A tightening pressure gradient associated with an approaching cold front produced strong south-southwest wind across portions of central and southwest Wyoming during the afternoon of Tuesday, April 14. The peak wind at the Casper/Natrona County International Airport was 63 mph at 1333MST.
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The episode as NWS RIW wrote it up.
A tightening pressure gradient associated with an approaching cold front produced strong south-southwest wind across portions of central and southwest Wyoming during the afternoon of Tuesday, April 14. The peak wind at the Casper/Natrona County International Airport was 63 mph at 1333MST. To the southwest, a remote sensor along Interstate 80 in Sweetwater County recorded sustained wind of at least 40 mph during the afternoon. Northwest wind behind the front was also strong with a peak gust of 59 mph at 1935MST at the North Big Horn County Airport near Cowley.
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 14, 11:08 AM MST, 2 hours 25 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 1208 PM MDT TUE APR 14 2015 .SHORT TERM...TODAY THROUGH THURSDAY NIGHT THE FLAT TRANSIENT RIDGE WILL EXIT TO THE EAST TODAY RESULTING IN A BACKING TIGHTENING SOUTHWEST FLOW OUT AHEAD OF THE NEXT APPROACHING STRENGTHENING DIGGING TROUGH. THIS WILL TRANSLATE INTO A VERY DRY WARM BUT WINDY DAY ACROSS MOST OF THE AREA. THIS PARTICULAR TROUGH WILL HAVE QUITE THE THERMAL RIBBON ALONG IT. IN FACT...TEMPERATURES WILL BE AS MUCH AS 40 DEGREES COLDER BEHIND THE FRONT IN MANY AREAS EAST OF THE DIVIDE WED...MORE ON THIS LATER. SO WITH THE DIFFERENCE IN TEMPERATURES ON EITHER SIDE OF THE STRONG PACIFIC COLD FRONT AND CORRESPONDING DIFFERENCE IN PRESSURE...WE ARE EXPECTING QUITE THE LARGE SCALE SOUTHWEST GRADIENT WIND AS THIS TROUGH APPROACHES FROM THE WEST. WENT AHEAD AND UPGRADED THE HIGH WIND WATCH TO A WARNING FOR SWEETWATER AND SOUTHERN LINCOLN COUNTY...THE GREEN MTNS AND THE EAST SLOPE OF THE WIND RVR MTNS. ALSO DECIDED TO ADD ON THE LOWER ELEVATIONS OF NATRONA COUNTY GIVEN THE 30 MPH SUSTAINED WIND IN THE MET MOS GUIDANCE WHICH WOULD EASILY TRANSLATE INTO A HIGH EVENT ALONG OUTER DRIVE. THE WARNING WILL RUN FROM 15Z THIS MORNING THROUGH 00Z WED. AND WITH THAT...THESE SOUTHWEST WINDS WILL CONTINUE TO USHER IN DRY AIR WITH AN RH OF 10 TO 15 PERCENT EXPECTED ACROSS MOST OF THE LOWER ELEVATIONS EAST OF THE DIVIDE WHICH HAS PROMPTED AN UPGRADE TO A RED FLAG WARNING FOR THESE AREAS VALID FROM 19Z THIS AFTERNOON THROUGH 02Z THIS EVENING. DECIDED NOT TO INCLUDE ZONE 276 AS THAT ZONE WILL BE TOO CLOSE TO EXPECTED CLOUDS AND SHOWERS MOVING IN FROM THE WEST AND NORTHWEST. AS