Two back country skiers were injured in an avalanche just below the summit of Snoqualmie mountain.
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 SEW wrote it up.
Two back country skiers were injured in an avalanche just below the summit of Snoqualmie mountain.
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 Apr 6, 1:40 AM PST, 6 hours 20 minutes earlier.
AREA FORECAST DISCUSSION...ADDED 3RD PARAGRAPH
NATIONAL WEATHER SERVICE SEATTLE WA
240 AM PDT WED APR 6 2011
.SYNOPSIS...A COLD UPPER LEVEL TROUGH WILL MOVE OVER WESTERN
WASHINGTON TODAY...WITH SHOWERS CONTINUING AND ADDING A CHANCE OF
AFTERNOON AND EVENING THUNDERSTORMS. SHOWERS WILL DECREASE THURSDAY
AS THE UPPER LEVEL TROUGH MOVES SOUTHEAST. AN UPPER LEVEL RIDGE WILL
MOVE BRIEFLY OVER THE AREA FRIDAY BRINGING MORE SUNSHINE AND DRY
WEATHER. ANOTHER FRONTAL SYSTEM WILL FOLLOW SATURDAY OR SATURDAY
NIGHT.
&&
.SHORT TERM...LATEST IR SATELLITE IMAGERY SHOWS WESTERLY FLOW ALOFT
OFFSHORE SENDING A STREAM OF SHOWERS TOWARD THE WA COAST. THE STREAM
OF SHOWERS WILL SHIFT FARTHER SOUTH DOWN THE COAST TODAY AS A LARGE
COLD UPPER LEVEL TROUGH MOVES SOUTH OVER THE AREA. THE COLD UNSTABLE
AIR MASS WITH THE TROUGH WILL MAINTAIN THE SHOWER ACTIVITY TODAY
WITH A CHANCE OF THUNDERSTORMS THIS AFTERNOON AND EVENING.
GFS 850-500MB LAPSE RATES ARE QUITE HIGH AT 8.0 C/KM AND LIFTED
INDICES REMAIN AROUND -1 OR -2. NAM BUFR SOUNDINGS PEG CONVECTIVE
TEMPERATURES IN THE LOWER 40S TODAY...WITHIN EASY REACH OF THE
CURRENT TEMPERATURES NEAR 40. WITH THE FREEZING LEVEL ONLY AT
2000-2500 FEET...HEAVIER SHOWERS WILL PROBABLY BRING SNOW DOWN TO
THE SURFACE. SMALL HAIL SHOULD BE FAIRLY COMMON. THE ONLY THING
MISSING IS ORGANIZED FORCING FOR CONVECTION...SO IT WILL BE HIT AND
MISS FOR WHERE SHOWERS AND THUNDERSTORMS FORM.
MOUNTAIN OBSERVATIONS SHOW FAIRLY STEADY LIGHT SNOW CONTINUING OVER
THE CASCADES. WITH THE WEST FLOW ALOFT EXPECTED TO CONTINUE PAST
SUNRISE BEFORE FINALLY WEAKENING LATER THIS MORNING THE 11 AM
EXPIRATION TIME FOR THE WINTER STORM WARNING LOOKS ON TARGET.
MODELS REMAIN CONSISTENT THURSDAY AND FRIDAY. THE LARGE TROUGH MOVES
SOUTH OVER THE SW U.S. ON THURSDAY WITH N FLOW ALOFT OVER W WA AND A
RESIDUAL CHANCE OF SHOWERS. THE UPPER LEVEL RIDGE OFFSHORE MOVES
OVER W WA ON FRIDAY FOR A DRY PARTLY SUNNY TO MOSTLY SUNNY DAY. A
FRONT FOLLOWS JUST W OF THE RIDGE AXIS WHICH WILL BRING A CHANCE OF
RAIN TO THE AREA FRIDAY NIGHT OR SATURDAY. GFS IS MORE AGGRESSIVE
WITH THE PRECIP THAN THE ECMWF BUT BOTH MODELS SUGGEST JUST LIGHT
RAIN. KAM
.LONG TERM...MEDIUM RANGE GFS/ECMWF CONTINUE TO HAVE PROBLEMS WITH
THE FRIDAY NIGHT THROUGH SATURDAY NIGHT PERIOD. EARLIER MODEL RUNS
HAD A STRONGER FRONT MOVING OVER THE AREA SATURDAY OR SATURDAY
NIGHT...WHEREAS THE LATEST SOLUTIONS HAVE A WEAKER OCCLUDED FRONT
REACHING THE AREA SATURDAY. THE NEW SOLUTIONS NOW HAVE A MORE
SIGNIFICANT WARM FRONT REACHING THE AREA LATE SATURDAY NIGHT
FOLLOWED BY A COLD FRONT LATER ON SUNDAY. CONFIDENCE IN THE DETAILS
FOR THIS PERIOD IS NOT THAT HIGH...BUT THE MODELS HAVE STUCK WITH
THE WET PATTERN AND HAVE BEEN CONSISTENTLY TRENDING EARLIER. KAM
&&
.HYDROLOGY...THE PATTERN FOR THE NEXT 10 DAYS IS GENERALLY WET...BUT
MODELS DO NOT INDICATE ANY PERIODS OF RAIN HEAVY ENOUGH OR LONG
ENOUGH IN DURATION TO CAUSE FLOODING...INCLUDING ON THE GREEN RIVER.
