A large and very moist Pacific storm system brought widespread heavy precipitation to Utah over a five day period. The storm pulled a continuous stream of tropical moisture ahead of it and, combined with numerous embedded shortwaves, resulted in almost non-stop rainfall across many of the lower elevations and wet, heavy snow in the mountains.
Every event with a place to put it. 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 SLC wrote it up.
A large and very moist Pacific storm system brought widespread heavy precipitation to Utah over a five day period. The storm pulled a continuous stream of tropical moisture ahead of it and, combined with numerous embedded shortwaves, resulted in almost non-stop rainfall across many of the lower elevations and wet, heavy snow in the mountains.
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 Salt Lake City, UT wrote its last area forecast discussion before the first event at Dec 17, 8:32 PM MST, 4 hours 28 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
832 PM MST FRI DEC 17 2010
.SYNOPSIS...AN INCREASINGLY MOIST AND MILD SOUTHWEST FLOW WILL
RESIDE ACROSS THE REGION THROUGH THE WEEKEND AND INTO THE FIRST
HALF OF NEXT WEEK. SEVERAL DISTURBANCES WITHIN THIS FLOW WILL
MAKE FOR A VERY ACTIVE WEATHER PATTERN.
&&
.DISCUSSION...WATER VAPOR LOOP SHOWS AN UPPER LOW NEAR 45N/145W
PIVOTING EASTWARD WITH A LEAD WAVE EJECTING TOWARD THE PACIFIC
NORTHWEST. ACARS 400-250MB WIND OBSERVATIONS PLACES A 110-130KT
WESTERLY JET FROM THE PACIFIC THROUGH CENTRAL CALIFORNIA AND NOSING
INTO NORTHWEST ARIZONA. 00Z 700MB ANALYSIS PLACES WEAK RIDGING
BREAKING DOWN ACROSS THE GREAT BASIN WITH A CYCLONE OFF THE PACIFIC
NORTHWEST. WARMING WAS OCCURRING LOCALLY WITH -9C AT KSLC AND -5C
ESTIMATED UPSTREAM AT NEAR LAS VEGAS VIA THE RUC. 00Z KSLC RAOB
SHOWS 3C OF WARMING BELOW 700MB DURING THE PAST 24 HOURS. THE
PROFILE HAS SATURATED IN THE MID LEVELS WITH SOME DRY AIR REMAINING
BELOW 700MB. THE WIND PROFILE SUGGEST STRONG WARM ADVECTION IN PLACE
WITH VEERING AND INCREASING SPEED WITH HEIGHT. A 2C INVERSION WAS
LOCATED NEAR 825MB.
GOES SOUNDER/RUC AND GPS PRECIPITABLE WATER SENSORS INDICATE VALUES
AROUND A THIRD OF AN INCH ACROSS MUCH OF THE REGION.
BASED ON ANOMALOUSLY HIGH MOISTURE IN PLACE...AN EVOLVING WARM
ADVECTION SCENERIO...AND WEB CAMERA IMAGERY ACROSS NORTHERN UTAH
THIS EVENING...HAVE RAISED A SNOW ADVISORY FOR MUCH OF THE NORTHERN
UTAH VALLEYS FOR THE OVERNIGHT AND SATURDAY MORNING HOURS. WE ARE
FOCUSING IN ON AREAS FAVORED IN SOUTHWEST FLOW WARM ADVECTION SUCH
AS EUREKA...PROVO CANYON...HEBER CITY...OGDEN VALLEY...AND THE
NORTHERN WASATCH FRONT. POPS AND QPF HAVE BEEN ADJUSTED THROUGH THE
DAY SATURDAY.
FEEL THE AMOUNT OF LOW LEVEL DRY AIR SAMPLED BY 00Z KSLC RAOB IS
ADEQUATE FOR EVAPORATIONAL COOLING...WHILE NOT OVERWHELMING
PRECIPITATION PROCESSES. CEILINGS HAVE BEEN LOWERING THROUGHOUT THE
EVENING AS AN INDICATION OF CONTINUED SATURATION.