THE TROUGH AND ASSOCIATED PACIFIC COLD FRONT APPROACH FROM THE WEST...NUMEROUS SHOWERS WITH SNOW AT THE HIGHEST ELEVATIONS WILL BREAK OUT IN FAR WESTERN WYOMING THIS AFTERNOON. WITH NEGATIVE LIFTED INDICES AND MUCH COLDER AIR EXPECTED TO MOVE IN ALOFT...ISOLATED THUNDERSTORMS ARE EXPECTED IN THESE AREAS THIS AFTERNOON AND EVENING AS WELL ALONG WITH GUSTY WINDS AND SMALL HAIL. THEN TONIGHT...THE SNOW LEVEL WILL QUICKLY LOWER TO THE VALLEY AND BASIN FLOORS AS THE SNOW SPREADS TO AREAS EAST OF THE DIVIDE AS THE STRONG CANADIAN COLD FRONT PUSHES SOUTH. THE ASCT 500MB LOW WILL TRACK SOUTHEAST ACROSS SW WY TONIGHT AND WEDNESDAY MORNING ACDG TO THE GFS WITH THE EURO TRACKING IT SOUTHEAST ACROSS SALT LAKE. EITHER WAY...THIS TRACK WILL BE IN A GOOD POSITION TO PRODUCE SUBSTANTIAL SNOWFALL TO MUCH OF THE CWA TONIGHT THROUGH WEDNESDAY NIGHT. ONCE THE SNOWFALL BECOMES ESTABLISHED LATE TONIGHT/WEDNESDAY MORNING...IT WILL CONTINUE THROUGH THE DAY WEDNESDAY WITH Q VECTOR FORCING AND WRAP AROUND ISENTROPIC LIFT TO KEEP THINGS GOING. THE ASCT CLOSED MID LEVEL LOW WILL STRENGTHEN OVER THE BIG HORN MTNS/JOHNSON COUNTY WHERE THE MOST SNOW IS LIKELY TO FALL WITH UP TO A FOOT EXPECTED IN THE BIG HORN MTNS THROUGH WED EVE. ONCE THE H7/H5 LOWS SPIN OFF TO OUR SOUTH...THE UPSLOPE LAYER EAST OF THE DIVIDE WILL DEEPEN DURING THE DAY WEDNESDAY. THE AFOREMENTIONED TRACK OF THE MAIN STORM CENTER IS A POPULAR ONE FOR THE EAST SLOPE OF THE WIND RVR MTNS/LANDER FOOTHILLS TO RECEIVE SUBSTANTIAL SNOWFALL. WITH THE SFC HIGH BUILDING IN FROM THE NW RATHER THAN THE NORTH...THIS WOULD FAVOR A NORTHERLY SFC WIND WHICH IS A FAVORABLE UPSLOPE FLOW FOR THE CASPER AREA TO RECEIVE ABUNDANT SNOWFALL. HAVE ALREADY MENTIONED THE FAVORABLE POSITION OF THE MID LEVEL LOW IN JOHNSON CO FOR THE BIG HORN MTNS/BUFFALO TO RECEIVE THEIR FARE SHARE. BUT IN ADDITION TO THAT...POST FRONTAL 3 HOURLY SFC PRESSURE RISES OF 10 MB WILL ASSURE THAT BYG AND SURROUNDING AREAS SEE 55 MPH WIND GUSTS FOR BLIZZARD CONDITIONS THERE FROM WED MORNING THROUGH 12 MIDNIGHT WED NT. THE SNOWFALL INTENSITY WILL DECREASE IN JOHNSON COUNTY WEDNESDAY EVENING BUT STRONG WINDS WILL CONTINUE. IN FACT...THE ABOVE MENTIONED FAVORED AREAS WILL SEE THE SNOWIEST CONDITIONS DURING THIS TIME FRAME BUT IT WILL TAKE LONGER FOR THE SNOW TO END IN CASPER THROUGH 12Z THURSDAY MORNING. NOT TOO WORRIED THAT MOS GUIDANCE IS KEEPING AREA HIGH TEMPS UP AROUND 40 DEGREES AS ADIABATIC COOLING FROM UPSLOPE AND EVAPORATIVE COOLING FROM HEAVIEST SNOW BANDS WILL KEEP TEMPS FROM RISING MUCH ABOVE THE LOW TO MID 3OS WEDNESDAY. THE SNOW WILL END FROM NW TO SE WED NT. ALMOST ALL OTHER AREAS OF THE CWA WILL SEE ACCUMULATING