Name: Debris Flow in Washington, March 22, 2014
Start: 2014-03-22T11:00
End: 2014-03-22T11:00
Location: Washington

Where it happened

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Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
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The toll

Deaths: 43
Injuries: 12
Property damage: $60 million
Crop damage: None recorded
Events: 1

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.

What happened

The episode as NWS SEW wrote it up.

A relatively dry October 2013 through early February 2014 period with precipitation running around only 50 percent of normal turned unusually wet one week into February and continued through March. Precipitation during February and March ranked in the top 10 all-time for this time period, running between 150 and 200 percent of average.

On a warm and dry 22nd of March, 2014, a large landslide occurred four miles east of the town of Oso, Washington. The slide debris, traveling at over 60 miles per hour, crossed the entire river valley, covering an area of over a square mile with an approximate deposit thickness of 15 to 75 feet in some areas. The force of the slide flow caused 43 fatalities, 12 injuries, destroyed 37 homes, and wiped out SR 530 for over a mile. In addition, the slide debris completely blocked the North Fork Stillaguamish River for over 24 hours, backing up a pool of water that flooded the valley about 2 miles upstream and reached approximately 20 feet deep, inundating an additional 6 homes. The cause of the slide is not fully known, though precipitation in the previous months to years contributed to the ground failure. A rain gage located 2 miles west of the slide had 19.93 inches of rain in the 40 days leading up to the slide. |As of March 19th the nearest reporting station Arlington, had reported 7.14 inches of rain, which is about 2 inches shy of the record 9.23 for the entire month of March. Three days before the slide, the area received close to an inch of rain in one day.

What forecasters said that day

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 Seattle, WA wrote its last area forecast discussion before the first event at Mar 22, 8:39 AM PST, 2 hours 21 minutes earlier.

Area forecast discussion, Mar 22, 8:39 AM PST, 2 hours 21 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
939 AM PDT SAT MAR 22 2014

.SYNOPSIS...A WEAK WARM FRONT WILL BRUSH BY NORTHWEST WASHINGTON
TODAY AND THIS EVENING. AN UPPER LEVEL RIDGE ACCOMPANIED BY LOW
LEVEL OFFSHORE FLOW WILL BRING MILD WEATHER SUNDAY AND MONDAY. THE
RIDGE WILL SHIFT EAST MONDAY NIGHT WITH THE NEXT FRONTAL SYSTEM
ARRIVING ON TUESDAY.

&&

.SHORT TERM...A SMALL SHORTWAVE SCOOTING ACROSS SRN B.C. TODAY WILL
BRING MODEST WARM ADVECTION AND AN INCRS IN MOISTURE TODAY...WITH
SOME LIGHT RAIN POSSIBLE ACROSS THE NRN THIRD OR HALF OF THE FCST
AREA. CURRENTLY HAVE LIKELY POPS THIS AFTN FOR THE NW OLYMPIC
PENINSULA...THE NORTH CASCADES...AND NEAR BLI. HAVE NO PRECIP IN THE
FCST OVER THE INTERIOR FROM SEATTLE ON SOUTH. THE FORECAST AND THE
WEATHER SETUP SEEM TO MATCH VERY WELL...SO NO FORECAST UPDATES THIS
MORNING.

AN UPPER RIDGE WILL AMPLIFY OUT NEAR 130W TONIGHT AND SUNDAY
MORNING. THE NW FLOW ALOFT WILL PUSH SOMEWHAT COOLER AIR INTO ERN WA
AND HELP INITIATE LOW-LEVEL OFFSHORE FLOW OVER WRN WA. THE UPPER
RIDGE AXIS WILL CROSS WRN WA ON MON MRNG...REACHING ERN WA ON MON
AFTN. WITH LOW-LEVEL OFFSHORE FLOW CONTINUING ON MON AND FLOW ALOFT
BECOMING SOUTHERLY...LOOKS LIKE A GOOD SETUP FOR ONE OF THE WARMER
DAYS SO FAR THIS YEAR. COULD SEE QUITE A FEW LOWLAND TEMPS REACHING
THE MID 60S...THAT IS IF THICKENING MID-UPPER LEVEL CLOUDS DO NOT
BLOT OUT TOO MUCH OF THE SUN'S WARMING RAYS.

