Warm temperatures, snow melt, and rainfall caused flooding on Imnaha River.
Every event with a place to put it. Tap one for its entry below.
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.
The episode as NWS PDT wrote it up.
Warm temperatures, snow melt, and rainfall caused flooding on Imnaha River.
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 Pendleton, OR wrote its last area forecast discussion before the first event at Apr 26, 3:50 PM PST, 40 minutes earlier.
AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PENDLETON OR 450 PM PDT THU APR 26 2012 UPDATED AVIATION DISCUSSION .SHORT TERM...TONIGHT THROUGH SUNDAY...A DEEP UPPER LEVEL TROUGH IS MOVING ONSHORE AND WILL MOVE ACROSS THE AREA TONIGHT AND FRIDAY. THE TROUGH WILL BE REPLACED BY A SOMEWHAT DRIER NWLY FLOW REGIME THROUGH THE WEEKEND. FOR THIS EVENING EXPECT THE RAIN SHIELD OVER NE OREGON AND EXTREME SE WASHINGTON TO GRADUALLY MOVE OUT OF THE AREA LEAVING JUST ISOLATED TO SCATTERED RAIN AND MOUNTAIN SNOW SHOWERS TONIGHT. FRIDAY THROUGH SUNDAY EXPECT MAINLY JUST A SLIGHT CHANCE OF RAIN/SNOW SHOWERS OVER THE NE MOUNTAINS IN UPSLOPE FLOW...AND PARTLY CLOUDY SKIES ELSEWHERE. IT WILL BE BREEZY TO WINDY FOR MUCH OF FRIDAY. TEMPERATURES WILL BE NOTICEABLY COOLER COMPARED TO RECENT DAYS FOR FRIDAY AND SATURDAY AVERAGING NEAR TO SLIGHTLY BELOW NORMAL. BY SUNDAY A WARMUP IS EXPECTED WITH HIGHS NEAR 70 LOWER ELEVATIONS. 78 .LONG TERM...SUNDAY NIGHT THROUGH TUESDAY NIGHT...ZONAL WESTERLY FLOW ALOFT WILL PREDOMINATE THROUGH MON DAY NIGHT, THUS PRODUCING DOWNSLOPE WINDS OFF THE CASCADES AND ATTENDANT SUBSIDENCE ACROSS LOWER ELEVATIONS IMMEDIATELY EAST OF THE CASCADES FOR DRY CONDITIONS AT LOWER ELEVATIONS THROUGH MONDAY NIGHT. AN UPPER LEVEL SHORT WAVE SWINGS ACROSS THE EASTERN SECTIONS OF WASHINGTON AND OREGON TUESDAY FOR A CHANCE OF RAIN DURING THE DAY ON TUESDAY IN NE OREGON, SE WASHINGTON AND ALONG THE SLOPES OF THE CENTRAL WASHINGTON CASCADES. WEAK DYNAMIC LIFT COMBINED WITH WESTERLY FLOW ALOFT ACROSS CENTRAL AND SOUTHERN OREGON WILL PUT CENTRAL AND NORTH CENTRAL OREGON AS WELL AS THE JOHN DAY BASIN AND THE OCHOCO-JOHN DAY HIGHLANDS IN A RAIN SHADOW DURING THE DAY ON TUESDAY. AS SUCH, I GAVE THOSE AREAS ONLY A SLIGHT CHANCE OF RAIN FOR TUESDAY. SURFACE PRESSURE GRADIENTS WILL INCREASE TUESDAY MONDAY AFTER DAYBREAK AS THE AXIS OF THE AFOREMENTIONED UPPER LEVEL SHORT WAVE MOVES EAST THE CASCADE CRESTS RESULTING IN INCREASING WINDS IN THE MORNING LEADING TO BREEZY CONDITIONS OF 15 TO 25 MPH TUESDAY AFTERNOON AND EVENING ACROSS THE LOWER COLUMBIA BASIN AND THE FOOTHILLS OF THE BLUE MOUNTAINS. AS THE SHORT WAVE EXITS THE REGION INTO IDAHO TUESDAY EVENING LOOK FOR PARTIAL CLEARING AND RAIN ENDING EARLY TUESDAY EVENING IN EASTERN OREGON AND SE WASHINGTON. THE MOUNTAINS IN SOUTHEAST WASHINGTON AND NE OREGON COULD SEE SOME LINGERING SCATTERED SHOWERS TUESDAY EVENING DUE TO OROGRAPHIC LIFT WITH SHOWERS TAPERING OFF AND ENDING OVER THE FAR EASTERN MOUNTAINS BEFORE MIDNIGHT. POLAN WEDNESDAY THROUGH THURSDAY...ZONAL WEST TO NORTHWEST FLOW IS SHOWN FOR WEDNESDAY AND THURSDAY WITH A SLIGHT CHANCE TO CHANCE OF PRECIPITATION...WITH THE HIGHEST CHANCES OVER THE MOUNTAINS. THE GFS MODEL IS A LITTLE FASTER AND STRONGER ON MOVING A LOW PRESSURE AREA ACROSS THE SOUTHERN PORTIONS OF CANADA THAN THE OTHER MODELS, SO WILL BLEND TOWARD THE SLOWER MOVEMENT AND PRECIPITATION AREAS. 