A storm moved out of the northern Great Basin and slowed down as it moved through Wyoming. This resulted in a rather prolonged period of snow that hampered Thanksgiving Week travel.
Every event with a place to put it; 6 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 storm moved out of the northern Great Basin and slowed down as it moved through Wyoming. This resulted in a rather prolonged period of snow that hampered Thanksgiving Week travel. Moisture overran a dome of cold air in place across central Wyoming and enhanced snowfall across Fremont and Natrona counties. The heaviest snow fell in the areas favored by north to northeast upslope flow, generally along the east slopes of the Wind River Mountains through the Lander Foothills and east to around Casper. Snow amounts of around one foot were common in the vicinity of Lander with totals of at least 14 in the mountains above town. Other locations with heavy snow included the Wind River Basin where 6 to 10 inches of snow fell and south of Casper where 6 to 8 inches was measured.
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 Nov 25, 3:34 AM MST, 3 hours 26 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 334 AM MST WED NOV 25 2015 .SHORT TERM...TODAY THROUGH FRIDAY NIGHT ...MAJOR WINTER STORM TO IMPACT MUCH OF THE AREA TODAY THROUGH THANKSGIVING DAY... IMAGERY SHOWING LARGE COLD DEEP TROF WRN CONUS W/ CLOSED PORTION OF LOW OVR NWRN NV. STRONG JET...95 TO 120 KTS... STRETCHES FROM THE BASE OF THE TROF...TO THE NE OVR WRN/NWRN/NRN WY AND INTO THE NRN PLAINS. ATTM...COLD PORTION OF LOW CURRENTLY SEPARATED FROM WCB... WHICH LIES ALONG AND S OF THE JET...INDICATING RAPID CYCLOGENESIS WILL FOLLOW ONCE COLD CORE LOW CAN TAP INTO THE HIGH ENERGY AIR LATER TODAY/TONIGHT. ALSO...MINOR BAROCLINIC LEAF CURRENTLY COMING TOGETHER FROM NRN UT INT WCNTRL WY. COMPLEX SFC PATTERN HAS DEVELOPING CYCLONE TO THE E SIDE OF THE UPR TROF OVR THE GREAT BASIN WITH DEVELOPING BOUNDARY/FRONT DRAPED UP ACROSS CNTRL WY...AND ANOTHER STRONGER FRONT TO THE N OVR ID AND WRN MT. LOW P ALSO STRETCHES S OF THIS BOUNDARY INTO THE CNTRL/NRN PLAINS. CYCLOGENESIS TODAY REALLY ACCELERATES LATER THIS AFTERNOON THROUGH MOST OF THE OVERNIGHT PERIOD WHILE THE UPR CLOSED LOW HEADS FOR UT. THE SFC PORTION OF THE LOW SHOULD ORIGINALLY SET-UP NEAR NWRN CO/BORDER WY...WITH EXTREMELY TIGHT P GRADS AND INCREASING WIND FROM CNTRL THRU SRN WY. AT THE SAME TIME...LOW P OVR THE PLAINS AND ATTENDING DEVELOPING COLD FRONT WILL PUSH QUICKLY THRU ERN WY AND CNTRL PLAINS...CURVING BACK INTO THE FRONT RANGE AREA AND BACK INTO CNTRL WY ALONG THE DIVIDE. BY THIS EVENING...STRONG UPSLOPE WILL BE PRESENT ACROSS CNTRL AND ERN WY...BRINGING A STRONG INCREASE IN PRECIPITATION/SNOW RATES...ESPECIALLY E OF THE DIVIDE...ALONG WITH INCREASED WIND AS 1040ISH HI P SETTLES INTO THE NRN FA. HAVE REMOVED FREEZING DRIZZLE FROM THE FORECAST AS CURRENT VERTICAL PROFILES ALONG WITH TIMING SHOW MOSTLY ALL SNOW. ALTHOUGH A VERY