A long-lasting Puget Sound Convergence Zone produced heavy snow in the Northern and Central Cascades, mainly in the vicinity of Stevens Pass.
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.
A long-lasting Puget Sound Convergence Zone produced heavy snow in the Northern and Central Cascades, mainly in the vicinity of Stevens Pass.
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 1, 2:55 PM PST, 1 hour 5 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
355 PM PDT WED APR 1 2009
.SYNOPSIS...A PACIFIC FRONTAL SYSTEM WILL CONTINUE TO SPREAD
PRECIPITATION OVER WESTERN WASHINGTON THROUGH TONIGHT. SNOW...
LOCALLY HEAVY...WILL DEVELOP OVER THE MOUNTAINS THIS EVENING. A COOL
AND UNSTABLE AIRMASS OVERHEAD WILL PRODUCE SHOWER ACTIVITY ON
THURSDAY BEFORE TAPERING OFF ON FRIDAY. AN UPPER LEVEL RIDGE WILL
BUILD OFFSHORE LATER ON FRIDAY...PROVIDING THE REGION WITH DRY AND
WARMER WEATHER THROUGH THE WEEKEND.
&&
.SHORT TERM...AN UPPER RIDGE PARKED AROUND 150W IS ALLOWING WARM
FRONTAL MOISTURE TO SLIDE DOWN IN NORTHWEST FLOW ALOFT.
PRECIPITATION WILL PICK UP AGAIN THIS EVENING AS THE AS SYSTEM SAGS
SOUTH WITH THE TRIPLE POINT APPROACHING QUILLAYUTE AROUND 6Z. THE
LOW WILL PASS INTO EASTERN WASHINGTON THURSDAY MORNING AND THE TROF
AXIS WILL SWING THROUGH WESTERN WASHINGTON AROUND 12Z. SHOWERS WILL
PERSIST MOST OF THURSDAY ALTHOUGH THERE SHOULD BE SOME SUN BREAKS
THURSDAY AFTERNOON. MODELS SHOW GOOD ONSHORE FLOW DEVELOPING
THURSDAY AFTERNOON AND A CONVERGENCE ZONE DEVELOPING THURSDAY OVER
THE CENTRAL/NORTH SOUND. IMPRESSIVE LAPSE RATES ON THURSDAY WITH THE
UPPER TROF OVERHEAD AND 500 MB TEMPS DIP BELOW -30C...SHOULD PRODUCE
A FEW RUMBLES OF THUNDER...ESPECIALLY NEAR THE CONVERGENCE ZONE.
IN FACT...WRF-GFS 4KM SHOWS DUAL CONVERGENCE ZONES AGAIN...WITH A
SECONDARY ONE FORMING DOWNWIND OF VANCOUVER ISLAND. MESOSCALE MODELS
ALSO SHOW A GOOD SURGE COMING DOWN THE STRAIT THURSDAY
AFTERNOON...NOT QUITE WIND ADVISORY BUT MAKING FOR SOME BREEZY
NORTHWESTERLY WINDS FOR AREAS ALONG THE STRAIT...ADMIRALTY INLET
AND PERHAPS AGAIN DUMPING OUT NEAR THE WESTERN KING/SNOHOMISH LINE.
BREEZY NORTHWESTERLIES SHOULD ALSO DEVELOP ALONG THE COAST.
SNOWFALL FOR THE MOUNTAINS WILL BEGIN TO PICK UP THIS
EVENING...TURNING TO SHOWERS ON THURSDAY. THE FOCUS FOR SNOWFALL ON
THURSDAY WILL BE CONVERGENCE ZONE ACTIVITY...PARTICULARLY AIMED AT
THE CENTRAL CASCADES FROM THE STEVENS PASS AREA TO SNOQUALMIE AREA.
STORM TOTALS BY LATE THURSDAY WILL RANGE FROM 1 TO 2 AND A HALF FEET
WITH THE HIGHER AMOUNTS OVER THE CENTRAL CASCADES. THE OLYMPICS WILL
ALSO GET A DECENT HELPING...AROUND 10-18 INCHES.
