An isolated thunderstorm moved across the northern portion of Canyonlands National Park. This storm produced enough rainfall to cause flash flooding in Upheaval Canyon.
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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.
An isolated thunderstorm moved across the northern portion of Canyonlands National Park. This storm produced enough rainfall to cause flash flooding in Upheaval Canyon.
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 Sep 2, 10:21 PM MST, 3 hours 39 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND JUNCTION CO 1121 PM MDT SUN SEP 2 2012 .SHORT TERM...(TODAY THROUGH MONDAY) ISSUED AT 227 PM MDT SUN SEP 2 2012 LATEST 18Z GUIDANCE CONTINUES TO FAVOR THE SAN JUANS AND ABAJO MOUNTAINS WITH PRECIPITATION THIS AFTERNOON AND EVENING WITH FORECAST FOLLOWING SUIT. RADAR MOSAIC HIGHLIGHTING PLENTY OF CONVECTION ALREADY HAVING FIRED TODAY BUT STORMS ARE QUITE WEAK AND BELIEVE THIS IS DUE TO MID-HIGH LEVEL CLOUD COVER LIMITING HEATING. DIFFERENTIAL HEATING MAY COME INTO PLAY ALONG EDGE OF CLOUD SHIELD AND IF THIS OCCURS...CONVECTION WILL SHIFT TO THE NORTH AND WEST TODAY...DID BUMP UP POPS IN THOSE AREAS WHICH INCLUDE THE UINTAH BASIN IN UTAH AND THE YAMPA RIVER BASIN IN CO BUT ONLY INTO ISOLD CATEGORY. THE RAPID REFRESH MODEL IS ALSO LOWERING QPF AMTS FOR REMAINDER OF TODAY AND TONIGHT WITH EACH HOURLY UPDATE AND IT APPEARS TO BE ON TRACK SO FAR. ONE FLY IN THE OINTMENT IS SOME BREAKS IN THE CLOUDS SEEN OVER SOUTHEASTERN UTAH ON THE VIS SATELLITE IMAGERY. IF ENOUGH HEATING PRESENTS ITSELF...MORE ORGANIZED CONVECTION IS POSSIBLE. THIS WILL BE MONITORED OVER THE NEXT FEW HOURS. TEMPS SHOULD HOVER RIGHT AROUND WHERE THEY SHOULD BE FOR THIS TIME OF YEAR. OVERNIGHT...NAM12 HAS DROPPED ALL QPF FROM OUR FORECAST AREA SHORTLY AFTER MIDNIGHT WHILE GFS KEEPS PRECIP GOING FOR MOST OF THE OVERNIGHT. LEANED TOWARDS NAM12 AS ITS DONE BETTER JOB LAST FEW DAYS WITH AREAL COVERAGE SO LOWERED QPF AMTS TO NIL IN THE EARLY MORNING HOURS THROUGH EARLY AFTERNOON MONDAY. FOR LABOR DAY...DRYING COMMENCES AS WINDS BECOME WESTERLY TO NORTHWESTERLY WITH PWATS DROPPING TO .3 TO .5 INCHES. MOISTURE TRANSPORT VECTORS DO SHOW SOME TRANSPORT OVER SOUTHERN REGIONS BUT TRAJECTORY WILL DROP SOUTHWARD THROUGH THE DAY. RESIDUAL MOISTURE WILL LEND ITSELF TO SOME CONVECTION IN THE AFTERNOON AND EVENING WITH THE SOUTHERN MTNS BEING FAVORED THOUGH HIGHER TERRAIN TO THE NORTH MAY ALSO SEE THE ODD CELL. REMAINING AREAS WILL SEE CONDITIONS IMPROVING THROUGH THE DAY WITH PLENTY OF SUN AND WARMING TEMPERATURES IN STORE. .LONG TERM...(MONDAY NIGHT THROUGH SATURDAY) ISSUED AT 227 PM MDT SUN SEP 2 2012 SEPTEMBER IS TYPICALLY A WET MONTH FOR THIS REGION. YET SEPTEMBER 2012 IS STARTING IN A DRY PERIOD. A DRY WEST FLOW WILL LIMIT MARGINAL MOISTURE TO JUST THE FOUR CORNERS AREA. THE WEAK JET STREAM LAYS ALONG THE WY-CO BORDER TUESDAY THROUGH WEDNESDAY NIGHT. IN THE WESTERLIES TO THE NORTH OF THE JET...A WEAK WAVE PASSES THROUGH THE NORTHERN ROCKIES TUESDAY NIGHT. WEDNESDAY NIGHT-THURSDAY THE JET SINKS INTO THE CENTRAL CWA AS A STRONGER WAVE DIGS INTO THE NORTHERN ROCKIES THEN PASSES ONTO THE HIGH PLAINS ON FRIDAY. THIS STRENGTHENS THE WEST GRADIENT WIND WED NIGHT-THURSDAY AND VEERS IT TO NW ON FRIDAY. SURFACE WINDS ARE STILL PROGGED TO REMAIN BELOW CRITICAL FIRE WEATHER PARAMETERS...BUT THIS NEEDS TO BE WATCHED. THIS ALSO EFFECTIVELY PUSHES THE REMAINING MOISTURE WELL SOUTH OF THE FOUR CORNERS FRIDAY INTO SATURDAY. LITTLE OR NO CONVECTION IS EXPECTED FOR THESE PERIODS. A RIDGE BUILDS INTO UTAH ON SATURDAY AND TO THE UTAH-COLORADO BORDER ON SUNDAY. MONSOONAL MOISTURE IS RIDING UP THE WEST SIDE OF THIS RIDGE THAT PROMISES TO WORK BACK INTO THE REGION EARLY NEXT WEEK. