Strong mid-level winds were mixed to the surface ahead of a trough of low pressure moving through the Great Basin. High winds were reported across Natrona County.
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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 RIW wrote it up.
Strong mid-level winds were mixed to the surface ahead of a trough of low pressure moving through the Great Basin. High winds were reported across Natrona County. A peak gust of 62 mph was registered along Outer Drive on the south side of Casper with a 59 mph peak gust clocked at the Casper/Natrona County International Airport.
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 Riverton, WY wrote its last area forecast discussion before the first event at Dec 19, 3:10 AM MST, 1 hour 21 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 310 AM MST SAT DEC 19 2015 .SHORT TERM...TODAY THROUGH MONDAY NIGHT HIGH WIND WARNING FOR THE WIND CORRIDOR THROUGH 5PM TODAY. IMAGERY SHOWS TROF/RIDGE/TROF PATTERN FROM W TO E ACROSS THE CONUS. RIDGING OVR WY THIS MORNING TRANSLATING TO UPR SW FLOW WITH MODEST MID/UPR MOISTURE IMPINGING ON THE NW FA. SFC HAS HIGH P ACROSS UT/CO AND SRN WY WITH LEE TROF/STATIONARY FRONT OVR ERN WY. A FEW FLURRIES/LIGHT SNOW SHOWERS OVR/NEAR THE NW/NRN BORDER REGION. TODAY...SFC SET-UP BECOMES FAVORABLE AGAIN FOR BREEZY TO WINDY CONDITIONS ACROSS THE WIND CORRIDOR WITH BOTH MID/UPPER AND SFC WINDS BECOMING LARGELY UNIDIRECTIONAL...OUT OF THE SW IN ADDITION TO JUST ENOUGH SHALLOW INSTABILITY AND DOWNWARD OMEGA TO BRING HIGHER SPEED WINDS...JUST 25 TO 50MB ABOVE THE GROUND...DOWN TO THE SFC. THIS WILL SUPPORT A HIGH WIND WARNING ACROSS ZONES 19 AND 20 FROM THE SOUTH PASS AREA...EWD TO CASPER. ON THE BRIGHT SIDE...SNOW COVER SHOULD RATHER CRUSTY AND STABLE AT THIS POINT...ELIMINATING (MOSTLY) THE NEED FOR A BLOWING SLOW ADVISORY. OTHERWISE...TRANSITION TO UPR SW FLOW WILL BE COMPLETE THIS MORNING...WITH JUST ENOUGH MID/LOW LVL MOISTURE HANGING AROUND OUT OVR THE WRN MOUNTAINS AND VALLEYS THAT A FEW LIGHT SNOW SHOWERS WILL CONTINUE ACROSS NW WY DURING THE DAY...JUST AHEAD OF THE NEXT RATHER WEAK BUT FLEET AFOOT TROF TONIGHT. AS THE TROF BEGINS TO PUSH ACROSS WY OVERNIGHT SAT/EARLY SUNDAY MORNING...TERRAIN FORCED PRECIPITATION WILL COMBINE WITH SOME EMBEDDED CONVECTIVE ELEMENTS...OFFERING LIGHT TO OCCASIONALLY MODERATE (CONVECTIVE) SNOW ACROSS THE WRN MOUNTAINS...WITH HEAVIEST SNOWFALL FROM THE TETONS NWD. ATTM SNOWFALL AMOUNTS FOR MOST OF THE WRN MOUNTAINS LOOK TO STAY BELOW ADVISORY CRITERIA...WITH ONLY A FEW LOCATIONS OVR THE WEST TO SOUTHWEST SLOPES OF THE TETONS SEEING SOME ADVISORY LVL SNOWFALL. PERHAPS WORTH A SECOND LOOK...BUT JUST STICKING WITH SPS FOR NOW. THROUGH THE REST OF THE DAY SUNDAY...LIGHT SNOW SHOWERS WILL LINGER ACROSS THE WEST...WITH A FEW FLURRIES POSSIBLE ACROSS THE NRN BASINS SUN AFTERNOON AS THE TROF AXIS MOVES THRU THE REST OF THE CWA. SUNDAY NIGHT...SW/JET