An upper level low pressure system moved over the Pacific Northwest. Moist and unstable conditions ahead of the low triggered widespread thunderstorms with heavy rainfall and isolated large hail.
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.
An upper level low pressure system moved over the Pacific Northwest. Moist and unstable conditions ahead of the low triggered widespread thunderstorms with heavy rainfall and isolated large hail. This combined with the abundant spring snow-pack and wet ground to cause flooding. A 75 yard wide mudslide closed Highway 410 at milepost 87. As the upper low brought colder air. late season heavy snow ended the episode in the Blue Mountains. Snowfall amounts in inches included Touchet Snotel (7).
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 13, 9:20 PM PST, 2 hours 40 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1020 PM PDT FRI MAY 13 2011
UPDATED THE AVIATION DISCUSSION
.UPDATE...THE LATEST RADAR WAS SHOWING AN AREA OF SHOWERS WITH
ISOLATED TSRA MOVG INTO PORTIONS OF GRANT/UNION/WALLOWA COUNTIES.
THESE SHOWERS WILL CONTINUE MOVG NORTH INTO MAINLY THE EASTERN HALF
OF THE AREA OVERNIGHT AND THIS IS COVERED IN THE FORECAST. THE
LATEST MODELS WERE CONTINUING TO FORECAST ABUNDANT RAIN AMOUNTS IN
THE YKM/KITTITAS VALLEYS SATURDAY AND SATURDAY NIGHT WHERE FLOOD
WATCHES/WARNINGS ARE IN PLACE.
.AVIATION...VFR CONDITIONS WILL CONTINUE WITH MAINLY MID AND HIGH
CLOUDS. HOWEVER ABUNDANT MOISTURE WILL POUR INTO THE AREA AND
LOWER CEILINGS OVERNIGHT FOR ALL TAF SITES. LCL MVFR CEILINGS IN
RAIN SHOWERS AND ISOLD TSRA WILL SLOWLY BECOME AREAS OF MVFR/IFR
CEILINGS AND VSBY IN HEAVIER SHOWERS/ISOLD TSRA INTO SATURDAY
EVENING.
&&
.PREV DISCUSSION... /ISSUED 200 PM PDT FRI MAY 13 2011/
SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT...WATER VAPOR SATELLITE
IMAGERY CONTINUES TO SHOW A LARGE LOW PRESSURE SYSTEM IN THE EAST
PACIFIC WITH A TROUGH OF LOW PRESSURE ROTATING TOWARD THE WEST
COAST. THIS SYSTEM IS EXPECTED TO SINK SOUTHWARD AND CONTINUE TO
BECOME MORE NEGATIVELY TITLED (ORIENTED NORTHWEST TO SOUTHEAST) BY
SATURDAY. THIS AFTERNOON...THE ONLY CONVECTION POPPING UP IS OVER
NORTHERN NEVADA. INVERSIONS OVER THE FORECAST AREA ARE EXPECTED TO
BREAK IN THE NEXT HOUR TO TWO...AND THEREFORE SHOULD SEE MORE
CUMULUS DEVELOPMENT OVER THE NORTHEAST MOUNTAINS LATER THIS
AFTERNOON AND INTO THE EVENING HOURS. A DISTURBANCE IS FORECAST TO
MOVE THROUGH THE SOUTHERLY FLOW AND OVER THE NORTHERN PORTION OF THE
FORECAST AREA THIS EVENING AND OVERNIGHT. WITH UNSTABLE
CONDITIONS...WARM SOUTHERLY FLOW AND A POSSIBLE TRIGGER WITH THE
DISTURBANCE...THERE IS A POTENTIAL FOR THUNDERSTORM DEVELOPMENT
LATER THIS AFTERNOON AND OVERNIGHT. SHEAR VALUES ARE MODERATE OVER
THE FAR NORTHEAST PORTION OF THE FORECAST AREA...THEREFORE A FEW
STORMS MAY BECOME STRONG WITH GUSTY WINDS AND MODERATE HAIL DURING
THE LATE AFTERNOON HOURS.
FOR SATURDAY...THE REGION WILL BE UNDER A SOUTH TO SOUTHEAST FLOW
WITH MORE DISTURBANCES ROTATING AROUND THE LOW PRESSURE SYSTEM.
MODELS CONTINUE TO SHOW VERY UNSTABLE CONDITIONS ACROSS NORTHEAST
OREGON AND EXTREME SOUTHEAST WASHINGTON. THUNDERSTORMS COULD
POTENTIALLY DEVELOP ANYWHERE ACROSS THE FORECAST AREA BY THE
AFTERNOON AND EVENING HOURS...THOUGH THE STRONGEST STORMS ARE
EXPECTED TO BE IN NORTHEAST OREGON AND EXTREME SOUTHEAST WASHINGTON.