SNOWFALL WITH MORE SNOW EXPECTED IN THE OTHER MTN RANGES. CONVECTIVE SNOW SHOWERS ARE EXPECTED WEST OF THE DIVIDE WED. THURSDAY WILL FEATURE DRIER AND MILDER CONDITIONS. .LONG TERM...FRIDAY THROUGH TUESDAY MODELS CONTINUE TO STRUGGLE WITH THE AMOUNT OF ENERGY THAT MAY DIVE S/SE ACROSS THE AREA OVER THE WEEKEND INTO EARLY NEXT WEEK. VERY BUSY NRN HEMISPHERE LOOKS TO BECOME QUITE AMPLIFIED IN THE MEDIUM RANGE PERIOD. COLD HIGH LATITUDE TROUGH ALMOST HALF WAY AROUND THE GLOBE MOVES EAST AND SETS OFF A CHAIN REACTION LEADING TO AMPLIFICATION OF A RIDGE OVER AND SOUTH OF KAMCHATKA WHICH LEADS TO STRONG TROUGH OVER THE ALEUTIAN/WRN GULF OF ALASKA AREA BY THE WEEKEND WHICH AIDS TO A DEVELOPING RIDGE ALONG THE WEST COAST OF NORTH AMERICA. THIS AMPLIFICATION LEADS TO A DECENT POTENTIAL OF S TO SEWD MOVING SHORTWAVES INTO OUR AREA LATE IN THE WEEKEND INTO EARLY NEXT WEEK. I THINK WITH TIME...THE MORE AGGRESSIVE SCENARIOS WILL PAN OUT SO AT LEAST KEEPING CHANCE POPS IN THE MOUNTAINS FROM LATE SATURDAY THROUGH MONDAY WITH 20-30 POPS IN THE LOWER ELEVATIONS EAST OF THE DIVIDE. PLENTY OF TIME TO SEE HOW THIS EVOLVES BUT STILL LEANING TOWARDS MORE THAN JUST A GLANCING FLOW IN THIS PATTERN. SO DRY AND WARMER FRIDAY. APPROACHING COLD FRONT SATURDAY WILL LEAD TO AN INCREASING CHANCE OF SHOWERS AND PERHAPS ISOLD TSTMS IN THE NW MOUNTAINS MAINLY BEFORE MOVING ONTO THE LOWER ELEVATIONS OF THE NORTH BY SATURDAY EVENING WITH THE FIRST SEWD MOVING DISTURBANCE. THIS WILL LIKE HAVE A SWATH OF SNOW SHOWERS OR MIXED RAIN AND SNOW AS IT DROPS INTO CENTRAL WYO SATURDAY NIGHT. THERE WILL LIKELY BE AT LEAST ONE OR TWO MORE DISTURBANCES OR EVEN A SIGNIFICANT SYSTEM DROPPING S-SE IN THIS PATTERN SO KEEPING AT LEAST 20-30 POPS ALONG AND EAST OF THE DIVIDE INTO SUNDAY AND MONDAY WITH HIGHS IN THE 30S AND SOME LOWER 40S MOUNTAINS WITH 40S AND SOME LOWER 50S LOWER ELEVATIONS EAST OF THE DIVIDE. WITH COLDER AIR ALOFT...THIS MAY END UP MOSTLY SNOW BUT NOT ENOUGH CONFIDENCE TO GO THAT COLD QUITE YET. DID ADJUST WX TOOL WITH WARMER TEMPS FOR SNOW THOUGH TO GET A LITTLE MORE SNOW OR MIX IN THE GRIDS. ANOTHER DISTURBANCE MAY EVEN MOVE IN FROM THE WEST OR NW ON TUESDAY SO MTN POPS WARRANTED FOR NOW. && .AVIATION.../18Z ISSUANCE/ EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES PLENTY OF SOUTH-SOUTHWEST WIND AND VFR CONDITIONS FOR THE EASTERN TERMINALS THROUGH EARLY THIS EVENING. GUSTS 35-40KTS POSSIBLE IN THE CORRIDOR FROM KRKS-KCPR...OTHERWISE 20-30KT WIND WILL BE COMMON. COLD FRONT TO OUR WEST WILL MAKE SLOW PROGRESS AND SWEEP FROM WEST-TO-EAST ACROSS THE TERMINALS BETWEEN ABOUT 04Z-08Z/WED. WINDS WILL QUICKLY SHIFT AROUND TO THE NORTH TO NORTHWEST