An unusually vigorous Puget Sound Convergence Zone produced heavy snow at Stevens Pass in the Cascades.
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.
An unusually vigorous Puget Sound Convergence Zone produced heavy snow at Stevens Pass in the Cascades.
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 Dec 2, 3:00 PM PST, 1 hour earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PST SUN DEC 2 2012
.SYNOPSIS...MOIST ONSHORE FLOW WILL BRING SHOWERS THROUGH MONDAY.
MORE WIDESPREAD RAIN AND WINDY CONDITIONS WILL RETURN MONDAY NIGHT
AND TUESDAY AS A VIGOROUS FRONT MOVES ONSHORE. MOIST ONSHORE FLOW
WILL MAINTAIN A SHOWERY PATTERN WEDNESDAY THROUGH SUNDAY.
&&
.SHORT TERM...MOIST ONSHORE FLOW WILL CONTINUE TONIGHT AND MONDAY
WITH SNOW CONTINUING IN THE MOUNTAINS. BOTH THE GFS AND NAM HAVE AN
UPPER SHORT WAVE ENHANCING THE SHOWERS ACROSS THE AREA LATE
TONIGHT/EARLY MONDAY MORNING. THE WINTER WEATHER ADVISORIES FOR THE
CASCADES HAVE BEEN EXTENDED TO 10 AM MONDAY TO ACCOUNT FOR THE
CONTINUED SHOWERS THROUGH TOMORROW MORNING. THERE WILL ALSO BE
BLUSTERY WINDS TONIGHT IN THE WAKE OF A FRONT WHICH MOVED THROUGH
LAST NIGHT. THESE WILL GRADUALLY EASE BY MONDAY MORNING AS ONSHORE
FLOW DECREASES.
THERE WILL BE A RELATIVE LULL IN THE ACTIVE WEATHER PATTERN LATER
MONDAY BUT THE NEXT VIGOROUS FRONTAL SYSTEM WILL BRING MORE RAIN AND
WIND MONDAY NIGHT AND TUESDAY. IT LOOKS LIKE WIND ADVISORIES WILL
EVENTUALLY BE NEEDED FOR THE COAST AND NORTH INTERIOR STARTING
MONDAY NIGHT BUT THAT IS STILL TOO FAR OUT TO BE ISSUING PRODUCTS
JUST YET. SNOW IN THE MOUNTAINS SHOULD NOT BE TOO MUCH OF AN ISSUE
MONDAY NIGHT AND TUESDAY AS SNOW LEVELS RISE SIGNIFICANTLY. LOW
LEVEL EASTERLY GRADIENTS COULD KEEP THINGS SLOPPY IN THE PASSES
HOWEVER.
TUESDAY NIGHT AND WEDNESDAY WILL BE A PERIOD OF DECREASING POST
FRONTAL SHOWERS AND WIND IN THE WAKE OF THE TUESDAY FRONT. HIGHS
SHOULD ALSO COOL SEVERAL DEGREES WEDNESDAY BEHIND THE FRONT.
SCHNEIDER
.LONG TERM...MODELS ARE IN POOR AGREEMENT BY THURSDAY AND CONTINUE
TO SHOW DIFFERENCES THROUGH THE WEEKEND. BASICALLY...THE GFS IS
WETTER AND COOLER WITH A BROAD UPPER TROUGH CARVING OUT OVER THE
AREA BY FRIDAY NIGHT. THE ECMWF AND CANADIAN SHOW LESS ACTIVE AND
SOMEWHAT WARMER WESTERLY FLOW ALOFT...BECOMING MORE NORTHERLY BY THE
WEEKEND. FOR NOW...THE FORECAST IS WEIGHTED TOWARDS THE
ECMWF/CANADIAN SOLUTIONS. THIS MEANS A CONTINUED THREAT OF SHOWERS
THURSDAY THROUGH SUNDAY BUT NO ORGANIZED WEATHER SYSTEM ARE EXPECTED
AND THE TREND SHOULD BE TOWARDS DRIER WEATHER BY THE END OF THE
WEEK. THE MEX MOS SHOWS HIGHS COOLING INTO THE UPPER 30S BY THE
WEEKEND BUT THE ECMWF MOS HAS HIGHS NEAR 50. SPLITTING THE
DIFFERENCE SEEMS LIKE A GOOD CHOICE UNTIL A CLEAR TREND EMERGES.