HOWEVER...THE GFS BRINGS SOME LIGHT RAIN ON MON NEAR THE CANADIAN
BORDER...AT THE NOSE OF THE WARMING LOW-LEVEL AIR MASS. THE 12Z NAM
KEEPS PRECIP NORTH OF THE BORDER. COULD EASILY ENVISION INTRODUCING
LOW POPS NEAR THE CANADIAN BORDER ON MON WITH THE RELEASE OF THE
AFTN FCST PACKAGE.      HANER

.LONG TERM...FROM PREVIOUS DISCUSSION...A FRONTAL SYSTEM WILL MOVE
THROUGH THE AREA MONDAY NIGHT THROUGH TUESDAY NIGHT...BRINGING RAIN
AT TIMES TO THE AREA. A BAGGY UPPER TROUGH WILL REMAIN OVER THE AREA
WEDNESDAY AND THURSDAY FOR COOL SHOWERY WEATHER. BOTH THE ECMWF AND
GFS ARE NOW SUGGESTING AN ATMOSPHERIC RIVER EVENT AT THE END OF NEXT
WEEK. THE CURRENT FORECAST DOES NOT HAVE THIS. LATER SHIFTS WILL
PROBABLY NEED TO BOOST POPS AND QPF IF MODELS CONTINUE TO TREND IN
THIS DIRECTION. SCHNEIDER

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED FOR THE NEXT 7 DAYS.

&&

.AVIATION...A WEAK UPPER LEVEL SHORT WAVE TROUGH WILL CLIP THROUGH
SOUTHERN B.C. TODAY. THE FLOW ALOFT IS NORTHWESTERLY. EXPECT
INCREASING CLOUDS ACROSS WESTERN WASHINGTON WITH LIGHT RAIN MAINLY
NEAR THE CANADIAN BORDER. VFR CONDITIONS WILL PREVAIL. AN UPPER
LEVEL RIDGE WILL BUILD OFFSHORE TONIGHT AND SUNDAY FOR DRY/STABLE
WEATHER. 33

KSEA...VFR CONDITIONS TODAY WITH LIGHT NORTHERLY FLOW AT THE
SURFACE. 33

&&

.MARINE...A WEAK FRONTAL SYSTEM WILL PASS INTO SOUTHERN BRITISH
COLUMBIA TODAY. HIGH PRES WILL BUILD OVER THE REGION ON SUNDAY FOR
GENERALLY LIGHT WINDS. OFFSHORE FLOW WILL INCREASE ON MON...WITH
SMALL CRAFT ADVISORY WINDS POSSIBLE OVER THE COASTAL WATERS AND
WESTERN STRAIT OF JUAN DE FUCA. A COLD FRONT WILL MOVE INLAND ON
TUE. 33

&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

1 debris flow. Local standard time, as filed.

Debris Flow, Snohomish

When: March 22, 11:00 AM PST
Where: Snohomish County, 3.1 mi E of Oso to 3.3 mi E of Oso
Cause: Heavy Rain
Deaths: 43 direct, 0 indirect
Injuries: 12 direct, 0 indirect
Property damage: $60 million
Reported by: County Official
Coordinates: 48.270, -121.853

On a warm and dry 22nd of March, 2014, a large landslide occurred four miles east of the town of Oso, Washington. The slide debris, traveling at over 60 miles per hour, crossed the entire river valley, covering an area of over a square mile with an approximate deposit thickness of 15 to 75 feet in some areas. The force of the slide flow caused 43 fatalities, 12 injuries, destroyed 37 homes, and wiped out SR 530 for over a mile. In addition, the slide debris completely blocked the North Fork Stillaguamish River for over 24 hours, backing up a pool of water that flooded the valley about 2 miles upstream and reached approximately 20 feet deep, inundating an additional 6 homes. The cause of the slide is not fully known, though precipitation in the previous months to years contributed to the ground failure. A rain gage located 2 miles west of the slide had 19.93 inches of rain in the 40 days leading up to the slide. |As of March 19th the nearest reporting station Arlington, had reported 7.14 inches of rain, which is about 2 inches shy of the record 9.23 for the entire month of March. Three days before the slide, the area received close to an inch of rain in one day. Most all of the fatalities occurred at the permanent homes impacted by the slide.

The people who died

As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.

Event	Date	Age	Sex	Where	Kind
Debris Flow, Snohomish	2014-03-22	45	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	55	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	69	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	5	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	66	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	41	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	71	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	46	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	47	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	49	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	21	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	59	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	6	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	55	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	31	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	64	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	0	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	63	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	58	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	65	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	60	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	23	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	65	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	19	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	34	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	13	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	67	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	75	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	61	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	30	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	2	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	58	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	74	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	91	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	55	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	14	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	52	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	64	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	4	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	52	Male	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	53	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	44	Female	Unknown	Direct
Debris Flow, Snohomish	2014-03-22	53	Male	Permanent Home	Direct

What these are

Debris Flow: A fast-moving slurry of mud, rock and debris, usually on a slope soaked by heavy rain or stripped by a fire.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in Washington in 2014 Every state in 2014 This day in weather history Warnings in Washington, March 2014

Sources

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: 505782.