A combination of rapid snowmelt, releases from the Boysen Reservoir and some log jams caused flooding along portions of the Greybull and Big Horn Rivers. The flooding remained over low lying areas and caused little or no property damage.
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The episode as NWS RIW wrote it up.
A combination of rapid snowmelt, releases from the Boysen Reservoir and some log jams caused flooding along portions of the Greybull and Big Horn Rivers. The flooding remained over low lying areas and caused little or no property damage.
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 Jun 22, 2:13 AM MST, 3 hours 47 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 313 AM MDT Thu Jun 22 2017 .SHORT TERM...Thursday through Saturday night A cold front is now dropping southward through the state as I write this. And normally, this would mean some sort of precipitation. However, the airmass with it is very dry so this will be a dry passage. There will be some decent northerly wind after the front passes, but that will be pretty much the only effects. Of course, a couple of the models are doing the Bighorn Mountain rain forest effect, but with the lack of moisture everyone should stay dry. The main effect will be cooler temperatures, generally 10 to 15 degrees cooler. We kept temperatures above MOS in most areas however, given a good amount of sunshine and being right around the solstice. There will still be a gusty breeze at times, but nothing unusual. Temperatures will continue to decrease on Friday. And again, with the very dry atmosphere, all areas should stay dry despite a shortwave moving through. Again the models are trying to bring showers to the mountains, but at this point we think that is bogus. The aforementioned temperatures will average around 10 to 15 degrees below normal for many areas once again. Yet another shortwave will move through on Saturday. There could be a bit more moisture recovery ahead of this system. However, the models again are not very impressed with the coverage of any precipitation. Even the European, which has been the wettest model, has continued to back off on QPF. As a result, we trimmed POPS back mainly to slight chance and halved QPF. And yes, there could be a bit of snow, but given that it is late June and most would fall during the day, it would be restricted to the higher elevations and would likely not stick. The chance of any showers or thunderstorms would run roughly north of a Riverton to Casper line. .LONG TERM...Sunday through Thursday Overview...Dry and milder conditions will occur Sunday, but temperatures will still be below seasonal normals. Much warmer conditions are expected Monday and Tuesday with isolated to widely scattered afternoon and evening thunderstorms across the north. Temperatures will likely trend slightly cooler mid-week with slight chances of thunderstorms across the far north. Discussion...Synoptic pattern on Sunday features upper ridge over the Intermountain West with NW flow aloft over Wyoming. Surface high pressure over the central plains will bring light east winds across eastern and central Wyoming, but better moisture and instability will be to our southeast across SE Wyoming and eastern Colorado. All in all, a Chamber of Commerce day Sunday across western and central Wyoming with most lower elevation highs in the 70s to lower 80s, light wind, and plentiful sunshine. Upper ridge will translate the Rockies Monday-Monday night with building heights and the return of summer heat through Tuesday. Pacific shortwaves riding through the ridge will bring some showers and thunderstorms across the north. A lee side surface trough is expected to intensify Tuesday bringing breezy to windy and very warm and dry conditions across the southern zones, elevating the fire danger. Spread between the GFS and ECMWF increases mid-week with GFS slower and more amplified with a trough across the northern Rockies while ECMWF keeps stronger upper high over Arizona/New Mexico, which blocks northern stream trough from digging south of the U.S. / Canadian border. Still much uncertainty at this stage, with climatology favoring ECMWF's stronger upper high over the southern Rockies. Forecast keeps temperatures above normal Wednesday with a hedge toward near normal values on Thursday. && .AVIATION...12Z Issuance VFR will prevail at all terminals through 12Z/Fri. A cool front will bring northerly oriented winds of 15-25kts (with higher gusts) through and into central and southern Wyoming respectively this morning. Generally few clouds expected around the forecast area through the period. A second cool front with gusty northerly winds will again burst through the region this (Thursday) evening...affecting most terminal sites east of the Divide. LLWS possible with the frontal passages at some locations. && .FIRE WEATHER... Expect cooler temperatures behind a cold front today. Some areas, especially across the west and in southern Wyoming will continue to a gusty breeze. Relative humidity should remain above critical levels for most locations, but will likely drop below 15 percent at times this afternoon across portions of Sweetwater and Lincoln Counties. All areas should have a rain free day today. Mixing and smoke dispersal will be generally good to excellent. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...Hattings LONG TERM...Meunier AVIATION...Braun FIRE WEATHER...Hattings
Hazardous Weather Outlook National Weather Service Riverton WY 318 AM MDT Thu Jun 22 2017 WYZ001>020-022>030-231100- 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- 318 AM MDT Thu Jun 22 2017 ...Flood warnings remain in effect for portions of western and central Wyoming... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight Flooding will continue along the South Fork of the Shoshone River, the Wind River and its tributaries, and the Green River today. Please see flood warnings and forecasts for details. Elevated fire weather conditions across the southwest with a gusty wind and low relative humidity. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Monday through Wednesday...Isolated to widely scattered afternoon and evening thunderstorms across northern Wyoming. Very warm, dry and breezy to windy conditions will bring elevated fire danger to southern Wyoming Tuesday and Wednesday. .SPOTTER INFORMATION STATEMENT...Spotters are urged to report any flooding. Thank you. Team Riverton
The national radar mosaic for the moment the first event began.
2 flood. Local standard time, as filed.
Emergency management reported flooding along the Greybull River. The flooding remained over low lying areas and caused little or no damage.
Emergency Managers reported flooding along the Big Horn River near Manderson. The flooding remained over low lying areas and caused no damage.
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, June 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: 704245, 704252.