SHORT PERIOD OF FREEZING LIQUID PRECIP COULD BE POSSIBLE ACROSS PORTIONS OF NATRONA COUNTY...IT SHOULD BE VERY SHORTLIVED AND TURN OVER TO SNOW QUICKLY. ADVISORIES/WARNINGS...INCLUDING BLIZZARD WARNING ACROSS SWEETWATER COUNTY AND I80...COVER THE ENTIRE FA THRU THANKSGIVING AFTERNOON. HEAVIEST SNOWS CURRENTLY LOOK TO FOLLOW THE FRONT AND NRN/NERN SLOPES OF ANY TERRAIN WITH PERHAPS AS MUCH AS 0.50 INCH OF TOTAL QPF AND SNOW ACCUMULATION OF 5 TO 10 INCHES ACROSS THE WIND RIVER BASIN...E THRU NATRONA COUNTY...WITH PERHAPS A FOOT OR MORE OVR THE ADJACENT FOOTHILLS/MOUNTAINS IN THIS AREA. CODY FOOTHILLS MAY ALSO BE SUBJECT TO SIMILAR AMOUNTS...ALBEIT ENDING A BIT EARLIER. MOSTLY ADVISORY AMOUNTS EVERYWHERE ELSE. ONE CAVEAT...SWEETWATER COUNTY WHICH MAY ONLY SEE 2 TO 4 INCHES ACROSS MUCH OF THE AREA...BUT WILL INSTEAD COMBINE WITH NRLY WINDS GUSTING 35 TO 45 MPH GIVING BLIZZARD CONDITIONS AT TIMES. SNOW WILL THEN TAPER OFF THRU THE REST OF THURSDAY...WITH PERHAPS FLURRIES ACROSS THE ERN FA THU NIGHT...AND CLEARING COLD SKIES ACROSS THE WEST. FRIDAY...1040 HIGH P MOVES ACROSS THE REST OF THE FA WITH THE COLD FRONT NOW WELL SOUTH WITH SUNNY...NORTH...TO PARTLY CLOUDY AND COLD SKIES ACROSS THE FA...BUT WITHOUT PRECIP CHANCES AT LEAST UNTIL FRI NIGHT WHEN SOME MOIST RETURN FLOW ENTERS SRN/SWRN WY...AND LIGHT SNOW CHANCES INCREASE ONCE AGAIN ACROSS THE SW/SRN CWA. FRIDAY MORNING WILL SEE QUITE COLD MORNING LOWS EVERYWHERE...AOB 0 FOR THE MOST PART...WITH LOWS ACROSS YELLOWSTONE RANGING FROM 10 TO 20 BELOW ZERO. .LONG TERM...SATURDAY THROUGH WEDNESDAY SYNOPSIS...THE LOW PRESSURE SYSTEM OVER THE GREAT BASIN WILL LIFT NORTHEAST ACROSS WYOMING OVER THE WEEKEND...SPREADING CHANCES OF LIGHT SNOW FROM THE SOUTHWEST TO NORTHEAST. CHANCES OF LIGHT SNOW MAY LINGER ACROSS THE NORTHERN MOUNTAINS AND EASTERN JOHNSON COUNTY INTO MONDAY. AN UPPER RIDGE WILL THEN PREVAIL ACROSS THE NORTHERN ROCKIES TUESDAY AND WEDNESDAY WITH THE STORM TRACK EXPECTED TO REMAIN WELL SOUTH OF THE AREA. DISCUSSION...UPPER LEVEL PRESSURE SYSTEM IS EXPECTED TO DISLODGE FROM REX BLOCK ACROSS THE WESTERN U.S. SHEARING NORTHEAST ACROSS WYOMING OVER THE WEEKEND. COMPLICATING MATTERS WILL BE INCOMING PACIFIC ENERGY THAT IS FORECAST TO CLOSE IN RESULTING IN A FUJIWARA INTERACTION...AND ALSO PROGRESSION OR RETROGRESSION OF UPPER HIGH OVER WESTERN CANADA. ECMWF IS ON THE FAST END OF SHEARING UPPER LOW OUT INTO THE NORTHERN HIGH PLAINS ON SUNDAY AS IT SHOWS UPPER HIGH TO THE NORTH DRIFTING WESTWARD TO NEAR VANCOUVER ISLAND. GFS TENDS TO KEEP THE REX BLOCK MOSTLY INTACT AND PROGRESSING SLOWLY EASTWARD OVER THE WEEKEND WITH THE UPPER LOW EVENTUALLY ESCAPING EASTWARD ON MONDAY. FORECAST GIVES MORE WEIGHT TO THE ECMWF WITH HIGHER POPS ACROSS THE SOUTH ON SATURDAY...AND THEN MAINLY SOME WRAPAROUND LIGHT SNOW ACROSS NORTHERN WYOMING ON THE BACK SIDE OF UPPER LOW OVER WESTERN SOUTH DAKOTA ON SUNDAY. ECMWF BUILDS A RIDGE INTO THE NORTHERN AND CENTRAL ROCKIES TUESDAY AND WEDNESDAY WHILE