A strong pacific trough and cold front moved across Wyoming and produced heavy snow in portions of central Wyoming. The heaviest snow fell along the east slopes of the Wind River Range where 18 inches of snow was reported at the St.
Every event with a place to put it; 4 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 RIW wrote it up.
A strong pacific trough and cold front moved across Wyoming and produced heavy snow in portions of central Wyoming. The heaviest snow fell along the east slopes of the Wind River Range where 18 inches of snow was reported at the St. Lawrence SNOTEL. Heavy snow also fell in and around Lander where amounts generally ranged from 6 to 8 inches. Other heavy snowfall amounts included 10 inches at Powder River in Natrona County and 7 inches at Jeffrey City.
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 Apr 15, 2:26 AM MST, 1 hour 34 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 326 AM MDT WED APR 15 2015 .SHORT TERM...WEDNESDAY THROUGH FRIDAY NIGHT MANY RIDDLES ABOUND TONIGHT AS THERE HAS BEEN MUCH MASHING OF TEETH IN THE RIVERTON WEATHER ABODE TONIGHT. SO FAR...AS OF 1 AM THE COLD FRONT IS DROPPING SOUTHWARD ACROSS THE AREA. SOME PRECIPITATION HAS BROKEN OUT ACROSS THE ABSAROKAS AND CODY FOOTHILLS. THE MODELS ARE HANDLING THIS FAIRLY WELL..ESPECIALLY THE NAM. HOWEVER...THERE IS STILL SOME UNCERTAINTY IN THE FORECAST. FOR TODAY...ALL MODELS SAY THERE WILL BE SNOW IN THE AREAS WITH HIGHLIGHTS. HOWEVER...THEY ARE ALL OVER THE PLACE WITH THE PLACEMENT OF SMALLER SCALE FEATURES THAT WILL HAVE A BIG IMPACT ON WHO GETS THE MOST SNOW. ALL MODELS HAVE A JET STREAK MOVING THROUGH THE AREA THIS MORNING AND EARLY AFTERNOON WITH CENTRAL AREAS OF THE CWA GETTING SOME ADDITIONAL UPPER LEVEL SUPPORT...SO THAT PART IS FAIRLY CERTAIN. AFTER THAT...THE MODELS CONTINUE TO BE SPLIT. THE NAM IS THE DRIEST WHILE THE GFS AND EUROPEAN ARE WETTER. AT THIS POINT...CONTINUITY LOOKS LIKE A REASONABLE COMPROMISE SO WE MADE FEW CHANGES FOR THE WEDNESDAY FORECAST. THINGS REALLY SPLIT TONIGHT...THE NAM SHOWS A BAND OF SNOW DEVELOPING ACROSS EASTERN PORTIONS OF THE COUNTY WARNING AREA LATER TONIGHT AND EARLY THURSDAY MORNING IN RESPONSE TO A 700 MILLIBAR FLOW OVER EASTERN WYOMING. THE GFS HAS A SIMILAR FEATURE BUT A BIT FURTHER SOUTH. THE NEW EUROPEAN HAS MAINLY LIGHT PRECIPITATION ACROSS THE AREA AS WELL. WITH THE UNCERTAINTY IN THE DETAILS...WE FELT THE BEST DECISION WITH THE HIGHLIGHTS WOULD BE TO KEEP THEM AS IS FOR NOW AND ISSUE SPECIAL WEATHER STATEMENTS FOR A FEW OTHER LOCATIONS. THE DIFFERENCES CONTINUE INTO THURSDAY AS WELL. THE NAM PUSHES A RIDGE OF HIGH PRESSURE INTO THE COWBOY STATE WITH THE UPPER LEVEL LOW DOWN OVER THE FOUR CORNERS REGION. THIS HAS BEEN