A low pressure system moved across southern Wyoming and northern Colorado. A strong west to southwest upslope flow brought moderate to heavy snowfall to the Snowy and Sierra Madre mountains.
Every event with a place to put it; 10 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 CYS wrote it up.
A low pressure system moved across southern Wyoming and northern Colorado. A strong west to southwest upslope flow brought moderate to heavy snowfall to the Snowy and Sierra Madre mountains. Storm total snowfall accumulations of 6 to 12 inches were estimated.
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 Cheyenne, WY wrote its last area forecast discussion before the first event at Nov 9, 10:56 PM MST, 1 hour 4 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 1056 PM MST FRI NOV 9 2012 .AVIATION...06Z TAF ISSUANCE...FOG AND LOW CEILINGS OVER NEBRASKA TAF SITES FOR TONIGHT INTO LATE SATURDAY MORNING. WIDESPREAD IFR CIGS WILL OCCUR WITH POCKETS OF DENSE FOG. FOG WILL SLOWLY DISSIPATE AFTER SUNRISE AND THROUGH SATURDAY MORNING. SNOW WILL SPREAD FROM SOUTHCENTRAL INTO THE LARAMIE RANGE LATE TONIGHT. MOUNTAINS WILL BE OBSCURED. AREAS OF SNOW ARE EXPECTED TO SPREAD ACROSS SOUTHEAST WYOMING LATE SATURDAY MORNING AND INTO THE NEBRASKA PANHANDLE SATURDAY AFTERNOON. PREDOMINATELY IFR TO MVFR CIGS SATURDAY. && .PREV DISCUSSION... /ISSUED 707 PM MST FRI NOV 9 2012/ UPDATE... UPDATED GRIDS FOR LOW CEILINGS AND FOG OVER THE NEBRASKA HANDLE TONIGHT. STATUS DECK CURRENTLY KNOCKING ON THE DOOR OF FAR EASTERN PORTIONS OF THE FORECAST AREA AND ADVANCING WESTWARD. HRRR MODEL SHOWING LOW CIGS PUSHING TO THE WYOMING BORDER LATE TONIGHT AND NAM MODEL SOUNDINGS SUGGESTING THE SAME UNDER LIGHT SOUTHEAST FLOW. COULD POSSIBLE SEE POCKETS OF DENSE FOG. LOW CIGS AND FOG SHOULD BEGIN TO DISSIPATE FOLLOWING THE PASSAGE OF THE COLD FRONT. WOULD NOT BE SURPRISED TO SEE PATCHY DRIZZLE MIXED IN WITH THE FOG. FORTUNATELY TEMPERATURES WILL MAINLY STAY ABOVE FREEZING AND SHOULD TEMPERATURES DIP SLIGHTLY BELOW FREEZING...ROAD TEMPERATURES SHOULD BE WARM ENOUGH TONIGHT SUCH THAT FREEZING DRIZZLE IS NOT A CONCERN. AVIATION...00Z TAF ISSUANCE...UPDATE... ADDED FOG AND LOW CEILINGS TO NEBRASKA TAF SITE FOR TONIGHT INTO LATE SATURDAY MORNING. STRATUS DECK OVER SOUTHWEST SD AND CENTRAL NE IS MOVING WESTWARD AND WILL AFFECT MUCH OF THE NEBRASKA PANHANDLE TONIGHT. WIDESPREAD IFR CIGS WILL OCCUR WITHIN THIS STATUS DECK WITH POCKETS OF DENSE FOG POSSIBLE. SNOW WILL FORM OVER SOUTHCENTRAL WYOMING THIS EVENING AND SPREAD INTO THE LARAMIE RANGE LATE TONIGHT. MOUNTAINS WILL BECOME OBSCURED. AREAS OF SNOW ARE EXPECTED TO SPREAD ACROSS SOUTHEAST WYOMING LATE SATURDAY MORNING AND INTO THE NEBRASKA PANHANDLE SATURDAY AFTERNOON. PREDOMINATELY IFR TO MVFR CIGS SATURDAY BUT SKIES. PREV DISCUSSION... /ISSUED 442 PM MST FRI NOV 9 2012/ AVIATION...00Z TAFS. SURFACE LOW PRESSURE WILL MOVE SOUTHEAST AND DEVELOP NEAR CHEYENNE BY 12Z SATURDAY WITH A COLD FRONT MOVING TO AN ALLIANCE