A moist northwest flow aloft resulted in significant snowfall in many mountain areas and some lower elevation zones in western Colorado.
Every event with a place to put it; 11 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
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 GJT wrote it up.
A moist northwest flow aloft resulted in significant snowfall in many mountain areas and some lower elevation zones in western Colorado.
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 Grand Junction, CO wrote its last area forecast discussion before the first event at Dec 10, 4:51 AM MST, 9 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND JUNCTION CO 451 AM MST MON DEC 10 2012 .SHORT TERM...(TODAY THROUGH TUESDAY) ISSUED AT 450 AM MST MON DEC 10 2012 WARM AIR ADVECTION UNDERWAY ACROSS THE NORTHERN CWA AS EVIDENCED BY THE INCREASE IN THE MID LEVEL CLOUD DECK SINCE MIDNIGHT. BUFKIT AND MODEL SOUNDINGS SHOW THIS WARM AIR ADVECTION CREATING A FAIRLY DEEP ISOTHERMAL LAYER ON THE COLD SIDE OF THE DENDRITIC LAYER. ADD SOME LARGE SCALE LIFT AND INCREASING OROGRAPHICS TO THIS AND SNOW SHOULD DEVELOP NEAR THE SUNRISE HOUR IN THE NORTHERN CWA AND SPREAD SOUTHWARD THROUGH THE DAY AS THE UPSTREAM SHORT WAVE TROF PUSHES THROUGH. COOLER CLOUD TOPS MOVING OVER WESTERN WYOMING ATTM CORRELATE WELL WITH THE H5-H3 QG FIELDS WHICH SHOW THIS LARGE SCALE ASCENT MOVING OVER THE NORTHERN AND CENTRAL MOUNTAINS THIS MORNING AND SNOW SHOULD START TO FALL. DERIVED SATELLITE NOT VERY PROMISING FOR A SIGNIFICANT MOISTURE TAP...BUT MODELS STILL INDICATE MIXING RATIO/S APPROACHING 2G/KG MOVING IN ON THE 290K SURFACE WITH THE ASCENT. WITH A FAIRLY DEEP AND COLD DENDRITIC LAYER HIGH SNOW-TO-LIQUID RATIO/S SHOULD LEAD TO A FLUFFY SNOWFALL...WITH INFLATED ACCUMULATIONS AND EASY TO BLOW AROUND. COLDER AIR ARRIVING THIS AFTERNOON INTO THE LATE EVENING HOURS WILL LEAD TO A MORE UNSTABLE ENVIRONMENT AND THIS SHOULD AID IN SOME SNOWFALL GENERATION INTO THE CENTRAL AND SOUTHERN MOUNTAINS AS THE MOISTURE SPREADS SOUTHWARD. OVERALL CONCUR WITH CURRENT THINKING THAT SNOWFALL TOTALS IN THE PARK AND FLAT TOP RANGES IN THE FAVORED NORTHWEST OROGRAPHIC REGIME WILL REACH LOW END CRITERIA BY THE TUESDAY MORNING BUT CONFIDENCE QUITE LOW ELSEWHERE. FOR NOW DID HOIST AND ADVISORY FOR THESE TWO ZONES WITH SOME CONCERN FOR THE SNOW GETTING BLOWN AROUND WITH SOME WIND GUSTS OVER 25 MPH POSSIBLE NEAR AND ABOVE PASS LEVEL. THE FAVORED TIME LINE WILL BE MID MORNING TODAY TO THE EARLY MORNING HOURS ON TUESDAY. THERE IS LEE-WAY ON EACH END OF THIS AS LIGHT SNOW BE FALLING UNTIL TUESDAY AFTERNOON WHEN MID LEVEL WAA BRINGS STABLE AND DRIER CONDITIONS TO THE REGION AHEAD OF A BUILDING SHORT WAVE RIDGE. LASTLY WILL STILL NEED TO MONITOR SBS TO CRAIG CORRIDOR WHERE COLD DOME IS IN PLACE AND LIFT MAY BE ENOUGH TO BRING LOW END SNOW CRITERIA IN UPGLIDE REGIME. THE WESTERN PORTION OF ZONE 10 COULD ALSO DO GOOD IN THE NORTHWEST FLOW BUT OVERALL FELT THIS ZONE SHOULD REMAIN BELOW CRITERIA. TEMPERATURES REMAIN WELL BELOW NORMAL TODAY BUT REMAIN WARMER TOMORROW NIGHT MOST AREAS UNDER BETTER CLOUD COVER. TEMPERATURES WILL MAKE A SLOW REBOUND ON TUESDAY BUT THE BUILDING INVERSION ALOFT SHOULD LIMIT MIXING INTO THE LOWER VALLEYS AND WILL HAVE TO WAIT UNTIL MID-WEEK FOR MORE SEASONABLE READINGS. .LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY) ISSUED AT 450 AM MST MON DEC 10 2012 TUESDAY NIGHT-WEDNESDAY NIGHT: MODELS REMAINED IN AGREEMENT WITH A PERIOD OF DRY AND MILDER WEATHER ACROSS THE REGION IN THE MIDDLE OF THE WEEK. A FLAT RIDGE DEVELOPS BEHIND THE SYSTEM WHICH WILL IMPACT THE AREA TODAY AND TOMORROW BRINGING AN END TO SNOW OVER THE NORTHERN AND CENTRAL MOUNTAINS TUESDAY NIGHT. A LOW PRESSURE SYSTEM DIGGING SOUTHWARD ALONG THE WEST COAST WILL CAUSE FLOW TO SHIFT TO THE SOUTHWEST