An upper level low pressure area over the Columbia Basin combined with daytime heating produced late afternoon and evening severe thunderstorms with heavy rainfall across northeast Oregon.
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 area over the Columbia Basin combined with daytime heating produced late afternoon and evening severe thunderstorms with heavy rainfall across northeast Oregon.
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 Aug 29, 2:52 PM PST, 2 hours earlier.
AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PENDLETON OR 352 PM PDT SAT AUG 29 2009 UPDATED AVIATION DISCUSSION .SHORT TERM...TONIGHT THROUGH MONDAY NIGHT...AN UPPER LOW PRESSURE SYSTEM IS CURRENTLY LOCATED OVER THE COLUMBIA BASIN. THIS LOW IS EXPECTED TO MOVE SOUTHEAST ACROSS THE REGION AND INTO IDAHO BY MONDAY. RADAR IMAGERY IS SHOWING SOME RETURNS ACROSS WESTERN YAKIMA COUNTY THOUGH NO LIGHTNING STRIKES HAVE BEEN DETECTED YET. CUMULUS HAVE BEEN DEVELOPING ACROSS THE HIGHER TERRAIN IN CENTRAL OREGON UP THROUGH WALLOWA COUNTY. EXPECT FURTHER CUMULUS AND THUNDERSTORM DEVELOPMENT TO BE MORE FOCUSED FROM GRANT COUNTY NORTHWARD ALONG THE BLUE MOUNTAINS AND EAST INTO WALLOWA COUNTY. ISOLATED SHOWERS AND THUNDERSTORMS CANNOT BE RULED OUT FOR THE COLUMBIA BASIN WESTWARD TOWARD THE CASCADES DUE TO THE UNSTABLE AIR WITH THE LOW PRESSURE SYSTEM. LIFT FROM THE LOW AND SOME WIND SHEAR COULD POTENTIALLY HELP THUNDERSTORMS BECOME STRONG THIS EVENING FROM GRANT COUNTY NORTH AND EASTWARD INTO WALLOWA COUNTY. CENTRAL OREGON SHOULD REMAIN OUT OF THE THUNDERSTORM THREAT AS A WESTERLY TO NORTHWEST FLOW BRINGS MORE STABLE AIR ACROSS THE CASCADES. AS THE LOW MOVES FURTHER EAST ON SUNDAY...WRAP AROUND MOISTURE WILL LEAD TO A CONTINUED THREAT OF SHOWERS AND THUNDERSTORMS IN THE BLUE MOUNTAINS EASTWARD. THE THREAT OF SHOWERS AND THUNDERSTORMS WILL THEN TAPER OFF ON MONDAY AS THE SYSTEM MOVES OUT OF THE REGION. TEMPERATURES WILL BEGIN TO WARM ON MONDAY AS THE FLOW TURNS TO THE SOUTHWEST. DMH .LONG TERM...TUESDAY THROUGH SATURDAY...THERE IS DECENT AGREEMENT IN THE MID RANGE MODELS CONCERNING THE PATTERN FOR TUESDAY. EXPECT TO SEE A LARGE LOW PRESSURE SYSTEM CENTERED ROUGHLY AROUND 45N/138W. THIS WOULD BUILD AN UPPER RIDGE OVER THE WESTERN U.S. WITH AN AXIS EXTENDING NORTH INTO IDAHO AND WESTERN MONTANA. THIS WOULD PUT THE PACIFIC NORTHWEST UNDER A SOUTHERLY UPPER LEVEL FLOW. THUS WILL CONTINUE TO INDICATE ABOVE SEASONAL TEMPS FOR TUESDAY. THERE LOOKS TO BE ENOUGH LOW LEVEL CONVERGENCE ALONG THE CASCADE CREST TUESDAY AFTERNOON AND EVENING TO CREATE INSTABILITY FOR STRAY THUNDERSTORMS. WITH THE SOUTHERLY FLOW...THESE STORMS WILL STAY NEAR THE CREST. WILL THEREFORE INTRODUCE A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS TO THE IMMEDIATE CASCADE CREST AREA. FORECAST UNCERTAINTY INCREASES A FAIR BIT FROM WEDNESDAY ONWARD...THOUGH THE OVERARCHING TREND IS TO HAVE THE UPPER LOW FILL AND GRADUALLY SWING ONSHORE...THEN TO BE FOLLOWED BY A SECONDARY LOW OR TROUGH SATURDAY. THERE ARE SIGNIFICANT DIFFERENCES IN THE SPEED OF ARRIVAL AND THE DEPTH OF THESE SYSTEMS THOUGH. DESPITE THE DIFFERENCES IN THE SPECIFICS...THE RETURN OF A TROUGHY PATTERN WOULD MEAN UNSETTLED AND COOLER CONDITIONS FOR THE PACIFIC NORTHWEST. AS A RESULT HAVE INTRODUCED SLIGHT CHANCES OF SHOWERS AND THUNDERSTORMS TO PORTIONS OF OUR AREA FROM WEDNESDAY AFTERNOON ONWARD. THE BEST CHANCES OF THUNDER SHOULD BE AFTERNOONS AND EVENINGS ON WEDNESDAY AND THURSDAY AHEAD OF THE APPROACHING UPPER TROUGHINESS. 90 && .AVIATION...00Z TAFS...VFR CIGS/VIS ARE EXPECTED AT ALL TAF SITES THROUGH THE NEXT 24 HOURS. SCT-BKN CLOUDS BETWEEN 7000 AND 12000 FT AGL WITH ISOLATED TO SCATTERED SHOWERS SHOULD AFFECT KPDT...KALW AND KPSC AT SOME POINT BETWEEN 30/03 UTC AND 30/18 UTC. KYKM...KDLS AND KRDM SHOULD SEE SCT CLOUDS EARLY THIS EVENING AT THE MOST. SUSTAINED SUSTAINED WINDS WILL RUN 5-15 KTS THROUGH THE PERIOD...EXCEPT FOR 10-20 KTS SUSTAINED AT KDLS AND KRDM THIS EVENING. 