TO CHEYENNE LINE. SCATTERED TO NUMEROUS SNOW SHOWERS DEVELOPING OVERNIGHT WEST OF INTERSTATE 25...PRODUCING MVFR AND IFR AND MOUNTAIN OBSCUREMENT...VFR EAST OF A DOUGLAS TO LARAMIE LINE. SURFACE LOW FROM EASTERN SOUTH DAKOTA TO LINCOLN NEBRASKA BY 00Z SUNDAY WITH A COLD FRONT HAVING MOVED ACROSS TAF SITES. AFTER 12Z SATURDAY...NORTH TO NORTHWEST WINDS GUSTING UP TO 35 KNOTS ALONG WITH SCATTERED TO NUMEROUS SNOW SHOWERS PRODUCING IFR AND MVFR AND MOUNTAIN OBSCURATION IN THE WAKE OF THE COLD FRONT. RUBIN PREV DISCUSSION... /ISSUED 403 PM MST FRI NOV 9 2012/ SHORT TERM...TONIGHT THROUGH SUNDAY... STRONG SOUTHERLY WINDS ARE STILL GUSTING AS HIGH AS 50 MPH OVER PARTS OF CARBON COUNTY EARLY THIS AFTERNOON. WILL CONTINUE THE HIGH WIND WARNING FOR THAT PART OF THE CWA UNTIL 01Z. THE REST OF THE FORECAST WILL CONTINUE TO BE DOMINATED BY THE WELL ADVERTISED STORM SYSTEM CURRENTLY OVER THE PACIFIC NORTHWEST. THE FEATURE MOVES QUICKLY EAST THROUGH SUNDAY AND BY 00Z MONDAY WILL BE OVER THE PLAINS. MOST OF THE ENERGY WILL TRACK ACROSS THE NORTHERN ROCKIES AND NORTHERN PLAINS ASSOCIATED WITH THE BROAD CLOSED LOW. IN THE SOUTHERN PORTION OF THE TROUGH...A 300 MB JET WILL NOSE INTO THE AREA ON SATURDAY. CURRENTLY... MODERATE SNOWFALL RATES WERE OCCURRING OVER PARTS OF NORTHERN UTAH AND FAR WESTERN WYOMING DUE TO THE LOCATION OF THAT 300 MB JET. ALSO MOVING OVER THE CWA WILL BE AN AREA OF MID LEVEL CONVERGENCE ON SATURDAY AND SATURDAY EVENING. STRONG COLD AIR ADVECTION WILL OCCUR OVER THE CWA SATURDAY AS THE TROUGH APPROACHES AND PASSES. COLD SURFACE AIR WAS MOVING THROUGH NORTHERN WYOMING EARLY THIS AFTERNOON. THE COLD FRONT WILL CONTINUE TO SLOWLY MOVE SOUTH AND ACROSS THE CWA LATER TONIGHT AND SATURDAY MORNING. THE RESULT WILL BE COLDER TEMPERATURES OVER THE CWA THROUGH SUNDAY AS WELL AS SNOW. THE MORE SIGNIFICANT SNOWFALL WILL OCCUR OVER THE MOUNTAINS LATE TONIGHT THROUGH SATURDAY NIGHT. OVER THE LOWER ELEVATIONS IT APPEARS THAT THERE WILL BE A PERIOD OF SIGNIFICANT SNOW SATURDAY AND EARLY SATURDAY NIGHT AS THE MORE FAVORABLE DYNAMICS MOVE EAST ACROSS THE CWA. GARCIA METHOD SHOWS THE POSSIBILITY OF SNOWFALL RATES OF UP TO AN INCH PER HOUR FOR A FEW HOURS DURING THAT TIME. THEN DRIER AND COLDER AIR MOVES OVER THE CWA SATURDAY NIGHT ALONG WITH A MORE WESTERLY WIND ALOFT TO REDUCE THE SNOWFALL RATES. THE SNOWY AND SIERRA MADRE RANGE WILL RECEIVE BETWEEN 6 AND 10 INCHES OF SNOW...WITH 1 TO 3 INCHES OVER THE REST OF THE CWA...ESPECIALLY SOUTHERN PARTS. WILL CONTINUE THE PREVIOUSLY ISSUED WINTER WEATHER ADVISORY FOR THE MOUNTAINS. THE SNOWFALL WILL BE FOCUSED ON THE WEST PART OF THE CWA FROM OROGRAPHICS LATER SATURDAY NIGHT AND SUNDAY. IN ADDITION... NORTHWEST SURFACE WINDS INCREASE BY SUNDAY WITH GUSTS AS HIGH AS 40 MPH MAINLY ALONG AND WEST OF THE LARAMIE RANGE. LONG TERM...SUNDAY NIGHT THROUGH FRIDAY. SUNDAY NIGHT...THE WEEKEND STORM SYSTEM WILL BE MOVING AWAY FROM THE REGION INTO THE CENTRAL PLAINS STATES...THUS DRY IN OUR COUNTIES DUE TO