A winter storm, associated with a strong west to southwesterly flow aloft, produced a 4-day period of moderate to heavy snow in the North Central Mountains. The combination of strong wind and heavy snow forced the closure of several mountain passes due to threat of avalanches.
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The episode as NWS BOU wrote it up.
A winter storm, associated with a strong west to southwesterly flow aloft, produced a 4-day period of moderate to heavy snow in the North Central Mountains. The combination of strong wind and heavy snow forced the closure of several mountain passes due to threat of avalanches. The Amtrack train route, which runs from Denver to California, was rerouted through Wyoming when Union Pacific closed its tracks along Interstate 70. Numerous accidents forced the closure of I-70 at times. Peak wind gusts over the higher mountain passes generally ranged from 45 to 60 mph. Storm totals ranged from 16 to 32 inches in the mountains, with 5 to 10 inches in the valleys of Grand and Jackson Counties.
In the mountains, storm totals included: 32 inches, 10 miles east of Silverthorne; 29 inches at Arapahoe Basin and Loveland Ski Area; 28 inches at Breckenridge Ski Area; 23 inches, 16 miles west-southwest of Walden; 21 inches at Willow Park; 20 inches at Copper Mountain; 18 inches at Zirkel SNOTEL; 16 inches at Eldora Ski Resort, Long Draw Reservoir SNOTEL and Never Summer.
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 Denver/Boulder, CO wrote its last area forecast discussion before the first event at Dec 18, 3:20 AM MST, 6 hours 54 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DENVER CO 320 AM MST SAT DEC 18 2010 .SHORT TERM...A STRONG NORTHWEST TO WESTERLY FLOW ALOFT WILL BE OVER THE CWFA TODAY...THEN IT WILL TRANSITION TO WEST-SOUTHWESTERLY TONIGHT. STLT AND MODEL DATA INDICATE THERE WILL BE A STEADY INCREASE OF PACIFIC MOISTURE INTO COLORADO THROUGH THE PERIOD. IN THE MOUNTAINS...700-500 MB LAPSE RATES IN THE 5-6C/KM TDA/TNGT. UPPER LEVEL JET STREAM WINDS INCREASE FM 100 KTS TDA TO 125 KTS OVERNIGHT. QG VERTICAL VELOCITIES ARE PROGGED TO BE NEUTRAL THROUGH THE PERIOD. SPATIAL CROSS-SECTIONS INDICATE GOOD OROGRAPHIC COMPONENT NEAR RIDGETOP MOISTURE DEEPENING TO AROUND 500 MB. 700 MB TEMPERATURES NOT TOO COLD INITIALLY AROUND -6 TO -8C...SO TEMPERATURE ADVECTION IS NEUTRAL AS WELL THROUGH TNGT. THE BOTTOM LINE...THERE WILL BE SNOW IN MOUNTAINS TODAY AND TNGT...BUT IT WILL REMAIN LIGHT FOR THE MOST PART...WILL GO WITH MINIMAL AMOUNTS ESPECIALLY IN ZONES 33/34. WILL START TO WINTER STORM WARNING IN ZONE 31 AT MIDNIGHT TONIGHT...WITH THE LION/S SHARE OF THE SNOW EXPECTED SUNDAY AND MONDAY...SEE THE LONG TERM DISCUSSION BELOW. AS FOR THE NERN PLAINS...HIGH CLOUDINESS WILL INCREASE THROUGH THE DAY. TEMPERATURES WILL BE A LITTLE WARMER BUT STILL JUST BLO SEASONAL NORMALS. WL ADD SOME PATCHY FREEZING FOG POSSIBLE FOR PORTIONS OF THE NERN PLAINS UNTIL AROUND 15Z. OVERALL ONLY MINOR ADJUSTMENTS TO THE TEMPERATURE GRIDS TONIGHT. CLOUD