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT) ISSUED AT 1119 PM MDT SUN SEP 2 2012 ISOLATED THUNDERSTORMS ACROSS NORTHWEST COLORADO WILL COME TO AN END BY 08Z...WITH VFR CONDITIONS PREVAILING AT ALL TERMINAL SITES THROUGH 18Z. ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS DEVELOPS OVER THE MOUNTAINS MONDAY AFTERNOON AND WILL DRIFT OVER THE VALLEYS DURING THE EVENING HOURS. BRIEF HEAVY RAIN...GUSTY WINDS TO 40 MPH AND SMALL HAIL WILL ACCOMPANY THE STRONGEST STORMS. BRIEF MVFR CIGS WILL ALSO BE POSSIBLE. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...NONE. UT...NONE. && SHORT TERM...TGR LONG TERM...JOE AVIATION...JDC
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE GRAND JUNCTION CO 532 AM MDT SUN SEP 2 2012 COZ001>014-017>023-UTZ022>025-027>029-031200- LOWER YAMPA RIVER BASIN-CENTRAL YAMPA RIVER BASIN- ROAN AND TAVAPUTS PLATEAUS-ELKHEAD AND PARK MOUNTAINS- UPPER YAMPA RIVER BASIN-GRAND VALLEY-DEBEQUE TO SILT CORRIDOR- CENTRAL COLORADO RIVER BASIN-GRAND AND BATTLEMENT MESAS- GORE AND ELK MOUNTAINS/CENTRAL MOUNTAIN VALLEYS- CENTRAL GUNNISON AND UNCOMPAHGRE RIVER BASIN- WEST ELK AND SAWATCH MOUNTAINS-FLATTOPS- UPPER GUNNISON RIVER VALLEY-UNCOMPAHGRE PLATEAU AND DALLAS DIVIDE- NORTHWEST SAN JUAN MOUNTAINS-SOUTHWEST SAN JUAN MOUNTAINS- PARADOX VALLEY/LOWER DOLORES RIVER- FOUR CORNERS/UPPER DOLORES RIVER-ANIMAS RIVER BASIN- SAN JUAN RIVER BASIN-SOUTHEAST UTAH-EASTERN UINTA MOUNTAINS- EASTERN UINTA BASIN-TAVAPUTS PLATEAU-ARCHES/GRAND FLAT- LA SAL AND ABAJO MOUNTAINS-CANYONLANDS/NATURAL BRIDGES- 532 AM MDT SUN SEP 2 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR EASTERN UTAH AND WESTERN COLORADO. .DAY ONE...TODAY AND TONIGHT ISOLATED TO SCATTERED THUNDERSTORMS WILL DEVELOP THIS AFTERNOON...MAINLY ACROSS THE MOUNTAINS OF SOUTHWEST COLORADO AND SOUTHEAST UTAH. GUSTY WINDS TO 50 MPH...SMALL HAIL AND HEAVY RAIN WILL ACCOMPANY THE STRONGER STORMS. THE SHOWERS AND THUNDERSTORMS WILL END SHORTLY AFTER SUNSET THIS EVENING. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THERE IS A SLIGHT CHANCE FOR AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS EACH DAY...MAINLY OVER THE MOUNTAINS. GUSTY WINDS TO 40 MPH...SMALL HAIL AND BRIEF HEAVY RAINFALL WILL OCCUR WITH THE STRONGER STORMS. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED.
The Grand Junction radar (KGJX), 168 km away, was scanning. The volume nearest the first event began at 08:59 UTC.
1 flash flood. Local standard time, as filed.
National Park Service personnel reported flash flooding along Upheaval Wash. The fast moving flood waters cut into the steep banks which damaged the White Rim Road and made it impassable.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Utah in 2012Every state in 2012This day in weather historyWarnings in Utah, September 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: 495213.