Unseasonably warm temperatures and above normal snowpack caused heavy snowmelt and was followed by heavy rainfall which led to minor flooding near Imnaha.
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.
Unseasonably warm temperatures and above normal snowpack caused heavy snowmelt and was followed by heavy rainfall which led to minor flooding near Imnaha.
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 May 18, 1:45 AM PST, 30 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PENDLETON OR 245 AM PDT SUN MAY 18 2008 .SHORT TERM...TODAY THROUGH MONDAY NIGHT...THE UPPER HIGH PRESSURE SYSTEM THAT HAS BEEN OVER THE REGION THE PAST SEVERAL DAYS HAS WEAKEND AS A PASSING WEATHER DISTURBANCE MOVED INTO IT LAST NIGHT AND EARLY THIS MORNING. THE RIDGE IS EXPECTED TO CONTINUE WEAKENING TODAY...AND THEN WILL REBUILD VERY SLIGHTLY ON MONDAY BEFORE A STRONGER COLD FRONT AND UPPER TROUGH APPROACH THE COAST FROM OFF THE PACIFIC MONDAY NIGHT AND TUESDAY. THIS STRONGER SYSTEM WILL HAVE SIGNIFICANTLY COOLER TEMPERATURES AND INCREASED MOISTURE. THERE WILL BE A LAG IN ANY TEMPERATURE DROPS AT THE SURFACE UP TO 850 MB TODAY AND MONDAY. THEREFORE...THE VERY WARM CONDITIONS WILL BE WITH US FOR 1 OR 2 MORE DAYS...THOUGH NOT NEARLY AS HOT AS ON SATURDAY...WITH MAXIMUM TEMPERATURE READINGS TODAY BEING AROUND 10 DEGREES LOWER THAN SATURDAY...AND THEN ANOTHER 4 TO 6 DEGREES COOLER ON MONDAY. THIS WILL ESPECIALLY BE TRUE IN WESTERN AREAS OF THE CWA WHERE THE COOLER MARINE AIR WILL FILTER INTO THE CWA THE SOONEST. THE DISTURBANCE PASSING THROUGH THE REGION AT THIS TIME IS ONLY PRODUCING SOME MID AND HIGH CLOUDS. HOWEVER THE STRONGER SYSTEM EXPECTED MONDAY NIGHT AND TUESDAY WILL BRING MUCH COOLER TEMPERATURES AND MUCH GREATER AMOUNTS OF MOISTURE WITH IT. AS SUCH THERE WILL BE AN INCREASING CHANCE OF SHOWERS MONDAY NIGHT THROUGH TUESDAY WITH TEMEPRATURES FALLING BACK TO NEAR OR BELOW NORMAL AGAIN. IN ADDITION TIGHTER SURFACE PRESSURE AND TEMPERATURE GRADIENTS WILL RESULT IN BREEZY TO WINDY CONDITIONS...ESPECIALLY IN THE LOWER COLUMBIA BASIN AND ALONG THE EAST SLOPES OF THE CASCADES AND IN THE EASTERN COLUMBIA RIVER GORGE. THE COOLER AND SHOWERY CONDITIONS WILL THEN PERSIST INTO THE EXTENDED RANGE FORECAST. 88 .LONG TERM...WEDNESDAY THROUGH SATURDAY NIGHT...A HIGHLY AMPLIFIED TROUGH WILL FORM OVER THE WESTERN U.S. ON WEDNESDAY. THIS TROUGH WILL BRING A SERIES OF DISTURBANCES THROUGH THE REGION. HOWEVER...DUE TO RAINSHADOWING AND A LACK OF MOISTURE...SIGNIFICANT PRECIPITATION IS NOT EXPECTED IN EITHER THE LOWER COLUMBIA BASIN OR CENTRAL OREGON. YET THE MOUNTAINS OF EASTERN OREGON AND SOUTHEAST WASHINGTON WILL LIKELY SEE ISOLATED TO SCATTERED SHOWERS THROUGHOUT THE PERIOD AS NORTHWESTERLY FLOW ALOFT FUELS