The pressure gradient across central Wyoming tightened in advance of an approaching low pressure system and associated cold front. This resulted in high wind occurring across many areas of Fremont County and the lower elevations of Natrona County.
Every event with a place to put it; 3 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.
The pressure gradient across central Wyoming tightened in advance of an approaching low pressure system and associated cold front. This resulted in high wind occurring across many areas of Fremont County and the lower elevations of Natrona County. Gusts of 60 mph to near 70 mph were common during the afternoon hours. In Ethete, portions of the Wyoming Indian High School gymnasium roof were ripped away by the gusty southwest wind.
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 20, 10:09 AM MST, 1 hour 51 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 1109 AM MDT SUN APR 20 2008 .UPDATE... ISSUED HIGH WIND WARNING FOR THE WIND CORRIDOR OF EASTERN SWEETWATER...THE GREEN MOUNTAINS AND RATTLESNAKE RANGE...AND NATRONA COUNTY FOR THIS AFTERNOON. WINDS ARE ALREADY BEGINNING TO INCREASE ACROSS THE IMPACTED AREAS...AND ARE EXPECTED TO CONTINUE TO STRENGTHEN THIS AFTERNOON IN RESPONSE TO A TIGHTENED PRESSURE GRADIENT. WINDS OF 40 TO 45 MPH WITH GUSTS TO 60 MPH WILL BE FOUND ACROSS THE LOWER ELEVATIONS OF THE IMPACTED AREAS...WITH CASPER MOUNTAIN SEEING WINDS OF 50 MPH WITH GUSTS OF 60 TO 65 MPH. && .PREV DISCUSSION... /ISSUED 328 AM MDT SUN APR 20 2008/ SHORT TERM...TODAY THROUGH TUESDAY NIGHT LARGE UPPER LOW CENTERED OVER NORTHERN WA/SOUTHERN BRITISH COLUMBIA THIS MORNING WILL BECOME NEGATIVELY TILTED TODAY...AS STRONG SHORTWAVE TROUGH MOVES AROUND THE BASE OF THE TROUGH FROM NORTHERN NV ACROSS WESTERN AND CENTRAL WY. STRONG DYNAMICS...INCREASING MOISTURE AND MODERATE INSTABILITY WILL MOVE INTO WESTERN WY THIS MORNING WITH WIDESPREAD SNOW SHOWERS WITH HEAVIER SNOW SHOWERS IN THE HIGHER ELEVATIONS. A COLD FRONT WILL CROSS WESTERN WY DURING THE MID TO LATE MORNING FOLLOWED BY UNSTABLE AIRMASS AND UPSLOPE FLOW WHICH WILL GENERATE SNOW SHOWERS THROUGH THIS EVENING. THE HIGHER ELEVATIONS OF OF WESTERN WY WILL RECEIVE 3 TO 7 INCHES OF SNOW THROUGH THIS EVENING. STATIONARY SFC BOUNDARY EXTENDING WESTWARD ACROSS CENTRAL JOHNSON COUNTY TO THE SOUTHERN BIGHORN BASIN AND THEN NORTHWESTWARD ALONG THE CODY FOOTHILLS EARLY THIS MORNING WILL SLOWLY SAG SOUTHWARD TODAY...AS MUCH COLDER AIR PUSHES SOUTHWARD FROM MT. UNSTABLE AIRMASS TO THE SOUTH OF THIS FRONT WILL DESTABILIZE FURTHER THIS AFTERNOON...AS SHORTWAVE MOVES NORTHEASTWARD ACROSS CENTRAL WY AND