A cold and stable airmass resulted in dense fog formation across the lower valleys of western Colorado and eastern Utah.
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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.
A cold and stable airmass resulted in dense fog formation across the lower valleys of western Colorado and eastern Utah.
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 18, 3:55 PM MST, 2 hours 5 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND JUNCTION CO 355 PM MST FRI DEC 18 2009 .SHORT TERM...TONIGHT THROUGH SUNDAY... THE TREND CONTINUES FOR THE SHORT TERM. NORTHWEST FLOW ALOFT WITH A FEW MINOR DISTURBANCES PRODUCING MAINLY INTERMITTENT MID TO UPPER LEVEL CLOUD COVER WITH A FEW SHOWERS OVER THE NORTHERN MOUNTAINS OF WESTERN CO. INCREASED SHOWERS OVER THE HIGHEST ELEVATIONS OF THE NORTHERN MOUNTAINS THIS EVENING AND TAPERED THEM OFF AFTER MIDNIGHT. EXPECT STRONG VALLEY INVERSIONS TO REMAIN OVERNIGHT AND KEPT PATCHY FOG. FOG MAY BECOME LOCALLY DENSE IN THE WEST CENTRAL VALLEYS AND EASTERN UINTA BASIN...BUT HELD OFF ON HILITES FOR NOW. MID LEVEL MOISTURE BEGINS TO TAPER OFF DURING THE DAY SATURDAY REDUCING CLOUD COVER AS THE RIDGE AXIS MOVES EAST. THE RIDGE WILL BECOME LESS AMPLIFIED AS IT SHIFTS EAST. EXPECT TEMPERATURES TO INCREASE SLIGHTLY THROUGH THE WEEKEND AND VALLEY INVERSIONS WILL ERODE SLIGHTLY. THERE IS NO FEATURES TO FLUSH THE VALLEYS OUT IN THE SHORT TERM. KEPT PATCHY FOG SATURDAY NIGHT INTO SUNDAY MORNING FOR THE WEST CENTRAL VALLEYS AND UINTA BASIN. .LONG TERM...SUNDAY NIGHT THROUGH FRIDAY... WESTERLY FLOW DEVELOPS SUN NIGHT INTO MON AS THE WESTERN RIDGE CONTINUES TO BREAK DOWN AS A TROUGH DEVELOPS ALONG THE WEST COAST. INITIAL EMBEDDED WAVE EJECTED FROM THE TROUGH WEAKENS AS IT MOVES ACROSS ON MON. CLOUDS/MOISTURE WILL INCREASE MON NIGHT-TUE AS FLOW BECOMES WEST-SOUTHWEST. 12Z GFS AND ECWMF MODELS NOTICEABLY DIFFERENT FROM EACH OTHER HANDLING THE TROUGHS INLAND MOVEMENT...UNLIKE LAST NIGHT/S RUNS WHICH WERE MORE SIMILAR. BOTH MODELS TRY TO PHASE A PAC SHORTWAVE MOVING INTO CA WITH A NRN STREAM SHORTWAVE DIVING DOWN ACROSS VANCOUVER ISL...BUT THE EC...AND TO SOME EXTENT THE 12Z CANADIAN GEM...FAVORS THE NRN STREAM SHORTWAVE BY CLOSING OFF AN UPPER LOW OVER NV/AZ TUE WHILE THE GFS FAVORS THE PAC SHORTWAVE AND IS MORE PROGRESSIVE. BOTH SCENARIOS RESULT IN DIFLUENT FLOW OVER ERN UT/WRN CO TUE-TUE NIGHT WITH AN INFLUX OF COLDER AIR TUE NIGHT. GFS SHOWS DECENT COLD FRONTAL PASSAGE TUE NIGHT. WILL BUMP POPS UP TUE- TUE NIGHT AS A RESULT BUT STILL STAY IN THE CHANCE CATEGORY. WED-FRI HINGES ON HOW THE TROUGH ACTUALLY DEVELOPS...BUT WITH NWLY WILL KEEP A CHANCE OF SNOW FOR THE MTNS AND NW CO WED AND THEN DECREASING POPS THU-FRI. WHILE THE STORM ANTICIPATED TUE-WED SHOULD OVERTURN THE STAGNANT AIR IN VALLEYS...INVERSIONS SHOULD RETURN LATE NEXT WEEK AS HIGH PRESSURE RETURNS AND COLD AIR AGAIN SETTLES INTO THE VALLEYS. && .AVIATION... AREAS OF MVFR/IFR WILL BE COMMON ACROSS THE LOWER RIVER VALLEYS WITH LOCAL VIS DROPPING BELOW 1SM AT TIMES FROM FOG. IMPROVEMENT WILL BE SLOW AND 5SM IN FOG OR HAZE WILL BE COMMON ACROSS THE VALLEYS OF NE UTAH AND KGJT. MVFR/IFR CONDITIONS WILL LIKELY DEVELOP TONIGHT. FOR THE HIGHER ELEVATIONS...LIGHT SNOW AT TIMES CAN BE EXPECTED THROUGH EARLY SATURDAY OVER THE NRN DIVIDE MOUNTAIN PASSES FOR MOUNTAIN OBSCURATIONS OTHERWISE VFR CONDITIONS WILL PREVAIL. ONLY A FEW SNOW SHOWERS ARE EXPECTED OVER THE NRN DIVIDE MOUNTAIN TONIGHT... BUT CLOUDS WILL STILL HUG THE HIGH TERRAIN. && .GJT WATCHES/WARNINGS/ADVISORIES... .CO...NONE. .UT...NONE. SHORT TERM...AS LONG TERM....JAD AVIATION.....TGJT