HAVE INCLUDED SMALL HAIL AND GUSTY WINDS INTO THE FORECAST FOR THE
AREAS MORE LIKELY TO SEE THE STRONGEST STORMS...THOUGH MODERATE
SIZED HAIL COULD ALSO BE A POTENTIAL. THE OTHER FORECAST CONCERN IS
HEAVY RAIN WITH THIS SYSTEM. A DEFORMATION BAND WILL FORM ACROSS THE
CENTRAL PART OF THE AREA FROM GRANT COUNTY NORTH AND WEST TO THE
EAST SLOPES OF THE CENTRAL CASCADES. WHEREVER THIS BAND SETS
UP...LOCATIONS WILL SEE VERY HEAVY RAIN WITH THUNDERSTORMS DURING
THE AFTERNOON AND THEN SEE A MORE STRATIFIED HEAVY RAIN BY THE
EVENING AND OVERNIGHT TIME PERIOD. THIS BAND WILL BE SLOW TO MOVE
NORTH AND EAST INTO SUNDAY MORNING. HAVE ISSUED AN AREAL FLOOD WATCH
FOR THE AREAS THE BAND IS EXPECTED TO DEVELOP. THE ONE LOCATION THAT
THE MODELS HAVE CONSISTENTLY SHOWN HEAVY RAIN FOR IS THE EAST SLOPES
OF THE WASHINGTON CASCADES. AN AREAL FLOOD WARNING HAS BEEN ISSUED
FOR THIS LOCATION THROUGH SUNDAY AFTERNOON. THERE ARE ALSO FLOOD
WATCHES FOR RIVER FORECAST POINTS ON THE JOHN DAY RIVER...IMNAHA
RIVER...GRANDE RONDE RIVER AND NACHES RIVERS. WOULD NOT BE SURPRISED
TO SEE MORE AREAL FLOOD WARNINGS ISSUED TOMORROW MORNING WHEN THE
DEFORMATION BAND SETS UP AND THERE IS A BETTER FEEL FOR ITS LOCATION.
THE LOW PRESSURE SYSTEM WILL CONTINUE TO ROTATE OFF THE OREGON AND
WASHINGTON COAST ON SUNDAY WITH CONVECTIVE SHOWERS CONTINUING OVER
THE FORECAST AREA. THE THUNDERSTORM POTENTIAL WILL BE LESS ON
SUNDAY...BUT LOCATIONS THAT SEE DAYTIME HEATING MAY HELP AID IN
DESTABILIZING THE ATMOSPHERE AND LEADING TO A SLIGHT CHANCE OF
THUNDERSTORMS IN THE AFTERNOON HOURS. OTHERWISE...LOCATIONS MAY SEE
EITHER THICK CLOUD COVER OR HAVE BEEN RAIN COOLED BY THE
PRECIPITATION FROM THE DEFORMATION BAND. DMH
LONG TERM...MONDAY THROUGH WEDNESDAY NIGHT...AREA WILL BE DOMINATED
BY A BROAD UPPER LEVEL TROUGH THROUGH MUCH OF THE PERIOD. THIS WILL
KEEP UNSETTLED WEATHER CONDITIONS AND A CHANCE FOR SHOWERS INTO
WEDNESDAY. WITH COLD AIR ALOFT UNDERNEATH THE TROUGH THERE WILL BE
SOME POTENTIAL FOR THUNDERSTORMS AT LEAST MONDAY AND TUESDAY
AFTERNOON ESPECIALLY EASTERN MOUNTAINS AND HAVE INCLUDED A SLGT CHC
TSTMS BOTH DAYS. AS THE TROUGH BEGINS TO PULL OFF TO THE EAST LATE
WEDNESDAY AND WEDNESDAY NIGHT PRECIPITATION CHANCES WILL DECREASE.