OROGRAPHIC LIFT. ALSO IN ASSOCIATION WITH THIS DEEP TROUGH...TIGHT PRESSURE GRADIENTS WILL CAUSE BREEZY WINDS ON WEDNESDAY AND THURSDAY WHILE TEMPERATURES WILL REMAIN AT OR BELOW NORMAL THROUGH THE WEEKEND. CALDER && .AVIATION...VFR CONDITIONS EXPECTED FOR THE NEXT 24 HOURS WITH MOSTLY CLEAR SKIES. HOWEVER...FEW TO BROKEN MID AND HIGH LEVEL CLOUDS CAN BE EXPECTED. SURFACE WINDS WILL INCREASE FROM LESS THAN 15 KTS TO 10-20 KTS WITH HIGHER GUSTS BY AFTERNOON. WINDS WILL THEN DECREASE AGAIN AFTER SUNSET. 82 && .HYDROLOGY...RAPID SNOWMELT RUNOFF WILL KEEP RIVERS AND STREAMS ACROSS THE FORECAST AREA RUNNING HIGH TODAY...THOUGH THE SNOW MELT WILL NOT BE AS GREAT AS THE LAST COUPLE DAYS DUE TO COOLER TEMPERATURES. CURRENT FLOOD WATCHES AND WARNINGS WILL REMAIN IN PLACE THROUGH THE REMAINDER OF THE WEEKEND INTO THE EARLY AND MIDDLE PART OF THIS COMING WEEK. MANY OTHER RIVERS AND STREAMS WILL APPROACH BANKFULL LEVELS BUT ARE NOT EXPECTED TO REACH FLOOD STAGE. THE CURRENT FLOOD WARNINGS INCLUDE THE NACHES RIVER AT CLIFFDELL AND NACHES...AND THE IMNAHA RIVER AT IMNAHA. FLOOD WATCHES WILL REMAIN IN EFFECT FOR THE YAKIMA RIVER FROM PARKER TO KIONA...AND ALSO THE GRANDE RONDE RIVER AT TROY. 88 && .PRELIMINARY POINT TEMPS/POPS... PDT 88 55 84 54 / 0 0 0 10 ALW 88 58 84 57 / 0 0 0 10 PSC 91 57 87 56 / 0 0 0 10 YKM 88 56 84 55 / 0 0 0 20 HRI 90 56 86 55 / 0 0 0 10 ELN 83 53 79 52 / 0 0 0 20 RDM 87 47 83 46 / 0 0 0 10 LGD 85 53 81 52 / 0 0 0 10 GCD 88 52 84 51 / 0 0 0 10 DLS 85 54 81 53 / 0 0 0 20 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...NONE. WA...NONE. && TI:YYG FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT... WWW.WEATHER.GOV/PENDLETON 88/82/82
HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
131 PM PDT SAT MAY 17 2008
UPDATED TO REMOVE FLOOD WATCHES
ORZ041>044-049-050-501>506-WAZ024-026>030-501-502-181415-
EASTERN COLUMBIA RIVER GORGE OF OREGON-NORTH CENTRAL OREGON-
CENTRAL OREGON-LOWER COLUMBIA BASIN OF OREGON-GRANDE RONDE VALLEY-
WALLOWA COUNTY-FOOTHILLS OF THE BLUE MOUNTAINS OF OREGON-
NORTHERN BLUE MOUNTAINS OF OREGON-
SOUTHERN BLUE MOUNTAINS OF OREGON-
NORTHERN WHEELER AND SOUTHERN GILLIAM COUNTIES-JOHN DAY BASIN-
OCHOCO-JOHN DAY HIGHLANDS-
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-
EAST SLOPES OF THE CENTRAL CASCADES OF WASHINGTON-
EAST SLOPES OF THE SOUTHERN CASCADES OF WASHINGTON-
131 PM PDT SAT MAY 17 2008
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 CENTRAL CASCADES OF WASHINGTON, KITTITAS
VALLEY, YAKIMA VALLEY, LOWER COLUMBIA BASIN OF WASHINGTON,
WALLOWA COUNTY
VERY WARM TEMPERATURES WILL CONTINUE TODAY WITH RAPID SNOW MELT
RUNOFF FROM THE HIGHER ELEVATIONS. THIS WILL CONTINUE TO CAUSE
SIGNIFICANT RISES IN RIVERS AND STREAMS THROUGHOUT THE AREA.