DOWNWARD MOTION AND DECREASING LOW AND MID LEVEL MOISTURE. SURFACE WINDS WILL INCREASE MARKEDLY WEST OF INTERSTATE 25 AS THE SURFACE GRADIENT STRENGTHENS...THUS PRODUCING BLOWING SNOW ACROSS CARBON...ALBANY AND CONVERSE COUNTIES AND OVER WESTERN LARAMIE AND PLATTE COUNTIES. MONDAY...FLOW ALOFT BACKS TO NORTHWEST INDUCING SURFACE LEE TROUGH TO DEVELOP...AND THUS PRODUCING A WARMING TREND WITH MAXIMA IN THE 30S TO LOWER 40S...DESPITE SOME MIDDLE AND HIGH CLOUD OPACITY. TUESDAY...ZONAL...WEST TO EAST FLOW...ALOFT ENSUES...AIDING EVEN MORE IN A WARMING TREND DUE TO BETTER KATABATIC WARMING OF THE LOW LEVELS DUE TO DOWNSLOPING. TEMPERATURES WILL AS USUAL BE HIGHLY DEPENDENT ON OPACITY OF MIDDLE AND HIGH CLOUDS IN THE FAST WESTERLY FLOW ALOFT. MIDDLE AND HIGH CLOUD OPACITY IS KEY FOR TEMPERATURE FORECASTING...ESPECIALLY OVER AND NEAR THE MOUNTAINS. WEDNESDAY...UNUSUALLY HIGH HEIGHTS ALOFT...WITH 500 MB HEIGHTS NEAR 5670 METERS...AND LOW AMPLITUDE SHORTWAVE RIDGING ALOFT WILL CONTINUE THE SLOW WARMING TREND. IT APPEARS THE MORE OPAQUE MIDDLE AND HIGH CLOUDS WILL STREAM ACROSS NORTHERN WYOMING OVER THE DIRTY RIDGE CENTERED OVER IDAHO AND NORTHWEST WYOMING...WITH SOME OF THESE MORE OPAQUE MIDDLE AND HIGH CLOUDS NORTH OF A RAWLINS TO SCOTTSBLUFF LINE. THURSDAY...NEXT NEGATIVELY TILTED SHORTWAVE TROUGH ALOFT APPROACHES FROM UTAH AND COLORADO...SPREADING MIDDLE AND HIGH CLOUDS NORTHEAST ACROSS OUR COUNTIES...THUS SLIGHTLY COOLER. FRIDAY...THE SHORTWAVE TROUGH ALOFT MOVES ACROSS SOUTH DAKOTA AND NEBRASKA...THUS THE SUBSIDENT SECTOR ACROSS OUR COUNTIES WILL KEEP IT DRY...ASIDE FROM ISOLATED OROGRAPHIC SHOWERS OVER THE SNOWY AND SIERRA MADRES IN MOIST NORTHWEST FLOW ALOFT. AVIATION...18Z TAF ISSUANCE... THROUGH 01Z...STRONG SOUTHWEST WINDS SUSTAINED NEAR 40 KNOTS GUSTING TO 50 KNOTS AT RAWLINS. THROUGH 00Z...VFR WITH SURFACE LOW STRENGTHENING ACROSS WESTERN WYOMING NEAR THERMOPOLIS...PRODUCING INCREASING SOUTH AND SOUTHEAST WINDS ACROSS TAF SITES. AFTER 00Z... SURFACE LOW DEVELOPING FROM NORTHEAST COLORADO TO NORTH CENTRAL NEBRASKA WITH A COLD FRONT MOVING EASTWARD AND STRETCHING FROM CHADRON TO FORT COLLINS BY 12Z SATURDAY. AFTER 04Z...SCATTERED SNOW SHOWERS AND AREAS OF FOG AT RAWLINS PRODUCING IFR AND MVFR AND MOUNTAIN OBSCUREMENT. VFR ELSEWHERE. AFTER 15Z...WINDS BECOMING NORTH AND NORTHWEST AFTER COLD FRONTAL PASSAGE AND INCREASING WITH WINDS GUSTING TO 30 KNOTS. SCATTERED SHOW SHOWERS PRODUCING MVFR AT RAWLINS TAF WITH VFR AT OTHER SITES. FIRE WEATHER... GUSTY SOUTHERLY SURFACE WINDS WILL CONTINUE OVER THE WEST PART OF THE CWA THROUGH SUNSET. THEN FIRE WEATHER CONCERNS WILL BE MINIMAL THROUGH MONDAY. A STORM SYSTEM WILL MOVE ACROSS THE REGION... BRINGING COLDER TEMPERATURES AND A GOOD CHANCE OF SNOW THROUGH THAT TIME. DRIER...WARMER AND BREEZY WEATHER WILL RETURN TO THE REGION TUESDAY THROUGH THE END OF NEXT WEEK. TEMPERATURES AT THIS TIME ARE NOT EXPECTED TO BE AS WARM AS RECENT DAYS. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...WINTER WEATHER ADVISORY UNTIL MIDNIGHT SUNDAY FOR WYZ112-WYZ114. NE...NONE. && UPDATE...LIEBL SHORT TERM/FIRE WEATHER...WEILAND LONG TERM...RUBIN AVIATION...LIEBL