TEMPERATURES THROUGH THE PERIOD WILL BE A LITTLE ON THE COOL SIDE
FOR THIS TIME OF YEAR AND WINDS SHOULD NOT BE OF SIGNIFICANT
CONCERN. 78
THURSDAY THROUGH FRIDAY NIGHT...CURRENT MODELS INDICATE A BRIEF
UPPER LEVEL RIDGE TO BUILD OVER THE AREA FOR THURSDAY. WENT AHEAD
AND BACKED OFF ON POPS FOR THURSDAY...BUT COULD NOT COMPLETELY DRY
OUT THE AREA. IF MODELS ARE ON TRACK EXPECT THURSDAY TO BE MOSTLY
DRY AND NEAR NORMAL FOR TEMPERATURES. A WEAK DISTURBANCE LOOKS TO
MOVE ACROSS THE AREA FRIDAY PROVIDING ANOTHER CHANCE FOR RAIN
EVERYWHERE. WEBER
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 53 73 50 59 / 40 70 80 80
ALW 57 74 54 63 / 40 70 90 90
PSC 55 77 55 65 / 40 70 90 80
YKM 49 73 50 64 / 40 90 90 90
HRI 52 75 52 64 / 40 70 80 70
ELN 50 73 49 59 / 40 90 90 90
RDM 41 69 39 54 / 30 60 80 60
LGD 53 73 48 56 / 40 70 70 80
GCD 49 73 47 55 / 50 70 80 70
DLS 53 70 52 61 / 30 70 80 70
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...FLOOD WATCH FROM SATURDAY MORNING THROUGH SUNDAY MORNING
ORZ041-042-503-505-506-508.
WA...FLOOD WATCH FROM SATURDAY MORNING THROUGH SUNDAY MORNING
WAZ024-026-027-521.
&&
THREAT INDEX
SATURDAY : RED
SUNDAY : YELLOW
MONDAY : 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
97/HAZARDOUS WEATHER OUTLOOK...UPDATE
NATIONAL WEATHER SERVICE PENDLETON OR
215 PM PDT FRI MAY 13 2011
UPDATED FOR FLOOD WARNING WASHINGTON ZONE 512
ORZ041-042-044-049-050-502-503-505>509-WAZ024-026>030-520-521-
141415-
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-
215 PM PDT FRI MAY 13 2011
THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL AND NORTHEAST OREGON
AS WELL AS SOUTH CENTRAL AND SOUTHEAST WASHINGTON.
.DAY ONE...TODAY AND TONIGHT
THUNDERSTORMS
LOWER COLUMBIA BASIN OF WASHINGTON, FOOTHILLS OF THE BLUE
MOUNTAINS OF WASHINGTON, NORTHWEST BLUE MOUNTAINS OF
WASHINGTON, GRANDE RONDE VALLEY, WALLOWA COUNTY, FOOTHILLS OF
THE NORTHERN BLUE MOUNTAINS OF OREGON, NORTHERN BLUE MOUNTAINS
OF OREGON, SOUTHERN BLUE MOUNTAINS OF OREGON, JOHN DAY BASIN,
OCHOCO-JOHN DAY HIGHLANDS
AN UPPER LOW OVER THE SOUTHERN GULF OF ALASKA WILL SHIFT SOUTH TO A
POSITION WEST OF THE PACIFIC NORTHWEST TODAY AND TONIGHT. THIS LOW
WILL CAUSE A MOIST...SOUTHERLY FLOW PATTERN TO SET UP OVER THE AREA
TODAY. AS SUCH INCREASING CHANCES OF SHOWERS AND THUNDERSTORMS CAN
BE EXPECTED TODAY AND TONIGHT. ISOLATED THUNDERSTORMS WILL START
OVER FAR EASTERN OREGON TOWARDS MID AFTERNOON. THE THUNDERSTORMS
SHOULD THEN SPREAD NORTH AND NORTH-NORTHWEST THIS EVENING AND
TONIGHT. SOME OF THESE THUNDERSTORMS MAY BECOME STRONG ACROSS
PORTIONS OF NORTHEAST OREGON. MEANWHILE ISOLATED TO SCATTERED
SHOWERS WILL SPREAD TO A GOOD PORTION OF EASTERN OREGON AND EASTERN
WASHINGTON TONIGHT.