EXPECT THE SALT LAKE VALLEY TO BE A RELATIVE LULL IN THIS PATTERN
WITH AN INCH OR SO. TEMPERATURES ARE ALSO SOMEWHAT WARMER ACROSS THE
VALLEY THAN ADJACENT ZONES. DID HOWEVER RAISE AN ADVISORY FOR THE
BENCHES...PARTICULARLY FOR NEAR BACCUS...HERRIMAN AND POINT OF THE
MOUNTAIN.
ANOTHER MESOSCALE ENHANCEMENT NOTICED IS IN THE VICINITY OF THE
PROVO CANYON WHERE COOLER EASTERLY FLOW WILL BE OVERRUN BY MOIST AND
INCREASINGLY WARMER AIRMASS. WEB CAMERAS INDICATE THIS WAS ONE OF
THE FIRST LOCAL AREAS TO SEE SNOW...LOCALLY HIGHER TOTALS CAN BE
EXPECTED NEAR WASATCH CANYONS. A SPOTTER JUST CALLED IN LOCALLY
HIGHER SNOW RATES IN THE VICINITY OF THE WEBER CANYON AS WELL.
LIGHT SNOW IS ALSO FORECAST FOR THE UPPER REACHES NEAR ST GEORGE
SUCH AS ZION NATIONAL PARK...THOUGH RISING SNOW LEVELS SHOULD KEEP
TOTALS BELOW ADVISORY CRITERIA.
EXPECTING AS THE WARM FRONT LIFTS THROUGH NORTHERN UTAH TOMORROW
MORNING...PRECIPITATION RATES WILL DECREASE. THIS...ALONG WITH
WARMING LOW LEVELS SHOULD END THE IMPACT FROM THE SNOW BY LATE
MORNING. QUESTION IS HOW LONG SNOW WILL HOLD ON DUE TO OVERRUNNING
IN THE CACHE VALLEY AND OGDEN VALLEY DUE TO TRAPPED COLD
AIR...PERHAPS INTO THE MID OR LATE AFTERNOON HOURS.
PREVIOUS DISCUSSION FOLLOWS...
MAY SEE A SLOWDOWN IN PRECIPITATION LATE SATURDAY AFTERNOON INTO
SATURDAY EVENING ONCE AFOREMENTIONED WARM FRONT LIFTS NORTHEAST.
THIS SLOWDOWN LOOKS TO BE SHORT LIVED HOWEVER...AS THE NEXT STRONGER
SURGE OF MOISTURE ARRIVES SUNDAY...AND INTERACTS WITH A COLD FRONT
PUSHING INTO NORTHERN UT LATE IN THE DAY. THIS FRONT SHOULD SERVE AS
THE FOCUS FOR VERY HEAVY SNOWFALL ACROSS THE NORTHERN UT
MOUNTAINS...WITH SNOW LEVELS FALLING BACK TO THE VALLEY FLOORS OF
THE WASATCH FRONT BY SUNDAY NIGHT.
WENT AHEAD AND UPGRADED GOING WATCH TO A WINTER STORM WARNING FOR
THE NORTHERN MOUNTAINS...AS ALTHOUGH PERIOD OF HEAVIEST SNOWFALL
WILL HOLD OFF UNTIL SUNDAY...SNOWFALL ACROSS THE NORTHERN
MOUNTAINS WILL REMAIN LARGELY CONTINUOUS THROUGH THIS TIME PERIOD.
FURTHER SOUTH BREAK IN SNOWFALL LOOKS TO BE LONGER LIVED...AND
WITH SNOW LEVELS RISING ABOVE 8 KFT ACROSS THE SOUTH BY SATURDAY
AFTERNOON OPTED TO GO WITH A WINTER WEATHER ADVISORY FOR CENTRAL
AND SOUTHERN MOUNTAINS THROUGH SATURDAY.
