This a continuation of the January 31st storm. A moist Pacific flow and a potent upper level system brought heavy snow to portions of western and northern Wyoming.
Every event with a place to put it; 5 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.
This a continuation of the January 31st storm. A moist Pacific flow and a potent upper level system brought heavy snow to portions of western and northern Wyoming. The heaviest snow fell in northwestern Wyoming, especially in the Absarokas where 22 inches of new snow fell at the Beartooth Lake SNOTEL site. Up to 18 inches of snow fell in Yellowstone Park. In the lower elevations East of the Divide, the highest amounts fell along the northern border. In Park County, Wapati picked up 13 inches of new snow. Almost 9 inches fell northwest of Shell in Big Horn County. Amounts dropped off significantly further south. In DuBois, a narrow band of very heavy snow developed and dropped 16 inches of new snow.
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 Jan 31, 11:37 PM MST, 23 minutes earlier.
Area Forecast Discussion...UPDATED National Weather Service Riverton WY 1137 PM MST Tue Jan 31 2017 .UPDATE...Added 06z Aviation Discussion. Winter Storm Warning for the Jackson Valley was downgraded to a Winter Weather Advisory with lighter snow amounts expected. && .AVIATION.../06Z ISSUANCE/ West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals VFR conditions continue at all terminals this morning. Light winds at the surface and stronger ridgetop winds will result in areas of LLWS through the morning, continuing through the afternoon and into Tuesday evening vicinity KBPI-KPNA. Expectation is for light snow to begin to works south across the northwest mountains between 12Z and 18Z/Tue. Snow will increase in coverage and intensity in the northwest and Jackson Hole after 20Z/Tue with IFR conditions expected to prevail vicinity KJAC from 23z Tuesday through Tuesday night. Mountain obscurations will become widespread vicinity and north of a KAFO-KPNA line after 00z Wednesday. East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals Expect VFR conditions through the morning. A cold front will push south to a vicinity KCOD-KBYG line by 18z Tuesday with areas of MVFR/IFR cigs and light snow developing behind the front. The front will continue south to a vicinity KRIW-KCPR line between 21z Tuesday and 00z Wednesday. The heavier snow is expected to remain across the northern third of Wyoming through Tuesday evening, but lower MVFR/IFR ceilings and areas of light snow prevail along and north of a KLND-KCPR line by 06z Wednesday. && .PREV DISCUSSION... /issued 315 PM MST Tue Jan 31 2017/ SHORT TERM...TONIGHT THROUGH FRIDAY THE STRONG ARCTIC FRONT HAS PROGRESSED SOUTH ACROSS THE NORTHERN BIG HORN BASIN WITH AREAS FROM CODY TO POWELL TO BUFFALO NOW SNOWING WITH LESS THAN AN INCH OF SNOWFALL SO FAR AS POTENT SUBTROPICAL PACIFIC MOISTURE IS ALREADY OVERRUNNING THE PROTRUDING COLD DOME OF AIR OVER THE NORTH ALONG WITH ISENTROPIC LIFT. THIS SNOWFALL WILL REACH ADVISORY CRITERIA OVER THE NEXT TWO DAYS AS THIS STEADY LIGHT TO OCCASIONALLY MODERATE SNOWFALL SLOWLY PILES UP. EVEN LANDER, RIVERTON, AND CASPER WILL GET INTO THE ACT AS LOW LEVEL UPSLOPE FLOW ESTABLISHES ITSELF BEHIND THE FROPA TONIGHT. UP TO 5 INCHES OF SNOW COULD FALL ON THE EAST SLOPE OF THE WIND RIVERS. THE SURFACE FRONT WILL REACH ITS SOUTHWEST EXTENT THURSDAY CLOSE TO THE DIVIDE BEFORE THE MOIST PACIFIC STREAM TAKES OVER AND PUSHES THE COLD AIR BACK TO THE NORTHEAST AS THE FRONT RETREATS. BEFORE THIS HAPPENS LIGHT SNOW SHOULD CONTINUE IN THE NORTH, EAST OF THE DIVIDE WITH PERHAPS THURSDAY SHOULD BE THE COLDEST DAY OF THE WEEK EAST OF THE DIVIDE WITH HIGHS 10 TO 15 IN MANY AREAS BEFORE WARMING UP DURING THE REST OF THE WEEK WITH THE COLDEST TEMPERATURES NORTH OF THE OWL CREEK MTNS AND IN JOHNSON COUNTY. IF THESE SHALLOW INVERSIONS HANG ON THROUGH THURSDAY (LIKE 2S OF RIVERTON WHERE IT IS STILL 12 DEGREES AT THE TIME OF THIS WRITING, THIS FRONT WILL BE NOTHING MORE THAN A WARM OCCLUSION. THE AFOREMENTIONED PACIFIC MOISTURE HAS BEGUN TO DUMP HEAVIER SNOWFALL IN NW WY AS THIS MOISTURE BISECTS AN APPROACHING PAC NW TROUGH ALONG WITH ADDED ISENTROPIC LIFT/UPSLOPE ENHANCING THE SNOWFALL UP THERE., HILITES LOOK GOOD ATTM WITH AN ADVISORY IN EFFECT THROUGH 1700L WED AND THE WINTER STORM WARNING THROUGH WED NT IN THE NW. THERE WILL BE A VERY SHORT RESPITE, IF ANY, WED NT AND INTO THU BEFORE SNOWFALL COMES BACK WITH A VENGEANCE AS INCREASING ISENTROPIC LIFT GETS UNDERWAY AHEAD OF THE PAC NW TROUGHPA DUE TO OCCUR THU NT. THE OCCASIONALLY HEAVY SNOWFALL WILL CONTINUE THU NT AHEAD OF THE NEXT OPEN TROUGH WHICH IS NOW STILL A PROMINENT CLOSED LOW WAY OUT AT 33N 143W. BY 00Z SATURDAY, THIS TROUGH WILL JUST BE MAKING LANDFALL SO THIS SIGNIFICANT SNOWFALL OUT WEST WILL CONTINUE CLEAR THROUGH THE DAY FRIDAY. WILL LET LATER SHIFTS EXTEND THE WESTERN/NORTHWEST WY WARNING WHICH WILL LIKELY BE NEEDED. 