SHOWER ACTIVITY WILL CONTINUE THURSDAY NIGHT IN THE MOUNTAINS AS THE
TROF SLOWLY SLIDES EAST. THE CONVERGENCE ZONE WILL BEGIN TO FIZZLE
OVERNIGHT. HOWEVER SOME OF THE HIGHER LOCATIONS IN THE EAST PUGET
SOUND LOWLANDS COULD SEE A FEW FLAKES OVERNIGHT. THE UPPER RIDGE
WILL BUILD OFFSHORE ON FRIDAY...HOWEVER A DISTURBANCE SLIDING DOWN
THE BACKSIDE OF THE TROUGH AND CONTINUED ONSHORE FLOW MADE IT TOUGH
TO COMPLETELY PULL SHOWERS OUT FOR THE CASCADES AND I-5 CORRIDOR IN
THE AFTERNOON.
LEFTOVER SHOWERS WILL COME TO AN END FRIDAY NIGHT AS THE UPPER RIDGE
AXIS MOVES OVERHEAD ON SATURDAY. TEMPERATURES ACTUALLY SHOULD WARM
TO SEASONAL NORMS...MID 50S FOR MOST OF THE LOWLANDS WITH A FAIR
AMOUNT OF SUNSHINE.
.LONG TERM...WITH SPLIT FLOW DEVELOPING ON SUNDAY...SOUTHERN STREAM
ENERGY DIVES SOUTH TO FORM A CUTOFF LOW OVER THE CALIFORNIA COAST.
SOUTHERLY FLOW ALOFT MAY STILL BRING A FAIR AMOUNT OF MID TO HIGH
LEVEL CLOUDS OVER THE AREA SUNDAY...BUT TEMPERATURES SHOULD WARM
INTO THE UPPER 50S WITH A FEW LOWER 60S POSSIBLE FOR INTERIOR SITES.
GFS HAS FINALLY BOUGHT INTO THE IDEA OF A CUT-OFF LOW LATER THIS
WEEKEND...BUT STILL MANAGES TO THROW SOME LIGHT SHOWERS TOWARD
SOUTHERN PARTS OF THE CWA MONDAY AND MONDAY NIGHT IN SOUTHERLY FLOW
ALOFT. LEFT CHANCE POPS FOR THOSE AREAS...BUT TRENDED TOWARD A DRIER
FORECAST THROUGH TUESDAY. DAMICO
&&
.AVIATION...WEAK UPPER RIDGE OVER WA TO MOVE TO NORTH ROCKIES BY THU
MORNING. UPPER TROF MOVING SE FROM THE GULF OF ALASKA TO MOVE OVER
WESTERN WA THU MORNING. STRONG WESTERLY SAGGING S OF WA. AT THE
SURFACE..A WARM FRONT JUST OFF THE COAST WILL MOVE INLAND THIS
EVENING WITH PLENTY OF MOISTURE. AIR MASS MOIST AND STABLE.
ASSOCIATED COLD FRONT TO MOVE ONSHORE EARLY THU. SURFACE HIGH PRES
TO BUILD OFF THE COAST FOR INCREASING LOW LEVEL ONSHORE FLOW INTO
WA. AIR MASS TO BECOME COLDER AND MORE UNSTABLE.
PRECIPITATION WITH THE WARM FRONT MOVED INLAND THIS MORNING AND WAS
EASING THIS AFTERNOON IN MANY PARTS OF WESTERN WA. LOW LEVEL AIR
MASS MODERATED ENOUGH FOR THE AREAS OF APRIL FOOLS WET SNOW TO TURN
TO RAIN. CEILINGS AND VISIBILITIES TO REMAIN MVFR THOUGH SOME AREAS
OF IFR IN RAIN AND FOG LIKELY OVERNIGHT.
A MORE SHOWERY REGIME ON THU. LIKELY TO HAVE THE PUGET SOUND
CONVERGENCE ZONE DEVELOP BEFORE MIDDAY AND WITH THE STRONGER FLOW IN
THE STRAIT...LIKELY WILL SAG SOUTHWARD THROUGH THE SOUND IN THE
AFTERNOON. ENOUGH INSTABILITY FOR A THREAT OF A TSTM TOO...NO APRIL
FOOLS.