STREAK AND INCREASED MOISTURE FROM THE EPAC WILL MOVE QUICKLY INTO THE WRN MOUNTAINS. AGAIN...WHILE A FAVORABLE TRAJECTORY FOR PRECIP ACROSS THE MOUNTAINS...THE SPEED OF THE SYSTEM AND ASSOCIATED MOISTURE WILL MOST LIKELY LEAVE THE MOUNTAINS WITH JUST UNDER ADVISORY LEVEL SNOW FOR MOST OF THE WESTERN MOUNTAIN REGION ONCE AGAIN...THROUGH MONDAY MORNING. THIS WILL CHANGE HOWEVER. THE REST OF THE DAY MONDAY WILL ONLY SEE ON AGAIN OFF AGAIN LIGHT SNOW SHOWERS ACROSS THE WRN MOUNTAINS...AND THIS AHEAD OF WHAT LOOKS TO BE A MUCH MORE PROMISING SNOW MAKER THAT WILL PLOW INTO THE WEST MONDAY NIGHT JUST AHEAD OF OR ON THE NOSE OF A STRONG JET...WITH FAVORABLE WNW FLOW ALOFT. THIS SYSTEM WILL PRODUCE STRONG PRECIPITATION THRU AT LEAST TUE NIGHT...PERHAPS WED MORNING...BEFORE CLEARING THE AREA...LEAVING WHAT COULD BE WARNING LEVEL SNOWFALL ACROSS MUCH OF THE MOUNTAIN WEST OF WY. .LONG TERM...TUESDAY THROUGH SATURDAY THE 00Z GFS AND ECMWF MODELS STILL BRINING IN DEEP MOISTURE ALONG WITH A STRONG JET STREAM TUESDAY INTO TUE NIGHT. THE WEST LOOKS TO GET THEIR BIGGEST STORM SO FAR THIS SEASON. LITTLE DOUBT THAT WINTER WEATHER HIGHLIGHTS WILL BE ISSUED FOR THIS EVENT MONDAY NIGHT THROUGH TUE EVENING IF MODEL TIMING REMAINS CONSISTENT. STAY TUNED. AS THE TROUGH BLOWS THROUGH AREAS EAST OF THE DIVIDE TUE NIGHT INTO WED MORNING...THERE WILL BE A QUICK SHOT OF SNOW OVER THE NORTH AND SOUTH ZONES WITH WINDY CONDITIONS IN THE FAVORED LOCATIONS. WED WILL STILL HAVE SOME LIGHTER SNOW IN THE WESTERN MOUNTAINS WHILE IN THE EAST CONDITIONS WILL DRY OUT WED AFTERNOON. THE FLOW ALOFT BACKS TO THE WEST THURSDAY AND THEN SW THURSDAY NIGHT AS THE NEXT TROUGH DIGS ALONG THE WEST COAST. THE GFS HAS MORE MOISTURE MOVING INTO THE WEST THURS WHILE THE ECMWF MODEL HAS LESS MOISTURE. WILL DECREASE THE SNOW IN THE WEST THURSDAY. THEN THURS NIGHT INTO FRIDAY THIS ELONGATED TROUGH WILL MOVE THROUGH THE REGION. BOTH MODELS SHOW SNOW DEVELOPING OVER THE WEST AND SOUTHWEST THURS NIGHT...SPREADING EAST NORTHEAST ON CHRISTMAS DAY. NOT EASY TO PINPOINT THE AREAS OF HEAVIEST SNOW THIS FAR OUT. THE SNOW WINDS DOWN FRIDAY NIGHT LEADING TO A DRY DAY NEXT SATURDAY. TEMPS WILL BE FAIRLY MILD TUESDAY THEN COLDER WEDNESDAY. THURSDAY THROUGH SATURDAY WILL BE SEASONABLY COLD. && .AVIATION.../12Z ISSUANCE/ WITH A WEAK LOW PRESSURE OVER EASTERN WY AND HIGH PRESSURE ACROSS SOUTHWESTERN WYOMING...THE SURFACE PRESSURE GRADIENT REMAINS TIGHT ENOUGH OVER CENTRAL AND SOUTHERN WY TO PRODUCE MODERATE TO STRONG SURFACE WIND AS WELL AS TURBULENCE AROUND THE HIGHER TERRAIN. WINDS WILL INCREASE TO 30 TO 40 KNOTS SUSTAINED FROM CENTRAL WY INTO KCPR THROUGH 20/00Z...WITH HIGHER GUSTS AND POSSIBLE LLWS. MOST LOCATIONS WILL SEE VFR CONDITIONS THROUGH SATURDAY NIGHT. HOWEVER...MVFR CONDITIONS WILL CONTINUE OVER THE TERRAIN OF NW WY THROUGH TODAY. CEILINGS WILL THEN BEGIN TO LOWER IN NORTHWEST/WEST WY BY 20/00Z WITH SNOW SHOWERS MOVING INTO KJAC 20/03 - 06Z. GENERALLY...WEST OF THE DIVIDE WILL SEE SNOW SHOWERS AND FREQUENT MOUNTAIN OBSCURATIONS FROM FROM 20/06Z THROUGH THE END OF THE FORECAST PERIOD. && .FIRE WEATHER... FIRE DANGER REMAINING LOW ACROSS THE FORECAST AREA TODAY THROUGH THE WEEKEND. HOWEVER AS BREEZY TO WINDY CONDITIONS CONTINUE ACROSS PORTIONS OF CENTRAL WYOMING TODAY...WITH GUSTS OUT OF THE SOUTHWEST 40 TO 60 MPH AT TIMES...MAY ENHANCE FIRE BEHAVIOR CONCERNS IN AREAS WITH LITTLE/NO SNOW COVER. OTHERWISE....OCCASIONAL LIGHT SNOW SHOWERS TODAY WILL GIVE WAY TO LIGHT TO MODERATE SNOW OR SNOW SHOWERS ONCE AGAIN ACROSS THE WESTERN MOUNTAINS AND VALLEYS TONIGHT THROUGH SUNDAY MORNING. ANOTHER LIGHT STORM WILL AGAIN SUNDAY NIGHT THROUGH MONDAY MORNING...WITH HEAVIER SNOW DUE TO ARRIVE MONDAY NIGHT...LASTING THROUGH WEDNESDAY MORNING. && .RIW WATCHES/WARNINGS/ADVISORIES... HIGH WIND WARNING UNTIL 5 PM MST THIS AFTERNOON FOR WYZ019-020. && SHORT TERM...BRAUN LONG TERM...AR AVIATION...MCDONALD FIRE WEATHER...BRAUN
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 340 AM MST SAT DEC 19 2015 WYZ001>020-022>030-201200- YELLOWSTONE NATIONAL PARK-ABSAROKA MOUNTAINS-CODY FOOTHILLS- NORTH BIG HORN BASIN-SOUTHWEST BIG HORN BASIN- SOUTHEAST BIG HORN BASIN-OWL CREEK AND BRIDGER MOUNTAINS- BIGHORN MOUNTAINS WEST-BIGHORN MOUNTAINS SOUTHEAST- NORTHEAST JOHNSON COUNTY-SOUTHEAST JOHNSON COUNTY- TETON AND GROS VENTRE MOUNTAINS-JACKSON HOLE- WIND RIVER MOUNTAINS WEST-WIND RIVER MOUNTAINS EAST- UPPER WIND RIVER BASIN-WIND RIVER BASIN-LANDER FOOTHILLS- GREEN MOUNTAINS AND RATTLESNAKE RANGE- NATRONA COUNTY LOWER ELEVATIONS-CASPER MOUNTAIN-STAR VALLEY- SALT RIVER AND WYOMING RANGES-UPPER GREEN RIVER BASIN FOOTHILLS- UPPER GREEN RIVER BASIN-SOUTH LINCOLN COUNTY- ROCK SPRINGS AND GREEN RIVER-FLAMING GORGE-EAST SWEETWATER COUNTY- 340 AM MST SAT DEC 19 2015 ...HIGH WIND WARNING FROM JEFFREY CITY TO CASPER THROUGH 5 PM TODAY... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT ANOTHER ROUND OF VERY STRONG WINDS ARE EXPECTED ACROSS THE GREEN MOUNTAINS AND RATTLESNAKE RANGE OVER TO THE LOWER ELEVATIONS OF NATRONA COUNTY THROUGH THIS AFTERNOON. TRAVELLERS NEED TO BE PREPARED FOR MORE STRONG WIND GUSTS OVER 60 MPH AND EVEN SOME BLOWING AND DRIFTING SNOW. LIGHT TO MODERATE SNOW ACROSS THE WEST TONIGHT. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY SUNDAY NIGHT AND MONDAY MORNING...LIGHT TO MODERATE SNOW ACROSS THE WEST. WINDY IN THE MOUNTAINS...FOOTHILLS AND EAST OF THE DIVIDE. MONDAY NIGHT THROUGH WEDNESDAY MORNING...A MAJOR WINTER STORM IS EXPECTED ACROSS THE WEST. SIGNIFICANT SNOW AND VERY STRONG WIND IS EXPECTED TO DEVELOP MONDAY NIGHT AND CONTINUE INTO WEDNESDAY MORNING. STRONG WINDS WITH GUSTS OVER 50 MPH POSSIBLE ACROSS MUCH OF CENTRAL AND SOUTHERN WYOMING. CHRISTMAS DAY...A CHANCE OF SNOW. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ENCOURAGED TO REPORT ANY SNOWFALL AMOUNTS OR WIND GUSTS IN EXCESS OF 50 MPH. THANK YOU.