AT KCOD AND KWRL FOLLOWING FRONTAL PASSAGE. PRECIPITATION...INITIALLY RAIN...WILL BEGIN SHORTLY THEREAFTER. KLND AND KRIW WILL SEE MORE OF A WEST-NORTHWEST WIND SHIFT WITH A MUCH STRONGER WIND AT TOPOGRAPHICALLY-FAVORED KRIW WHERE G35KT IS POSSIBLE. PRECIP BY 12Z/WED WILL LIKELY BE ALL SNOW WITH IFR/MVFR CONDITIONS IN PLACE BY THAT TIME. MOUNTAIN OBSCURATIONS WILL ALSO BECOME WIDESPREAD BY 12Z/WED. KCPR IS LIKELY TO BE THE EXCEPTION TO THIS SCENARIO. PRECIP PUSH IS LIKELY TO OCCUR AFTER 12Z/WED. CURRENT THOUGHTS ARE THAT A MORE COHESIVE AREA OF RAIN OR RAIN/SNOW MIX MAY HOLD-OUT UNTIL AROUND 18Z/WED. WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES CONDITIONS WILL REMAIN BREEZY/WINDY AND VFR THROUGH 00Z/WED. GUSTY SOUTH-SOUTHWEST WIND OF 20-35KTS WILL BE COMMON ACROSS THE WEST THROUGH THIS AFTERNOON. SHOWERS WILL DEVELOP BETWEEN 18Z-20Z THIS AFTERNOON OVER THE WESTERN MOUNTAINS AND INSTABILITY IS SUFFICIENT TO PRODUCE ISOLATED THUNDERSTORMS. GIVEN THE GRADIENT WIND...ANY OUTFLOW FROM CONVECTION COULD PUSH THE SEVERE THRESHOLD OF 50KTS. COLD FRONT PROGRESSING EAST ACROSS IDAHO WILL MOVE INTO THE WEST AROUND 00Z/WED. TIGHT TEMPERATURE GRADIENT WILL QUICKLY ALLOW FOR RAIN TO CHANGE TO SNOW BY 02Z/WED AT KJAC AND BY 04Z/WED AT KPNA AND KBPI. SNOW AND IFR/MVFR WILL PERSIST AT KJAC UNTIL AROUND 12Z/WED BEFORE GRADUALLY DECREASING BY 18Z/WED AS FLOW GOES TO A MORE NORTHWESTERLY DOWNSLOPE DIRECTION. BEST CHANCE FOR KBPI SNOWFALL MAY OCCUR THIS EVENING WITH THE FRONTAL PASSAGE AS DOWNSLOPE FLOW WILL HINDER PRECIP DEVELOPMENT. HAVE CONTINUED CURRENT THINKING AT KPNA ALTHOUGH CONFIDENCE IN PERSISTENT SNOWFALL AND IFR/MVFR OVERNIGHT IS NOT HIGH. DOWNSLOPE MAY BEGIN TO RULE BY 08Z/WED AT KPNA. KRKS PRECIP WILL BE MORE SHOWERY IN NATURE WITH THE BULK OF THE ENERGY AND MOISTURE REMAINING TO THE NORTH. GUSTY WEST-NORTHWEST WIND EXPECTED AT KBPI...KPNA...AND KRKS BEHIND THE FRONTAL PASSAGE. && .FIRE WEATHER... RED FLAG WARNING UNTIL 2000 ACROSS MOST OF THE LOWER ELEVATIONS OF AREAS EAST OF THE CONTINENTAL DIVIDE. STRONG DRY SOUTHWEST WINDS WILL DEVELOP TODAY USHERING IN VERY DRY AIR RESULTING IN ELEVATED BURNING CONDITIONS FOR THIS AFTERNOON...ESPECIALLY IN AREAS EAST OF THE DIVIDE AT THE LOWER ELEVATIONS. A VERY STRONG COLD FRONT WILL PRODUCE SCATTERED SHOWERS AND A FEW THUNDERSTORMS MAINLY IN WESTERN WYOMING THIS AFTERNOON...FOLLOWED QUICKLY BY SUBSTANTIAL SNOWFALL AND COLD NORTH WINDS TONIGHT THROUGH WEDNESDAY NIGHT. HIGH TEMPERATURES WEDNESDAY WILL RANGE FROM AS MUCH AS 40 DEGREES COLDER EAST OF THE DIVIDE TO 25 DEGREES COLDER WEST. && .RIW WATCHES/WARNINGS/ADVISORIES... HIGH WIND WARNING FROM 9 AM THIS MORNING TO 