A strong cold front moved across Wyoming and brought showers and thunderstorms to Wyoming. Large dew point depressions and strong mid level winds mixing to the surface brought very strong wind gusts to portions of central Wyoming.
Every event with a place to put it; 3 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.
A strong cold front moved across Wyoming and brought showers and thunderstorms to Wyoming. Large dew point depressions and strong mid level winds mixing to the surface brought very strong wind gusts to portions of central Wyoming. Wind gusts past 60 mph occurred in portions of Big Horn, Fremont, Park, Washakie, Johnson and Natrona Counties with a maximum gust of 70 mph at the Natrona County airport.
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 Apr 27, 3:45 AM MST, 4 hours 45 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 445 AM MDT Thu Apr 27 2023 .DISCUSSION...Today through Wednesday Issued at 156 AM MDT Thu Apr 27 2023 Thursday will be the most active day of the forecast with an approaching cold front from the north that will affect much of the CWA. A progressive shortwave down the longwave ridge will quickly push through during the afternoon hours, before exiting to the southeast after sunset. With increasing divergence aloft, a strong and quick cold front, supported from above, will slide through north to south from mid morning to mid afternoon. Increasing west to northwesterly winds ahead of the front as the gradient tightens associated with it. Directly behind the cold front will expect gusty northerly winds up to 30-40 mph for much of the valleys with the strongest gusts over 50 mph for the Bighorn Basin and points east where the higher PVA anomalies will occur. As a result, the higher snowfall accumulations are expected for the Bighorns around 6-10 inches with less for the mountains along the Divide. Valley rain showers are likely for much of the area east of the Divide with isolated rumbles of thunder possible during the peak heating of the afternoon with the strongest instability seeing CAPE values up to 300-500 J/kg. A quick punch from the front will see easing winds and tapering precipitation towards sunset and especially into the overnight by midnight as the shortwave slides to the southeast rather quickly. Otherwise, a strong ridge will build back in across much of the Rocky Mountain west starting Friday with increasing convergence aloft. As a result, any of the Pacific lows will be suppressed to the West Coast of the US. This will bring warmer temperatures through the weekend and much of the next work week, with 70s east of the Divide and pushing the 80 degree mark for the Bighorn Basin. West of the Divide will see 50s and 60s that will bring a risk of flooding early next week due to melting snow in the lower elevations of Teton and Lincoln counties, including near Hoback Junction. The foothills in the 6-9kft range could also be affected by these warmer temperatures. Prolonged above average temperatures are expected, as the omega blocked ridge continues to sit in place with little movement or breakdown as depicted with many of the longer term models both deterministic and probabilistic. Very minor mid level shortwaves are the only details across the ridge that might see some brief spits of upper level mountain snow west of the Divide, but nothing significant to even note at this point. Stay tuned for any updates over the weekend for any river flood stage updates as temperatures warm beyond the Thursday cold front. && .AVIATION...For the 12Z TAFS through 12Z Friday Issued at 444 AM MDT Thu Apr 27 2023 West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals. VFR conditions prevail much of the period at all terminals, except KRKS which is under the threat of MVFR in association with late day convection. A shortwave dropping south through Montana traverses the state this afternoon generating increasing west to northwest wind gusting 24 to 36kts. Instability along the leading edge of a cold front will produce scattered showers, primarily along the Continental Divide and over southern Wyoming. The best chance for TSRA and brief MVFR conditions at KRKS would be from 22Z/Thu to 02Z/Fri. The cold front backs into KRKS around 02Z/Fri, leading to an abrupt east- northeast shift of the wind. Wind speeds gradually diminish at all terminals between 01Z-05Z/Fri. All terminals VFR by 03Z/Fri. Mountain tops occasionally obscured between 20Z/Thu and 03Z/Fri. East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals. VFR conditions prevail at all terminals through most of the period. The exception will be brief MVFR conditions along and ahead of a vigorous cold front associated with a fast-moving shortwave diving south through Wyoming this afternoon. West to northwest wind increases through the morning at all terminals before becoming more northerly following frontal passage. The main frontal push occurs around 18Z/Thu at KCOD and it continues a southward trek to the Continental Divide by 22Z/Thu. Frequent wind gusts of 25-40kts to occur much of the day, most especially during the afternoon hours. Hi-res models have been consistent in showing a 2-3 hours period ahead of and just behind the front as the best chance for showers, thunderstorms, and brief MVFR. Precipitation ends and conditions are VFR by mid- evening with wind speeds gradually diminishing by 06Z/Fri. Mountain tops frequently obscured between 18Z/Thu and 03Z/Fri. 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 156 AM MDT Thu Apr 27 2023 After a brief break from any precipiation, snow and rain will return Thursday. Mountain snow and valley rain with a isolated rumble of thunder possible for much of the area east of the Divide given more instability further east. Highest snowfall totals expected for the Bighorns, where a Winter Weather Advisory is in effect. Winds will increase through the morning hours with gusts up to 30-40 mph ahead of an approaching cold front that will quickly turn more northerly into the afternoon hours. Strongest gusts over 50 mph are expected for the Bighorn Basin and towards the I-25 corridor with the strongest mixing of cooler air for a few hours behind the aforementioned front. Winds will quickly diminish towards sunset and especially before midnight with clearing skies and weakening gradient as high pressure starts to build in from the north and northwest. Dry conditions and a warming trend expected to start Friday and into the weekend through much of next week as well. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 1 AM MDT Friday for WYZ008-009. && DISCUSSION...Lowe AVIATION...Jones/LaVoie FIRE WEATHER...Lowe
Hazardous Weather Outlook National Weather Service Riverton WY 203 AM MDT Thu Apr 27 2023 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- 203 AM MDT Thu Apr 27 2023 This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Tonight. Mountain snow behind a cold front will begin by mid to late morning Thursday for the Bighorns seeing 6 to 10 inches with lesser amounts towards the Divide. Gusty north winds behind the cold front with the highest speeds for the Bighorn Basin and points east to the I-25 corridor of over 50 mph. Valley rain showers and some isolated areas of thunder will be prevalent through the afternoon east of the Divide. Winds will diminish and any precipiation will taper off after sunset and towards midnight to the southeast. .DAYS TWO THROUGH SEVEN...Friday through Wednesday. Warming temperatures and dry conditions expected through the long term period. West of the Divide will see 50s and 60s that will bring a risk of flooding early next week due to melting snow in the lower elevations of Teton and Lincoln counties, including near Hoback Junction. The foothills in the 6-9kft range could also be affected by these warmer temperatures. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to Standard Operating Procedures.
The Riverton/Lander radar (KRIW), 187 km away, was scanning. The volume nearest the first event began at 16:37 UTC.
3 high wind, 3 thunderstorm wind. Local standard time, as filed.
A maximum wind gust occurred of 59 mph occurred at the Johnson County airport.
A 60 mph wind gust was reported at the Powell airport.
A 61 mph wind gust was reported at the Worland airport as a line of thunderstorms passed.
High wind occurred at the Greybull airport, with a maximum gust of 63 mph.
A 70 mph wind gust was reported at the Natrona County airport.
A 62 mph wind gust was reported at the Riverton airport.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2023Every state in 2023This day in weather historyWarnings in Wyoming, April 2023
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: 1096776, 1096780, 1096781, 1096783, 1096785, 1096786.