.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY
FLOODING SATURDAY
EAST SLOPES OF THE WASHINGTON CASCADES, SIMCOE HIGHLANDS,
EASTERN COLUMBIA RIVER GORGE OF WASHINGTON, KITTITAS VALLEY,
YAKIMA VALLEY, EASTERN COLUMBIA RIVER GORGE OF OREGON, NORTH
CENTRAL OREGON, SOUTHERN BLUE MOUNTAINS OF OREGON, FOOTHILLS
OF THE SOUTHERN BLUE MOUNTAINS OF OREGON, JOHN DAY BASIN,
OCHOCO-JOHN DAY HIGHLANDS
THUNDERSTORMS SATURDAY
EAST SLOPES OF THE OREGON CASCADES
STRONG THUNDERSTORMS SATURDAY
LOWER COLUMBIA BASIN OF WASHINGTON, FOOTHILLS OF THE BLUE
MOUNTAINS OF WASHINGTON, NORTHWEST BLUE MOUNTAINS OF
WASHINGTON, LOWER COLUMBIA BASIN OF OREGON, GRANDE RONDE
VALLEY, WALLOWA COUNTY, FOOTHILLS OF THE NORTHERN BLUE
MOUNTAINS OF OREGON, NORTHERN BLUE MOUNTAINS OF OREGON
FLOODING SUNDAY
EAST SLOPES OF THE WASHINGTON CASCADES, SIMCOE HIGHLANDS,
EASTERN COLUMBIA RIVER GORGE OF WASHINGTON, KITTITAS VALLEY,
YAKIMA VALLEY, EASTERN COLUMBIA RIVER GORGE OF OREGON, NORTH
CENTRAL OREGON, SOUTHERN BLUE MOUNTAINS OF OREGON, FOOTHILLS
OF THE SOUTHERN BLUE MOUNTAINS OF OREGON, JOHN DAY BASIN,
OCHOCO-JOHN DAY HIGHLANDS
THUNDERSTORMS SUNDAY
NORTHWEST BLUE MOUNTAINS OF WASHINGTON, EAST SLOPES OF THE
OREGON CASCADES, GRANDE RONDE VALLEY, WALLOWA COUNTY, NORTHERN
BLUE MOUNTAINS OF OREGON
THE REGION WILL REMAIN UNDER THE MOIST...UNSTABLE SOUTH FLOW THROUGH
THE WEEKEND. A STRONGER DISTURBANCE EMBEDDED WITH THE FLOW WILL
BRING EVEN BETTER CHANCES OF SHOWERS AND THUNDERSTORMS ON SATURDAY
AND SATURDAY NIGHT. STRONG STORMS ARE POSSIBLE MAINLY ACROSS
NORTHEAST OREGON AND SOUTHEAST WASHINGTON ON SATURDAY WITH THE
POTENTIAL FOR HEAVY RAIN...LARGE HAIL AND DAMAGING WINDS. THE UPPER
LOW RESPONSIBLE FOR THE UNSTABLE SOUTHERLY FLOW MAY SHIFT ONSHORE
MONDAY...AND INLAND ON TUESDAY. AS THIS SYSTEM MOVES INLAND...
CHANCES FOR SHOWERS AND THUNDERSTORMS SHOULD PERSIST INTO WEDNESDAY.
WEAK UPPER RIDGING MAY BRING RELATIVELY DRIER CONDITIONS TO THE
REGION THURSDAY.
HEAVY RAIN SATURDAY INTO SUNDAY WILL LEAD TO RISES ON AREA RIVERS.
FLOOD WATCHES ARE IN EFFECT FOR THESE LOCATIONS. ALSO FLASH FLOODING
CAN NOT BE RULED OUT WITH STRONG THUNDERSTORM POTENTIAL. PLEASE
REFER TO PRODUCTS PDXFLWPDT AND PDXFFAPDT FOR MORE DETAILS.
.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.The Seattle radar (KATX), 196 km away, was scanning. The volume nearest the first event began at 07:58 UTC.
4 flood, 2 thunderstorm wind, 1 lightning, 1 debris flow. Local standard time, as filed.
Lightning started a roof fire which damaged a few other rooms of a residence.
Microburst like wind gust blew trampoline over and kicked up several pieces of debris. Several tree limbs 1 to 3 inches in diameter have fallen.
Flood waters damaged or closed 22 roads along Manastash, Taneum, Cooke, Coleman, Wilson, and Caribou Creeks. Bridges and irrigation systems were also impacted.
Flooding closed sections of Highway 410 and other roads along the Naches River from Cliffdell to Yakima. High water and large debris damaged bridges. The Naches River crested at 20.4 on May 15th, which was 3.4 feet above flood stage. At Cliffdell, the river crested at 32.2 feet on May 15th, which was 1.3 feet above normal.
The Yakima River at Umtanum crested at 36.5 feet on May 16th, which was 1 foot above flood stage. At Parker the crest was 13.2 feet on May 16th, which was 3.2 feet above flood stage. Reported rainfall amounts on May 14-15 were between 3 and 4 inches.
The Yakima River at Kiona crested at 15.5 feet on May 18th, which was 2.5 feet above flood stage. The flooding damaged several businesses in Prosser and farmland, roads, businesses, and residential areas from Prosser to Richland, including the Beach RV Park in Benton City and the West Richland Golf Course.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Washington in 2011Every state in 2011This day in weather historyWarnings in Washington, May 2011
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: 312868, 312814, 312816, 312855, 312845, 312873, 312836, 312828.