An upper level low pressure area combined with daytime heating and an unstable atmosphere produced showers and thunderstorms.
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 combined with daytime heating and an unstable atmosphere produced showers and thunderstorms.
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 28, 1:30 PM PST, 2 hours 45 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PENDLETON OR 230 PM PDT FRI MAY 28 2010 .SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT...LATEST SATELLITE IMAGERY SHOWS A WAVE ROTATING AROUND A LARGE UPPER TROUGH OVER THE PACIFIC NORTHWEST ALONG THE WASHINGTON/OREGON COAST NEAR THE MOUTH OF THE COLUMBIA RIVER. THIS WAVE OF ENERGY IS MOVING TO THE S-SE. MEAN WHILE ANOTHER WAVE IS TRYING TO SPIN UP THE EAST SIDE OF THE UPPER LOW ALONG THE SE OREGON/SW IDAHO BORDER. THE FIRST WAVE IS WHAT IS PRODUCING THE SHOWERS OVER THE CWA AT THE CURRENT TIME. THE LATEST SHORT RANGE MODELS...ESPECIALLY THE GFS...SHOWS THE NORTHERN SYSTEM VORTICITY MAXIMUM (AREA OF GREATEST SPIN AND DYNAMIC LIFT) TO SLIDE SE OVER THE NORTH AND NORTHEAST PORTIONS OF THE FORECAST AREA TONIGHT AND SATURDAY WHILE THE AREA OF ENERGY OVER SE OREGON ROTATES UP NORTHEASTWARD INTO IDAHO AND WESTERN MONTANA AND MISSING THE FORECAST AREA. IN EITHER CASE CAN EXPECT AT LEAST SCATTERED SHOWERS TO CONTINUE THROUGH TONIGHT AS THE NORTHERN WAVE CROSSES THE CWA. AT THIS TIME AM NOT EXPECTING MUCH IN THE WAY OF RAINFALL ACCUMULATION. HOWEVER...MARGINALLY UNSTABLE AIR LINGERING OVER EXTREME NE OREGON/SE WASHINGTON THIS AFTERNOON AND EVENING MAY SPAWN AN ISOLATED THUNDERSTORM WHICH MAY PRODUCE VERY LOCALIZED HEAVY RAIN AMOUNTS...OR AT LEAST BRIEF DOWNPOURS. THE UPPER LOW IS FORECAST TO SWING UP NE INTO ALBERTA CANADA WITH AN UPPER RIDGING STARTING TO BUILD ALONG THE OREGON/WASHINGTON COAST AND GRADUALLY MOVING INLAND. THIS WILL CAUSE A WARMING AND DRYING TREND TO BEGIN OVER THE CWA BY LATE SATURDAY CONTINUING INTO SUNDAY AND MONDAY. TEMPERATURES ARE EXPECTED TO INCREASE BACK TO NORMAL BY SUNDAY AFTERNOON. THE NEXT SYSTEM WILL MOVE INTO THE REGION LATE SUNDAY NIGHT INTO THE EARLY PART OF NEXT WEEK. 88 .LONG TERM...MEMORIAL DAY THROUGH FRIDAY...ON MEMORIAL DAY THE NAM AND GFS MODELS SHOW A MID/UPPER LEVEL SHORT WAVE MOVING INTO THE FORECAST AREA...WHICH WILL TRIGGER SHOWERS. MONDAY AFTERNOON GUIDANCE SHOWS A MARGINALLY UNSTABLE AIRMASS AHEAD OF THE WAVE OVER THE BLUE MOUNTAINS EASTWARD INTO IDAHO. AS SUCH I HAVE ADDED A SLIGHT CHANCE OF AFTERNOON AND EVENING THUNDERSTORMS MONDAY FOR THE BLUE MOUNTAINS...THE GRANDE RONDE VALLEY AND WALLOWA COUNTY. A LARGE MID/UPPER LEVEL LOW REMAINS STATIONARY IN THE GULF OF ALASKA FROM TUESDAY THROUGH THURSDAY. THIS FEATURE ALLOWS A MOISTURE PLUME EMBEDDED IN SOUTHWESTERLY FLOW ALOFT TO REMAIN OVER THE FORECAST AREA THUS KEEPING A CHANCE OF SHOWERS IN THE FORECAST EACH DAY. POLAN && .AVIATION...PREVIOUS AVIATION DISCUSSION...18Z TAFS...VFR CONDITIONS WILL BE PREVALENT FOR THE NEXT 24 HOURS THOUGH SHOWERS OVER THE REGION WILL CREATE MVFR CEILINGS AT TIMES...ESPECIALLY NEAR KALW AND