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE GRAND JUNCTION CO 600 AM MST FRI DEC 18 2009 COZ001>014-017>023-UTZ022>025-027>029-191300- ANIMAS RIVER BASIN-ARCHES/GRAND FLAT-CANYONLANDS/NATURAL BRIDGES- CENTRAL COLORADO RIVER BASIN- CENTRAL GUNNISON AND UNCOMPAHGRE RIVER BASIN- CENTRAL YAMPA RIVER BASIN-DEBEQUE TO SILT CORRIDOR- EASTERN UINTA BASIN-EASTERN UINTA MOUNTAINS- ELKHEAD AND PARK MOUNTAINS-FLAT TOPS- FOUR CORNERS/UPPER DOLORES RIVER- GORE AND ELK MOUNTAINS/CENTRAL MOUNTAINS-GRAND AND BATTLEMENT MESAS- GRAND VALLEY-LA SAL AND ABAJO MOUNTAINS-LOWER YAMPA RIVER BASIN- NORTHWEST SAN JUAN MOUNTAINS-PARADOX VALLEY/LOWER DOLORES RIVER- ROAN AND TAVAPUTS PLATEAUS-SAN JUAN RIVER BASIN-SOUTHEAST UTAH- SOUTHWEST SAN JUAN MOUNTAINS-TAVAPUTS PLATEAU- UNCOMPAHGRE PLATEAU AND DALLAS DIVIDE-UPPER GUNNISON RIVER VALLEY- UPPER YAMPA RIVER BASIN-WEST ELK AND SAWATCH MOUNTAINS- 600 AM MST FRI DEC 18 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR EASTERN UTAH AND WESTERN COLORADO. .DAY ONE...TODAY AND TONIGHT AREAS OF FOG...AT TIMES DENSE...WILL CONTINUE TO CAUSE REDUCED VISIBILITY IN SOME WESTERN VALLEYS EARLY THIS MORNING. VISIBILITY MAY FALL BELOW ONE QUARTER MILE AT TIMES...ESPECIALLY IN THE GRAND VALLEY IN WESTERN COLORADO...AND IN THE GRAND FLAT AND THE UINTA BASIN IN EASTERN UTAH. THE FOG IS EXPECTED TO DIMINISH BY LATE THIS MORNING. VISIBILITY WILL AGAIN DIMINISH AS FOG DEVELOPS AGAIN THIS EVENING IN THE CENTRAL VALLEYS OF FAR WESTERN COLORADO...AND IN THE CENTRAL AND NORTHERN VALLEYS OF EASTERN UTAH. ALSO LIGHT SNOW IS POSSIBLE OVER THE NORTHERN MOUNTAINS NEAR THE CONTINENTAL DIVIDE THROUGH TONIGHT. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY LIGHT SNOW WILL BE POSSIBLE AT TIMES OVER THE NORTHERN MOUNTAINS... THROUGH MONDAY. BY TUESDAY THE CHANCE FOR SNOW WILL INCREASE AND SPREAD ACROSS MOST OF EASTERN UTAH AND WESTERN COLORADO...THEN DIMINISH AGAIN BY THURSDAY. SIGNIFICANT MOUNTAIN SNOW WILL BE POSSIBLE AND PEOPLE PLANNING TRAVEL SHOULD LOOK FOR UPDATED FORECASTS ON THIS DEVELOPING WINTER STORM. THE SNOW WILL BE FOLLOWED BY COLDER TEMPERATURES ON THURSDAY...MOST NOTABLY ACROSS THE NORTHERN AREAS. .SPOTTER INFORMATION STATEMENT SPOTTER ACTIVATION IS NOT ANTICIPATED TODAY OR TONIGHT. TGJT
The national radar mosaic for the moment the first event began.
2 dense fog. Local standard time, as filed.
Dense fog frequently reduced visibilities to near one quarter mile, especially along I-70 from the Colorado state line to Green River, Utah, and also along highway 191 between Crescent Junction and Moab.
Dense fog frequently reduced visibilities to below one quarter mile, particularly along highway 40 between the Colorado border and Ballard, Utah.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Utah in 2009Every state in 2009This day in weather historyWarnings in Utah, December 2009
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: 203111, 203110.