A strong thunderstorm moved across the City of the Cheyenne producing large amounts of dime size hail. An observer noted over an inch of accumulation on Interstate 25 created problems for motorists and required plows to clear roadway of the hail.
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The episode as NWS CYS wrote it up.
A strong thunderstorm moved across the City of the Cheyenne producing large amounts of dime size hail. An observer noted over an inch of accumulation on Interstate 25 created problems for motorists and required plows to clear roadway of the hail.
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 Cheyenne, WY wrote its last area forecast discussion before the first event at May 14, 10:41 PM MST, 9 minutes earlier.
Area Forecast Discussion National Weather Service Cheyenne WY 1141 PM MDT Thu May 14 2020 .UPDATE... Issued at 722 PM MDT Thu May 14 2020 Showers are expected to continue across southeast Wyoming and the western Nebraska Panhandle overnight as a weak disturbance aloft continues to track eastward across the region. A few isolated lightning strikes are possible, generally across the Colorado border and the northwestern Panhandle, but this threat will end by midnight tonight as the showers continue afterwards. Looking for a mild night tonight with temperatures only dropping into the 40s as a cloud deck aloft prevents radiative transfer of heat from occurring. Looking at a stormy day tomorrow as a low pressure center develops on the lee-side of the Laramie Range, just ahead of a defined disturbance aloft. Heightened surface dewpoints (in the 40s and 50s) will combine with steep lapse rates and modest instability as storms start to develop along the high terrain. Just as these storms move into the High Plains, an increased flow aloft will will contribute to enough vertical shear to support strong to severe thunderstorm development. This threat will begin by midafternoon and continue through sundown. Large hail up to half dollar size, and damaging winds are possible with any storms that develop. In accordance with this threat, SPC has placed much of the High Plains under Marginal and Slight Categories. && .SHORT TERM...(Late this afternoon - Friday) Issued at 245 PM MDT Thu May 14 2020 Scattered convection continued to develop and move east across northern CO. This activity is focused along a 700-500 mb front. Small hail, gusty winds to 45 mph and brief heavy rain accompanied the stronger convection. Widely scattered showers and isolated thunderstorms were also developing from west-southwest of Cheyenne to near Elk Mountain WY, and over portions of northwest NE. Latest hi-res model guidance indicates an increase in convective coverage over much of the CWA after 00Z this evening. Not expecting strong or severe convection with MUCAPES less than 500 j/kg and marginal low level shear. Shower coverage will decrease from west to east overnight tonight. Short range models are portraying a more conducive environment for strong to severe convection Friday afternoon and early evening over much of the high plains. Latest NAM MUCAPEs rise to 1000-1500 j/kg with 0-6km bulk shear 35-45 kt, supportive of supercells. Severe thunderstorm coverage will be isolated, with the primary threats of hail up to half dollar size and wind gusts to 60 mph. SPC upgraded the Marginal Risk to a Slight Risk along and east of a line from Pine Bluffs WY to Scottsbluff and Hemingford NE. A few strong to marginally severe thunderstorms will be possible from Cheyenne to Torrington WY to Harrison and Chadron NE. High temperatures Friday will be in the 60s to lower 70s. .LONG TERM...(Friday Night - Thursday) Issued at 328 AM MDT Thu May 14 2020 The short wave responsible for convection on Friday is expected to intensify overnight, thus slowing down and continuing to influence our local weather into Saturday as well. A few showers will likely persist with cool northwest flow on the back side of the departing system. A substantial warming/drying trend will commence Sunday as high-amplitude upper-level ridging builds into the region. 500 hpa heights climb to to 585 dam by late Monday, likely supporting high temperatures in the 80s and even lower 90s by Mon/Tue. Sunday will certainly be dry, but we will be keeping our close eye on the next potential major weather maker. A significant trough is expected to deepen considerably and dig into the southwest US on Sunday night/ Monday. A vigorous closed low will lift northeast across the Great Basin through Wednesday, with strong south-southwest flow expected to overspread the CWA through the entire period from Mon-Wed. Lee- troughing will support significant moisture return with dew points in the upper 50s and low 60s possible over the plains w/ resulting CAPEs in excess of 2500 J/kg. The biggest uncertainty right now is how much forcing will be available for convection on Monday, but a few storms are definitely possible with any lead waves. Tuesday is likely to see an uptick in convection across the area, w/ the most widespread activity most likely occurring Wednesday w/ the arrival of the strongest jet energy. Environmental parameters will support all forms of severe weather with any thunderstorms. This is likely to be a multi-day threat for severe weather across southeast Wyo & the western Neb Panhandle, mainly along/east of the Laramie Range. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1131 PM MDT Thu May 14 2020 Rain showers passing through area terminals overnight could result in MVFR ceilings for a brief period of time. Lightning is also possible with these storms. Showers should be out of the area by 12z Friday. Afternoon thunderstorms will be possible again after 18z for many area terminals. && .FIRE WEATHER... Issued at 215 PM MDT Thu May 14 2020 Fire weather concerns will be low through Saturday with minimum relative humidities above 20 percent and chances of showers and a few thunderstorms. Warm, breezy and mainly dry conditions will return Sunday and continue into early next week. Although minimum humidities will fall to 10 to 20 percent across most of southeast Wyoming, fuels will be unsupportive of large fire growth. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && UPDATE...AB SHORT TERM...MAJ LONG TERM...CLH AVIATION...MB FIRE WEATHER...MAJ
Hazardous Weather Outlook National Weather Service Cheyenne WY 546 AM MDT Thu May 14 2020 NEZ002-003-019>021-054-055-095-096-WYZ101-102-107-108-118-119- 151200- Dawes-Box Butte-Scotts Bluff County-Banner County-Morrill- Kimball County-Cheyenne-North Sioux-South Sioux- Converse County Lower Elevations-Niobrara County- East Platte County-Goshen County-Central Laramie County- East Laramie County- 546 AM MDT Thu May 14 2020 This hazardous weather outlook is for portions of panhandle Nebraska...western Nebraska...east central Wyoming and southeast Wyoming. .DAY ONE...TODAY AND TONIGHT Scattered showers and thunderstorms are expected to develop across much of the area this afternoon, likely persisting overnight into early Friday morning. Severe weather is not expected. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY Thunderstorms are expected once again on Friday. A few storms may be strong to locally severe, with hail up to the size of quarters and wind gusts to 60 MPH. Severe weather chances will increase considerably Monday through Wednesday of next week. Plan now by reviewing severe weather safety rules to keep you and your family safe when severe storms threaten. .Spotter information statement... Spotters are encouraged to report significant weather to the National Weather Service in Cheyenne. WYZ103>106-109>117-151200- North Laramie Range-Ferris/Seminoe/Shirley Mountains- Shirley Basin-Central Laramie Range and Southwest Platte County- Central Carbon County-North Snowy Range Foothills- Southwest Carbon County-Sierra Madre Range- Upper North Platte River Basin-Snowy Range-Laramie Valley- South Laramie Range-South Laramie Range Foothills- 546 AM MDT Thu May 14 2020 This hazardous weather outlook is for portions of south central Wyoming and southeast Wyoming. .DAY ONE...TODAY AND TONIGHT Scattered showers and thunderstorms are expected to develop across much of the area this afternoon, likely persisting overnight into early Friday morning. Severe weather is not expected. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY Daily chances for thunderstorms will exist through Wednesday. .Spotter information statement... Spotter activation will not be needed.
Special Weather Statement National Weather Service Cheyenne WY 1147 PM MDT Thu May 14 2020 WYZ117>119-150630- Central Laramie County WY-South Laramie Range Foothills WY- East Laramie County WY- 1147 PM MDT Thu May 14 2020 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN LARAMIE COUNTY UNTIL 1230 AM MDT... At 1147 PM MDT, Doppler radar was tracking a strong thunderstorm near South Greeley, or 7 miles southwest of Cheyenne, moving east at 40 mph. Penny size hail and winds in excess of 40 mph will be possible with this storm. Locations impacted include... Cheyenne, Burns, South Greeley, Hillsdale, Warren AFB, Frontier Park, Warren Af Base, Carpenter, Ranchettes, Fox Farm-College and South Greeley High. This includes the following highways... Interstate 25 in Wyoming between mile markers 1 and 13. Interstate 80 in Wyoming between mile markers 352 and 393. PRECAUTIONARY/PREPAREDNESS ACTIONS... Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. To report severe weather, contact your nearest law enforcement agency. They will relay your report to the National Weather Service office in Cheyenne. && LAT...LON 4112 10501 4137 10429 4100 10417 4100 10496 TIME...MOT...LOC 0547Z 251DEG 34KT 4107 10488 Hammer
The Cheyenne radar (KCYS), 6 km away, was scanning. The volume nearest the first event began at 05:49 UTC.
1 hail. Local standard time, as filed.
Enough dime size hail from a thunderstorm left accumulations of over one inch along Interstate 25 south of the City of Cheyenne to create dangerous travel conditions until plows could clear.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2020Every state in 2020This day in weather historyWarnings in Wyoming, May 2020
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: 887726.