KPDT. ATMOSPHERIC CONDITIONS WILL BE MORE STABLE TODAY AND A SLIGHT CHANCE OF AFTERNOON THUNDERSTORMS IS POSSIBLE IN UNION AND WALLOWA COUNTIES IN NORTHEAST OREGON. CEILINGS WILL GENERALLY BE AROUND 4000-8000 FEET AGL ASIDE FROM 1800-4000 FEET AGL AT KALW AND KPDT. SURFACE WINDS WILL START OUT BELOW 15 KTS BUT WILL INCREASE TO 10 TO 20 KTS WITH GUSTS TO 30 KTS BY 21Z THIS AFTERNOON. WINDS WILL GENERALLY DIMINISH TO BELOW 15 KTS AFTER 05Z THIS EVENING...EXCEPT AT KPDT...KALW AND KDLS...WHICH WILL REMAIN AT 10 TO 20 KTS WITH GUSTS TO 25 KTS UNTIL 29/12Z. POLAN && .PRELIMINARY POINT TEMPS/POPS... PDT 45 64 44 70 / 40 30 10 10 ALW 48 65 47 71 / 40 40 10 10 PSC 48 71 44 74 / 30 20 0 10 YKM 43 69 42 69 / 30 10 0 10 HRI 46 70 43 74 / 30 20 0 10 ELN 44 66 43 70 / 30 20 10 0 RDM 33 65 33 64 / 20 10 0 10 LGD 43 60 37 66 / 60 40 20 10 GCD 40 61 37 69 / 60 30 10 10 DLS 48 66 46 69 / 30 20 10 10 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...NONE. WA...NONE. && THREAT INDEX SATURDAY : GREEN SUNDAY : GREEN 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 88/99/99
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PENDLETON OR
507 AM PDT FRI MAY 28 2010
ORZ041>044-049-050-501>506-WAZ024-026>030-501-502-291200-
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 OF WASHINGTON-
EAST SLOPES OF THE CENTRAL CASCADES OF WASHINGTON-
EAST SLOPES OF THE SOUTHERN CASCADES OF WASHINGTON-
507 AM PDT FRI MAY 28 2010
THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL AND NORTHEAST OREGON
AS WELL AS SOUTH CENTRAL AND SOUTHEAST WASHINGTON.
.DAY ONE...TODAY AND TONIGHT
THUNDERSTORMS
GRANDE RONDE VALLEY, WALLOWA COUNTY
AN UPPER LOW WILL SLOWLY DRIFT EAST ACROSS THE REGION TODAY AND
TONIGHT. THIS SYSTEM WILL CAUSE SCATTERED TO NUMEROUS SHOWERS
THROUGH TONIGHT...THOUGH THE COVERAGE OF SHOWERS WILL GRADUALLY
DECREASE OVERNIGHT. INSTABILITY MAY BECOME STRONG ENOUGH FOR A STRAY
THUNDERSTORM THIS AFTERNOON OVER UNION AND WALLOWA COUNTIES.
PRESSURE GRADIENTS WILL INCREASE WITH BREEZY CONDITIONS EXPECTED
OVER THE COLUMBIA BASIN AND THROUGH THE CASCADE GAPS.
.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY
THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.
ISOLATED TO SCATTERED SHOWERS WILL LINGER OVER THE AREA ON
SATURDAY...MAINLY OVER THE MOUNTAINS. WEAK HIGH PRESSURE WILL KEEP
CONDITIONS MOSTLY FAIR AND DRY SUNDAY. ANOTHER DISTURBANCE WILL MOVE
ACROSS THE REGION SUNDAY NIGHT AND MONDAY FOR ANOTHER ROUND OF
SHOWERS. A WESTERLY ONSHORE FLOW LOOKS TO SET UP AFTER THE MONDAY
SYSTEM. THIS FLOW PATTERN WOULD KEEP CONDITIONS UNSETTLED THROUGH
THURSDAY.
.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 Pendleton radar (KPDT), 73 km away, was scanning. The volume nearest the first event began at 00:13 UTC.
1 funnel cloud. Local standard time, as filed.
Spotter observed wall cloud with small funnel cloud about 2000 feet above ground.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Washington in 2010Every state in 2010This day in weather historyWarnings in Washington, May 2010
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: 223438.