A feed of Pacific moisture moved into western Wyoming and brought heavy snow to portions of the western Mountains. A foot and a half of new snow fell at Grand Targhee in the Tetons.
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 feed of Pacific moisture moved into western Wyoming and brought heavy snow to portions of the western Mountains. A foot and a half of new snow fell at Grand Targhee in the Tetons. Strong wind occurred East of the Divide, Wind gusts as high as 60 mph occurred at the Sweetwater County airport and 58 mph at Buffalo.
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 5, 4:30 PM MST, 1 hour 30 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Riverton WY 530 PM MDT Sun May 5 2024 .KEY MESSAGES... - Strong winds today, with warm temperatures east of the Continental Divide. - Snow and rain is spreading eastward today, with chances moving east of the Continental Divide by this evening as a cold front moves through. - Cool and unsettled weak ahead, with mountain snow and lower elevation rain. Gusty winds through the start of the workweek. && .DISCUSSION... Issued at 110 PM MDT Sun May 5 2024 A messy forecast the next few days, from wind to snow to rain. The driver of all of this? A potent Pacific low moving across the state today and tomorrow, parking itself over eastern Montana a couple days. Will divide the forecast into sections based on the differing weather elements. Snow/Rain West of the Continental Divide: Precipitation has already begun across the west, slowly spreading eastward as the upper low approaches. Snow levels generally above 8000 feet Sunday morning drop to 6000 feet Monday afternoon, then down to near 5000 feet Monday night, before settling between 6000 and 7000 feet Monday afternoon. These snow levels will determine that transition between snow and rain. In summary, snow occurs for the mountains beginning this afternoon as those levels drop. The lower elevations are favored for snow overnight as levels drop further, before favoring rain once again Monday afternoon. This system is fairly moist, so lower elevations may see a couple tenths to around half an inch of liquid precipitation through Monday afternoon. For the mountains, winter highlights are in effect. Snow ramps up this evening and overnight. Heaviest snow occurs over the Tetons and southwest Yellowstone, with rates near 1 inch per hour possible Monday morning and afternoon. Lesser rates look to occur Tuesday night as the upper low moves up near the Montana/North Dakota border, and slightly drier air advects in. Rates increase once again Tuesday morning as the low retrogrades slightly, returning the better moisture. A Winter Storm Warning over the Tetons and Gros Ventres covers this snow threat, where 1 to 2 feet of snow is forecast through Tuesday, with the higher Teton elevations possible seeing up to 3 feet of snow. Being of Pacific origin, the snow should be fairly wet, with snow ratios about 12:1 to 15:1. Winter Weather Advisories are in effect for Yellowstone, the Wind River Range, and the Salt/Wyoming Ranges. Snow totals to around a foot are forecast for these areas through Tuesday. The western Absarokas are also forecast for these amounts, but given the lesser extent of these amounts, no highlight is expected for the Absarokas at this time. The highest peaks, especially in the Wind River Range, the Salt River Range, and southwest Yellowstone could see localized totals higher than a foot. Of note, the northern half of Yellowstone is only forecast to get 0.5 to 5 inches. Strong Wind: Strong winds occur today. The upper low brings a southerly flow, as well as a 100+ knot jet. The main focus today is over Sweetwater County, far southern Fremont County and southwestern Natrona County. High Wind Warnings are in effect, as gusts over 58 mph are likely (70%). Models, as well as shift of tails, continues to highlight southern Sweetwater County, south of I-80, as the most favorable location for strong gusts, up to 70 mph. Over much of the remaining CWA (excluding northwest portions) gusts 40 to 50 mph are possible through the afternoon today; Special Weather Statements (SPS) are in effect for applicable locations today. Winds begin to decrease after sunset today. As the low moves through, winds also shift southwesterly. Winds across portions of southern and central