MOISTURE INCREASES FROM THE SOUTHWEST. EXPECT SCATTERED SNOW SHOWERS ACROSS THIS AREA FROM SWEETWATER COUNTY NORTHWARD TO THE WIND RIVER BASIN AND NATRONA COUNTY WITH ISOLATED THUNDERSHOWERS WITH SNOW. H25 JET BETWEEN 80 AND 90 KT WILL DRIFT NORTHWARD INTO SOUTHERN WY THIS AFTERNOON AND SFC PRESSURE GRADIENT WILL INCREASE AS THE COLD FRONT FROM THE WEST SWEEPS ACROSS THE REGION. SOUTHWEST TO WEST WINDS WILL INCREASE TO BETWEEN 25 AND 35 MPH THIS AFTERNOON FROM THE WIND RIVER BASIN AND NATRONA COUNTY SOUTHWARD WITH GUSTS AS HIGH AS 50 MPH...MAINLY BENEATH THE H25 JET ACROSS SWEETWATER COUNTY AND SOUTHERN NATRONA COUNTY. COLD FRONT WILL MOVE ACROSS NORTHEASTERN WY THIS AFTERNOON...AND SNOW SHOWERS...MODERATE TO OCCASIONALLY HEAVY WILL DEVELOP ACROSS THE BIGHORN MOUNTAINS AND CONTINUE TONIGHT...AS A SERIES OF WEAK VORT MAXIMA MOVE ACROSS THE AREA. THE NORTHERN BIGHORNS COULD RECEIVE 2 TO 5 INCHES OF SNOW THROUGH MONDAY MORNING. OTHERWISE...STRONG COLD AIR ADVECTION TONIGHT WILL RESULT IN LOW TEMPERATURES 10 TO 15 F BELOW NORMAL. UPPER LOW WILL LIFT SLOWLY INTO SOUTHERN ALBERTA/SOUTHERN SASKATCHEWAN MONDAY...AND COLD CORE OF AIR WILL REMAIN ACROSS THE NORTHERN ROCKIES. H7 TEMPERATURES BETWEEN MINUS 8 AND MINUS 14 C MONDAY AFTERNOON WILL RESULT IN HIGH TEMPERATURES 15 TO 20 F BELOW NORMAL. A WEAK SHORTWAVE WILL MOVE ACROSS WESTERN AND NORTHERN WY MONDAY AND BRING SCATTERED SNOW SHOWERS TO THESE AREA...WHILE DOWNSLOPING WEST WINDS WILL KEEP THE WEATHER EAST OF THE DIVIDE MAINLY DRY..EXCEPT FOR ISOLATED SOW SHOWERS IN THE BIGHORN BASIN AND JOHNSON COUNTY. TEMPERATURES WILL MODERATE TUESDAY BUT WILL STILL BE AROUND 10 F BELOW NORMAL..AS THE UPPER LOW LIFTS NORTHEASTWARD INTO CENTRAL CANADA. A FEW SNOW SHOWERS ARE POSSIBLE TUESDAY IN THE WESTERN MOUNTAINS WITH WEST UPSLOPE FLOW AND RESIDUAL MOISTURE...BUT THIS ACTIVITY WILL DIMINISH TUESDAY NIGHT WITH A WEAK RIDGE BUILDING ACROSS THE REGION. LONG TERM...WEDNESDAY THROUGH SUNDAY NEXT TROUGH DIGS INTO THE PACNW WEDNESDAY AND THEN MOVES ACROSS THE AREA DURING THE DAY THURSDAY...SIMILAR TO TODAYS SYSTEM. HAVE HIT THE WEST WITH MUCH HIGHER POPS WEDNESDAY AND WEDNESDAY NIGHT AND THEN BROUGHT CHANCE POPS ACROSS OUR NRN ZONES FOR STARTERS ON THURSDAY. IF TRENDS CONTINUE...WILL NEED TO CONTINUE HITTING THE WEST AND NORTH HARDER AND POSSIBLY EVEN FURTHER SOUTH...ESPECIALLY WITH POSSIBLE NOSE OF CYCLONICALLY CURVED JET STREAK FORECAST TO BE NOSING INTO THE AREA BY THURSDAY MORNING ALONG WITH STEEP LAPSE RATES AND LOW LIS. MODELS DIVERGE SOME ON FRIDAY WITH THE GFS SHOWING A SOMEWHAT MOIST NW FLOW AND THE ECMWF SHOWING A FLAT RIDGE WITH MOST OF THE DEEPER