An upper level disturbance passed over Wyoming and brought locally heavy snow to the Tetons. The highest amount recorded was 14 inches at the Grassy Lake SNOTEL.
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The episode as NWS RIW wrote it up.
An upper level disturbance passed over Wyoming and brought locally heavy snow to the Tetons. The highest amount recorded was 14 inches at the Grassy Lake SNOTEL.
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 Dec 27, 10:00 AM MST, 0 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1000 AM MST Tue Dec 27 2016 .SHORT TERM...Tuesday through Thursday night (issued 753 AM MST Tue Dec 27) The weather pattern today reminds me of the classic poem The Charge of the Light Brigade. The most famous line in the poem is "Cannons to the left of them, cannons to the right of them." For the next day to day and a half, the meteorological equivalent would be "Snow to the left, wind to the right, substitute west and east for left and right." So, we will split the discussion into West of the Divide and East of the Divide. West of the Divide...Snow is the big story here. Things are quiet right now but precipitation should begin to develop this morning as some overrunning moves into the area. At this point, the models are showing mainly light precipitation through most of the day, although wind will increase significantly through the afternoon. The rubber will likely meet the road tonight and early Wednesday morning as a powerful 150 knot jet moves into the area and enhances lift. Things will likely get nasty across the area for around a 12 hour period as bulk of the storm moves across. As mentioned in the previous discussion, there will be a lot of wind with this system as well. As a result, we have upgraded most of the watches to warnings with all the models zeroing in on the Tetons and Jackson Valley as the epicenter for the heaviest snow. The models are indicating not as much for the Salt and Wyoming Range so we opted to go with an advisory since the any warning level amounts would be above pass level and impact a bit less. Most of the models show the best moisture moving out of the area by mid Wednesday morning. However, with gusty winds continuing and unstable northwesterly flow resulting in possible snow banding, we elected to run the highlights through the afternoon across northern areas. Conditions should improve late in the day as the jet moves away and winds decrease. The exception may be in Sweetwater County. MOS is close to high wind criteria there. For now, we will punt on that and let the day crew consider any potential highlights since it would not be until the 3rd period. Otherwise, ridging building over the area will bring a tranquil pattern from later Wednesday through Thursday night as the models have trended slower with the arrival of the next system. And like the previous couple of systems, the air behind this system is Pacific in origin, not Arctic, so temperatures will be chilly be not overly cold. East of the Divide...Again, the concern here shifts to wind. With the powerful jet moving into the area and most of the area in the favored right front quadrant to enhance downward momentum, the 700 millibar winds of 50 to 55 knots will be forced down in many areas and bring gusty winds. At this point, the high wind warnings look good and will be continued as is for now. And with the wind, low visibility with blowing snow will also continue. One question today is how far with the wind be able to mix out the inversions. And the models are split on that. For now, we decided to let continuity ride and kept things on the cool side. As for the chance of precipitation, other than the slight chance of some blowover, it would be restricted to the mountains with the strong downsloping flow. Late tonight, 700 millibar flow will decrease after the passage of the cold front so the wind should decrease somewhat. Wednesday at this point looks more tranquil and mainly dry. The inversions should be gone so most areas should get to or close to the 30s with a decent breeze in many areas. However, as the winds decouple Wednesday night and the sky clears, it will get chilly Wednesday night, but not bitterly cold. At this point, Thursday looks dry under a ridge of high pressure. .LONG TERM...Friday through Tuesday Friday and Friday night, a shortwave trough over southern Alberta/Saskatchewan will push east southeast into the Upper Midwest/N. Great Lakes area while a stronger shortwave trough off the Pacific NW Coast pushes south, and becomes closed off across northern/central California. A weak cold front is expected to push south across the area late Friday into Friday night. Ahead of this front there could be strong to high wind in the Absaroka/Cody Foothills and windy conditions in typical wind corridor. Looks like much of the snowfall will remain north of the area Friday, but should spread south into the area Friday evening. Although forcing looks to be weak with this system it does have a shear axis and possibly some right entrance region of an upper jet. North & Northwest Wyoming will have the best shot of light snowfall with this system. By Saturday mainly