Thunderstorms initiated along a dry line in central Colorado moving east and forming a cluster of supercells that produced up to 70 mph wind gusts and large hail up to tennis ball in size across Yuma County. Supercells developed over Cheyenne County as the northern cluster crossed into Kansas and Nebraska.
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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 GLD wrote it up.
Thunderstorms initiated along a dry line in central Colorado moving east and forming a cluster of supercells that produced up to 70 mph wind gusts and large hail up to tennis ball in size across Yuma County. Supercells developed over Cheyenne County as the northern cluster crossed into Kansas and Nebraska. The southern cells eventually formed a cluster that was able to produce up to half dollar sized hail, a landspout, and caused a portion of Highway 385 to become impassable due to flash flooding.
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 Goodland, KS wrote its last area forecast discussion before the first event at Jul 12, 1:17 PM MST, 1 hour 49 minutes earlier.
Area Forecast Discussion National Weather Service Goodland KS 217 PM MDT Sun Jul 12 2020 .UPDATE... Issued at 217 PM MDT Sun Jul 12 2020 Severe Thunderstorm Watch #363 has been issued for northeast Colorado and adjacent counties in Kansas until 900 pm MDT. Forecast has been updated. Threats are large hail and damaging winds. && .SHORT TERM...(This evening through Monday night) Issued at 143 PM MDT Sun Jul 12 2020 Across the region this afternoon, skies are mainly sunny with some scattered low/high cloud portions of the area. Temperatures are ranging from the mid 80s into the mid 90s, with an area-wide southerly gradient gusting to 30-40 mph at times. For the remainder of the afternoon hrs into tonight, the focus will be just west of the CWA in central Colorado, where convection is expected to initiate along a dryline then shift east with the arrival of a shortwave, then shift SE later tonight as the convection works over the northern periphery of the strong h5 ridge over the southern portion of the country. SPC mesoanalysis has Dcape values 1300-1700 from the Colorado border west, 40-45kts of bulk shear, and decent mid level lapse rates should allow for strong to severe storms to develop. Large hail parameter does indicate large than 1 inch possible. Severe Thunderstorm Watch will probably be issued for portions of the area later this afternoon, with wind and hail highlights. Precipitation that does shift over the CWA will taper by 06z Monday, allowing for dry conditions thru sunrise Monday and a portion of the morning hours. This will lead into Monday/Monday night where a stronger shortwave moves over the region, triggering a potential stronger round of storms. SPC has highlighted most of the CWA in Slight Risk for wind/hail threats, but last outlook update has the enhanced portion sliding further south, which may change later tonight for portions of the CWA. With the potential for more widespread areal coverage of storms, have increased pops slightly, but still in the chance category due to timing into the CWA. For temps, mid to upper 90s for Monday highs, with 60s for lows tonight and Monday night. .LONG TERM...(Monday night through Sunday) Issued at 143 PM MDT Sun Jul 12 2020 This this period of the forecast the long wave trough continues to reside over the central CONUS, flattening the ridge. The resulting zonal flow over the forecast area will allow an upper level short wave trough to move through each afternoon and evening. The GEFS members show a higher high probability of rainfall occurring Tuesday and Wednesday over the Southeast Colorado extending into the southwest part of the forecast area. The dry line will move east of the forecast area Thursday, through the rest of the period. This lowers confidence of storms occurring due to drier air present behind the dry line, despite the aid of the upper level short wave troughs moving through. Am thinking the best chance for any severe thunderstorms will be Tuesday and Wednesday afternoon and evenings before the dry line is pushed east. The cold front still looks to move through Tuesday, lingering into Wednesday. This may also serve as a focus for storm development Tuesday afternoon over the southwestern part of the forecast area. The hot air mass will return Thursday as the cooler air mass is pushed east of the forecast area. Friday and Saturday relative humidity values will fall close to 15% for the northwest part of the forecast area. Winds are forecast to remain below 25 MPH at this time for that part of the forecast area. && .AVIATION...