A Pacific trough developed into an upper low over eastern Utah and western Colorado which produced significant snowfall in most mountains and some lower elevation areas of western Colorado.
Every event with a place to put it; 13 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 Pacific trough developed into an upper low over eastern Utah and western Colorado which produced significant snowfall in most mountains and some lower elevation areas of 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 21, 4:49 AM MST, 1 hour 11 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
449 AM MST WED DEC 21 2011
.SHORT TERM... /TODAY THROUGH THURSDAY NIGHT/
00Z UPPER AIR ANALYSIS AT H5 SHOWED A PAIR OF LOWS OVER THE MID
MISSOURI VALLEY AND NORTHERN TIP OF BAJA. STRONG HEIGHT FALLS OVER
THE NORTHERN ROCKIES AHEAD OF THE NEXT CONTINENTAL POLAR SYSTEM
WHICH WATER VAPOR SHOWED DISTINCTLY MOVING THROUGH THE IDAHO
PANHANDLE THE PAST FEW HOURS. GOES DERIVED PWAT PRODUCTS AND
PRECIPITABLE H2O PLOTS SHOW NARROW RIBBON OF MOISTURE AHEAD OF
THIS SYSTEM THAT 295K MOISTURE TRANSPORT VECTS BRING INTO THE OUR
CWA TODAY. HOWEVER AS NOTED IN EARLIER DISCUSSION THIS MOISTURE IS
FAIRLY LIMITED AND MIXING RATIO/S CONTINUE TO REMAIN AROUND 2G/KG AS
THE SYSTEM PASSES THROUGH AND THIS SHOULD KEEP SNOWFALL AMOUNTS
UNDER WARNING CRITERIA. THE MAIN CONCERN WILL CONTINUE TO BE THE
IMPACT OF ACCUMULATING SNOWFALL ON AREA ROADWAYS DURING THE HOLIDAY
TRAVEL PERIOD AND DID NOT MAKE ANY CHANGES TO WINTER WEATHER
ADVISORIES IN PLACE.
THE SNOWFALL LOOKS TO GET GOING THIS MORNING ACROSS THE NORTHERN
COLORADO MOUNTAINS. WHAT MOISTURE IS IN PLACE WILL BE WORKED ON BY
INCREASING LARGE SCALE ASCENT AS THE SYSTEM DROPS TO NEAR THE I-80
CORRIDOR. MID LEVEL FRONTOGENESIS AND A FAVORABLE WESTERLY
OROGRAPHIC FLOW WILL HELP LINK INTO THIS LARGE SCALE LIFT WITH A
FRONT ARRIVING LATE THIS AFTERNOON HELPING TO BOOST SNOWFALL
PRODUCTION ACROSS THE LOWER ELEVATIONS OF NORTHWEST COLORADO. THE
COLD FRONT SHOULD BEGIN TO ACCELERATE SOUTHWARD AFTER SUNSET AS A
CLOSED MID LEVEL CIRCULATION FORMS OVER NORTHEAST UTAH AND STRONG PV
LOBE ROTATING AROUND THIS LOW PROMOTES FALLING PRESSURE OVER
SOUTHERN COLORADO. QG FORCING WILL BE MAXIMIZED OVER NORTHWEST
WESTERN COLORADO OVERNIGHT AS WE WITH THE STRONG ASCENT COMBINING
WITH THE SAGGING COLD FRONT TO BOOST SNOWFALL RATES. WESTERLY FLOW
INTO THE GRAND VALLEY AND STRONG DYNAMICS SHOULD BE ABLE TO GET SOME
PRECIPITATION TO THE GROUND.
THE UPPER LOW WILL BE SETTLING NEAR THE FOUR CORNERS ON THURSDAY
PULLING BROAD SCALE LIFT INTO THE SOUTHERN MOUNTAINS. SOUTHERLY
OROGRAPHICS AND INSTABILITY FROM DYNAMIC TROP NOSING INTO SOUTHWEST
COLORADO MAY ENHANCE THE SNOWFALL BUT MOISTURE SEEMS TO BE WANING
SIGNIFICANTLY AND WITH THE EXCEPTION OF THE HIGHEST
PEAKS...CONFIDENCE NOT VERY HIGH FOR SIGNIFICANT SNOWFALL. HAVE
DECIDED TO HOLD OF ON ISSUING HIGHLIGHTS AT THIS TIME WITH MODELS
CONTINUING TO BACK OFF ON SNOW AMOUNTS.
.LONG TERM... /FRIDAY THROUGH TUESDAY/
BULGING HIGH PRESSURE ALONG THE CALIFORNIA COAST ON FRIDAY TILTS
NORTHEAST WITH THE AXIS SHIFTING OVER UTAH AND COLORADO BY SUNDAY.
THERE IS A SHORT WAVE THAT TRIES TO ROUND THE TOP OF THIS RIDGE...
BUT THE SHORT WAVE SPLITS AND MOST OF THE ENERGY MOVES DOWNSTREAM
ALONG THE NRN TIER STATES. WHAT WAS ONCE A REMOTE CHANCE OF
FLURRIES OVER THE PARK AND GORE RANGE FOR CHRISTMAS EVE APPEARS
GONE. SHORT WAVE THAT CROSSES WRN COLORADO EARLY SATURDAY MORNING
WILL ESSENTIALLY BE A DEFORMATION ZONE THAT ATTACHES THE NRN BRANCH
WITH THE EJECTING CLOSED LOW FORMERLY FROM THE FOUR CORNERS REGION.