KAM
&&
.AVIATION...UPPER LEVEL TROUGH WILL DIG SE OVER THE WEST COAST THRU
THU. STRONG WLY FLOW ALF OVER WA WILL DECREASE TODAY AND BECOME
LIGHT NLY FLOW THU. STRONG ONSHORE LOW LEVEL FLOW INTO WRN WA EARLY
THIS MORNING WILL RELAX BY AFTERNOON. MOIST UNSTABLE AIR WITH GOOD
OROGRAPHICS AND MTNS OBSCURED IN SNOW SHOWERS. CHANCE OF A FEW TSTMS
AND GRAUPEL SHOWERS THIS AFTERNOON AS THE COLDEST AIR ALOFT MOVES
OVER WRN WA. 19
KSEA...BLUSTERY EARLY THIS MORNING WITH SHOWERS AND THE SFC PRES
TROF WAS MOVING THRU WITH CONSIDERABLE COLD CU STREAMING INTO THE
AREA AND MUCH LESS OF A RAINSHADOW BEHIND THE OLYMPICS NOW. TOWERING
CU A GOOD BET BY AFTERNOON WITH THE CHANCE OF A TSTM.
&&
.MARINE...VIGOROUS TROF MOVG THRU WRN WA EARLY THIS MORNING. STRONG
ONSHORE/WLY FLOW THIS MORNING WILL EASE BY AFTERNOON. 15-20 FT SEAS
COASTAL WATERS THIS MORNING WILL EASE TNGT...HIGH SURF ADVISORY
CONTINUES FOR NOW. LIGHT GRADIENTS THU AND FRI...THEN ANOTHER FNTL
SYS ARRIVES ARND SAT NITE. 19
&&
.AVALANCHE...AVALANCHE WARNING CONTINUES THROUGH WEDNESDAY MORNING
AFTER MOST WEST SLOPE AREAS...VOLCANIC PEAKS AND OLYMPIC SITES
RECEIVED 10-25 INCHES OF NEW SNOW AS OF TUESDAY MORNING. STRONG
WINDS AND LOADING HAVE CREATED DANGEROUS AVALANCHE CONDITIONS...
ESPECIALLY HIGHER ELEVATIONS ON STEEP EXPOSED LEE SLOPES. ANOTHER
FRONT SHOULD SPREAD RENEWED WINDS AND SNOWFALL TO ALL AREAS TUESDAY
NIGHT AND THIS SHOULD MAINTAIN OR INCREASE THE CURRENT DANGER.
THEREFORE, BACKCOUNTRY TRAVEL IN AVALANCHE TERRAIN IS NOT
RECOMMENDED UNTIL THESE UNSTABLE CONDITIONS IMPROVE. SEE
HTTP://NWAC.US FOR DETAILS. KRAMER
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER STORM WARNING OLYMPICS AND CASCADES.
HIGH SURF ADVISORY NORTH AND CENTRAL COAST.
PZ...SMALL CRAFT ADVISORY ALL WATERS.
SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.
WWW.WEATHER.GOV/SEATTLE1 avalanche. Local standard time, as filed.
Two back country skiers were injured in an avalanche just below the summit of Snoqualmie mountain.
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, April 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: 300726.