FAIRLY CONSISTENT THE PAST DAY OF SO. THE GFS MEANWHILE KEEPS PRECIPITATION ACROSS MUCH OF THE AREA INTO THURSDAY MORNING AS WELL. THE EUROPEAN IS IN THE MIDDLE WITH LIGHT PRECIPITATION...SOME OF WHICH COULD BE RAIN INSTEAD OF SNOW. WE DID BRING SOME SLIGHT POPS BACK FURTHER NORTH AND WEST BUT DECIDED NOT TO GO FOR MAJOR CHANGES WITH THE MODELS DIFFERENCES. THERE IS EVEN SOME UNCERTAINTY INTO FRIDAY. AGAIN...MUCH HAS TO DO WITH WHAT HAPPENS WITH THAT CUT OFF UPPER LEVEL LOW...THE UPPER LEVEL DEVIL THAT COULD REEK HAVOC INTO THE FORECAST. AGAIN...THE MODELS ARE ALL OVER THE PLACE...WITH THE NAM THE DRIEST AND THE OTHER MODELS A LITTLE WETTER. AGAIN...NOTICING A TREND HERE...WE MADE FEW CHANGES TO CONTINUITY UNTIL...HOPEFULLY...THINGS COME INTO SOMEWHAT BETTER AGREEMENT. .LONG TERM...SATURDAY THROUGH WEDNESDAY NIGHT THE CUT OFF LOW WILL KEEP SLIGHT CHANCES OF RAIN AND SNOW GOING OVER SOUTHEAST PORTIONS OF THE FORECAST AREA SATURDAY...AS THIS FEATURE SLOWLY MAKES ITS WAY INTO THE CENTRAL PLAINS. AS IT DOES SO...A NEW CANADIAN COLD FRONT WILL QUICKLY MOVE INTO NORTHERN PORTIONS SATURDAY NIGHT INTO SUNDAY MORNING. THIS WILL KEEP A SLIGHT CHANCE TO CHANCE RAIN AND SNOW SHOWERS ACROSS MUCH OF THE FORECAST AREA...MAINLY EAST OF THE DIVIDE. THE REST OF THE FORECAST PERIOD WILL BE UNDER THE INFLUENCE OF A NORTHWEST FLOW PATTERN...AS AN UPPER LEVEL LOW BEGINS TO STALL NORTH OF THE GREAT LAKES OVER NORTHERN ONTARIO. THE GFS AND ECMWF DIFFER ON ROTATING SHORTWAVES FROM THIS FEATURE IMPACTING THE COWBOY STATE TUESDAY AND WEDNESDAY. KEPT A SLIGHT CHANCE FOR RAIN/SNOW SHOWERS AT THIS TIME IN A FEW LOCATIONS...MAINLY ALONG SOUTHERN PORTIONS OF THE CONTINENTAL DIVIDE. OVERALL...TEMPERATURES ARE EXPECTED TO BE NEAR NORMAL...WITH NO PERIODS OF GUSTY WINDS. && .AVIATION.../12Z ISSUANCE/ EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES RAIN AND SNOW DEVELOPS OVER MANY LOCATIONS BY 12Z. A MIX OF RAIN AND SNOW MAY OCCUR IN THE BIGHORN BASIN INCLUDING AROUND KWRL THROUGH THE DAY. THE OTHER TERMINAL SITES WILL SEE SNOW PREVAILING TODAY AND TONIGHT. EXPECT MVFR TO IFR CONDITIONS TO PREVAIL. AFTER 01Z CONDITIONS IN THE NORTH WILL IMPROVE SOME WITH VFR CONDITIONS OCCURRING BY 06Z. MOUNTAINS WILL BE FREQUENTLY OBSCURED. PLEASE SEE INDIVIDUAL TERMINAL SITES FOR MORE DETAILS. WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES EXPECT SCATTERED AREAS OF SNOW TO OCCUR TODAY...DECREASING IN COVERAGE AFTER 00Z. EXPECT AREAS OF MVFR/IFR CONDITIONS THROUGH THE DAY INTO THE EVENING. MOUNTAINS WILL BE FREQUENTLY OBSCURED INTO THIS EVENING. VFR CONDITIONS WILL BEGIN TO OCCUR AT SOME OF THE TERMINAL SITES AFTER 19Z. PLEASE SEE INDIVIDUAL TERMINAL SITES FOR MORE DETAILS. && .FIRE WEATHER... SNOW WILL SPREAD FROM