Wyoming continue to gust 20 to 30 mph overnight. Winds over these locations increase again around sunrise Monday morning. Strong gusts over 50 mph occur for the Wind Corridor (Sweetwater County through Natrona County) late morning and through the afternoon. Winds gusting 20 to 40 mph occur elsewhere. Given a more westerly flow, locations east of mountain ranges are favored for some higher gusts, closer to that 40 mph mark. Northern Johnson County will be another place to watch,as northwest wind gusts 40 to 50 mph Monday afternoon. The current High Wind Warning covers this threat Monday, with a High Wind Watch in effect for Natrona County (including Casper and Outer Drive) for Monday. Impact-wise, expect strong crosswinds for I-80 and South Pass/Red Canyon today and Monday. Gusty winds continue Tuesday. Still not seeing strong indications for high winds, but gusts 35 to 45 mph are still forecast. Widespread gusts 20 to 30 mph also occur for most of the area. Will have to watch trends the next few model runs for better confidence. Uncertainty when it gets to Wednesday, as there is lower confidence in storm track. However, flow is looking to turn more northerly, which would favor gusty winds in the Bighorn Basin and Johnson County. Precipitation East of Continental Divide: Snow levels drop to around 6000 feet Sunday night, so most lower elevation locations should receive rain with this upcoming system. Rain chances begin to cross the Continental Divide mid-afternoon, but the better chances don't begin until after 00Z (6pm) as the jet shifts east and the cold front advances through. Rain chances (20% to 90%) spread through the area through Monday. That chance range is large because there will be the initial wave of chances overnight and into Monday morning, with scattered (30%-60%) chances through the afternoon. All locations have at least 40% precipitation chances through Monday. Total liquid at a location will depend on if you get a scattered shower in the afternoon, but current forecast has anywhere from 0.10 to 0.50 inches. Basins (like the Wind River and Bighorn) are favored for lesser totals given unfavored, westerly flow, with totals less than 0.10 through Monday. Inversely, the eastern Bighorn Basin is favored for the upper of that range. With favorable jet placement and low track Monday, Johnson and eastern Natrona Counties could see a better push of moisture, and therefore heavier rain, Monday morning to early afternoon. Heavier showers are possible, with precipitable water values upwards of 200% of normal; localized amounts to 1.50 inches are possible by late Monday afternoon. The Weather Prediction Center (WPC) has these locations in a marginal (at least 5% chance) excessive rainfall outlook for Monday. For the Bighorn Mountains, models have come into more alignment for storm track Tuesday, favoring a slightly drier pattern. Moderate confidence now exists for 8 to 10 inches across the northern range through Monday, with only light snow into Tuesday. Lesser amounts (6 inches or less) for the southern portions of the range. Gusty winds up to 60 mph are also possible for the passes. Another push of moisture comes Wednesday as the low moves into a more favorable position. Some uncertainty still exists with the storm track Wednesday, however. A Winter Weather Advisory is in effect for the Bighorn Range to cover this first round of snow Monday and the gusty winds there. Wednesday and Beyond: As mentioned, models diverge Wednesday. This will determine the placement of the upper low and how quickly it begins to move eastward. Best estimate as of now is that precipitation chances continue for at least the northern and eastern portions of the CWA through at least Thursday. Given the focus on the next few days, have not looked extensively at this period. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 525 PM MDT Sun May 5 2024 Showers and thunderstorms will continue off and on through the next 24 hours for all sites, as activity continues to shift east across the state. Thunder possibilities will be the most concern during the next 3 hours with daytime heating, and being able to tap gusty winds aloft. Have focused tempo groups in that period for thunder and variably gusty winds, mostly from a southerly direction. Variable mountain obscuration continues with these showers into the day Monday. Expect numerous showers through the day Monday, with thunder probabilities increasing during the afternoon. Current gusty winds will relax a bit overnight, but gusts are still expected through the night. Another round of gusty winds returns tomorrow with frequent gusts above 25kts. Any larger storms would be able to produce enhanced gusty winds in their vicinity as well. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 11 PM this evening to 6 PM MDT Tuesday for WYZ001. Winter Weather Advisory from 1 AM to 11 PM MDT Monday for WYZ008-009. Winter Storm Warning until 11 PM MDT Tuesday for WYZ012. Winter Weather Advisory until 6 PM MDT Monday for WYZ014-015. High Wind Warning until 9 PM MDT Monday for WYZ019-028>030. High Wind Watch from Monday morning through Monday evening for WYZ020. Winter Weather Advisory from 11 PM this evening to 6 PM MDT Monday for WYZ024. && DISCUSSION...Wittmann AVIATION...Straub
Hazardous Weather Outlook National Weather Service Riverton WY 128 PM MDT Sun May 5 2024 WYZ001>020-022>030-061300- Yellowstone National Park-Absaroka Mountains-Cody Foothills- North Bighorn Basin-Southwest Bighorn Basin-Southeast Bighorn 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- 128 PM MDT Sun May 5 2024 ...Winter Storm Warning and Winter Weather Advisories in effect for western mountains Sunday evening through Tuesday evening... ...Winter Storm Advisory for Bighorn Mountains early Monday morning through Monday night... ...High Wind Warning for most of Sweetwater County and parts of Fremont and Natrona Counties Sunday through Monday evening... ...High Wind Watch for lower elevations of Natrona County Monday... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...This Afternoon and Tonight. Strong to high wind for many locations, particularly across south and central Wyoming. Snow returning to the western mountains, especially tonight into Monday morning. .DAYS TWO THROUGH SEVEN...Monday through Saturday. Monday and Tuesday...Cool and unsettled with rain and mountain snow. Heavy rain possible for Johnson and eastern Natrona Counties Monday morning and early afternoon. Light snow in western valleys for Monday and Tuesday. Gusty to strong wind possible across much of the area. Wednesday and Thursday...Unsettled weather pattern keeps cool temperatures and precipitation chances. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to Standard Operating Procedures.
Special Weather Statement National Weather Service Riverton WY 335 PM MDT Sun May 5 2024 WYZ013-023-061300- Jackson Hole-Star Valley- Including the cities of Jackson, Afton, Alpine, Star Valley Ranch, and Thayne 335 PM MDT Sun May 5 2024 ...Snow Sunday Night through Tuesday... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Rain changing to snow Sunday night. Accumulations of 2 to 5 inches. * WHERE...Jackson and Star Valleys. * WHEN...Late Sunday night through Tuesday. * ADDITIONAL DETAILS...Accumulations will be less on paved surfaces, especially during the daylight hours.
Special Weather Statement
National Weather Service Riverton WY
418 PM MDT Sun May 5 2024
WYZ004-052245-
North Bighorn Basin-
418 PM MDT Sun May 5 2024
...A THUNDERSTORM WITH GUSTY OUTFLOW WIND WILL IMPACT NORTHERN BIG
HORN COUNTY THROUGH 445 PM MDT...
At 417 PM MDT, Doppler radar was tracking a strong thunderstorm near
Byron, which is near Lovell, moving north at 40 mph.
HAZARD...Wind gusts around 50 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
This strong thunderstorm will be near...
Lovell, Cowley, and Byron around 420 to 430 PM MDT.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4470 10832 4471 10857 4500 10861 4500 10827
TIME...MOT...LOC 2216Z 180DEG 33KT 4478 10845
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH
CNJThe national radar mosaic for the moment the first event began.
2 high wind, 1 winter storm. Local standard time, as filed.
Around 18 inches of new snow fell at the Grand Targhee and Philips Bench SNOTEL sites.
A 58 mph wind gust occurred in Buffalo.
Wind gusts as high as 60 mph occurred at the Southwest Wyoming Regional Airport near Rock Springs.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2024Every state in 2024This day in weather historyWarnings in Wyoming, May 2024
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: 1184641, 1184642, 1184643.