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE CHEYENNE WY 714 PM MST FRI NOV 9 2012 WYZ101>119-101245- CONVERSE COUNTY LOWER ELEVATIONS-NIOBRARA COUNTY- NORTH LARAMIE RANGE-FERRIS/SEMINOE/SHIRLEY MOUNTAINS- SHIRLEY BASIN-CENTRAL LARAMIE RANGE AND SOUTHWEST PLATTE COUNTY- EAST PLATTE COUNTY-GOSHEN COUNTY-CENTRAL CARBON COUNTY- NORTH SNOWY RANGE FOOTHILLS-SOUTHWEST CARBON COUNTY- SIERRA MADRE RANGE-UPPER NORTH PLATTE RIVER BASIN-SNOWY RANGE- LARAMIE VALLEY-SOUTH LARAMIE RANGE-SOUTH LARAMIE RANGE FOOTHILLS- CENTRAL LARAMIE COUNTY-EAST LARAMIE COUNTY- 714 PM MST FRI NOV 9 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR EAST CENTRAL WYOMING... SOUTH CENTRAL WYOMING AND SOUTHEAST WYOMING. .DAY ONE...THIS AFTERNOON AND TONIGHT SNOW WILL DEVELOP OVER SOUTH CENTRAL PORTIONS OF WYOMING TONIGHT. SNOW ACCUMULATIONS TONIGHT WILL GENERALLY BE AROUND 1 INCH WITH SEVERAL INCHES EXPECTED IN THE SNOWY AND SIERRA MADRE MOUNTAINS. A SNOW ADVISORY IS IN EFFECT TONIGHT THROUGH SATURDAY FOR THE MOUNTAINS. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY A STRONG COLD FRONT WILL SWEEP ACROSS THE AREA EARLY SATURDAY BRINGING MUCH COLDER TEMPERATURES...SNOWFALL AND WINDY CONDITIONS. LIGHT SNOWFALL ACCUMULATIONS WILL BE POSSIBLE WITH THIS STORM SYSTEM...MOST OF WHICH WILL FALL DURING THE AFTERNOON AND EVENING HOURS ON SATURDAY. HIGH TEMPERATURES WILL ONLY REACH THE 20S AT MOST LOCATIONS ON SUNDAY WITH LOW TEMPERATURES FALLING INTO THE SINGLE DIGITS TO NEAR ZERO FOR AREAS WEST OF THE LARAMIE RANGE ON SUNDAY NIGHT. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED THIS AFTERNOON AND TONIGHT. && THIS PRODUCT...ALONG WITH OTHER WEATHER...HYDROLOGIC...AND CLIMATE INFORMATION IS AVAILABLE ON THE WEB AT... HTTP://WEATHER.GOV/CHEYENNE NEZ002-003-019>021-054-055-095-096-101245- DAWES-BOX BUTTE-SCOTTS BLUFF-BANNER-MORRILL-KIMBALL-CHEYENNE- NORTH SIOUX-SOUTH SIOUX- 714 PM MST FRI NOV 9 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE WESTERN NEBRASKA PANHANDLE. .DAY ONE...THIS AFTERNOON AND TONIGHT FOG WILL DEVELOP ACROSS MUCH OF THE NEBRASKA PANHANDLE TONIGHT. THE FOG COULD BECOME DENSE AT TIMES...MAKING FOR POOR TRAVEL CONDITIONS. FOG WILL DISSIPATE THROUGH LATE SATURDAY MORNING. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY A STRONG COLD FRONT WILL SWEEP ACROSS THE AREA SATURDAY MORNING WITH MUCH COLDER TEMPERATURES...SNOWFALL AND WINDY CONDITIONS. LIGHT SNOWFALL ACCUMULATIONS WILL BE POSSIBLE WITH THIS STORM SYSTEM...MOST OF WHICH WILL FALL SATURDAY AFTERNOON AND EVENING. HIGH TEMPERATURES WILL ONLY REACH THE 20S AT MOST LOCATIONS ON SUNDAY WITH LOW TEMPERATURES FALLING INTO THE SINGLE DIGITS SUNDAY NIGHT. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED THIS AFTERNOON AND TONIGHT. && THIS PRODUCT...ALONG WITH OTHER WEATHER...HYDROLOGIC...AND CLIMATE INFORMATION IS AVAILABLE ON THE WEB AT... HTTP://WEATHER.GOV/CHEYENNE WEILAND/LIEBL