KSEA...A MIX OF LOWER END MVFR AND HIGHER END IFR CEILINGS UNTIL THE
COLD FRONT ARRIVES NEAR 12Z THU OR SO. VISIBILITIES TO VARY BETWEEN
ROUGHLY 2 TO 5 MILES AS WELL. S TO SE WINDS 8-12 KTS TO CONTINUE
TONIGHT AND SHIFT TO SW 10-15 KT POST COLD FRONT. BUEHNER
&&
.MARINE...A WARM FRONT JUST OFF THE COAST IS EXPECTED TO MOVE INLAND
THIS EVENING. ENOUGH SOUTHERLY ONSHORE FLOW FOR SMALL CRAFT ADVISORY
WINDS IN ALL WATERS BUT THE CENTRAL STRAIT TIL THIS EVENING.
THE ASSOCIATED COLD FRONT IS FORECAST TO SWING ONSHORE EARLY THU.
HIGHER PRES WILL THEN BUILD OFF THE COAST CREATING STRONG ONSHORE
FLOW THU WITH POSSIBLE GALE FORCE WINDS IN THE CENTRAL AND EASTERN
STRAIT. STRONG COLD ADVECTION LATER THU AFTERNOON AND EVENING OVER
THE COASTAL WATERS WITH GALES POSSIBLE THERE AS WELL. A PUGET SOUND
CONVERGENCE ZONE IS LIKELY TO DEVELOP AGAIN DURING THE DAY THU AND
EXTEND INTO THE EVENING BEFORE DISSIPATING.
WINDS EASING ALL WATERS ON FRIDAY AS HIGHER PRESSURE BUILDS OVER THE
REGION FROM THE WEST. LOW LEVEL FLOW GOING OFFSHORE ON SAT AND
REMAINING OFFSHORE ON SUN AS A FRONT WEAKENS OVER THE COASTAL
WATERS. BUEHNER
&&
.AVALANCHE...WHATS IT TAKE TO BECOME AN APRIL FOOL...BEING UNAWARE
IS A GENERAL RULE. ANOTHER STRONG STORM IN THIS CONTINUING
WINTER-LIKE FLOW SHOULD RAVAGE THE MOUNTAINS LATER WEDNESDAY
AFTERNOON AND NIGHT. INCREASING LIGHT TO MODERATE SNOW EARLY
WEDNESDAY AFTERNOON SHOULD PICK UP SIGNIFICANTLY LATER WEDNESDAY
AFTERNOON AND NIGHT WITH HEAVY SNOW OR SNOW SHOWERS AND STRONG WINDS
CONTINUING INTO THURSDAY EVENING BEFORE SLOWLY DECREASING. ALONG
WITH SOME BRIEF WARMING WEDNESDAY EVENING AND A POOR BOND OF NEW
SNOW TO THE EXISTING SNOW SURFACES THIS WEATHER SHOULD ADD UP TO A
SUBSTANTIAL INCREASE IN THE AVALANCHE DANGER LATE WEDNESDAY. EARLIER
AVALANCHE WATCH NOW UPGRADED TO WARNING. TRAVEL IN AVALANCHE TERRAIN
APPEARS INCREASINGLY FOOLISH LATER TODAY THROUGH TOMORROW WITH THESE
DANGEROUS CONDITIONS. SEE NWAC.US FOR DETAILS. MOORE
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER STORM WARNING CENTRAL CASCADES.
WINTER WEATHER ADVISORY FOR THE NORTHERN CASCADES AND OLYMPICS
AVALANCHE WARNING...NORTHERN AND CENTRAL CASCADES AND
OLYMPICS FOR WEDNESDAY NIGHT AND THURSDAY
PZ...SMALL CRAFT ADVISORY ALL WATERS EXCEPT CENTRAL STRAIT
GALE WATCH CENTRAL AND EASTERN STRAIT THU AFTERNOON AND NIGHT.
GALE WATCH COAST THURSDAY EVENING INTO FRIDAY MORNING.
SMALL CRAFT ADVISORY GRAYS HARBOR BAR FOR ROUGH BAR CONDITIONS.
WWW.WEATHER.GOV/SEATTLE/2 heavy snow. Local standard time, as filed.
NWAC station at Stevens Pass recorded heavy snowfall (17 inches).
NWAC station at Stevens Pass recorded heavy snowfall (17 inches).
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Washington in 2009Every state in 2009This day in weather historyWarnings in Washington, April 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: 164110, 164112.