93 && .AVIATION...00Z TAFS...THE COLD FRONT HAS EXITED INTO IDAHO TAKING STEADY RAIN WITH IT THUS ALLOWING FOR IMPROVING CONDITIONS THIS AFTERNOON. AS SUCH VFR CONDITIONS ARE EXPECTED OVER THE NEXT 24 HOURS. SCATTERED SHOWERS WILL LINGER OVER THE BLUE MOUNTAINS AND THE BLUE MOUNTAIN FOOTHILLS FOR ANOTHER 2-3 HOURS AND THEN TAPER OFF THIS EVENING. WIND SPEEDS WILL DECREASE THROUGH TONIGHT AND THEN INCREASE AGAIN FROM FRIDAY MID MORNING INTO FRIDAY AFTERNOON WITH SUSTAINED WINDS REACHING 10-18 KTS BY MID TO LATE AFTERNOON. POLAN && .HYDROLOGY...HEAVY RAIN HAS INCREASED RUNOFF INTO THE NORTHEAST OREGON MOUNTAINS WITH CORRESPONDING RISES EXPECTED ON THE GRANDE RONDE AND IMNAHA RIVERS WITH FLOOD WARNING FOR THOSE LOCATIONS. ALONG THE EAST SLOPES OF THE WASHINGTON CASCADES...WATER LEVELS HAVE BEEN FAIRLY STEADY BUT SOME RISES ARE EXPECTED THIS EVENING AND EARLY FRIDAY WITH FLOOD WARNINGS CONTINUING FOR NACHES NEAR NACHES AND YAKIMA RIVER NEAR PARKER. WE WILL HAVE TO KEEP AN EYE ON THE YAKIMA RIVER AT KIONA AS GUIDANCE SHOWS THIS LOCATION CRESTING JUST BELOW FLOOD STAGE. 93 && .PRELIMINARY POINT TEMPS/POPS... PDT 39 56 38 60 / 40 10 10 10 ALW 43 57 41 59 / 40 20 10 10 PSC 42 63 40 66 / 30 10 10 0 YKM 37 57 39 60 / 20 10 10 0 HRI 41 60 39 64 / 30 10 10 10 ELN 38 52 38 55 / 20 10 10 10 RDM 29 52 33 59 / 20 10 10 10 LGD 36 49 35 53 / 60 30 20 20 GCD 34 47 34 53 / 30 20 20 10 DLS 41 58 41 61 / 30 10 20 20 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...NONE. WA...NONE. && THREAT INDEX FRIDAY : GREEN SATURDAY : GREEN SUNDAY : GREEN GREEN: NONE OR LIMITED NEED FOR WATCHES, WARNINGS, OR ADVISORIES. YELLOW: A FEW WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT. RED: NUMEROUS WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT. FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT... WWW.WEATHER.GOV/PENDLETON 78/99/99/93
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PENDLETON OR
500 AM PDT THU APR 26 2012
ORZ041-042-044-049-050-502-503-505>509-WAZ024-026>030-520-521-
271145-
EASTERN COLUMBIA RIVER GORGE OF OREGON-NORTH CENTRAL OREGON-
LOWER COLUMBIA BASIN OF OREGON-GRANDE RONDE VALLEY-WALLOWA COUNTY-
NORTHERN BLUE MOUNTAINS OF OREGON-
SOUTHERN BLUE MOUNTAINS OF OREGON-JOHN DAY BASIN-OCHOCO-
JOHN DAY HIGHLANDS-
FOOTHILLS OF THE NORTHERN BLUE MOUNTAINS OF OREGON-
FOOTHILLS OF THE SOUTHERN BLUE MOUNTAINS OF OREGON-
EAST SLOPES OF THE OREGON CASCADES-
EASTERN COLUMBIA RIVER GORGE OF WASHINGTON-KITTITAS VALLEY-
YAKIMA VALLEY-LOWER COLUMBIA BASIN OF WASHINGTON-
FOOTHILLS OF THE BLUE MOUNTAINS OF WASHINGTON-
NORTHWEST BLUE MOUNTAINS OF WASHINGTON-
EAST SLOPES OF THE WASHINGTON CASCADES-SIMCOE HIGHLANDS-
500 AM PDT THU APR 26 2012
THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL AND NORTHEAST OREGON
AS WELL AS SOUTH CENTRAL AND SOUTHEAST WASHINGTON.