NORTHWEST ACROSS THE AREA TODAY. STRONG NORTH WINDS WILL BE AROUND AS WELL. SOME LOWER ELEVATION AREAS IN THE BIGHORN BASIN...JOHNSON COUNTY...NATRONA COUNTY AND THE WIND RIVER BASIN MAY SEE SNOW CHANGE TO RAIN OR MIX WITH RAIN DURING THE DAY TODAY. THE SNOW WILL START ENDING IN THE NORTHWEST WEDNESDAY EVENING CONTINUING ON IN THE EAST UNTIL THURSDAY. TEMPERATURES WILL BE MUCH COLDER WITH SIGNIFICANT INCREASE IN RELATIVE HUMIDITY. && .RIW WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY FROM 6 AM THIS MORNING TO 6 AM MDT THURSDAY WYZ008-009-019. WINTER WEATHER ADVISORY UNTIL 6 AM MDT THURSDAY WYZ016>018. WINTER WEATHER ADVISORY UNTIL 6 PM MDT THIS EVENING WYZ012. WINTER WEATHER ADVISORY FROM NOON TODAY TO 6 AM MDT THURSDAY WYZ010-011-020-022. WINTER STORM WARNING UNTIL 6 AM MDT THURSDAY WYZ014-015. WINTER WEATHER ADVISORY UNTIL MIDNIGHT MDT TONIGHT WYZ005>007. WINTER WEATHER ADVISORY UNTIL MIDNIGHT MDT TONIGHT WYZ002-003. && SHORT TERM...HATTINGS LONG TERM...LAVOIE AVIATION...AR FIRE WEATHER...HATTINGS
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 958 PM MDT TUE APR 14 2015 WYZ001>020-022>030-151200- ABSAROKA MOUNTAINS-BIGHORN MOUNTAINS SOUTHEAST- BIGHORN MOUNTAINS WEST-CASPER MOUNTAIN-CODY FOOTHILLS- EAST SWEETWATER COUNTY-FLAMING GORGE- GREEN MOUNTAINS AND RATTLESNAKE RANGE-JACKSON HOLE-LANDER FOOTHILLS- NATRONA COUNTY LOWER ELEVATIONS-NORTH BIG HORN BASIN- NORTHEAST JOHNSON COUNTY-OWL CREEK AND BRIDGER MOUNTAINS- ROCK SPRINGS AND GREEN RIVER-SALT RIVER AND WYOMING RANGES- SOUTH LINCOLN COUNTY-SOUTHEAST BIG HORN BASIN- SOUTHEAST JOHNSON COUNTY-SOUTHWEST BIG HORN BASIN-STAR VALLEY- TETON AND GROS VENTRE MOUNTAINS-UPPER GREEN RIVER BASIN- UPPER GREEN RIVER BASIN FOOTHILLS-UPPER WIND RIVER BASIN- WIND RIVER BASIN-WIND RIVER MOUNTAINS EAST-WIND RIVER MOUNTAINS WEST- YELLOWSTONE NATIONAL PARK- 958 PM MDT TUE APR 14 2015 ...A WINTER STORM WARNING IS IN EFFECT FOR THE WIND RIVER MOUNTAINS TONIGHT THROUGH EARLY THURSDAY MORNING... ...VARIOUS WINTER WEATHER ADVISORIES ARE IN EFFECT FOR MUCH OF WESTERN AND CENTRAL WYOMING TONIGHT THROUGH EARLY THURSDAY MORNING... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT AREAS OF SNOW OVER THE WEST AND SOUTH OVERNIGHT. SOME OF THIS SNOW MAY SPREAD INTO THE NORTH AND CENTRAL BY WEDNESDAY MORNING. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY WEDNESDAY THROUGH WEDNESDAY NIGHT...WIDESPREAD SNOW SHOWERS WILL BE ONGOING DURING MUCH OF THE DAY...WITH AREAS OF BLOWING SNOW FOR THE BIG HORN BASIN AND JOHNSON COUNTY. WINTER WEATHER HIGHLIGHTS COVER PORTIONS OF CENTRAL WYOMING DURING THIS PERIOD. SEE THE LATEST WINTER WEATHER STATEMENTS FOR FURTHER DETAILS. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ENCOURAGED TO REPORT WIND GUSTS OVER 50 MPH TODAY AND SNOWFALL AMOUNTS TONIGHT AND WEDNESDAY. TEAM RIVERTON