MOISTURE IN MT. WILL KEEP THE CHANCE POPS ACROSS THE MOUNTAINS AS RIDGES HAVE BEEN HARD TO COME BY FOR MANY MONTHS AND EVEN THE ECMWF HAS LIGHT QPF IN THE NRN MTNS. THE PATTERN CHANGES LITTLE INTO SATURDAY BEFORE THE NEXT TROUGH BEGINS TO APPROACH THE NW COAST ON SUNDAY. FLAT RIDGE AXIS PASSES BY AND SW FLOW BEGINS TO DEVELOP FOR WARMER AND DRIER WEATHER SUNDAY. AVIATION... A NEARLY STATIONARY FRONTAL BOUNDARY EXTENDING ALONG THE OWL CREEK MOUNTAINS WILL BE OVERRUN BY A STRONG UPPER LEVEL TROUGH TODAY. NUMEROUS SNOW SHOWERS AND IFR/MVFR CONDITIONS WILL SPREAD INTO THE WEST THIS MORNING ALONG WITH A FEW THUNDERSTORMS. SCATTERED PRIMARILY MVFR RAIN AND SNOW SHOWERS ALONG WITH A FEW THUNDERSTORMS WILL SPREAD INTO CENTRAL WYOMING 16Z-18Z ALONG WITH GUSTY VARIABLE WINDS. NORTH OF THE STATIONARY FRONT...LOW IFR OR LIFR CLOUDS AND LIGHT SNOW WILL PUSH INTO THE NORTHERN BIG HORN BASIN AND KCOD AREA IN THE AFTERNOON. STRONG DOWNSLOPE WEST WINDS WILL DEVELOP BEHIND THE UPPER TROUGH ACROSS CENTRAL AND SOUTHERN WYOMING SUNDAY AFTERNOON. AREAS OF LLWS WILL BE ENCOUNTERED...ESPECIALLY ALONG THE EAST SLOPES OF THE MOUNTAIN RANGES 15Z-21Z SUNDAY. FIRE WEATHER... A STRONG COLD FRONT WILL CROSS WESTERN WYOMING THIS MORNING AND CENTRAL WYOMING THIS AFTERNOON. SNOW SHOWERS WILL MOVE INTO WESTERN WYOMING THIS MORNING AND WILL BE HEAVIEST IN THE HIGHER ELEVATIONS. SNOW SHOWERS WILL CONTINUE THIS AFTERNOON IN WESTERN WYOMING...AND DAYTIME RELATIVE HUMIDITY WILL BE SIGNIFICANTLY HIGHER TODAY. A STATIONARY BOUNDARY ACROSS THE BIGHORN BASIN AND JOHNSON COUNTY TODAY WILL KEEP COOLER AIRMASS AND HIGHER RELATIVE HUMIDITY ACROSS THIS AREA. STRONG WEST TO SOUTHWEST WINDS WILL DEVELOP TO THE SOUTH OF THIS BOUNDARY FROM THE WIND RIVER BASIN AND NATRONA COUNTY SOUTHWARD. WIND SPEEDS ACROSS THIS AREA WILL RANGE BETWEEN 25 AND 35 MPH WITH GUSTS TO BETWEEN 40 AND 50 MPH. SNOW SHOWERS WILL DEVELOP EAST OF THE DIVIDE THIS AFTERNOON...AS THE COLD FRONT MOVES ACROSS THE AREA. MUCH COLDER TEMPERATURES ARE EXPECTED TONIGHT AND MONDAY ACROSS THE ENTIRE REGION WITH HIGHS MONDAY 15 TO 20 F BELOW NORMAL. SIGNIFICANT SNOWFALL IS POSSIBLE THIS AFTERNOON THROUGH MONDAY MORNING IN THE NORTHERN BIGHORN MOUNTAINS...AS A SERIES OF UPPER LEVEL DISTURBANCES MOVES ACROSS NORTH CENTRAL WYOMING. && .RIW WATCHES/WARNINGS/ADVISORIES... HIGH WIND WARNING UNTIL 9 PM MDT THIS EVENING FOR WYZ019-020-022- 030. && UPDATE...BRANHAM SHORT TERM...SMITH LONG TERM...SKRBAC AVIATION...AEM FIRE WEATHER...SMITH
