A storm system with strong dynamic features tracked across central Wyoming. Strong mid level east to southeasterly wind coupled with light northwesterly surface wind behind a shallow cold front caused numerous funnel clouds in and east of Greybull.
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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.
A storm system with strong dynamic features tracked across central Wyoming. Strong mid level east to southeasterly wind coupled with light northwesterly surface wind behind a shallow cold front caused numerous funnel clouds in and east of Greybull.
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 May 24, 3:09 AM MST, 10 hours 36 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 409 AM MDT MON MAY 24 2010 .SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT THE CIRCULATION NOW OVER SOUTHWEST UTAH IS SPREADING A LONG STREAM OF MOISTURE NORTH INTO SOUTH CENTRAL THROUGH NORTH CENTRAL WYOMING UNDERNEATH THE TROWEL. AS MUCH AS OVER AN INCH OF RAINFALL HAS ALREADY BEEN REPORTED IN BYG WITH MORE RAIN ON THE WAY. MANY AREAS HAVE REPORTED FROM ONE QUARTER TO ONE THIRD OF AN INCH OF PRECIP FROM THE WIND RIVER BASIN TO THE BIG HORN BASIN. BOUNDARY LEVEL CONVERGENCE HAS SET UP FROM THE GREEN MOUNTAINS TO THE CASPER ARCH AND INTO THE BIG HORN MTNS. WINDS DURING THE LAST FEW HOURS IN CASPER HAVE BEEN FROM THE EAST TO NORTHEAST WITH HIGHLAND HAVING BEEN BLOWING FROM THE WEST AT 10 TO 20 MPH. A BAND OF CONVECTION HAS BEEN FORMING ALONG THAT BOUNDARY MARKING THE EASTERN EDGE OF THE AFOREMENTIONED STRATIFORM SHIELD OF PRECIP. THE LIGHTNING HAS BEEN CONCENTRATED OVER JEFFRY CITY EARLIER THIS EVENING AND HAS RACED TO JUST EAST OF MONETA AND THEN TO BYG WHERE SMALL HAIL WAS REPORTED. EXPECT THAT THIS CONVECTION WILL CONTINUE TO PROPAGATE NORTHEAST ALONG THIS BOUNDARY EVEN THOUGH THE INDIVIDUAL CELLS ARE TRACKING DUE NORTH. THIS MEANS MORE SIGNIFICANT PRECIP FOR JOHNSON COUNTY. WE CURRENTLY HAVE AN URBAN AND SMALL STREAM FLOOD ADVISORY OUT FOR THE BIG HORN BASIN EXCLUDING PARK COUNTY AS WELL AS NORTHERN JOHNSON COUNTY THROUGH 830 THIS MORNING. WITH THE SNOW LEVEL DOWN TO ABOUT 7K THE THREAT OF SNOW MELT IS NOT THE CONCERN...RATHER LOW ELEVATION STREAMS. A JET COUPLET...ISENTROPIC LIFT AND Q VECTOR FORCING ARE CONTRIBUTING TO THE FAST MOVING STRATIFORM PRECIP OVER CENTRAL AND WESTERN WY ATTM. AT LEAST NOW THERE IS MORE CONSISTENCY WITH THE MODEL RUNS AS THE 00Z MODEL RUN IS A LOT LIKE THE LAST 18Z RUN IN THAT THEY KEEP THE TRACK OF THE LOW JUST TO THE SOUTH AND EAST OF RIVERTON WITH THE NAM A LITTLE FARTHER SOUTHEAST. THIS TRACK WOULD GIVE EVEN CENTRAL WY A BETTER SHOT AT ADDITIONAL PRECIP TODAY THAN YESTERDAYS 00Z RUN ALLUDED TO. WILL INCREASE POPS SOMEWHAT TO ACCOUNT FOR THIS FROM THE WIND RIVER BASIN TO THE BIG HORN BASIN WITH THE HIGHER POPS REMAINING IN NORTHERN WY. VERY STRONG Q VECTOR FORCING IS PROGGED BY THE NAM...ESPECIALLY OVER NORTHERN WY WHERE