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE RIVERTON WY
1251 AM MDT WED APR 15 2015
...TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
...DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0835 PM NON-TSTM WND GST 2 NE COWLEY 44.91N 108.45W
04/14/2015 M59 MPH BIG HORN WY AWOS
COWLEY AIRPORT
&&
21SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 251 AM MDT WED APR 15 2015 WYZ023-024-026>030-152200- EAST SWEETWATER COUNTY-FLAMING GORGE-ROCK SPRINGS AND GREEN RIVER- SALT RIVER AND WYOMING RANGES-SOUTH LINCOLN COUNTY-STAR VALLEY- UPPER GREEN RIVER BASIN- 251 AM MDT WED APR 15 2015 ...GUSTY WIND AND OCCASIONAL SNOW TODAY... OCCASIONAL SNOW WILL CONTINUE INTO TODAY...OCCASIONALLY MODERATE ACROSS PORTIONS OF THE AREA. ACCUMULATIONS OF 1 TO 3 INCHES WILL BE POSSIBLE IN THE LOWER ELEVATIONS WITH 3 TO 6 INCHES IN THE MOUNTAINS. HOWEVER...LOCALLY HIGHER ACCUMULATIONS MAY OCCUR IN HEAVIER BANDS. IN ADDITION...GUSTY NORTH WINDS WILL BLOW AND DRIFT THE SNOW AND MAY REDUCE VISIBILITY AT TIMES. MOTORISTS ARE URGED TO WATCH FOR SLICK OR SNOW COVERED ROADS ALONG WITH RAPID CHANGES IN VISIBILITY. WYZ004-152200- NORTH BIG HORN BASIN- 251 AM MDT WED APR 15 2015 ...GUSTY WIND AND OCCASIONAL SNOW TODAY... OCCASIONAL SNOW WILL DEVELOP TODAY...MIXED WITH RAIN AT TIMES AT THE ONSET...OCCASIONALLY MODERATE ACROSS PORTIONS OF THE AREA. ACCUMULATIONS OF 1 TO 2 INCHES WILL BE POSSIBLE IN THE LOWER ELEVATIONS WITH 3 TO 6 INCHES IN THE MOUNTAINS WITH LOCALLY HIGHER ACCUMULATIONSIN HEAVIER BANDS.. IN ADDITION...GUSTY NORTH WINDS WILL BLOW AND DRIFT THE SNOW AND MAY REDUCE VISIBILITY AT TIMES. MOTORISTS ARE URGED TO WATCH FOR SLICK OR SNOW COVERED ROADS ALONG WITH RAPID CHANGES IN VISIBILITY. TEAM RIVERTON
The national radar mosaic for the moment the first event began.
4 winter storm. Local standard time, as filed.
The SNOTEL site at St. Lawrence recorded 18 inches of new snow. Other notable amounts included 16 inches at the Cold Springs SNOTEL and 13.5 inches at the University of Missouri Geology Camp.
The observer at the Lander Airport measured 7.6 inches of snow. Amounts around the Lander foothills generally ranged from 3 to 9 inches, with the higher amounts in the high elevations toward Sinks Canyon State Park.
The cooperative observer measured ten inches of snow at Powder River. Accumulations were less across the remainder of Natrona County, generally ranging from two to five inches.
The cooperative observer measured seven inches of snow at Jeffrey City.
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, April 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: 566845, 566844, 566841, 566843.