REGARDING TEMPS...COOL WINTERTIME AIR MASS LINGERS FOR ONE MORE DAY.
WARM ADVECTIVE PATTERN BEGINS IN EARNEST IN THE WAKE OF SATURDAYS
MORNING SHORT WAVE THAT CONTINUES INTO SUNDAY MORNING. MOST OF THE
WARMING OCCURS ALOFT...BUT EXPECT A BIG JUMP IN TEMPERATURES IN THE
HIGH COUNTRY FROM FRIDAY INTO SUNDAY. THE TEMPERATURE INVERSION
OVER THE UINTA BASIN WILL BE PROBLEMATIC...BUT FOR MOST OF THE
FORECAST AREA WILL UNDERGO SOME WARMING.
SUNDAY NIGHT THROUGH TUESDAY...PERSISTENT RIDGE THAT WAS ANCHORED
OVER THE NERN PACIFIC WILL BREAK DOWN AND FASTER WESTERLY FLOW TAKES
AIM TOWARD THE PACIFIC NORTHWEST. THE ECMWF AND GFS DIVERGE WITH
RESPECT TO THE TIMING OF THESE SHORT WAVES...BUT FORECAST IMPACT FOR
OUR FORECAST AREA WILL BE MINIMAL AS MOST OF THE ENERGY REMAINS
NORTH OF THE COLORADO BORDER. THE ECMWF SHOWS AN AMPLIFIED SHORT
WAVE THAT WOULD BRING A QUICK SHOT OF SNOW TO THE NRN MOUNTAINS...
WHILE THE GFS IS FASTER WITH LESS AMPLIFICATION. NOT MUCH HOPE FOR
ANY DECENT SNOWFALL IN THE EXTENDED PERIOD. MODERATING TEMPERATURES
(EXCEPT THE UINTA BASIN...SORRY VERNAL) AND DRY WEATHER IS THE MAIN
THEME IN THE EXTENDED GRIDS AND FORECASTS.
&&
.AVIATION... /12Z TAF ISSUANCE/
VFR TIL 00Z...THEN THE CHANCE OF SNOW INCREASES CONSIDERABLY
ACROSS ALL TAF SITES. CONDITIONS WILL DETERIORATE WITH MVFR/IFR
CONDITIONS WITH VIS BLO 3SM -SN BR CIGS AOB OVC030 AT MOUNTAIN TAF
SITES AT KASE AND KEGE. THESE CONDITIONS MAY BE MET AT VALLEY
AIRPORTS...INCLUDING KMTJ...KGJT...AND KRIL.
KEGE...CIGS ARE EXPECTED TO BE BELOW TAKE OFF MINIMUMS FOR MUCH OF
THE DAY. HOWEVER THEIR MAY BE BRIEF PERIODS WHEN BKN050 BECOMES
SCT050 BEFORE DETERIORATING CONDITIONS ARRIVE TONIGHT.
KVEL...VFR CONDITIONS TODAY WITH A 30 PERCENT CHANCE THAT MVFR
CONDITIONS WILL OCCUR FROM 22Z-02Z LATER TODAY AS THE SURFACE COLD
ARRIVES WITH SNOW IN THE VICINITY. GUSTY NORTHEAST WINDS WILL DEVELOP
AFTER 02Z.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY FROM NOON TODAY TO NOON MST THURSDAY FOR
ZONES 001>003.
WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 PM MST
THURSDAY FOR ZONES 007>012-014.
WINTER WEATHER ADVISORY UNTIL NOON MST THURSDAY FOR ZONES 004-
005-013.
WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO NOON MST
THURSDAY FOR ZONE 006.
UT...WINTER WEATHER ADVISORY FROM NOON TODAY TO NOON MST THURSDAY FOR
ZONE 023.
&&
SHORT TERM...15
LONG TERM....PF
AVIATION.....PFThe national radar mosaic for the moment the first event began.
13 winter weather. Local standard time, as filed.
Snowfall ranged from 4 to 10 inches across the area. Wind gusts of 25 to 50 mph produced areas of blowing and drifting snow.
Snowfall ranged from 5 to 12 inches across the area. Wind gusts of 20 to 30 mph produced localized blowing and drifting snow.
Snowfall ranged from 3 to 8 inches across the area. Wind gusts of 20 to 30 mph produced localized blowing and drifting snow.
Snowfall ranged from 3 to 10 inches across the area.
Snowfall ranged from 7 to 12 inches across the area. Locally higher amounts included 13 inches at Powderhorn Ski Area.
Snowfall ranged from 4 to 8 inches across about half of the area. Wind gusts of 30 to 50 mph produced areas of blowing and drifting snow.
Snowfall ranged from 5 to 7 inches across the area. Wind gusts of 25 to 45 mph produced areas of blowing and drifting snow.
Snowfall ranged from 3 to 6 inches across the area.
Snowfall ranged from 3 to 6 inches across the western portion of the area.
Snowfall ranged from 3 to 6 inches across the area.
Snowfall ranged from 3 to 7 inches across the area. Wind gusts of 25 to 50 mph produced areas of blowing and drifting snow.
This was the first significant snowfall of the season in the Grand Valley, with snowfall accumulations that ranged from 1 to 4 inches. The slick roads resulted in numerous vehicle accidents.
Snowfall ranged from 2 to 4 inches across the area.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2011Every state in 2011This day in weather historyWarnings in Colorado, December 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: 355473, 355475, 355480, 355484, 355479, 355481, 355483, 355485, 355482, 355487, 355486, 355488, 355477.