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE CHEYENNE WY 934 PM MST FRI NOV 9 2012 NEZ002-003-019>021-054-055-095-096-100600- DAWES-BOX BUTTE-SCOTTS BLUFF-BANNER-MORRILL-KIMBALL-CHEYENNE- NORTH SIOUX-SOUTH SIOUX- INCLUDING THE CITIES OF...CHADRON...ALLIANCE...SCOTTSBLUFF... GERING...HARRISBURG...BRIDGEPORT...BAYARD...KIMBALL...SIDNEY... HARRISON...AGATE 934 PM MST FRI NOV 9 2012 AREAS OF FOG AND LOCALLY DENSE FOG WILL SPREAD ACROSS THE WESTERN NEBRASKA PANHANDLE TONIGHT. VISIBILITIES MAY BE REDUCED TO 1/4 MILE AT TIMES. AS OF 930 PM MST...FOG EXTENDED FROM AROUND CHADRON TO ALLIANCE TO NEAR SIDNEY. THE FOG IS EXPECTED TO SPREAD WEST TO THE WYOMING BORDER TOWARDS MIDNIGHT. FOG WILL REMAIN ACROSS THE AREA THROUGH MUCH OF SATURDAY MORNING BEFORE DISSIPATING. MOTORISTS TRAVELING ACROSS THIS AREA THIS MORNING SHOULD AND USE LOW BEAM HEADLAMPS AND ALLOW PLENTY OF EXTRA TIME TO REACH THEIR DESTINATION. LIEBL
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE CHEYENNE WY 1101 PM MST FRI NOV 9 2012 NEZ002-003-019>021-054-055-095-096-101100- DAWES-BOX BUTTE-SCOTTS BLUFF-BANNER-MORRILL-KIMBALL-CHEYENNE- NORTH SIOUX-SOUTH SIOUX- INCLUDING THE CITIES OF...CHADRON...ALLIANCE...SCOTTSBLUFF... GERING...HARRISBURG...BRIDGEPORT...BAYARD...KIMBALL...SIDNEY... HARRISON...AGATE 1101 PM MST FRI NOV 9 2012 AREAS OF FOG AND LOCALLY DENSE FOG WILL PERSIST ACROSS THE NEBRASKA PANHANDLE TONIGHT. VISIBILITIES MAY BE REDUCED TO 1/4 MILE AT TIMES. FOG WILL REMAIN ACROSS THE AREA THROUGH MUCH OF SATURDAY MORNING BEFORE DISSIPATING. MOTORISTS TRAVELING ACROSS THIS AREA THIS MORNING SHOULD AND USE LOW BEAM HEADLAMPS AND ALLOW PLENTY OF EXTRA TIME TO REACH THEIR DESTINATION. LIEBL
The national radar mosaic for the moment the first event began.
10 winter weather. Local standard time, as filed.
The Sage Creek SNOTEL site (elevation 7850 ft) estimated eight inches of snow.
The Battle Mountain SNOTEL site (elevation 7440 ft) estimated six inches of snow.
The Sandstone Ranger Station SNOTEL site (elevation 8150 ft) estimated eight inches of snow.
The Old Battle SNOTEL site (elevation 10000 ft) estimated seven inches of snow.
The Webber Springs SNOTEL site (elevation 9250 ft) estimated seven inches of snow.
The Whiskey Park SNOTEL site (elevation 8950 ft) estimated seven inches of snow.
The Blackhall Mountain SNOTEL site (elevation 9820 ft) estimated ten inches of snow.
The North French Creek SNOTEL (elevation 10130 ft) estimated six inches of snow.
The Sand Lake SNOTEL site (elevation 10050 ft) estimated six inches of snow.
The Divide Peak SNOTEL site (elevation 8880 ft) estimated 12 inches of snow.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2012Every state in 2012This day in weather historyWarnings in Wyoming, November 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: 412658, 412659, 412660, 412661, 412662, 412665, 412668, 412669, 412670, 412671.