6 PM MDT THIS EVENING WYZ015-019-020-027>030. RED FLAG WARNING UNTIL 8 PM MDT THIS EVENING WYZ275-280>283. WINTER STORM WATCH FROM LATE TONIGHT THROUGH WEDNESDAY EVENING WYZ008-009-015-018. BLIZZARD WATCH FROM LATE TONIGHT THROUGH WEDNESDAY EVENING WYZ010-011. WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE WEDNESDAY NIGHT WYZ020-022. && SHORT TERM...LIPSON LONG TERM...SKRBAC AVIATION...CNJ FIRE WEATHER...LIPSON
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 1034 AM MDT TUE APR 14 2015 WYZ001>020-022>030-151330- 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- 1034 AM MDT TUE APR 14 2015 ...RED FLAG WARNING FOR MOST LOWER ELEVATIONS EAST OF THE CONTINENTAL DIVIDE TUESDAY AFTERNOON AND EARLY EVENING... ...HIGH WIND WARNING FOR SOUTHERN WYOMING AND PORTIONS OF CENTRAL WYOMING TUESDAY FROM 900 AM UNTIL 600 PM... ...BLIZZARD WATCH LOWER ELEVATIONS OF JOHNSON COUNTY LATE TONIGHT THROUGH WEDNESDAY EVENING... ...WINTER STORM WATCH FOR PORTIONS OF CENTRAL WYOMING LATE TONIGHT THROUGH WEDNESDAY NIGHT... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT WIDESPREAD EXTREME FIRE WEATHER CONDITIONS EXPECTED IN THE LOWER ELEVATIONS EAST OF THE DIVIDE THIS AFTERNOON AND EARLY EVENING. HIGH WINDS ARE FORECAST ACROSS SOUTHERN WYOMING INTO PORTIONS OF CENTRAL WYOMING THIS MORNING THROUGH LATE AFTERNOON. WIND SPEEDS OF 35 TO 40 MPH WILL BE COMMON WITH GUSTS FROM 55 TO 65 MPH. LOCALLY HIGHER WIND GUSTS COULD OCCUR. ISOLATED THUNDERSTORMS WITH POSSIBLE DAMAGING WIND GUSTS WILL BE EMBEDDED IN THE AREA OF HIGH WINDS. THE COMBINATION MAY PRODUCE ISOLATED WIND GUSTS TO 75 MPH OVER AND NEAR THE WESTERN MOUNTAINS EXTENDING INTO THE BIGHORN...WIND RIVER AND GREEN RIVER BASINS. A POWERFUL SPRING STORM SYSTEM WILL BRING A RETURN OF MUCH COLDER... WINDY AND SNOWY CONDITIONS TO MUCH OF THE AREA. ONLY MINOR SNOW ACCUMULATIONS ARE EXPECTED TONIGHT...AS THE RAIN CHANGES TO SNOW. .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 AND BLIZZARD CONDITIONS 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
The national radar mosaic for the moment the first event began.
3 high wind. Local standard time, as filed.
The ASOS at the Casper/Natrona County International Airport had a wind gust to 63 mph.
A WYDOT mesonet sensor near Continental Divide on I-80 registered sustained wind over 40 mph for more than one hour late in the afternoon.
The peak wind at North Big Horn County Airport near Cowley was clocked at 59 mph at 1935MST. The AWOS at Powell Municipal Airport recorded sustained wind over 40 mph for more than an hour during the late evening.
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: 566840, 569158, 569157.