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 134 AM MST SAT DEC 19 2015 WYZ001-002-012>015-023>025-027-192300- YELLOWSTONE NATIONAL PARK-ABSAROKA MOUNTAINS- TETON AND GROS VENTRE MOUNTAINS-JACKSON HOLE- WIND RIVER MOUNTAINS WEST-WIND RIVER MOUNTAINS EAST-STAR VALLEY- SALT RIVER AND WYOMING RANGES-UPPER GREEN RIVER BASIN FOOTHILLS- SOUTH LINCOLN COUNTY- INCLUDING THE CITIES OF...LAKE...MAMMOTH...OLD FAITHFUL... JACKSON...AFTON...ALPINE...STAR VALLEY RANCH...THAYNE... PINEDALE...KEMMERER...COKEVILLE 134 AM MST SAT DEC 19 2015 ...A SERIES OF STORM SYSTEMS WILL IMPACT WESTERN WYOMING WITH SNOW AND WIND BETWEEN THIS WEEKEND AND THE MIDDLE OF NEXT WEEK... THE FIRST SYSTEM WILL MOVE IN LATE THIS AFTERNOON AND INTO THE EVENING...LASTING INTO SUNDAY MORNING BEFORE DECREASING. THIS STORM MAY PRODUCE 1 TO 3 INCHES ACROSS THE LOWER ELEVATIONS WITH 3 TO 8 INCHES IN THE MOUNTAINS. ANOTHER SYSTEM WILL MOVE QUICKLY IN SUNDAY NIGHT AND LAST INTO MONDAY MORNING WITH SIMILAR AMOUNTS. THEN...A MUCH MORE SIGNIFICANT WINTER STORM IS EXPECTED TO ARRIVE MONDAY NIGHT AND LAST INTO WEDNESDAY MORNING WITH PLENTY OF SNOW AND INCREASINGLY STRONG SOUTHWEST WINDS. THIS TYPE OF STORM SYSTEM CAN EASILY DUMP 6 TO 12 INCHES OF SNOW IN THE WESTERN VALLEYS WITH 1 TO 2 FEET IN THE HIGH COUNTRY. THESE ARE JUST PRELIMINARY AMOUNTS TO INDICATE THAT THIS IS A POTENTIALLY MAJOR WINTER STORM. IN ADDITION TO THE HEAVY SNOW POTENTIAL VERY STRONG WEST TO SOUTHWEST WINDS ARE EXPECTED WITH THIS STORM WHICH WILL LIKELY CAUSE CONSIDERABLY BLOWING AND DRIFTING SNOW. TRAVELERS AND OTHERS WITH OUTDOOR INTERESTS WILL NEED TO PAY CLOSE ATTENTION TO THE WEATHER THIS UPCOMING WEEK. THE WEATHER WILL CHANGE RAPIDLY AND MAY BECOME QUITE SEVERE WITH THIS STORM SYSTEM MONDAY NIGHT INTO TUESDAY NIGHT. CHECK THE LATEST WEATHER FORECASTS AT WWW.WEATHER.GOV/RIW AND ROAD REPORTS AT WYOROAD.INFO. SKRBAC/JB
The national radar mosaic for the moment the first event began.
1 high wind. Local standard time, as filed.
The wind sensor at Outer Drive had several wind gusts past 58 mph including a maximum of 62 mph. The Casper airport had several wind gusts of 59 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2015Every state in 2015This day in weather historyWarnings in Wyoming, December 2015
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: 607273.