WEDNESDAY. DRY...WARM AIR OVER THE DESERT SOUTHWEST WILL MOVE OVER THE AREA THROUGH WEDNESDAY NIGHT. AS A RESULT... TEMPERATURES WILL RISE TO 5 TO 10 DEGREES ABOVE NORMAL WEDNESDAY AFTERNOON WITH OVERNIGHT LOWS SHOWING A SIMILAR TREND. THURSDAY-SUNDAY: ECMWF AND GFS IN FAIRLY CLOSE AGREEMENT WITH MOVEMENT OF THE CLOSED PACIFIC LOW...MOVING ITS CENTER SLOWLY ACROSS SOUTHERN CALIFORNIA THROUGH 12Z FRIDAY. HOWEVER...THE GFS BEGINS TO GENERATE SOME LIGHT QPF OVER THE NORTHERN HALF OF THE CWFA THURSDAY BENEATH AN AREA OF DIFLUENT FLOW. GFS AND EC QPF FIELDS WERE IN BETTER AGREEMENT THURSDAY NIGHT AS THE LOW SLIDES SLOWLY EAST SPREADING LIGHT PRECIPITATION OVER THE SOUTHWEST CORNER OF THE CWFA. SNOWFALL SHOULD PICK UP ACROSS THE SOUTH FRIDAY AS THE LOW CENTER SLIDES EASTWARD JUST SOUTH OF THE COLORADO BORDER. IF MODELS VERIFY THIS WOULD GENERATE SOME OF THE BEST SNOW OVER THE SOUTHERN MOUNTAINS THIS SEASON. MODELS BEGIN TO DIVERGE THIS WEEKEND AS MORE PROGRESSIVE GFS BRINGS A SHORTWAVE ACROSS THE GREAT BASIN IMPACTING THE REGION WITH SHOWERS AS EARLY AS SATURDAY. IN CONTRAST...EC DIGS A DEEPER LOW ALONG THE WEST COAST AND BRINGS THIS SYSTEM IN SUNDAY. GIVEN THE LACK OF CONSISTENCY WILL LEAVE BLENDED MODELS UNCHANGED. && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING) ISSUED AT 450 AM MST MON DEC 10 2012 A VIGOROUS STORM MOVING SOUTHEASTWARD ACROSS THE REGION WILL BRING ANOTHER ROUND OF SNOW TODAY AND TONIGHT. THE NORTHERN AND CENTRAL MOUNTAINS AND ADJACENT AIRFIELDS WILL BE MOST PROFOUNDLY IMPACTED BY THIS STORM. MOUNTAINS FROM THE ELKHEAD IN THE NORTH TO THE SAWATCH AND NORTHWEST SAN JUANS WILL EXPERIENCE PROLONGED PERIODS OF OBSCURATION. MEANWHILE...KCAG...KHDN...KSBS...KEEO...KRIL... KEGE...AND KASE WILL BEGIN TO EXPERIENCE MVFR VSBY AND CIGS IN SNOW AS EARLY AS THIS MORNING IN THE NORTH AND DURING THE AFTERNOON ACROSS THE CENTRAL VALLEYS. BRIEF IFR CONDITIONS ARE POSSIBLE. AFTER 00Z TUESDAY...KMTJ AND KGUC MAY BE SIMILARLY IMPACTED UNTIL MIDNIGHT. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...WINTER WEATHER ADVISORY UNTIL NOON MST TUESDAY FOR COZ004-013. UT...NONE. && SHORT TERM...15 LONG TERM...NL AVIATION...NL && CORRECTED TYPOS IN SHORT TERM DISCUSSION
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
147 AM MST MON DEC 10 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1203 AM SNOW MONTROSE 38.48N 107.87W
12/10/2012 M3.0 INCH MONTROSE CO TRAINED SPOTTER
24HR SNOWFALL
&&
EVENT NUMBER GJT1200542
DCThe national radar mosaic for the moment the first event began.
11 winter weather. Local standard time, as filed.
Snowfall accumulations of 9 to 12 inches were measured across the area. Locally higher amounts included 22 inches at the Tower SNOTEL site.
Snowfall accumulations of 4 to 10 inches were measured across the area.
Snowfall accumulations of 6 to 12 inches were measured across the area.
Snowfall accumulations of 3 to 7 inches were measured across the area.
Snowfall accumulations of 3 to 4 inches were measured across the area.
Snowfall accumulations of 8 to 12 inches were measured across the area.
Snowfall accumulations around 3 inches were measured across most of the area.
Snowfall accumulations around 5 inches were measured above the 8000 foot level.
Snowfall accumulations of 3 to 8 inches were measured across the area.
Snowfall accumulations of 3 to 6 inches were measured across the area. Locally higher amounts included 9 inches in the Glenwood Springs area and in Glenwood Canyon.
Snowfall accumulations of 2 to 7 inches were measured across the area.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2012Every state in 2012This day in weather historyWarnings in Colorado, 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: 432364, 432367, 432365, 432369, 432371, 432372, 432373, 432366, 432368, 432374, 432370.