A combination of rain and snow melt brought minor flooding around DuBois. Flooding was restricted to the low lands and caused no damage.
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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 combination of rain and snow melt brought minor flooding around DuBois. Flooding was restricted to the low lands and caused no damage. Flooding near Highway 132 also caused the closing of a lane of traffic along the Blue Sky Highway.
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 May 27, 1:35 AM MST, 6 hours 25 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 235 AM MDT Sun May 27 2018 .SHORT TERM...(Today through Tuesday night) Issued at 231 AM MDT Sun May 27 2018 Strong southerly difluent flow and left front quad dynamics over our CWA, out ahead of the prominent low spinning around the vcnty of Las Vegas early this morning, has produced training convection, mainly over our northern CWA since earlier this evening. Currently, training convection is ongoing across the Interstate 25/90 corridor from south to north in Johnson County, laying the ground work for increasingly saturated soil for this next round of convection expected this afternoon and evening. Todays convection will result from the 500mb low tracking east northeast into Utah with an asct 700mb circulation out ahead of the main 700mb low (also over Utah) expected to develop over Southwest Natrona County before tracking east to the vcnty of Casper later today. This weak 700mb circulation will likely be a bulls eye for the heaviest precip to fall from afternoon and evening thunderstorms. In addition, Johnson County will be under the gun later today where the lifted indices are progged to be -6 to -7 along with the highest capes. Since this area is already getting heavy rainfall from ongoing thunderstorms followed by relatively strong convection expected later today, decided to issue a flash flood watch to cover the lower elevations of Johnson/Natrona counties as well as Casper Mountain, valid from 18z this afternoon to 06Z Monday. A 35 knot easterly wind will aid in drawing in juicy air into the area from the east and influence back building along east slopes today. SPC has the entirety of Natrona County under a slight risk today. The flood watch for most of the northern half of the CWA, west of the flash flood watch remains in effect through Monday morning to account for the warm temps as well as for rain on snow melt. The 700mb low is progged to take an odd turn to the northwest tonight and into Monday as it becomes more well defined over Southern montana by later Monday. With the low just to our north, instability and moisture will again influence another round of convection Monday afternoon and evening, Our eastern zones will be in a marginal risk so the potential for significant convection is expected Monday, although, not quite to the degree we are expecting today. Some convection will take place behind the exiting low Tuesday under dirty nw flow. After a cool down expected today and Monday, temps will begin a warming trend again Tuesday. .LONG TERM...(Wednesday through Sunday) Issued at 231 AM MDT Sun May 27 2018 The next Pacific trough will move onto the west coast and into the Intermountain West on Thursday and Thursday night, and then shear northeast across the area Friday and Saturday. The area will see a break between systems on Wednesday with dry and warmer weather prevailing, except for a few late day thunderstorms over the mountains. Shortwaves from western trough should begin to eject northeast across western Wyoming on Thursday, bringing isolated to scattered showers and thunderstorms to the west and far north, while dry, warm and breezy conditions prevail across south and central Wyoming. Southwest flow with lee side low near the Bighorn mountains will bring modest instability across northern Johnson County and the northern Bighorn basin Thursday where stronger thunderstorms are likely to develop. Forecast generally follows ECMWF's slower and more consistent solution lifting the main upper trough northeast across the area late Friday into Saturday; the associated Pacific cold front pushing across the area Friday-Friday evening. Higher chances of precipitation will remain across the west and north Friday, with a few strong thunderstorms still possible east of the Bighorn Range. Cooler conditions and mainly dry conditions are expected to prevail through the day Saturday behind the cold front. && .AVIATION...(For the 12Z TAFS through 12Z Monday morning) Issued at 231 AM MDT Sun May 27 2018 West of the Continental Divide...KJAC/KBPI/KPNA/KRKS Isolated showers will occur through the morning. Scattered showers and thunderstorms will develop over the west around 18Z and continue through 06Z Monday. Then isolated showers and storms will occur after 06Z Monday. Wind gusts to 35 knots and small hail will be likely with the stronger storms. Mountains will be obscured at times. Expect VFR conditions at the terminal sites, but MVFR conditions will occur in thunderstorms. East of the Continental Divide...KCPR/KCOD/KRIW/KLND/KWRL Isolated showers will occur through the morning. Scattered showers and thunderstorms will develop over the area around 18Z and continue through 06Z Monday. Isolated showers and storms will linger after 06Z Monday. Wind gusts to 35 knots and hail will be likely with stronger storms. Heavy rain will also be possible. Mountains will be obscured at times. Expect VFR conditions at the terminal sites, but MVFR conditions will occur in thunderstorms. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts.*&& .FIRE WEATHER... Issued AT 231 AM MDT Sun May 27 2018 As a Pacific low pressure trough over the western Great Basin shifts slowly east, moisture and instability will increase in the southwest flow bringing a significant increase in showers and thunderstorms on Sunday. Temperatures will begin to cool today. The still relatively warm temperatures and breezy conditions will accelerate snow melt runoff with most rivers and streams expected to rise to near bankfull with some flooding. Please check on local flood products in your area. Today and Monday significant rainfall of 1 to 2 inches will be possible adding to flooding concerns. Showers and isolated thunderstorms will decrease in overall coverage on Tuesday with warming temperatures. Mixing heights in the afternoons should be high enough for good smoke dispersal except in areas with heavier precipitation. && .RIW WATCHES/WARNINGS/ADVISORIES... Flood Watch from 6 AM MDT this morning through Monday afternoon for WYZ002>004-006-008-009-012-015>017. Flash Flood Watch from noon MDT today through this evening for WYZ010-011-020-022. && SHORT TERM...Lipson LONG TERM...Meunier AVIATION...Ross FIRE WEATHER...Lipson
Hazardous Weather Outlook National Weather Service Riverton WY 242 AM MDT Sun May 27 2018 WYZ001>020-022>030-281100- 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- 242 AM MDT Sun May 27 2018 ...Flash Flood Watch in effect from noon through this evening for Natrona and Johnson Counties... ...Flood Watch from this morning through Monday afternoon... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight Scattered showers and thunderstorms developing over most of the area. Locally heavy rainfall is possible and will elevate the flood threat along rivers and creeks already running high from snowmelt. Isolated strong to severe thunderstorms are possible. .DAYS TWO THROUGH SEVEN...Memorial Day through Saturday Memorial Day...Scattered showers and thunderstorms developing over most of the area. Locally heavy rain may elevate the flood threat along rivers and creeks already running high from snowmelt. Tuesday...Isolated to scattered showers and thunderstorms across the area. Thursday and Friday...Isolated to scattered showers and thunderstorms mainly in the north and west. .SPOTTER INFORMATION STATEMENT... Spotters are urged to report hail, wind gusts past 45 mph and any flooding. Thank you.
The national radar mosaic for the moment the first event began.
3 flood. Local standard time, as filed.
Minor flooding occurred along the Wind River near Dubois. No damage occurred.
Heavy rain caused flooding along Piney and Rock Creeks to the north of Buffalo. Old Highway 87 was closed for a time as water was running over it.
Fremont County emergency management reported flooding near the Wind River and Highway 132. The south lane of traffic was covered with water for a day.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2018Every state in 2018This day in weather historyWarnings in Wyoming, May 2018
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: 749616, 749620, 749618.