A Pacific frontal system brought heavy snow to the mountains, especially the central Washington 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.
A Pacific frontal system brought heavy snow to the mountains, especially the central Washington 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 1, 10:18 AM PST, 4 hours 42 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
1018 AM PST SAT DEC 1 2012
.SYNOPSIS...MOIST SOUTHWEST FLOW ALOFT WILL CONTINUE OVER THE REGION
TODAY. LOOK FOR A VIGOROUS LOW PRESSURE SYSTEM TO IMPACT THE REGION
TONIGHT THROUGH MONDAY FOR WINDY CONDITIONS AND LOCALLY HEAVY SNOW
IN THE MOUNTAINS. A FAST MOVING WEATHER DISTURBANCE EMBEDDED IN THE
STRONG WESTERLY FLOW ALOFT WILL RACE ACROSS THE REGION SUNDAY NIGHT.
MOIST WESTERLY FLOW ALOFT WILL KEEP A THREAT OF SHOWERS GOING ON
MONDAY...ESPECIALLY OVER THE MOUNTAINS.
&&
.SHORT TERM...
THE LEFT ENTRANCE REGION OF THE JET HAS NOSED INTO SOUTHWEST WA THIS
MORNING AND HELPED DESTABILIZE THE AIR MASS OVER THE FAR SOUTHWEST
PART OF THE CWA. ISOLATED TSTMS HAVE BEEN OCCURRING OVER THIS
AREA...PROMPTING AN UPDATE TO THE GRIDDED FORECAST TO INCLUDE
ISOLATED TSTMS OVER THE CENTRAL COAST AND THE COASTAL WATERS.
ALSO...INCLUDED A MENTION OF A SLIGHT CHANCE OF TSTMS FROM THE
CENTRAL PUGET SOUND REGION SOUTHWARD THIS AFTERNOON DUE TO THE
PROXIMITY OF THE LEFT ENTRANCE REGION OF THE JET.
IT APPEARED THAT SNOWFALL AMOUNTS IN THE MOUNTAINS WILL BE IN THE
ADVISORY CRITERIA RANGE TODAY...WITH THE HEAVIEST SNOW OCCURRING ON
THE SOUTHWEST FACING SLOPES OF THE OLYMPICS AND NORTH CASCADES ABOVE
3500 FEET. HOWEVER THE CENTRAL CASCADES...FROM MOUNT RAINIER...
SOUTHWARD /ABOVE 4K FEET/ WILL ALSO RECEIVE ADVISORY AMOUNTS...
ESPECIALLY IF THERE ARE ANY TSTMS THIS AFTERNOON.
AN UPPER TROF AND ASSOCIATED FRONTAL SYSTEM WILL HEAD TOWARD THE
PACIFIC NORTHWEST TONIGHT FOR AN UPSWING IN PRECIP AS WELL AS THE
DEVELOPMENT OF WINDY CONDITIONS. IT LOOKS LIKE THE HEAVIEST SNOWFALL
WILL PROBABLY OCCUR ON THE OLYMPICS AND CENTRAL CASCADES TONIGHT.
PREFER THE NAM SOLUTION IN REGARDS TO THE STRENGTH AND TRACK OF THE
SURFACE LOW LATE TONIGHT THROUGH SUNDAY MORNING AS IT APPEARED MORE
REASONABLE IN LIGHT OF THE LOCATION OF THE UPPER LEVEL FEATURES.
WITH THAT IN MIND...ANTICIPATE WINDY CONDITIONS TO DEVELOP OVER THE
SOUTHERN PART OF THE CWA...ESPECIALLY...EARLY SUNDAY MORNING. WILL
NEED TO WATCH THE CENTRAL COAST /ABOUT KHQM SOUTHWARD/ BECAUSE...
DEPENDING ON THE TRACK OF THE LOW...THERE COULD BE A BRIEF PERIOD OF
HIGH WINDS SIMILAR TO WHAT OCCURRED BACK ON THE 19TH OF NOVEMBER.
ANTICIPATE SHOWERY WEATHER IN THE WAKE OF THE UPEPR TROF ON SUNDAY.
THE HEAVIEST SNOW WILL LIKELY FALL ON THE NORTH CASCADES DURING THE
DAY SUNDAY AS OPPOSED TO TONIGHT.
STRONG ONSHORE OR WESTERLY FLOW ALOFT WILL PERSIST SUNDAY NIGHT...