VALUES OF -57M^2/1E16S ARE INDICATED. THE FORCING JUST GETS EVEN STRONGER WHEN THE DYNAMICS REACH MONTANA TONIGHT NIGHT WHERE VALUES OF -88M^2/1E16S ARE INDICATED. WILL CONTINUE THE HIGHER POPS THROUGH 06Z TONIGHT ACROSS NORTHERN WYOMING. AFTER 06Z TONIGHT ANY LEFT OVER PRECIP WILL BE DUE TO RESIDUAL WRAP AROUND SHOWERS BUT MOISTURE WILL BE RESTRICTED TO THE FAR NORTH. THE SNOW LEVEL IS EXPECTED TO DROP BACK DOWN TO 8000 FEET TODAY AND THEN TO 6K TONIGHT MANY AREAS. WILL ISSUE A SNOW ADVISORY FOR THE BIG HORN MTNS WHERE UP TO OVER AN ADDITIONAL INCH OF PRECIP COULD OCCUR WHICH WOULD TRANSLATE INTO 6 TO 12 INCHES OF SNOW FOR THAT AREA AFFECTING GRANITE AND POWDER RIVER PASSES. WILL START THE ADVISORY AT 18Z TODAY WHEN THE NEXT BATCH OF SIGNIFICANT PRECIP DIRECTLY FROM THE LOW ITSELF AFFECTS THE BIG HORNS MTNS...AFTER H7 TEMPS DROP...AND WILL KEEP IT GOING THROUGH 12Z TUESDAY. WILL ALSO ISSUE ONE FOR YNP FOR THE SAME TIME FRAME WITH LOW END AMOUNTS EXPECTED THERE TAKING INTO ACCOUNT THE VOLUME OF TOURISTS THERE NOW. WEST WINDS WILL PICK UP ALMOST EVERYWHERE FOR A COUPLE OF HOURS WHEN THE ASSOCIATED TROUGHPA TRACKS NE ACROSS THE AREA LATE THIS AFTERNOON AND EVENING. 5 ISOHYPSE OF 3 UNIT INCREMENTS ARE INDICATED ACROSS THE CWA WHICH WOULD INDICATE AREAS OF 25 TO 40 MPH WINDS WITH SOME GUSTS OF 40 TO 50 MPH IN SOME AREAS. DRIER WEATHER WILL INFILTRATE THE AREA BY TUESDAY AFTERNOON AS A TRANSITORY RIDGE BUILDS INTO THE AREA BEFORE STEERING WINDS BACK ONCE AGAIN TO THE SOUTH SOUTHWEST WHEN THE STRONG CIRCULATION NOW OVER 51N/136W APPROACHES NORTHERN CALIFORNIA AND KEEPS THE THREAT OF PRECIP OVER NW WY WED AND WED NT. .LONG TERM...THURSDAY THROUGH MEMORIAL DAY AN UNSEASONABLY WARM SOUTHERLY FLOW TO PREVAIL THURSDAY AND FRIDAY WITH CHANCES SHOWERS AND LATE DAY THUNDERSTORMS ACROSS THE WEST AND MAINLY ALONG AND EAST OF INTERSTATE 25. COOLER WEATHER WITH CHANCES OF SHOWERS AND THUNDERSTORMS SPREAD ACROSS THE AREA SATURDAY WITH SHOWERS AND STORMS MOSTLY CONFINED TO THE NORTH SUNDAY. MEMORIAL DAY LOOKS DRY AND WARMER ACROSS WEST AND CENTRAL WYOMING. MEDIUM-RANGE GLOBAL MODELS HAVE REACHED MORE OF A CONSENSUS...LESS SPREAD COMPARED TO GEFS ENSEMBLE MEAN ON SPEED OF CLOSED UPPER LOW COMING SLOWLY ONSHORE THURSDAY...LIFTING ACROSS THE NORTHERN GREAT BASIN AND WYOMING ON SATURDAY. THE SPREAD EXISTS WITH THE EXTENT OF THE UPPER LOW DIGGING ACROSS THE INTERMOUNTAIN WEST WITH THE GEM THE FLATTEST AND WEAKEST AMONG THE DETERMINISTIC OUTPUT WITH THE GFS ON THE OTHER EXTREME SHOWING THE MOST AMPLIFICATION WITH OVERALL PATTERN ACROSS NORTH AMERICA AND THE EASTERN PACIFIC. GEFS MEAN CONTINUES TO BE A GOOD COMPROMISE TO USE FOR FORECAST. MAIN CHANGE TO FORECAST WAS TO SLIGHTLY INCREASE POPS WITH ACROSS WEST FRIDAY WITH SLIGHTLY FASTER PROGRESSION OF BAROCLINIC ZONE INTO THE WEST. WARM SOUTHERLY FLOW BETWEEN STRONG RIDGE OVER CENTRAL PLAINS AND UPPER LOW OFF WEST COAST ADVECTS 14-15C H7 TEMPERATURES INTO CENTRAL WYOMING