.DAY ONE...TODAY AND TONIGHT
FLOODING
EAST SLOPES OF THE WASHINGTON CASCADES, SIMCOE HIGHLANDS, THE
YAKIMA VALLEY, AND WALLOWA COUNTY IN OREGON.
EXCESSIVE RAINFALL AND STILL SOME SNOW MELT WILL CAUSE MINOR
FLOODING ON PORTIONS OF THE NACHES RIVER AND THE YAKIMA RIVER IN
YAKIMA COUNTY TODAY AND TONIGHT. MINOR FLOODING IS ALSO EXPECTED OR
ALREADY OCCURRING ON PORTIONS OF THE GRANDE RONDE RIVER AND THE
IMNAHA RIVER IN WALLOWA COUNTY. THESE LOCATIONS ARE IN THE LISTED
FORECAST ZONES ABOVE. PLEASE SEE NATIONAL WEATHER SERVICE RIVER
FLOOD STATEMENTS (PDXFLSPDT) FOR MORE DETAILS. THE RAINFALL WILL
CONTINUE FOR THROUGH MID DAY TODAY AND THEN WILL TAPER OFF BY LATE
THIS AFTERNOON AS A COLD FRONT PUSHES ACROSS THE REGION. IT WILL
ALSO BECOME BREEZY TO WINDY IN MOST LOCATIONS BY THIS AFTERNOON...
ESPECIALLY IN CENTRAL AND NORTH CENTRAL OREGON...THE COLUMBIA BASIN
AND THE BLUE MOUNTAIN FOOTHILLS.
.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY
FLOODING FRIDAY
EAST SLOPES OF THE WASHINGTON CASCADES, SIMCOE HIGHLANDS,
YAKIMA VALLEY, WALLOWA COUNTY.
FLOODING SATURDAY
EAST SLOPES OF THE WASHINGTON CASCADES, SIMCOE HIGHLANDS,
YAKIMA VALLEY, WALLOWA COUNTY.
THE RIVER LEVELS ARE EXPECTED TO CREST AND THEN DROP EITHER BY LATE
FRIDAY OR BY SATURDAY MORNING. ONCE THIS CURRENT WEATHER SYSTEM
MOVES TO THE EAST OF THE FORECAST AREA A COOLER AND DRIER NORTHWEST
FLOW ALOFT WILL DEVELOP. THIS WILL RESULT IN DRY CONDITIONS FOR THE
ADJACENT VALLEYS OF THE CASCADE EAST SLOPES AND IN THE LOWER
COLUMBIA BASIN DUE TO DOWN SLOPE WINDS OFF THE CASCADE EAST SLOPES.
SCATTERED RAIN OR SNOW SHOWERS WILL PERSIST OVER THE EASTERN AND
NORTHEAST MOUNTAINS DUE TO AN UP SLOPE LOW LEVEL FLOW THERE.
.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION MAY BE REQUIRED.
WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.
GRAPHICAL FORECASTS OF WEATHER HAZARDS OUT TO SEVEN DAYS
ARE DISPLAYED ON THE WORLD WIDE WEB AT:
WWW.WRH.NOAA.GOV/PDT/CURRENTHAZARDS/HWO.HTML
ALL LETTERS IN THE ABOVE URL ARE LOWER CASE.The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
The Imnaha River at Imnaha crested at 5.94 feet on April 26 at 10:30 pm. Flood stage is 5.5 feet.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2012Every state in 2012This day in weather historyWarnings in Oregon, April 2012
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: 368601.