THIS FRONT LOOKS TO STALL ACROSS CENTRAL UT MONDAY NIGHT BEFORE
QUICKLY RETURNING NORTHWARD TUESDAY AS A WARM FRONT...LIKELY
BRINGING ANOTHER ROUND OF PRECIPITATION TO NORTHERN UT.
OF ADDITIONAL CONCERN IS THE POTENTIAL FOR HEAVY RAINFALL AND
POSSIBLE FLOODING ACROSS SOUTHWEST UT BEGINNING SUNDAY...AND
CONTINUING INTO THE FIRST HALF OF NEXT WEEK. 12Z/18Z NAM AND GFS
BOTH CONTINUE TO HIT SOUTHWEST UT HARD SUNDAY INTO MONDAY. PER
COORDINATION WITH RIVER FORECAST CENTER IT APPEARS MAIN-STEM
RIVERS SUCH AS THE VIRGIN SHOULD SEE SIGNIFICANT RISES BUT BE
ABLE TO HANDLE RUNOFF THROUGH MONDAY UNLESS FORECAST AMOUNTS
CHANGE. HOWEVER THIS RUNOFF WILL LIKELY CONTRIBUTE TO HIGH FLOWS
THROUGH NORMALLY DRY WASHES...SMALL STREAMS AND SLOT CANYONS.
MEDIUM RANGE MODELS HAVE BEEN OSCILLATING A BIT WITH RESPECT TO
HOW AMPLIFIED THE PATTERN BECOMES DURING THE MIDDLE PORTION OF THE
UPCOMING WEEK. THIS WILL HAVE A LARGE IMPACT ON PLACEMENT AND
DURATION OF WELL ESTABLISHED SUBTROPICAL MOISTURE TAP FORECAST
SPREAD SOMEWHERE FROM SOUTHERN CA INTO THE SOUTHERN GREAT BASIN.
&&
.AVIATION... CIG TRENDS AT THE KSLC TERMINAL CONTINUE TO LOWER
SLOWLY...WITH SUB 6000FT AGL CIGS EXPECTED BETWEEN 04-05Z. A THREAT
OF LIGHT SNOW EXISTS LATER TONIGHT LASTING THROUGH 16Z BEFORE
TURNING TO RAIN. AT THIS TIME...THE HIGHEST THREAT FOR MVFR SNOWFALL
WILL OCCUR IN THE 10-16Z TIMEFRAME...WITH A 30 PERCENT CHANCE IT
WILL ARRIVE EARLIER THAN CURRENT TAF SUGGESTS. WINDS TO PREVAIL FROM
THE SOUTH THROUGH MIDDAY TOMORROW.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER STORM WARNING FROM 2 AM SATURDAY TO 4 PM MST MONDAY FOR
UTZ007>010.
WINTER WEATHER ADVISORY UNTIL 11 AM MST SATURDAY FOR
UTZ001-002-004>006-015.
WINTER WEATHER ADVISORY UNTIL 11 AM MST SATURDAY FOR THE BENCHES
IN UTZ003.
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 4 PM MST
SATURDAY FOR UTZ517-518.
WY...NONE.