THURSDAY AND FRIDAY SO...AS MENTIONED THE LAST FEW DAYS...THIS SCENARIO WILL ACCELERATE MELTING OF MID-MOUNTAIN SNOWPACK...WITH THE GREATEST POTENTIAL FLOODING CONCERNS ACROSS THE WIND RIVER AND POWDER- TONGUE DRAINAGES WHERE SNOW WATER EQUIVALENTS ARE NEAR 140 PERCENT OF AVERAGE WITH EVEN MORE SNOW EXPECTED OVER THE BIG HORN RANGE IN THE SHORTTERM. MEAN THETA-E RIDGE WILL BE OVER THE HIGH PLAINS WRAPPING WESTWARD ACROSS THE BIG HORN MOUNTAINS INTO SOUTH CENTRAL MONTANA THURSDAY AND FRIDAY WITH ISOLATED THUNDERSTORMS LIKELY INITIATING OFF EAST SLOPES OF THE BIG HORN MOUNTAINS AND HIGH TERRAIN OF NATRONA COUNTY. ANAFRONT SLOWLY PUSHES INTO WEST FRIDAY AND ACROSS CENTRAL WYOMING SATURDAY WITH CHANCES OF SHOWERS AND THUNDERSTORMS ALONG AND AHEAD OF THE FRONT. UPPER LOW LIFTS INTO MONTANA SUNDAY WITH DRIER WESTERLY CONFLUENT FLOW ALOFT PREVAILING OVER WYOMING. UPPER RIDGE BUILDS OVER ROCKIES AND HIGH PLAINS MEMORIAL DAY BRINGING DRY AND SEASONABLY MILD CONDITIONS. && .AVIATION... A STORM SYSTEM WILL BE MOVING THROUGH WY TODAY BRINGING WIDESPREAD SHOWERS AND SNOW FOR THE MOUNTAINS. ISOLATED THUNDERSTORMS ARE POSSIBLE. VFR TO MVFR CONDITIONS WILL BE ENCOUNTERED TODAY ACROSS THE REGION. SOME IFR CONDITIONS WILL OCCUR IN THE WEST WHERE SNOW WILL OCCUR THROUGH THE AFTERNOON HOURS. WIND SPEEDS WILL BE INCREASING FROM WEST TO EAST ACROSS WY TODAY AS THE STORM MOVES INTO NORTHEAST WY BY 00Z TUE. VFR CONDITIONS WILL PREVAIL ACROSS THE SOUTH AND CENTRAL AFTER 00Z TUE. IN THE NORTH AND NORTHWEST VFR TO MVFR CONDITIONS WILL PERSIST INTO THE EVENING HOURS AS LOW CLOUDS AND SHOWERS LINGER IN THIS AREA. && .FIRE WEATHER... SIGNIFICANT PRECIPITATION IS EXPECTED ACROSS THE AREA TODAY...ESPECIALLY IN NORTHERN WYOMING. THE PRECIPITATION WILL LINGER IN NORTHERN WYOMING TONIGHT. SIGNIFICANT AMOUNTS OF SNOWFALL ARE EXPECTED IN THE NORTHERN WYOMING MOUNTAINS THROUGH TONIGHT...ESPECIALLY IN THE BIG HORN MOUNTAINS. WEST WINDS WILL INCREASE FOR A COUPLE OF HOURS WITH GUSTS OF 40 TO 50 MPH IN SOME AREAS AS THE TROUGH SWINGS ACROSS THE AREA LATE THIS AFTERNOON AND EVENING. MILDER AND DRIER WEATHER IS EXPECTED TUESDAY. BY WEDNESDAY HIGH TEMPERATURES WILL BE IN THE 70S IN THE LOWER ELEVATIONS EAST OF THE DIVIDE AND THE 60S WEST. THE MINIMUM RELATIVE HUMIDITY WILL BE IN THE MID TEENS OVER SWEETWATER COUNTY...THE UPPER GREEN RIVER BASIN AND THE GREEN MOUNTAINS ON WEDNESDAY. ANOTHER PACIFIC STORM SYSTEM WILL BRING MORE PRECIPITATION TO THE AREA LATER IN THE WEEK. && .RIW WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY FROM NOON TODAY TO 6 AM MDT TUESDAY WYZ001-008-009. && SHORT TERM...LIPSON LONG TERM...AEM AVIATION...AR FIRE WEATHER...LIPSON