50 MPH WIND GUSTS WILL CONTINUE OVER THE HIGHER ELEVATIONS THROUGH TONIGHT AND INTO WEDNESDAY MORNING AND THEN AGAIN ON THURSDAY NIGHT. LONG TERM...FRIDAY NIGHT THROUGH TUESDAY Models in good agreement through the medium-range forecast period as the GFS has come more in-line with the ECMWF and GEM solutions. Friday night starts off with another round of enhanced snow across the far west. Open wave moves onshore with Pacific moisture feeding east ahead of this feature. This moisture fetch will favor snow in the western mountains and valleys, although surface temperatures near freezing may temper accumulations in the valleys. Moisture fetch eases a bit on Sunday as moisture wraps north around an upper low off the Pacific Northwest coast. While light snow will continue across the far west and northwest mountains Sunday, amounts should not be as much as Saturday. East of the Continental Divide, drier, downslope flow will lead to warmer temperatures along with dry conditions through the weekend. Wind will gradually pick-up across the wind corridor from Sweetwater County to Natrona County. The combination of warmer air and strong wind aloft will help to erode some of the colder air in the interior snow-covered basins over the weekend. Shortwave ejects out of the Pacific Northwest low Monday and Tuesday with another round of snow across the west. Cyclonic flow on Tuesday on the backside of this shortwave may lead to an increased chance of snow in the lower elevations east of the Divide. Therefore, would likely need to boost snow chances in the east if current trend continues. Cooler northwest flow aloft will drop temperatures several degrees for Tuesday. AVIATION.../00Z ISSUANCE/ West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals Still appears that KJAC will see deteriorating conditions late this afternoon and early this evening. However, moisture and best dynamics look to arrive in the 06Z-12Z/Wed timeframe. Several different waves have already reached the region today with little impact to sensible weather. Expect persistent IFR conditions during this period. South wind 10-20kts will also create occasional blowing snow. Moisture wanes a bit after 14Z/Wed with brief improvement to MVFR until around 20Z/Wed. Expect conditions to drop to low end MVFR or to IFR late Wednesday afternoon. Timing of quick-moving impulses within progressive westerly flow will be difficult. Same 06Z-12Z/Wed period will favor IFR conditions at KPNA as moisture and lift increase. Light snow will continue through the day at KPNA with MVFR or perhaps even VFR with flurries by late in the day. While ceilings will lower at KBPI, upper flow is not as favorable for snow and have continued with VCSH in the forecast. Conditions at KRKS will remain VFR with 20-30kt winds this afternoon. The wind will decrease after 00Z/Wed with 10-15kt west wind the rest of the forecast period. Mountain obscurations will be widespread across northwest Wyoming through 00Z/Thu, mainly north of a KAFO-KPNA line. To the south, mountain top obscurations will become more widespread after 06Z/Wed. East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals Upper flow is generally paralleling the cold front this afternoon, and it has shown slow progress to the south. Occasional light snow and MVFR conditions are found north of a line from KP60 to KWRL to central Johnson County between KBYG and Kaycee. Conditions at KCOD will be MVFR this afternoon before deteriorating to IFR or LIFR this evening. Should be gradual improvement late tonight and early Wednesday, but MVFR will remain through Wednesday. The front will continue a southward push into early this evening, reaching a KLND- KCPR line around 00Z/Wed. MVFR ceilings already at KWRL and expect that KCPR will see