNESDAY...TARGETING 8000 CFS AT THE GLENWOOD BRIDGE GAGE. THIS
WILL KEEP THE RIVER AT MINOR FLOOD LEVEL THROUGH BOISE BUT
INUNDATION OF GREENBELT PATH AND LOW LYING AREAS ADJACENT TO THE
RIVER WILL BE INCREASING. OTHERWISE...RIVERS AND CREEKS ARE
GENERALLY RUNNING SWIFT AND HIGH ACROSS SOUTHEAST OREGON AND
SOUTHWEST IDAHO...TYPICAL FOR THIS TIME OF YEAR.

&&

.PREV DISCUSSION...
SHORT TERM...TONIGHT THROUGH WEDNESDAY...RAIN SHOWERS WITH SNOW
ABOVE 7500 FEET /AS SEEN ON BOGUS BASIN PINE CREEK TOP/ WERE OVER
SOUTHWEST IDAHO TO NORTHEAST OREGON THIS AFTERNOON. GREATEST
PRECIPITATION WILL BE ACROSS THE BOISE MOUNTAINS THIS AFTERNOON
AND SOUTHERN HIGHLANDS/SOUTHERN TWIN FALLS COUNTY THIS EVENING AS
AN UPPER LEVEL DISTURBANCE AND CONVERGENCE AHEAD OF BUILDING HIGH
PRESSURE MOVE IN. GUSTY WINDS WILL DIMINISH SOMEWHAT OVERNIGHT BUT
STAY UP ENOUGH TO LIMIT FOG POTENTIAL AND KEEP MINS UP. COOL
PROGRESSIVE TROUGH WILL SEND A WEAK DISTURBANCE THROUGH NORTHERN
ZONES 06Z-18Z WEDNESDAY. MAIN EFFECT SOUTH WILL BE BREEZY
AFTERNOON WEDNESDAY.

LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...MODEL CONSISTENCY AND
CONTINUITY REMAIN ABOVE AVERAGE THROUGH THE PERIOD. TWO SYSTEMS WILL
AFFECT OUR AREA DURING THIS PERIOD. THE FIRST WILL BE A RELATIVELY
SHALLOW SHORTWAVE TROUGH WEDNESDAY NIGHT AND THURSDAY. THIS WILL BE
THE BETTER PRECIPITATION PRODUCER OWING TO GOOD JET SUPPORT. THE
TROUGH EXITS BY THURSDAY NIGHT LEAVING US UNDER A MOIST SOUTHWEST
FLOW ALOFT FOR A CONTINUED CHANCE OF SHOWERS. THE SECOND SYSTEM IS A
HIGHER AMPLITUDE TROUGH WHICH MOVES INTO THE INTERMOUNTAIN REGION
FRIDAY NIGHT AND SATURDAY AND CLOSES OFF OVER THE AREA SUNDAY AND
MONDAY...KEEPING TEMPERATURES A FEW DEGREES BELOW NORMAL WITH A
CHANCE OF SHOWERS EACH DAY.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
OR...NONE.
&&

WEATHER.GOV/BOISE

DISCUSSION...BW
AVIATION.....RD
HYDROLOGY....TAL
PREV SHORT TERM...VM
PREV LONG TERM....JT/MT

Hazardous weather outlook, Apr 30, 4:40 AM MST, 19 hours 20 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BOISE ID
540 AM MDT MON APR 30 2012

IDZ012-014-011200-
LOWER TREASURE VALLEY ID-UPPER TREASURE VALLEY-
540 AM MDT MON APR 30 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST
IDAHO.

.DAY ONE...TODAY AND TONIGHT

THERE IS MINOR FLOODING ON THE BOISE RIVER BELOW LUCKY PEAK.
PLEASE SEE THE RIVER FLOOD PRODUCT FOR ADDITIONAL DETAILS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED.

IDZ011-013-015-016-028>030-033-ORZ061>064-011200-
WEST CENTRAL MOUNTAINS-BOISE MOUNTAINS-SOUTHWEST HIGHLANDS-
WESTERN MAGIC VALLEY-CAMAS PRAIRIE-OWYHEE MOUNTAINS-
SOUTHERN TWIN FALLS COUNTY-UPPER WEISER RIVER-HARNEY COUNTY-
BAKER COUNTY-MALHEUR COUNTY-LOWER TREASURE VALLEY OR-
540 AM MDT MON APR 30 2012 /440 AM PDT MON APR 30 2012/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTH CENTRAL
IDAHO...SOUTHWEST IDAHO...WEST CENTRAL IDAHO...NORTHEAST OREGON
AND SOUTHEAST OREGON.