THE GFS IS FASTER TO USHER IN AND SPLIT PACIFIC ENERGY. EITHER WAY IT LOOKS LIKE A DRY PATTERN FOR MOST OF WYOMING. THOUGH AN OVERALL WARMING TREND IS EXPECTED MONDAY THROUGH WEDNESDAY...SNOW-COVERED CENTRAL BASINS ARE EXPECTED TO LAG SEVERAL DEGREES WITH INVERSIONS ONLY STEEPENING THROUGH MID-WEEK. && .AVIATION.../12Z ISSUANCE/ A LARGE UPPER LEVEL DISTURBANCE WILL THEN BRING CHANCES FOR PREVAILING SNOW...FROM 12Z TO 18Z WEDNESDAY...ALONG AND NORTH OF A LINE FROM KJAC TO KLND TO KCPR...WITH SNOW PUSHING FROM NORTH TO SOUTH DURING THIS TIME PERIOD. IN ADDITION ICING CONDITIONS AND FREEZING DRIZZLE AT THE SURFACE WILL BE POSSIBLE ACROSS CENTRAL TERMINALS INCLUDING KLND...KRIW...AND KCPR WEDNESDAY MORNING...BEFORE THE CHANGE OVER TO SNOW. AFTER 18Z...SNOW WILL CONTINUE ACROSS THESE AREAS MENTIONED...AND CONTINUE TO PUSH SOUTH ACROSS THE STATE. WINDS WILL ALSO BE BREEZY ON WEDNESDAY. WINDS...COMBINED WITH SNOWFALL...AND LOW CEILINGS WILL BRING MVFR TO IFR CONDITIONS ACROSS MOST SITES WEDNESDAY...WITH THE MVFR COMING ACROSS WESTERN AND SOUTHWESTERN SITES. WIDESPREAD SNOW TO CONTINUE WEDNESDAY NIGHT...WITH WIDESPREAD IFR CONDITIONS ALSO LIKELY. IN ADDITION...WITH SNOW AND LOWER CEILINGS...EXPECTED THE MOUNTAINS TO BE OBSCURED ACROSS WESTERN AND CENTRAL WYOMING. SOMEWHAT BETTER CONDITIONS ARE EXPECTED WEST OF THE DIVIDE...ESPECIALLY AT KJAC WHERE DOWNSLOPING MAY KEEP CONDITIONS MVFR OR EVEN IFR. && .FIRE WEATHER... FIRE DANGER LOW FOR ALL LOCATIONS THROUGH THIS WEEK/WEEKEND. ONLY VERY STRONG NORTH TO NORTHEAST WINDS INCREASING WITH THE APPROACH OF A STRONG COLD FRONT WOULD BE OF SOME MINOR CONCERN BEFORE PRECIPITATION/SNOW BEGINS ACROSS THE SOUTHERN DISPATCH ZONES. OTHERWISE...EXPECT SNOW AND BLOWING SNOW...INCLUDING BLIZZARD-LIKE CONDITIONS ACROSS SWEETWATER COUNTY AND THE I 80 CORRIDOR. MODERATE TO OCCASIONALLY HEAVY SNOWFALL CAN ALSO BE EXPECTED AT TIMES...ESPECIALLY THIS EVENING. SNOW WILL THEN TAPER OFF ACROSS THE FORECAST AREA THURSDAY MORNING...WITH CLEARING SKIES AND BITTERLY COLD LOW TEMPERATURES FRIDAY MORNING. SMALL CHANCES FOR SOME LIGHT SNOW WILL AGAIN BE POSSIBLE ACROSS SOUTHERN/SOUTHWESTERN WY FRIDAY NIGHT. && .RIW WATCHES/WARNINGS/ADVISORIES... BLIZZARD WARNING FROM 2 PM THIS AFTERNOON TO 5 PM MST THURSDAY FOR WYZ028>030. WINTER STORM WARNING FROM 5 AM EARLY THIS MORNING TO 5 PM MST THURSDAY FOR WYZ005-011-014>020-022. WINTER WEATHER ADVISORY FROM NOON TODAY TO 5 PM MST THURSDAY FOR WYZ013-023-025. WINTER WEATHER ADVISORY FROM 5 AM EARLY THIS MORNING TO 5 PM MST THURSDAY FOR WYZ001-002-004-006>010-012. WINTER STORM WARNING FROM 2 PM THIS AFTERNOON TO 5 PM MST THURSDAY FOR WYZ026-027. WINTER WEATHER ADVISORY FROM 2 PM THIS AFTERNOON TO 5 PM MST THURSDAY FOR WYZ024. WINTER STORM WARNING UNTIL 5 PM MST THURSDAY FOR WYZ003. && SHORT TERM...BRAUN LONG TERM...AEM AVIATION...HATTINGS FIRE WEATHER...BRAUN