conditions deteriorate between 02Z-05Z/Wed. Best chance for accumulating snow and IFR conditions will be 02Z-12Z/Wed. Pattern and upslope flow not as favorable for KRIW and KLND, but still have period of MVFR conditions after 08Z-09Z/Wed. Daytime hours Wednesday at KLND/KRIW could be MVFR with ongoing flurries but little additional accumulation from late morning on. Mountain obscurations will be widespread behind the front and prevalent across all areas by 09Z/Wed. FIRE WEATHER... SIGNIFICANT SNOWFALL IS EXPECTED IN WESTERN AND NORTHWEST WYOMING FOR THE REMAINDER OF THE WEEK. ACCUMULATING SNOWFALL IS ALSO EXPECTED EAST OF THE DIVIDE TONIGHT THROUGH WEDNESDAY WITH MOST OF THE SNOW ALONG AND NORTH OF THE OWL CREEK MOUNTAINS. THE BASIN AND VALLEY SHALLOW TEMPERATURE INVERSIONS HAVE FINALLY DISSOLVED. HOWEVER, A SHALLOW MODIFIED ARCTIC FRONT WILL COOL DOWN THE TEMPERATURES ONCE AGAIN TONIGHT WITH THE COLDEST TEMPERATURES EXPECTED THURSDAY EAST OF THE DIVIDE WHEN MANY HIGH TEMPERATURES WILL ONLY REACH 10 TO 15 DEGREES. THE FRONT WILL THEN RETREAT TO THE NORTHEAST BY LATE THURSDAY. THE FRONT WILL NOT AFFECT AREAS WEST OF THE DIVIDE MUCH. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning until 11 PM MST Wednesday for WYZ001>003- 012. Winter Weather Advisory until 5 PM MST Wednesday for WYZ023. Winter Weather Advisory until 11 PM MST Wednesday for WYZ004- 008>010-013. && SHORT TERM...Lipson LONG TERM...CNJ AVIATION...AEM FIRE WEATHER...Lipson
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 259 AM MST TUE JAN 31 2017 WYZ001>020-022>030-011300- 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- 259 AM MST TUE JAN 31 2017 ...HIGH WIND WARNING FOR GREEN MOUNTAINS AND RATTLESNAKE RANGE UNTIL NOON TODAY... ...WINTER STORM WARNINGS AND WINTER WEATHER ADVISORIES ARE IN EFFECT FOR MUCH OF NORTHWEST AND NORTH CENTRAL WYOMING... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT STRONG WINDS WILL CONTINUE THIS MORNING...MAINLY BETWEEN JEFFREY CITY AND MUDDY GAP. PLEASE SEE HIGH WIND WARNING FOR THE LATEST INFORMATION. SNOW WILL BEGIN ACROSS NORTHERN PORTIONS THIS MORNING...SPREADING SOUTHWARD OVER THE WESTERN MOUNTAINS AND VALLEYS AND THE BIG HORN BASIN...THE BIGHORN MOUNTAINS AND NORTHERN JOHNSON COUNTY. THIS ACTIVITY WILL CONTINUE THROUGH WEDNESDAY EVENING. PLEASE SEE WINTER STORM WARNINGS AND WINTER WEATHER ADVISORIES FOR ADDITIONAL INFORMATION. LIGHT SNOW WILL SPREAD INTO CENTRAL PORTIONS DURING THE OVERNIGHT HOURS. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY WEDNESDAY AND THURSDAY...SNOW WILL CONTINUE TO FALL ACROSS NORTHERN AND WESTERN PORTIONS THROUGH WEDNESDAY NIGHT. MOST OF THE SNOWFALL WILL RETREAT NORTHWARD DURING THE OVERNIGHT HOURS WEDNESDAY NIGHT. ANOTHER ROUND OF MODERATE SNOW WILL IMPACT WESTERN PORTIONS THURSDAY...BEFORE FINALLY SUBSIDING THURSDAY NIGHT. FRIDAY NIGHT AND SATURDAY...SIGNIFICANT SNOW AGAIN POSSIBLE OVER THE WEST. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ENCOURAGED TO REPORT SNOWFALL AMOUNTS. THANK YOU.
The national radar mosaic for the moment the first event began.
4 winter storm, 1 winter weather. Local standard time, as filed.
Several locations of the Absaroka Mountains received over a foot of new snow. The highest amounts included 24 inches at Pahaska and 22 inches at the Beartooth Lake SNOTEL site.
Heavy snow fell in northern portions of the Cody Foothills. The highest amount was in Wapati where 13 inches of new snow fell. Around Cody, amounts generally ranged from 3 to 7 inches. Snowfall amounts dropped off rapidly further south.
Heavy snow fell in a narrow band across portions of Big Horn County. Almost 9 inches of snow was measured north of Shell with up to 6 inches around Greybull. North and south of this line snow fall amounts were much less.
Rangers at Yellowstone National Park measured 18 inches of new snow at the east entrance to the Park and 13 inches at the Old Faithful Ranger Station.
A narrow band of heavy snow fell near Dubois. There were numerous reports of a foot of new snow with a maximum amount of 16 inches. Snowfall amounts fell rapidly further southeast with little snow reported at Crowheart.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2017Every state in 2017This day in weather historyWarnings in Wyoming, February 2017
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: 674331, 674524, 674525, 674330, 674526.