A very dry airmass over the Big Horn Basin set the stage for gusty outflow wind from thunderstorms tracking east across the basin. One collapsing thunderstorm generated outflow wind that swept across Big Horn County and produced a 60 mph wind at the airport north of Greybull.
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The episode as NWS RIW wrote it up.
A very dry airmass over the Big Horn Basin set the stage for gusty outflow wind from thunderstorms tracking east across the basin. One collapsing thunderstorm generated outflow wind that swept across Big Horn County and produced a 60 mph wind at the airport north 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 Jul 19, 10:25 AM MST, 2 hours 48 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1125 AM MDT TUE JUL 19 2016 .SHORT TERM...Today through Thursday night ...Fire Weather Watch for portions western and central Wyoming Wednesday afternoon and evening... Fire danger moderate to elevated today (with less wind overall)then elevated to extreme across the lower elevations east of the Divide and also over the west central and southwest mountains Wednesday. As fuel status has now changed across the FA and includes more zones, the Fire Weather Watch for Wednesday now includes the west central/southwest mountains along with portions of lower elevations of central WY. Natrona county lays at the far eastern extension of the Watch and may end up not being included in the Red Flag Warning at issuance time. Imagery shows broad ridge across the central CONUS with bookend trofs over each coast. Upper broad central high pressure is located over the plains. Embedded disturbance continue riding through/around the ridge touching off showers/storms where sfc/mid level fronts exist (high/central plains) or capping is weak...such as higher terrain features. Mid level moisture flowing around the high out of the tropics and across the desert SW...then southern and central Rockies. Surface has generally weak high pressure across southern WY with lower pressure off to the north, west and southwest from the northern Great Basin into the desert southwest. This is setting up a brief period of monsoonal type flow through the southern and central Rockies into the central plains...but mostly missing WY except across the far south and southeast. Through the forecast period: Upper ridge moves further east into the plains while the ridge center sets up across the southern/central plains. With good mid-level moisture feeding around the high and heat induced low pressure setting up across the Great Basin and Desert Southwest, a monsoonal type flow is setting up across the southern and central Rockies. However, and unfortunately, the moisture at this time is being directed through the southern/central Rockies and then eastward into the eastern high/central plains...including mainly eastern/southern portions of WY and leaving most of the FA, except for the south, rain free. Through Wednesday, a lee side trof/weak surface low will try to build over central/eastern WY. With the upper ridge axis then tilted slightly from southeast to northwest, the upper level flow over most of the CWA will be from the southwest and quite dry and capped. Today through Wednesday, convection will then lay across southern/southeastern WY with only a few isolated showers/storms over possibly initiating across the higher terrain of the areas mountains with little to offer but light rain and gusty winds. The Uinta and Medicine Bow mountains will have the best chances for laying down measurable precip. Thursday, a front moves through eastern Wyoming from north to south in the morning...effectively shutting off what little moisture was getting into the FA...with only a few late day/evening showers/storms possible across mainly the southwest mountains...which could only provide gusty erratic winds to the fires instead of any helpful rainfall. .LONG TERM...Friday Through Tuesday Hot and breezy to windy on Friday ahead of our MT shortwave which will push a front sewd into at least our nrn zones Friday night. A little moisture may be drawn up ahead of this system with a few light showers around mainly the mountains in the morning with isolated, gusty thunderstorms late in the day in the mtns and sern zones. Saturday looks dry in the wly flow behind this shortwave and not as hot. Temps may cool as much as 10 to 15 degrees in the far north with only a few degrees of cooling in the southwest. Temperatures start to rebound again Sunday into Monday a few degrees each day with limited tstm chances. There is a significant difference though between the Euro and GFS on a potential shortwave moving in from the wsw late Sunday. The GFS is much stronger and generates more potential for a few storms just about anywhere