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 343 AM MST WED NOV 25 2015 WYZ001>020-022>030-261045- 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- 343 AM MST WED NOV 25 2015 ...BLIZZARD WARNING FOR SWEETWATER COUNTY AND INTERSTATE 80 LATE TODAY AFTERNOON THROUGH THURSDAY... ...WINTER STORM WARNING FOR PARTS OF CENTRAL AND SOUTHWEST WYOMING TODAY THROUGH THURSDAY... ...WINTER WEATHER ADVISORY FOR PORTIONS OF WESTERN AND CENTRAL WYOMING TODAY THROUGH THURSDAY... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT TODAY AND TONIGHT...A SIGNIFICANT WINTER STORM WILL GAIN STRENGTH OVER THE GREAT BASIN INTO SOUTHWESTERN WYOMING TODAY...IMPACTING MUCH OF THE AREA BEGINNING THIS MORNING UP NORTH...PROCEEDING SOUTHWARD THROUGH THE DAY...THEN CONTINUING THROUGH THE OVERNIGHT PERIOD. SNOW WILL BE HEAVY AT TIMES...ESPECIALLY TONIGHT. GUSTY STRONG NORTH TO NORTHEAST WINDS WILL ACCOMPANY THIS STORM SYSTEM...CREATING AREAS OF BLOWING AND DRIFTING SNOW. ALL THIS WILL CREATE HAZARDOUS DRIVING CONDITIONS IN MANY LOCATIONS. PEOPLE PLANNING TRAVEL TODAY AND TONGIHT SHOULD CHECK ON THE LATEST FORECASTS...EITHER FROM OUR WEBSITE OR FROM OUR SOCIAL MEDIA OUTLETS. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY THANKSGIVING DAY...MODERATE TO OCCASIONALLY HEAVY SNOW WILL CONTINUE THANKSGIVING MORNING...TAPERING OFF IN THE AFTERNOON. GUSTY TO STRONG NORTH TO NORTHEAST WINDS WILL CREATE AREAS OF BLOWING AND DRIFTING SNOW. ALL THIS WILL CONTINUE HAZARDOUS DRIVING CONDITIONS ACROSS MANY LOCATIONS. PEOPLE PLANNING TRAVEL THANKSGIVING DAY SHOULD CHECK ON THE LATEST FORECASTS...EITHER FROM OUR WEBSITE OR FROM OUR SOCIAL MEDIA OUTLETS. FRIDAY NIGHT AND SATURDAY...LIGHT AREAS OF SNOW EXPECTED TO SPREAD MAINLY INTO SOUTHWEST AND SOUTH CENTRAL WYOMING. SUNDAY...LIGHT AREAS OF SNOW POSSIBLY SPREADING INTO NORTH AND CENTRAL WYOMING. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ENCOURAGED TO REPORT FINAL SNOWFALL AMOUNTS. THANK YOU.
The national radar mosaic for the moment the first event began.
6 winter storm. Local standard time, as filed.
Heavy snow fell in portions of the Wind River Mountains above Lander. Snowfall at Homestead Park was measured at more than a foot with the bulk of the snow occurring on Wednesday, November 25.
Heavy snow fell across much of the region. The highest amount measured was 9 inches at Jeffrey City.
Heavy snow fell throughout the Lander Foothills. Widespread amounts of 10 to 12 inches were recorded including 11.4 inches at the Lander Airport.
Heavy snow fell across the Wind River Basin. Amounts ranged from 6 inches at Shoshoni to 9.6 inches at the Riverton Airport.
Snowfall of 6 to 8 inches fell in Big Piney/Marbleton northeast along the Green River.
Moderate to heavy snow fell across Natrona County. The heaviest snow occurred in areas closer to Casper Mountain and southwest of Casper. Amounts of around 6 to 8 inches were common in this area.
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, November 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: 606602, 606599, 606600, 606601, 609818, 606598.