WITH AN EMBEDDED SHORT WAVE TROF LIKELY ENHANCING SNOWFALL RATES IN
THE CASCADES. THE BEST CHANCE OF SHOWERS ON MON WILL LIKELY BE OVER
THE MOUNTAINS IN BETWEEN SYSTEMS. THE NEXT SYSTEM WILL BRING MORE
LOCALLY HEAVY PRECIP TO THE CWA MON NIGHT.
.LONG TERM FROM THE PREV DISCUSSION...
ON TUESDAY...ANOTHER STRONG WET AND WINDY UPPER LEVEL TROUGH WILL
MOVE ACROSS THE AREA. RECENT MODEL RUNS HAVE BEEN SHIFTING BETWEEN A
MORE PROGRESSIVE PATTERN AND A ATMOSPHERIC RIVER EVENT WITH MORE
SUSTAINED PRECIP. THE LATEST 00Z/06Z GFS IS MORE PROGRESSIVE AND
BRINGS ABOUT AN 18 HOUR STRETCH OF HEAVY RAIN TO THE OLYMPICS AND N
CASCADES. GFS/ECMWF PRESSURE GRADIENTS LOOK STRONG ENOUGH TO KEEP
POTENTIAL HIGH WINDS IN MIND. MODERATE WESTERLY FLOW BEHIND THE
TROUGH WILL MAINTAIN SHOWERS THROUGH WEDNESDAY NIGHT. THE GFS SHOWS
A SHORT DRY PERIOD THURSDAY AND PART OF FRIDAY AS A LOW AMPLITUDE
SHORTWAVE RIDGE CROSSES THE REGION. HOWEVER THE 00Z ECMWF IS WETTER
SO NO CHANGES WILL BE MADE TO THE EXTENDED FORECAST. KAM
&&
.HYDROLOGY...HEAVY RAIN FELL OVER THE SOUTHERN OLYMPICS OVER THE
LAST TWO DAYS. THE AMOUNTS OVER THE SKOKOMISH RIVER BASIN STAND
OUT...EVEN FOR THAT NORMALLY WET PLACE. THE JEFFERSON CREEK RAWS
STATION RECEIVED 6.19 INCHES IN THE LAST 24 HOURS AND AN AMAZING
11.17 INCHES IN THE LAST 48 HOURS. IT SHOULD COME AS NO SURPRISE
THAT THE SKOKOMISH RIVER FLOODED.
ANOTHER BATCH OF HEAVY RAIN IS FORECAST FOR THE SOUTHERN OLYMPICS
THIS AFTERNOON AND TONIGHT. THE SKOKOMISH RIVER WILL REMAIN ABOVE
FLOOD STAGE AND REACH ANOTHER CREST SOMETIME SUNDAY.
OTHER RIVERS IN WESTERN WASHINGTON ARE NOT EXPECTED TO REACH FLOOD
STAGE THIS WEEKEND...AS PRECIPITATION AMOUNTS ARE INSUFFICIENT AND
THE SNOW LEVEL WILL BE TOO LOW...AROUND 4000 FEET.
CURRENT MODELS SHOW A VERY WET BUT PROGRESSIVE SYSTEM MONDAY NIGHT
AND TUESDAY. IF THE SKOKOMISH RIVER HAS MANAGED TO FALL BELOW FLOOD
STAGE BY THEN IT WILL CERTAINLY GO BACK ABOVE. AT THIS POINT THE
MODELS DO NOT APPEAR TO HAVE ENOUGH RAIN TO MAKE ANY OTHER RIVER
FLOOD. HOWEVER BOTH THE GFS AND EURO SHOW CONSIDERABLY HEAVIER RAIN
OVER VANCOUVER ISLAND...SO IT WOULD NOT TAKE MUCH OF AN ERROR TO
SHIFT THE RAIN OVER WASHINGTON. THE USUAL CAVEAT APPLIES...WHEN
THERE IS THIS MUCH RAIN IN THE MODELS THEY HAVE TROUBLE WITH THE
DETAILS. BURKE
&&
.AVIATION...MOIST SOUTHWEST FLOW ALOFT WILL CONTINUE OVER WASHINGTON
TODAY AND TONIGHT. AT THE SURFACE MODERATE TO STRONG SOUTHEASTERLY
GRADIENTS WILL CONTINUE. AIR MASS IS MOIST AND SLIGHTLY UNSTABLE. A
FRONT WILL MOVE THROUGH THE REGION TONIGHT...GIVING STRONG ONSHORE
PRESSURE GRADIENTS SUNDAY.