dry conditions are expected as the shear axis should be weakening, and any impact from the upper jet will be moving away. Global models are in decent agreement with a strong upper low/trough sliding south along the British Columbia Coast Saturday and into the Pacific Northwest by Saturday night. At the same time models show strong upper level ridging building into Alaska in wake of this system which will allow for some Arctic air to push into the Cowboy State early next week. On Sunday as the main trough becomes established over the Western U.S., the combination of QG forcing with the trough, baroclinic zone becoming established over the west, and a moist southwest flow should result in snow breaking out over much of the west Sunday. As the Arctic cold front pushes south across the area Sunday night and Monday, there is a good potential for snow breaking out east of the Divide if model trends continue. Overall the ECMWF is a tad faster than the GFS and Canadian models. It is still early, but this system has the potential for significant snowfall. Have begun to increase PoPs for this system, but they are still relatively low especially east of the Divide. By Tuesday, a moist westerly flow will continue the chance of light snowfall across western Wyoming, along with bitter cold temperatures. .AVIATION.../12Z ISSUANCE/ West of the divide...KBPI/KJAC/KPNA/KRKS Terminals Areas of snow have developed over NW WY and will continue to spread east and south through the afternoon. Widespread MVFR/IFR conditions will occur in NW WY through 06Z Wed. KJAC airport will be impacted by wind and snow today into tonight and Wednesday. VFR conditions will prevail in southwest WY through 21Z. Then snow is expected at the KPNA airport after 21Z through 18Z Wed with MVFR to IFR conditions. Wind will combine with the snow by 12z. MVFR conditions will occur at KBPI airport by 03Z with lower ceilings and VCSH and IFR to MVFR conditions by 06Z with -sn and blsn. KRKS airport will remain VFR through the period with a gusty west wind through the period. East of the divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals VFR conditions will occur at the terminal sites. Strong wind will create blowing and drifting snow at KCPR and KCOD airports, with visibility below 6NM at times. .FIRE WEATHER... Another system moving into the west will bring another round of moderate to heavy snow to many areas in the western mountains, along with some very gusty winds. Meanwhile, dry weather will be the rule East of the Divide. Inversions should weaken a bit today allowing for slightly warmer temperatures in the basins. Strong winds will continue in the lee of the Absarokas and across the southwestern Wind Corridor from the Red Desert through Casper. Wednesday should be more tranquil with less wind for most areas with the exception of Sweetwater County. && .RIW WATCHES/WARNINGS/ADVISORIES... High Wind Warning until 5 AM MST Wednesday for WYZ003-019-020. Winter Weather Advisory until 5 PM MST Wednesday for WYZ024-025. Winter Storm Warning until 5 PM MST Wednesday for WYZ013-023. Winter Storm Warning until 5 PM MST Wednesday for WYZ012. Winter Weather Advisory until 5 PM MST Wednesday for WYZ014-015. Winter Weather Advisory until 11 AM MST Wednesday for WYZ001. Winter Weather Advisory until 11 AM MST Wednesday for WYZ002. && SHORT TERM...Hattings LONG TERM...WM AVIATION...LaVoie FIRE WEATHER...Hattings
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 216 AM MST TUE DEC 27 2016 WYZ001>020-022>030-281215- 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- 216 AM MST TUE DEC 27 2016 ...HIGH WIND WARNINGS FOR THE CODY FOOTHILLS...GREEN MOUNTAINS...AND NATRONA COUNTY THROUGH TONIGHT... ...WINTER STORM WARNING AND ADVISORIES IN EFFECT FOR MUCH OF THE WESTERN MOUNTAINS AND VALLEYS THROUGH WEDNESDAY... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT SNOW AND WIND INCREASING ACROSS THE WESTERN MOUNTAINS AND VALLEYS. PLEASE SEE WINTER WEATHER PRODUCTS AND FORECASTS FOR DETAILS. BREEZY TO WINDY CONDITIONS DEVELOPING ACROSS MUCH OF THE AREA WITH HIGH WINDS LIKELY IN THE CODY FOOTHILLS AND FROM THE RATTLESNAKE RANGE TO NATRONA COUNTY. PLEASE SEE HIGH WIND WARNINGS AND FORECASTS FOR DETAILS. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY WEDNESDAY...LINGERING SNOW AND WIND ACROSS THE WEST. STRONG WIND POSSIBLE IN SWEETWATER COUNTY. SUNDAY AND MONDAY...A STORM SYSTEM COULD BRING SIGNIFICANT SNOWFALL OVER THE WEST. AN ARCTIC COLD FRONT EXPECTED SUNDAY NIGHT AND MONDAY WITH SOME SNOWFALL SPREADING EAST OF THE DIVIDE. BITTER COLD TEMPERATURES ACROSS THE ENTIRE AREA MONDAY AND TUESDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ARE ENCOURAGED TO REPORT SNOWFALL AMOUNTS AND ANY WIND DAMAGE. THANK YOU.
The national radar mosaic for the moment the first event began.
1 winter storm. Local standard time, as filed.
The Grassy Lake SNOTEL reported 14 inches of snow. On top of the Jackson Hole Ski Resort, 12 inches of new snow was measured.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2016Every state in 2016This day in weather historyWarnings in Wyoming, December 2016
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: 666082.