COVER WILL ALLOW FOR LESS FRIGID MIN TEMPERATURES VS THIS MORNING. .LONG TERM...STRONG WEST-SOUTHWEST JET OVER THE EASTERN PACIFIC OCEAN AND WESTERN U.S. WILL CONTINUE TO PUMP MOISTURE INTO THE STATE SUNDAY AND INTO NEXT WEEK. IF SNOW HAS NOT BECOME WIDESPREAD IN THE MOUNTAINS IT WILL ON SUNDAY AS THE AIRMASS BECOMES SATURATED UP TO 400MB. SNOW MAY START OFF SUNDAY BEING PRIMARILY OROGRAPHIC. HOWEVER...A SHORT WAVE EMBEDDED IN THE FLOW WILL PRODUCE LIFT AND WIDESPREAD MOUNTAIN SNOW BY SUNDAY EVENING. SNOW WILL ALSO BECOME HEAVY AT TIMES SUNDAY NIGHT. SOME OF THE PRECIPITATION WILL SPREAD ACROSS THE DIVIDE SUNDAY NIGHT BECAUSE OF THE QG LIFT. EVEN THOUGH DOWNSLOPE FLOW ACROSS THE MOUNTAINS WILL BE STRONG...WILL KEEP LOW POPS ACROSS THE PLAINS SUNDAY NIGHT BECAUSE OF THE LIFT ALOFT. THE PACIFIC ORIGIN OF THIS AIRMASS MEANS MILD TEMPERATURES WITH SOME MOUNTAIN VALLEYS SEEING RAIN AT TIMES. SNOW WILL CONTINUE MONDAY AND TUESDAY IN THE MOUNTAINS AS MOISTURE CONTINUES TO STREAM INTO THE AREA. HOWEVER...THE SNOW WILL BE MAINLY PRODUCED BY OROGRAPHIC LIFT SO THE HEAVIER SNOW AMOUNTS WILL BE ON WEST FACING SLOPES. WINTER WEATHER HIGHLIGHTS WILL BE IN EFFECT UNTIL MONDAY EVENING AND MAY EVEN NEED TO BE EXTENDED AS LIGHT SNOW CONTINUES INTO MONDAY NIGHT AND TUESDAY. TOTAL SNOW AMOUNTS WILL GREATLY VARY. ON WEST FACING SLOPES...SNOW AMOUNTS OF 1 TO 3 FEET APPEAR LIKELY THROUGH THE DURATION OF THIS STORM. WHILE THE MILD PROTECTED VALLEYS COULD RECEIVE LESS THAN 2 INCHES OF SNOW. THERE WILL BE A CHANCE FOR LIGHT MOUNTAIN SNOW THROUGH THURSDAY AS MOISTURE CONTINUES TO MOVE OVER THE MOUNTAINS. ONCE THE TROUGH AXIS PUSHES EAST OF THE AREA THE CHANCE FOR MOISTURE WILL END. THIS WILL NOT HAPPEN UNTIL THURSDAY OR FRIDAY. WILL HAVE LOW POPS FOR THE PLAINS THURSDAY...AS THE CHANCE FOR MOISTURE INCREASES BECAUSE OF THE UPPER LEVEL TROUGH PASSING OVER THE STATE. && .AVIATION...VFR CONDITIONS EXPECTED THROUGH THE PERIOD. HIGH LEVEL CLOUDINESS WILL INCREASE ESPECIALLY AFTER 18Z AND CONTINUE INTO SUNDAY. ONLY QUESTIONABLE PERIOD MAY BE BETWEEN 00Z-06Z TNGT WHEN SEE OCNL BKN CIGS OF 5-7K FT AGL CUD DEVELOP...WL GO WITH SCT CLOUD GROUP IN THIS RANGE WITH THE 12Z TAF. LGT SFC WINDS SHUD CONTINUE THROUGH THE DAY. WL FOLLOW THE RUC13 MDL WITH LGT SLY WINDS THROUGH 18Z...WITH WEAK NNELY WINDS THIS AFTN AS SFC TROUGH ALONG THE FRONT RANGE STARTS TO STRENGTHEN. AFTER 02Z...SFC WINDS SHUD START TO SWITCH BACK TO DRAINAGE. .BOU WATCHES/WARNINGS/ADVISORIES...WINTER STORM WARNING MIDNIGHT TNGT UNTIL 5 PM MST MONDAY FOR THE PARK/NRN GORE RANGE ZONE 31. WINTER STORM WATCH FOR THE RMNDR OF THE NORTH CENTRAL MTNS ZONES 33 AND 34 LATE TNGT THROUGH MONDAY AFTN. COOPER/MEIER