90 && .PRELIMINARY POINT TEMPS/POPS... PDT 56 84 58 90 / 40 30 20 10 ALW 59 86 61 91 / 40 30 20 10 PSC 58 89 60 93 / 30 10 10 10 YKM 56 89 58 90 / 30 10 10 10 HRI 55 87 58 92 / 30 10 10 10 ELN 55 89 58 90 / 30 10 10 10 RDM 43 84 46 88 / 10 10 10 10 LGD 52 79 51 83 / 50 40 40 30 GCD 47 78 51 87 / 30 40 20 20 DLS 56 87 57 88 / 20 10 10 10 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...NONE. WA...NONE. && THREAT INDEX SUNDAY : GREEN MONDAY : GREEN TUESDAY : 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 84/90/90
HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
830 AM PDT SAT AUG 29 2009
UPDATED TODAY DISCUSSION
ORZ041>044-049-050-501>506-WAZ024-026>030-501-502-301215-
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-
530 AM PDT SAT AUG 29 2009
THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL AND NORTHEAST OREGON
AS WELL AS SOUTH CENTRAL AND SOUTHEAST WASHINGTON.
.DAY ONE...TODAY AND TONIGHT
THUNDERSTORMS
EAST SLOPES OF THE CENTRAL CASCADES OF WASHINGTON, EAST SLOPES
OF THE SOUTHERN CASCADES OF WASHINGTON, 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, EASTERN COLUMBIA
RIVER GORGE OF OREGON, NORTH 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
A STRONG PACIFIC WEATHER SYSTEM WILL MOVE INTO HE PACIFIC NORTHWEST
TODAY. THE INITIAL COLD FRONT WITH THIS SYSTEM IS CURRENTLY MOVING
ACROSS NORTHEAST OREGON AND SOUTHEAST WASHINGTON AND IS PUSHING INTO
WARMER AND UNSTABLE AIR AHEAD OF THE SYSTEM. THIS IS RESULTING IN
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS THIS MORNING. THE
COLD FRONT AND ASSOCIATED THUNDERSTORMS WILL MOVE OUT OF THE AREA BY
LATE THIS MORNING. THERE WILL BE A BREAK WITH SOME SURFACE SOLAR
HEATING TAKING PLACE LATE THIS MORNING THROUGH EARLY THIS AFTERNOON.
THIS WILL SET THE STAGE FOR ADDITIONAL SHOWERS AND AFTERNOON/EVENING
THUNDERSTORMS...AS A SOUTHERLY FLOW AHEAD OF THE LOW PRESSURE SYSTEM
BRINGS MORE INSTABILITY AND MOISTURE INTO THE AREA. THUNDERSTORMS
WILL LIKELY PERSIST THROUGH THIS EVENING.
.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY
THUNDERSTORMS SUNDAY
NORTHWEST BLUE MOUNTAINS, GRANDE RONDE VALLEY, WALLOWA COUNTY,
NORTHERN BLUE MOUNTAINS OF OREGON, SOUTHERN BLUE MOUNTAINS OF
OREGON, JOHN DAY BASIN, OCHOCO-JOHN DAY HIGHLANDS
SURFACE HEATING COMBINED WITH AFTERNOON INSTABILITY AND MOISTURE
WILL ONCE AGAIN BRING A THREAT OF ISOLATED TO SCATTERED
THUNDERSTORMS TO THE NORTHEAST OREGON AND SOUTHEAST WASHINGTON
MOUNTAINS ON SUNDAY. BY SUNDAY NIGHT THE WEATHER SYSTEM MOVING INTO
THE REGION TODAY WILL MOVE TO THE EAST AND THEN SLOW DOWN. MOISTURE
WILL WRAP AROUND THE BACK SIDE OF THE LOW PRESSURE SYSTEM BRINGING A
POSSIBILITY OF MORE STEADY STRATIFORM PRECIPITATION SUNDAY NIGHT
INTO MONDAY. DRIER AND MORE STABLE CONDITIONS WILL THEN ARRIVE ON
TUESDAY.
.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION MAY BE REQUIRED FOR THUNDERSTORMS TODAY AND
TOMORROW.
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 Pendleton radar (KPDT), 126 km away, was scanning. The volume nearest the first event began at 00:53 UTC.
2 hail, 2 heavy rain. Local standard time, as filed.
Spotter reported the ground was white with hail and small branches were knocked down.
Rainfall of 1.1 inches was measured in 20 minutes.
In additon, heavy rain fell for almost 1 hour.
Rainfall of 1.5 inches was observed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2009Every state in 2009This day in weather historyWarnings in Oregon, August 2009
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: 194172, 194173, 194174, 194175.