but especially mtns and sern zones. Just have a few storms in some of the mtns right now but we'll see how this evolves because the evolution is already different than last night. A few storms still possible Monday mainly around the mountains as weak ripples will likely be around with limited moisture in the w/sw flow. Another shortwave is forecast to move ewd across us on Tuesday with potential for a higher low level moisture in our far ern zones. Will add in isolated storms in the ern zones for this. Not a lot of hope for any real rain during this period so the main weather concern will be elevated fire concerns due to ever drying fuels, breezy periods, hot temps and isolated thunderstorms. && .AVIATION.../18Z ISSUANCE/ Showers and thunderstorms will continue to develop this afternoon, especially east of a line from Evanston to Buffalo. Showers look most favorable across the south, impacting KRKS. A few showers will also be possible across the Absaroka mountain range in north-central Wyoming, which may result in some mountain obscurations for those traveling across the northern third of the area. Showers will taper off this evening, only lingering over southern Wyoming after 06z. Aside from shower activity, smoke from growing wildfires is the other aviation concern, with FU being reported at KJAC this afternoon. With ongoing southwesterly flow, additional limits in visibility area anticipated to continue, with periods of related MVFR conditions. With other wildfires across the area, additional visibility restrictions may occur across north-central Wyoming, potentially impacting KWRL, KGEY, and KCOD. No mention of this threat has been included in their TAFs, but the situation will be monitored. && .FIRE WEATHER... ...Fire Weather Watch for portions of the southwest/west central mountains in addition to central Wyoming lower elevations... Fire danger will elevated for all lower elevation zones over the next several days with moderate to elevated conditions in the mountains as warm/hot, dry conditions prevail with little chance for rainfall relief across most of the forecast area (except for perhaps the far southern zones. Otherwise, extreme fire conditions expected again Wednesday this time possibly across portions of the southwest/west central mountains in addition to portions of the lower elevations of central Wyoming in the afternoon through early evening as low rh and very gusty winds combine with Haines instability values of 5 to 6 and critically dry fuels. Natrona county, fire wx zone 280, is definitely the most marginal of the Watch group and may end up not making the cut at Warning issuance. Three large incident fires are currently burning in the west central/southwest forecast area. && .RIW Watches/Warnings/Advisories... Fire Weather Watch from Wednesday afternoon through Wednesday evening for WYZ280-283-414>416. && SHORT TERM...Braun LONG TERM...Skrbac AVIATION...Branham FIRE WEATHER...Braun
HAZARDOUS WEATHER OUTLOOK...CORRECTED NATIONAL WEATHER SERVICE RIVERTON WY 230 AM MDT TUE JUL 19 2016 WYZ001>020-022>030-201200- 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- 230 AM MDT TUE JUL 19 2016 ...FIRE WEATHER WATCH IN EFFECT FROM WEDNESDAY AFTERNOON AND EVENING FOR PORTIONS OF THE WESTERN MOUNTAINS...AS WELL AS THE LOWER ELEVATIONS OF FREMONT AND NATRONA COUNTIES... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT ISOLATED TO WIDELY SCATTERED AFTERNOON AND EVENING THUNDERSTORMS IN THE SOUTH AND SOUTHERN NATRONA COUNTY AREAS. GUSTY WIND AND LIGHTNING WILL BE THE MAIN THREATS. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY WEDNESDAY...ELEVATED TO EXTREME FIRE WEATHER CONDITIONS...ESPECIALLY OVER THE WESTERN MOUNTAINS AND THE LOWER ELEVATIONS OF NATRONA AND FREMONT COUNTIES WHERE FUELS ARE CRITICAL. ISOLATED AFTERNOON AND EVENING THUNDERSTORMS IN THE SOUTH. GUSTY WIND ARE THE MAIN HAZARDS. THURSDAY...ISOLATED AFTERNOON AND EVENING THUNDERSTORMS...MAINLY ACROSS SOUTHERN WYOMING AND THEN THE SOUTHWEST MOUNTAINS IN THE EVENING. FRIDAY...ISOLATED LATE DAY THUNDERSTORMS...MAINLY MOUNTAINS AND FROM SWEETWATER COUNTY OVER TO SOUTHERN NATRONA. ELEVATED FIRE DANGER DUE TO BREEZY TO WINDY CONDITIONS...HOT TEMPERATURES... AND VERY LOW RH'S. MONDAY...ISOLATED LATE DAY THUNDERSTORMS IN THE MOUNTAINS. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE URGED TO REPORT STRONG WIND GUSTS OVER 40 MPH. THANK YOU. TEAM RIVERTON
The Billings radar (KBLX), 154 km away, was scanning. The volume nearest the first event began at 20:14 UTC.
1 thunderstorm wind. Local standard time, as filed.
The ASOS at the South Big Horn County Airport just north of Greybull reported a wind gust of 60 mph.
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, July 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: 641374.