.DAY ONE...TODAY AND TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED.

In the hours before

Special weather statement, Apr 30, 6:32 PM MST, 5 hours 28 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BOISE ID
732 PM MDT MON APR 30 2012

IDZ011>013-033-010215-
PAYETTE ID-VALLEY ID-BOISE ID-WASHINGTON ID-GEM ID-
732 PM MDT MON APR 30 2012

THE NATIONAL WEATHER SERVICE IN BOISE HAS ISSUED A

SIGNIFICANT WEATHER ADVISORY FOR...
  EAST CENTRAL GEM COUNTY IN SOUTHWEST IDAHO...
  NORTHEASTERN PAYETTE COUNTY IN SOUTHWEST IDAHO...
  SOUTHEASTERN WASHINGTON COUNTY IN SOUTHWEST IDAHO...
  NORTHWESTERN BOISE COUNTY IN WEST CENTRAL IDAHO...
  AND SOUTHWESTERN VALLEY COUNTY IN WEST CENTRAL IDAHO...

UNTIL 815 PM MDT.

AT 723 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 11 MILES EAST OF WEISER...MOVING EAST AT 25 MPH.

HAIL UP TO THE SIZE OF PENNIES AND WIND GUSTS UP TO 40 MPH ARE
EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN.

THE THUNDERSTORM WILL BE NEAR...
  BEAR CREEK SUMMIT AND PRESLEY BRIDGE AROUND 730 PM MDT...
  PADDOCK VALLEY RESERVOIR AROUND 740 PM MDT...
  DODSON PASS AROUND 810 PM MDT...
  OLA...HIGH VALLEY AND SAGE HEN RESERVOIR AROUND 815 PM MDT.

LIGHTNING IS ONE OF NATURES NUMBER ONE KILLERS. TAKE SHELTER INSIDE A
BUILDING OR VEHICLE WHEN THUNDERSTORMS APPROACH. LIGHTNING CAN OCCUR
15 MILES OR MORE AWAY FROM THE CENTER OF A STORM. IF YOU CAN HEAR
THUNDER...YOU ARE CLOSE ENOUGH TO BE STRUCK BY LIGHTNING.

LAT...LON 4435 11613 4410 11615 4416 11683 4434 11682
TIME...MOT...LOC 0131Z 272DEG 22KT 4424 11668

BW

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

2 flood. Local standard time, as filed.

Flood, Ada

When: May 1, 12:00 AM MST to May 15, 2:45 PM MST
Where: Ada County, 3.16 mi SE of Barber to 1.72 mi SSW of Star
Cause: Planned Dam Release
Reported by: Official NWS Observations
Coordinates: 43.535, -116.079

Regulated flows on the Boise River increased above flood flow (7,000 cfs) on April 28, and were reduced below flood flow on May 15. Flood impacts were minor. Lowland flooding occurred along the river from Boise downstream through Caldwell to Parma. Sections of the greenbelt path were flooded along with some pasture and fields near the river. Floodwaters inundated a section of Boise River Road between Highway 95 and Notus. Several large trees were up-rooted and became snagged on bridges.

Flood, Canyon

When: May 1, 12:00 AM MST to May 15, 2:45 PM MST
Where: Canyon County, 2.74 mi E of Stoddard to 1.12 mi WSW of Apple Vly
Cause: Planned Dam Release
Reported by: Official NWS Observations
Coordinates: 43.682, -116.495

Regulated flows on the Boise River increased above flood flow (7,000 cfs) on April 28, and were reduced below flood flow on May 15. Flood impacts were minor. Lowland flooding occurred along the river from Boise downstream through Caldwell to Parma. Sections of the greenbelt path were flooded along with some pasture and fields near the river. Floodwaters inundated a section of Boise River Road between Highway 95 and Notus. Several large trees were up-rooted and became snagged on bridges.

What these are

Flood: Flooding that develops more slowly than a flash flood: rivers leaving their banks, or water standing over land for an extended time.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in Idaho in 2012 Every state in 2012 This day in weather history Warnings in Idaho, May 2012

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 386776, 386777.