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DENVER CO 431 AM MST SAT DEC 18 2010 COZ030>051-181800- JACKSON COUNTY BELOW 9000 FEET-WEST JACKSON AND WEST GRAND COUNTIES ABOVE 9000 FEET-GRAND AND SUMMIT COUNTIES BELOW 9000 FEET-SOUTH AND EAST JACKSON/LARIMER/NORTH AND NORTHEAST GRAND/ NORTHWEST BOULDER COUNTIES ABOVE 9000 FEET-SOUTH AND SOUTHEAST GRAND/WEST CENTRAL AND SOUTHWEST BOULDER/GILPIN/CLEAR CREEK/ SUMMIT/NORTH AND WEST PARK COUNTIES ABOVE 9000 FEET-LARIMER AND BOULDER COUNTIES BETWEEN 6000 AND 9000 FEET-JEFFERSON AND WEST DOUGLAS COUNTIES ABOVE 6000 FEET/GILPIN/CLEAR CREEK/NORTHEAST PARK COUNTIES BELOW 9000 FEET-CENTRAL AND SOUTHEAST PARK COUNTY-LARIMER COUNTY BELOW 6000 FEET/NORTHWEST WELD COUNTY-BOULDER AND JEFFERSON COUNTIES BELOW 6000 FEET/WEST BROOMFIELD COUNTY-NORTH DOUGLAS COUNTY BELOW 6000 FEET/DENVER/WEST ADAMS AND ARAPAHOE COUNTIES/ EAST BROOMFIELD COUNTY-ELBERT/CENTRAL AND EAST DOUGLAS COUNTIES ABOVE 6000 FEET-NORTHEAST WELD COUNTY-CENTRAL AND SOUTH WELD COUNTY-MORGAN COUNTY-CENTRAL AND EAST ADAMS AND ARAPAHOE COUNTIES- NORTH AND NORTHEAST ELBERT COUNTY BELOW 6000 FEET/NORTH LINCOLN COUNTY-SOUTHEAST ELBERT COUNTY BELOW 6000 FEET/SOUTH LINCOLN COUNTY-LOGAN COUNTY-WASHINGTON COUNTY-SEDGWICK COUNTY-PHILLIPS COUNTY- 431 AM MST SAT DEC 18 2010 ...WINTER STORM WARNING FOR THE EAST SLOPES OF THE PARK AND GORE MOUNTAINS MIDNIGHT TONIGHT THROUGH 5 PM MST MONDAY AFTERNOON... ...WINTER STORM WATCH FOR THE REMAINDER OF THE NORTH CENTRAL MOUNTAINS LATE TONIGHT THROUGH MONDAY AFTERNOON... THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST AND NORTH CENTRAL COLORADO. .DAY ONE...TODAY AND TONIGHT A STRONG NORTHWESTERLY FLOW ALOFT WILL TRANSITION TO WEST TO SOUTHWESTERLY TONIGHT. A STEADY INCREASE IN PACIFIC MOISTURE WILL ALLOW FOR LIGHT SNOW TO CONTINUE IN THE MOUNTAINS THROUGH TONIGHT. SNOW ACCUMULATIONS WILL RANGE FROM 2 TO 6 INCHES PRIMARILY ALONG THE HIGHER WEST FACING SLOPES. WESTERLY WINDS 15 TO 30 MPH CAN BE EXPECTED IN THE MOUNTAINS WITH GUSTS IN EXCESS OF 60 MPH ABOVE TIMBERLINE. AS A RESULT...AREAS OF BLOWING AND DRIFTING SNOW WILL ALSO OCCUR. ACROSS THE NORTHEAST PLAINS...PATCHY FREEZING FOG IS POSSIBLE EARLY THIS MORNING. TEMPERATURES WILL MODIFY SOMEWHAT THIS AFTERNOON BUT WITH ALL THE CLOUDINESS EXPECTED...THEY WILL REMAIN JUST BELOW SEASONAL NORMALS. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY SNOW WILL CONTINUE IN THE MOUNTAINS SUNDAY AND BECOME MODERATE TO HEAVY AT TIMES SUNDAY AFTERNOON THROUGH MONDAY MORNING. SIGNIFICANT SNOW ACCUMULATIONS ARE POSSIBLE THROUGH TUESDAY WITH UP TO A COUPLE FEET OVER THE HIGHER TERRAIN AND POSSIBLY UP TO 3 FEET IN WESTERN JACKSON COUNTY. WINDS WILL BE STRONG ABOVE TIMBERLINE THROUGH THE MONDAY PRODUCING BLOWING SNOW. THE PLAINS WILL SEE A CHANCE FOR RAIN AND SNOW SUNDAY NIGHT AND EARLY MONDAY...OTHERWISE DRY CONDITIONS WILL PREVAIL. PERIODS OF LIGHT SNOW WILL CONTINUE WEDNESDAY AND THURSDAY OVER THE MOUNTAINS WHILE THE PLAINS REMAIN DRY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT. COOPER/MEIER
The national radar mosaic for the moment the first event began.
3 winter storm, 3 winter weather. Local standard time, as filed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2010Every state in 2010This day in weather historyWarnings in Colorado, December 2010
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: 271797, 271798, 271803, 271804, 271805, 271800.