SCHNEIDER
&&
.HYDROLOGY...SHOWERS ARE FORECAST UNTIL THE NEXT SYSTEM ARRIVES
MONDAY NIGHT AND TUESDAY. RAINFALL IN THE SHOWERS IS UNLIKELY TO BE
HYDROLOGICALLY SIGNIFICANT. THE SKOKOMISH RIVER WILL SLOWLY RECEDE
TONIGHT AND MONDAY BUT MAY NOT ACTUALLY FALL BELOW FLOOD STAGE.
THE NEXT SYSTEM WILL PROBABLY BRING 2-3 INCHES TO THE SOUTHERN
OLYMPICS. THE SKOKOMISH RIVER...IF IT HAS MANAGED TO FALL BELOW
FLOOD STAGE BY THEN...WILL RISE BACK ABOVE FLOOD STAGE. ONLY MINOR
FLOODING IS FORECAST. FLOODING IS UNLIKELY ON ANY OTHER RIVERS.
AFTER TUESDAY NO MAJOR SYSTEMS ARE FORECAST THROUGH NEXT WEEKEND AT
LEAST. THE SKOKOMISH WILL FALL BELOW FLOOD STAGE AROUND MID WEEK AND
FLOODING IS UNLIKELY ON ANY RIVERS. BURKE
&&
.AVIATION...FLOW ALOFT WILL BE WESTERLY TONIGHT AND MONDAY IN A
MOIST AND SLIGHTLY UNSTABLE AIR MASS. MODERATE TO STRONG ONSHORE
SURFACE PRESSURE GRADIENTS WILL PERSIST THIS EVENING THEN TAPER
OVERNIGHT. SCATTERED SHOWERS WILL TAPER THIS EVENING.
CEILINGS ARE MOSTLY VFR 3-4K FT BUT IN AND NEAR SHOWERS CEILINGS
FALL TO THE 2-3K FT RANGE. CEILINGS WILL DISSIPATE SOMEWHAT THIS
EVENING AS THE CONVECTION DIES OUT...BUT MVFR CEILINGS ARE LIKELY
TO FORM AGAIN OVERNIGHT.
KSEA...DISCUSSION ABOVE APPLIES. SOUTHERLY WINDS 15 TO 20 KNOTS WITH
GUSTS TO 30 KNOTS WILL SLOWLY DIMINISH TONIGHT. CHB
&&
.MARINE...SMALL CRAFT ADVISORY WINDS ARE OCCURRING OVER ALL WATERS.
STRONG POST FRONTAL ONSHORE FLOW WILL EASE OVERNIGHT BUT NOT ENOUGH
TO KEEP THE WINDS FROM FALLING BELOW SMALL CRAFT ADVISORY CRITERIA.
AFTER A BREAK LATE TONIGHT AND MONDAY THE NEXT SYSTEM ARRIVES MONDAY
NIGHT AND EARLY TUESDAY MORNING. THIS IS LIKELY TO BRING SOUTHEAST
GALES TO MOST WATERS FOLLOWED BY STRONG ONSHORE FLOW. GRADIENTS EASE
CONSIDERABLY AFTER THAT SYSTEM. CHB
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER STORM WARNING NORTH CASCADES ABOVE 3000 FEET UNTIL 6
PM TODAY.
.WINTER WEATHER ADVISORY CENTRAL CASCADES ABOVE 3000 FEET
UNTIL 10 AM MONDAY.
PZ...SMALL CRAFT ADVISORY ALL WATERS.
.SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.
.GALE WATCH COAST...ENTRANCES...NORTHERN INLAND WATERS FOR
MONDAY NIGHT AND TUESDAY.
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...VISIT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML2 heavy snow. Local standard time, as filed.
USFS NWAC station at Stevens Pass recorded 22 inches of snow during 24 hours ending 9 am Dec 3.
USFS NWAC station at Stevens Pass recorded 22 inches of snow during 24 hours ending 9 am Dec 3.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Washington in 2012Every state in 2012This day in weather historyWarnings in Washington, December 2012
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: 424947, 424948.