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 149 PM MDT MON MAY 24 2010 WYZ001>020-022>030-251102- 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- 149 PM MDT MON MAY 24 2010 ...AREAL FLOOD WARNING FOR NORTHERN JOHNSON COUNTY THIS AFTERNOON AND EVENING... ...WINTER WEATHER ADVISORY FOR THE BIG HORN MOUNTAINS FOR THIS AFTERNOON AND TONIGHT... ...URBAN AND SMALL STREAMS FLOOD ADVISORY FOR SOUTHERN BIG HORN BASIN THIS AFTERNOON AND EVENING... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT SIGNIFICANT SNOWFALL WILL OCCUR TODAY AND TONIGHT IN THE BIG HORN MOUNTAINS WITH MOST OF THE SNOW OCCURRING THIS AFTERNOON AND TONIGHT. 3 TO 6 INCHES OF SNOWFALL IS EXPECTED ACROSS MUCH OF THE WESTERN MOUNTAINS...AND 6 TO 12 INCHES OF SNOWFALL ARE EXPECTED OVER THE BIG HORN MOUNTAINS ABOVE 9000 FEET. 4 TO 8 INCHES ARE EXPECTED BELOW 9000 FEET WITH LITTLE ACCUMULATION BELOW 7000 FEET. RAINFALL IN JOHNSON COUNTY WILL CAUSE LOCAL RIVER AND STREAM RISES IN NORTHERN JOHNSON COUNTY. UP TO AN INCH OF RAIN IS POSSIBLE TODAY ND TONIGHT IN THIS AREA. WEST WINDS OF 25 TO 35 MPH WITH GUSTS OF 40 TO 50 MPH ARE EXPECTED EARLY THIS EVENING FROM ROCK SPRINGS TO CASPER. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY UNSEASONABLY WARM TEMPERATURES ARE EXPECTED THURSDAY AND FRIDAY THAT WILL LIKELY ACCELERATE SNOWMELT IN THE EASTERN WIND RIVER AND EASTERN BIG HORN MOUNTAINS WHERE SNOWPACK REMAINS WELL ABOVE AVERAGE. RIVERS AND CREEKS IN THESE AREAS WILL LIKELY EXPERIENCE SIGNIFICANT RISES LATE THIS WEEK. SHOWERS AND THUNDERSTORMS WILL INCREASE ACROSS THE WEST FRIDAY AND SPREAD INTO CENTRAL WYOMING SATURDAY. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ENCOURAGED TO REPORT RAINFALL OVER A QUARTER OF AN INCH...SNOWFALL AMOUNTS...AND ANY STREAMS OR RIVERS RISING RAPIDLY OR NEAR BANKFULL. THANK YOU. TEAM RIVERTON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 956 AM MDT MON MAY 24 2010 WYZ001-002-012>015-023>025-250400- ABSAROKA MOUNTAINS-JACKSON HOLE-SALT RIVER AND WYOMING RANGES- STAR VALLEY-TETON AND GROS VENTRE MOUNTAINS- UPPER GREEN RIVER BASIN FOOTHILLS-WIND RIVER MOUNTAINS EAST- WIND RIVER MOUNTAINS WEST-YELLOWSTONE NATIONAL PARK- 956 AM MDT MON MAY 24 2010 A SPRING STORM WILL AFFECT THE AREA THROUGH TUESDAY MORNING. UNSEASONABLY COOL TEMPERATURES ARE EXPECTED. WESTERN MOUNTAINS ARE EXPECTED TO RECEIVE 3 TO 6 INCHES OF ACCUMULATING SNOW. ISOLATED AREAS WILL RECEIVE HIGHER AMOUNTS...PARTICULARLY IN THE TETON RANGE. USE CAUTION WHEN TRAVELING AS MOUNTAIN PASSES COULD BECOME SNOW PACKED AND SLICK. DSB
The Billings radar (KBLX), 156 km away, was scanning. The volume nearest the first event began at 20:46 UTC.
3 funnel cloud. Local standard time, as filed.
A small, narrow funnel persisted with little movement west of Greybull. The funnel lasted ten minutes and no damage was reported.
The Big Horn county sheriff's office reported that a deputy in Greybull was witnessing a funnel cloud over town.
A funnel cloud was seen by the public moving east. The funnel lasted five minutes.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2010Every state in 2010This day in weather historyWarnings in Wyoming, May 2010
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: 229253, 229254, 229255.