FLOODING AND/OR BANKFULL LEVELS WILL BE REACHED OR EXCEEDED ON SOME
RIVERS THAT ARE MOST PRONE TO FLOODING.
CURRENTLY A FLOOD WARNING REMAINS IN EFFECT FOR THE NACHES RIVER
FROM CLIFFDELL DOWNSTREAM TO NACHES. THE RIVER IS FORECAST TO RISE
AND/OR REMAIN ABOVE FLOOD STAGE TODAY AND TONIGHT AND THREATEN
NEARBY AREAS. THE FLOODING IS EXPECTED TO CONTINUE THROUGH MUCH OF
NEXT WEEK. FOR MORE DETAILED INFORMATION ON FLOODING IN THIS
AREA...PLEASE REFER TO THE NWS PRODUCT PDXFLSPDT WGUS86 KPDT.
A FLOOD WARNING ALSO REMAINS IN EFFECT FOR THE IMNAHA RIVER AT
IMNAHA FROM TODAY THROUGH FRIDAY...WITH MINOR FLOODING POSSIBLE
ALONG THE IMNAHA RIVER NEAR THE TOWN OF IMNAHA. PLEASE REFER TO THE
NWS PRODUCT PDXFLSPDT WGUS46 KPDT FOR MORE DETAILS.
.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY
FLOODING SUNDAY
EAST SLOPES OF THE CENTRAL CASCADES OF WASHINGTON, KITTITAS
VALLEY, YAKIMA VALLEY, LOWER COLUMBIA BASIN OF WASHINGTON,
WALLOWA COUNTY
FLOODING MONDAY
EAST SLOPES OF THE CENTRAL CASCADES OF WASHINGTON, KITTITAS
VALLEY, YAKIMA VALLEY, LOWER COLUMBIA BASIN OF WASHINGTON,
WALLOWA COUNTY
FLOODING TUESDAY
EAST SLOPES OF THE CENTRAL CASCADES OF WASHINGTON, YAKIMA
VALLEY, WALLOWA COUNTY
FLOODING WEDNESDAY
EAST SLOPES OF THE CENTRAL CASCADES OF WASHINGTON, YAKIMA
VALLEY, WALLOWA COUNTY
FLOODING THURSDAY
EAST SLOPES OF THE CENTRAL CASCADES OF WASHINGTON, YAKIMA
VALLEY, WALLOWA COUNTY
FLOODING FRIDAY
EAST SLOPES OF THE CENTRAL CASCADES OF WASHINGTON, YAKIMA
VALLEY, WALLOWA COUNTY
THE FLOOD WARNING FOR THE NACHES RIVER FROM CLIFFDELL DOWNSTREAM TO
THE NORTH END OF THE YAKIMA IS IN EFFECT UNTIL FRIDAY MAY 23. THE
FLOOD WARNING FOR THE IMNAHA RIVER AT THE TOWN OF IMNAHA IS ALSO IN
EFFECT FROM TODAY UNTIL NEXT FRIDAY MAY 23. FOR MORE DETAILED
INFORMATION ON FLOODING OF THESE RIVERS PLEASE REFER TO THE NWS
PRODUCT PDXFLSPDT WGUS86 KPDT.
A FLOOD WATCH REMAINS IN EFFECT FOR THE YAKIMA RIVER FROM PARKER TO
NEAR KIONA THROUGH TUESDAY. PLEASE REFER TO THE NWS PRODUCT
PDXFFAPDT WGUS66 KPDT FOR MORE DETAILS.
THE UNSEASONABLE VERY WARM TEMPERATURES WILL CONTINUE THROUGH MONDAY
WITH RAPID SNOWMELT RUNOFF CONTINUING. A COLD FRONT WITH COOLER
TEMPERATURES AND A CHANCE OF SHOWERS WILL THEN MOVE ACROSS THE
REGION ON TUESDAY WITH THE COOLER TEMPERATURES AND A CHANCE OF
SHOWERS CONTINUING THROUGH THE REST OF THE WEEK.
.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION WILL BE LIKELY.
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...EXCEPT THE H IN
CURRENTHAZARDS.The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
The Imnaha River gage crested several times above flood stage with a peak of 6.26 on May 19.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2008Every state in 2008This day in weather historyWarnings in Oregon, May 2008
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: 102582.