(For the 18Z TAFS through 18Z Monday afternoon) Issued at 1106 AM MDT Sun Jul 12 2020 At this time, VFR conditions are forecast for both terminals. There is the potential for storms to affect KGLD later today, but with timing issues into the area, have left out mention for now. Potential for storms to be in the vicinity of both KGLD/KMCK by the end of the forecast period Monday. Timing issues into the region here as well, so have left out mention of at this time. Winds for KGLD, S around 15-25kts thru 03z Monday, then diminishing to around 10-15kts. Winds for KMCK, S around 15-25kts thru 02z Monday, then SE around 10-15kts. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && UPDATE...JN SHORT TERM...JN LONG TERM...JTL AVIATION...JN
Hazardous Weather Outlook National Weather Service Goodland KS 216 PM MDT Sun Jul 12 2020 COZ090>092-KSZ001>004-013>016-027>029-041-042-NEZ079>081-132015- Yuma County-Kit Carson County-Cheyenne County-Cheyenne-Rawlins- Decatur-Norton-Sherman-Thomas-Sheridan-Graham-Wallace-Logan-Gove- Greeley-Wichita-Dundy-Hitchcock-Red Willow- 216 PM MDT Sun Jul 12 2020 /316 PM CDT Sun Jul 12 2020/ This hazardous weather outlook is for extreme southwest Nebraska... northwest Kansas and east central Colorado. .DAY ONE...THIS AFTERNOON AND TONIGHT... A Severe Thunderstorm Watch is in effect for northeast Colorado and adjacent Kansas counties until 900 PM MDT. Marginal and Slight Risk areas for severe thunderstorms are issued for areas mainly along and west of Highway 25. The main area of focus will be in northeast Colorado and adjacent Kansas counties south of Interstate 70. Threats for severe storms to develop will be around 3-9 pm MDT. Main possible weather threats will be wind gusts to 70 mph and hail up to 1 to 2 inches. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SUNDAY... There is a Slight Risk for severe storms on Monday July 13th. Thunderstorms developing along the Front Range of the Rockies in Colorado and Wyoming may grow upscale and develop into a squall line capable of producing widespread damaging winds late Monday afternoon and evening. .SPOTTER INFORMATION STATEMENT... Spotter activation may be required.
The Goodland radar (KGLD), 101 km away, was scanning. The volume nearest the first event began at 22:08 UTC.
11 hail, 1 thunderstorm wind, 1 flash flood, 1 tornado. Local standard time, as filed.
Trained spotter reported a large, dead tree blown over along with numerous tree limbs down on the property due to strong winds associated with a thunderstorm.
Trained spotter observed pea to nickel sized hail.
Public citizen observed nickel sized hail with winds gusting up to 40 mph.
A public citizen reported hail slightly larger than golf ball sized that was on the ground for approximately 10 minutes before being estimated for size.
Public citizen observed hail up to tennis ball in size. Most of the hail was nickel to quarter in size. As hail fell at the location, winds were estimated to have 40 mph gusts.
Local law enforcement and a trained storm spotter provided several reports of several inches of water flowing across Hwy 385 at mile marker 147 south of Cheyenne Wells.
Received a couple different reports of landspouts around this time. However, based on radar imagery and pictures/videos received, it appears that one single longer-lasting landspout tornado occurred. Reports described the times accurately and indicated the tornado occurred for around 10 minutes in duration, remaining nearly stationary.
Trained spotter and Cheyenne Wells law enforcement observed hail up to half dollar in size over a duration of twenty minutes in the town of Cheyenne Wells.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2020Every state in 2020This day in weather historyThe tornado archive for Colorado, 2020Warnings in Colorado, July 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: 909639, 909623, 909625, 909633, 909628, 909630, 909631, 909636, 909632, 909635, 909634, 909640, 911317, 909638.