CEILINGS ARE MAINLY VFR THIS MORNING AND WILL REMAIN VFR TODAY AND
THIS EVENING. CEILINGS WILL FALL TO 2-3K FT LATER TONIGHT AS A FRONT
MOVES THROUGH. THERE IS A SLIGHT CHANCE OF THUNDERSTORMS ON THE
COAST AND OVER THE SOUTHWEST TODAY.
KSEA...DISCUSSION ABOVE APPLIES. RISK OF A THUNDERSTORM APPEARS TOO
LOW TO PUT IN THE TAF. SOUTHEAST WINDS 10-15 KT TODAY WILL DIMINISH
TONIGHT...THEN AS POST FRONTAL GRADIENTS INCREASE SUNDAY WINDS WILL
RISE TO SOUTHWEST 10-20 KT. CHB
&&
.MARINE...GALE FORCE WINDS STILL NOTED ALONG THE COAST BUT WINDS
HAVE DIMINISHED BELOW GALE STRENGTH INLAND. WINDS STILL REMAIN
SOLIDLY IN THE SMALL CRAFT ADVISORY CATEGORY OVER INLAND WATERS.
SOUTHEAST WINDS WILL PICK UP AGAIN TONIGHT...THEN IN POST FRONTAL
ONSHORE GRADIENTS WILL TURN SOUTHWEST WITH SOME GALES POSSIBLE OVER
ALL WATERS. CURRENTLY HAVE HIGH END SMALL CRAFT ADVISORY WINDS
INDICATED FOR SUNDAY.
NEXT SYSTEM ARRIVES MONDAY NIGHT AND TUESDAY...GIVING ANOTHER ROUND
OF SOUTHEAST GALES FOLLOWED BY STRONG ONSHORE FLOW. GRADIENTS EASE
CONSIDERABLY AFTER THAT SYSTEM.
MARGINAL MINOR TIDAL OVERFLOW IS AGAIN POSSIBLE WITH HIGH TIDES
SUNDAY MORNING AND WILL ISSUE ANOTHER STATEMENT TO COVER THAT THIS
AFTERNOON. CHB
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER STORM WARNING IN EFFECT FOR THE OLYMPICS AND NORTH
CASCADES ABOVE 3500 FEET FROM 6 PM THIS EVENING TO NOON SUNDAY.
WINTER WEATHER ADVISORY IN EFFECT FOR THE OLYMPICS AND
CASCADES ABOVE 3500 FEET UNTIL 6 PM THIS EVENING.
WINTER STORM WATCH IN EFFECT FOR THE CENTRAL CASCADES
FROM LATE TONIGHT THROUGH SUNDAY AFTERNOON.
PZ...GALE WARNING IN EFFECT FOR THE COASTAL WATERS UNTIL 4 PM
THIS AFTERNOON.
SMALL CRAFT ADVISORY IN EFFECT FOR THE REMAINING WATERS
UNTIL 4 AM SUNDAY.
SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR CONDITIONS
UNTIL 4 AM SUNDAY.
&&
WWW.WEATHER.GOV/SEATTLE
FOR THE GRAPHICAL AFD...VISIT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTMLPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
957 AM PST SAT DEC 01 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0855 AM HEAVY RAIN 4 SW MONTESANO 46.97N 123.65W
12/01/2012 M2.09 INCH GRAYS HARBOR WA TRAINED SPOTTER
24 HOUR TOTAL RAINFALL.
0956 AM HEAVY RAIN 4 N MAPLE FALLS 48.98N 122.08W
12/01/2012 M2.50 INCH WHATCOM WA TRAINED SPOTTER
24 HOUR RAINFALL
&&
GRUBPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
1202 PM PST SAT DEC 01 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1200 PM HEAVY RAIN 3 SW BRINNON 47.65N 122.94W
12/01/2012 M2.95 INCH JEFFERSON WA TRAINED SPOTTER
SINCE 4 PM YESTERDAY.
&&
GRUBPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
1223 PM PST SAT DEC 01 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1222 PM HEAVY RAIN 1 ENE ELWHA 48.06N 123.57W
12/01/2012 M2.36 INCH CLALLAM WA TRAINED SPOTTER
FROM 8 PM YESTERDAY TO NOON TODAY.
&&
GRUB1 heavy snow. Local standard time, as filed.
USFS NWAC station at Paradise recorded 19 inches snow during 24 hours ending 4 pm Dec 2.
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: 424944.