&&
PUBLIC...ROGOWSKI/SEAMAN
AVIATION...MERRILL
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION
VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP (ALL LOWER CASE)HAZARDOUS WEATHER OUTLOOK...UPDATED NATIONAL WEATHER SERVICE SALT LAKE CITY UT 833 PM MST FRI DEC 17 2010 UTZ001>016-019>021-517-518-WYZ021-181300- CACHE VALLEY/UTAH PORTION-NORTHERN WASATCH FRONT- SALT LAKE AND TOOELE VALLEYS-SOUTHERN WASATCH FRONT- GREAT SALT LAKE DESERT AND MOUNTAINS-WASATCH MOUNTAIN VALLEYS- WASATCH MOUNTAINS I-80 NORTH-WASATCH MOUNTAINS SOUTH OF I-80- WESTERN UINTA MOUNTAINS-WASATCH PLATEAU/BOOK CLIFFS- WESTERN UINTA BASIN-CASTLE COUNTRY-SAN RAFAEL SWELL- SANPETE/SEVIER VALLEYS-WEST CENTRAL UTAH-SOUTHWEST UTAH- UTAHS DIXIE AND ZION NATIONAL PARK-SOUTH CENTRAL UTAH- GLEN CANYON RECREATION AREA/LAKE POWELL-CENTRAL MOUNTAINS- SOUTHERN MOUNTAINS-SOUTHWEST WYOMING- 833 PM MST FRI DEC 17 2010 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE WESTERN TWO THIRDS OF UTAH AND SOUTHWEST WYOMING. .DAY ONE...TONIGHT A MOIST SOUTHWEST FLOW WILL DEVELOP TONIGHT AS A WARM FRONT LIFTS ACROSS THE OUTLOOK AREA. PRECIPITATION WILL INCREASE OVERNIGHT...WITH ACCUMULATING SNOW AFFECTING MUCH OF NORTHERN AND CENTRAL UTAH ALONG WITH THE HIGHER ELEVATION OF SOUTHERN UTAH. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY AN EXTENDED PERIOD OF MOIST AND RELATIVELY MILD WEST TO SOUTHWEST FLOW WILL CONTINUE THROUGH THE FIRST HALF OF NEXT WEEK. SEVERAL WEATHER DISTURBANCES WITHIN THIS FLOW WILL IMPACT MUCH OF THE OUTLOOK AREA...BRINGING SNOWFALL TO THE HIGHER TERRAIN...AND PERIODS OF RAIN AND SNOW TO MOST WESTERN VALLEYS. THE HEAVIEST SNOWFALL LOOKS TO COME SUNDAY AFTERNOON THROUGH SUNDAY NIGHT AS A COLD FRONT PUSHES SOUTHWARD ACROSS NORTHERN AND CENTRAL UTAH SUNDAY NIGHT. SNOW LEVELS BEHIND THIS FRONT ARE EXPECTED TO FALL TO THE VALLEY FLOORS. ADDITIONALLY...PERIODS OF HEAVY RAINFALL ARE EXPECTED ACROSS SOUTHWEST UTAH BEGINNING SUNDAY...AND CONTINUING THROUGH THE FIRST HALF OF NEXT WEEK. RAINFALL SUNDAY INTO MONDAY IS EXPECTED TO RESULT IN HIGH FLOWS AND POSSIBLE FLOODING THROUGH SMALL STREAMS...SLOT CANYONS AND NORMALLY DRY WASHES. ALTHOUGH NO FLOODING IS FORECAST ALONG MAIN-STEM RIVERS SUCH AS THE VIRGIN AND SANTA CLARA...SIGNIFICANT RISES ARE POSSIBLE. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. ROGOWSKI FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT... HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
The national radar mosaic for the moment the first event began.
12 winter storm, 2 flood. Local standard time, as filed.
The Ben Lomond Peak SNOTEL received 9.00 inches of liquid equivalent precipitation, or approximately 65 inches of snow based on snow ratios at similar elevations. Snowbasin Resort also reported 43 inches of new snow for the event.
The Brown Duck SNOTEL received 6.30 inches of liquid equivalent precipitation, or approximately 55 inches of new snow.
Storm totals for the 5-day event included 84 inches at Brighton Crest, 76 inches at Deer Valley Daly West, 73 inches at Sundance - Mid Mnt., 70 inches at Alta Ski Lifts, 70 inches at Provo Canyon, 54 inches at Solitude Mountain Resort, and 50 inches at Snowbird Ski and Summer Resort.
The Indian Canyon SNOTEL received 7.30 inches of liquid equivalent precipitation, or approximately 58 inches of snow based on snow ratios at similar elevations.