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 1104 AM MDT SUN APR 20 2008 WYZ001>020-022>030-211100- 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- 1104 AM MDT SUN APR 20 2008 ...HIGH WIND WARNING IN EFFECT UNTIL 9 PM FOR EASTERN SWEETWATER COUNTY...NATRONA COUNTY...AND THE GREEN MOUNTAINS AND RATTLESNAKE RANGE... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT A STRONG COLD FRONT WILL MOVE ACROSS THE AREA TODAY WITH SNOW SPREADING ACROSS THE WESTERN MOUNTAINS AND A RAIN AND SNOW MIX QUICKLY CHANGING TO SNOW IN THE WESTERN VALLEYS. UP TO SIX INCHES OF SNOW MAY FALL ON THE HIGHER PEAKS AND PASSES OF WESTERN WYOMING BY THIS EVENING. THE FRONT WILL BRING VERY WINDY CONDITIONS ALONG WITH SCATTERED RAIN AND SNOW SHOWERS AND POSSIBLY A FEW THUNDERSTORMS TO CENTRAL WYOMING TODAY. WINDS WILL BE SUSTAINED 40 TO 45 MPH ACROSS THE WIND CORRIDOR OF SOUTHEASTERN WYOMING THIS AFTERNOON...WITH GUSTS OF 50 TO 55 MPH EXPECTED. THESE STRONGER WINDS WILL CONTINUE INTO THE EVENING HOURS TONIGHT BEFORE WEAKENING AFTER SUNSET. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. SPOTTER INFORMATION STATEMENT... REPORTS OF SNOWFALL AMOUNTS AND WIND SPEEDS OF 40 MPH OR GREATER TODAY AND TONIGHT WOULD BE GREATLY APPRECIATED. TEAM RIVERTON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 1133 AM MDT SUN APR 20 2008 WYZ017-018-201830- LANDER FOOTHILLS-WIND RIVER BASIN- 1133 AM MDT SUN APR 20 2008 ...WINDY CONDITIONS WILL BE FOUND THIS AFTERNOON... THE PASSAGE OF A COLD FRONT WILL RESULT IN A TIGHTENED PRESSURE GRADIENT OVER THE WIND RIVER BASIN THIS AFTERNOON. THIS SCENARIO WILL CREATE STRONG WINDS OF 30 TO 35 MPH...WITH GUSTS OF 50 MPH. MOTORISTS...ESPECIALLY THOSE IN HIGH PROFILE VEHICLES WILL NEED TO USE CAUTION ON ROADWAYS THIS AFTERNOON. WINDS ARE EXPECTED TO WEAKEN DURING THE LATER PORTION OF THE AFTERNOON...THOUGH WILL REMAIN BREEZY. BRANHAM
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 1233 PM MDT SUN APR 20 2008 WYZ017-018-201930- LANDER FOOTHILLS-WIND RIVER BASIN- 1233 PM MDT SUN APR 20 2008 THE PASSAGE OF A COLD FRONT WILL RESULT IN A TIGHTENED PRESSURE GRADIENT OVER THE WIND RIVER BASIN THIS AFTERNOON. THIS SCENARIO WILL CREATE STRONG WINDS OF 30 TO 35 MPH...WITH GUSTS UP TO 50 MPH. MOTORISTS...ESPECIALLY THOSE IN HIGH PROFILE VEHICLES WILL NEED TO USE CAUTION ON ROADWAYS THIS AFTERNOON. WINDS ARE EXPECTED TO WEAKEN DURING THE LATER PORTION OF THE AFTERNOON...THOUGH WILL REMAIN BREEZY. BRANHAM
The national radar mosaic for the moment the first event began.
3 high wind. Local standard time, as filed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2008Every state in 2008This day in weather historyWarnings in Wyoming, April 2008
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: 83813, 83812, 83810.