The Midway Valley SNOTEL received 10.20 inches of liquid equivalent precipitation, or approximately 70 inches of new snow over the 5-day event.
The Buck Flat SNOTEL received 5.80 inches of liquid equivalent precipitation for the storm, or approximately 50 inches of new snow.
Heavy rain caused widespread significant flooding across Washington County. Rainfall and significantly increased river flows began on December 19th, with many rivers and streams around Zion National Park and St. George near bankfull. Reports of road flooding began on December 20th. SR-9 was closed in Zion National Park due to flooding between the tunnel and Mt. Carmel Junction, and flooding and rockslides occurred on SR-18 between Enterprise and Central.
The worst of the flooding occurred on December 21st, when the flow of the Santa Clara River increased to an estimated 5000 cfs, and the Virgin River near Bloomington was measured at 12400 cfs. Zion National Park was closed due to flooding, and the Zion Park Lodge was evacuated due to the danger of landslides. One historic landslide, in particular, was moving through the day as the riprap structure was eroded away. Old Highway 91 was also closed, as flooding and debris washed out and damaged much of the road. Many other roadways across the county were flooded, including many roads in the city of St. George, many rural roads along the Santa Clara, SR-18 south of Central, in Enterprise along Center Street and Main Street, and the road into Snow Canyon State Park, which closed the park to tourists. Many bridges were damaged or destroyed, including the foot bridge over the Fort Pearce Wash, the Tobin Wash Bridge near Gunlock, a foot bridge at the Sunbrook Golf Course, the bridge at 2500 South in New Harmony, and the bridge at Brookside. Residential flood damage was reported in Enterprise, Springdale, Rockville, and St. George. Contaminated water became a problem along the Virgin River, and culinary water became unavailable in the town of Gunlock. The Southgate Golf Course in St. George suffered extensive damage due to erosion.
Flooding continued on December 22nd. Flood waters damaged a bridge in New Harmony Heights, closed many roadways including a bridge near the Enterprise Reservoir, and up to 15 homes were damaged to varying degrees in Brookside. River flows stayed high on December 23rd before receding.
Damage estimates were obtained from the Utah Emergency Management Association, and included damages of $4.7 million to infrastructure and $15 million to other properties. In addition, $300,000 worth of heavy construction equipment was saved when the NWS forecast office in Salt Lake City called the Washington City Public Works, notifying of them of the upcoming high flows expected on the Virgin River. The Public Works pulled all of their equipment out of the Virgin River, which they said would have been swept away and lost if not for the phone call.
While flooding in Kane County was less than in nearby Washington County, significant damage still occurred. Many roads were closed or impassable due to flood waters, including Highway 14, the 3rd South Connector in Kanab, and US-89 east of Kanab, the last of which had 12 inches of water flowing over the road. A landslide also occurred on US-89 near milepost 93, where debris was approximately 4 feet deep and 50-60 feet wide. Residential flooding occurred in Orderville and Glendale, and many private roads in those two towns were washed out.
The southern Wasatch Front received heavy snowfall in the southwesterly flow, with 28 inches of snow recorded in Levan, 26 inches in Nephi, and 22 inches in Santaquin.
New snowfall in the Wasatch mountain valleys included 25 inches in Heber City, 22 inches in Park City, 16 inches at Deer Creek Dam, 13 inches in Morgan, and 12 inches in Eden.
Storm totals in the Uinta Basin included 28 inches of snow in Altamont and 27 inches in Duchesne.
Storm total snowfall included 21 inches in Salina and 20 inches in Richfield.
Fillmore received 21 inches of new snow. Other reports included 16 inches in Oak City and 9 inches in Delta.
Milford received 15 inches of new snow.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Utah in 2010Every state in 2010This day in weather historyWarnings in Utah, 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: 274462, 274463, 274460, 274461, 274554, 274553, 275462, 275465, 274561, 274562, 274555, 274556, 274558, 274559.