EF2 tornado, Hereford to (82v)Pine Bluffs Airport, Colorado, June 12, 2017

1. EF065 to 85 mph

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. EF186 to 110 mph

   Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

3. EF2111 to 135 mphthis tornado

   Considerable damage. Roofs torn off well-built houses, frame homes shifted on their foundations, mobile homes destroyed, large trees snapped or uprooted, cars lifted off the ground.

4. EF3136 to 165 mph

   Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

5. EF4166 to 200 mph

   Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

6. EF5over 200 mph

   Incredible damage. Strong frame houses swept off their foundations, car-sized missiles thrown more than 100 meters, steel-reinforced concrete badly damaged, high-rise buildings deformed.

7. Unrated

   The survey recorded a tornado but could not put a number on it, most often because it crossed open country and damaged nothing a rating can be read from.

Rating

EF2

Date

June 12, 2017

Touchdown

5:40 PM CDT (22:40 UTC)

Lifted

6:08 PM CDT (23:08 UTC)

On the ground

28 minutes

Path length

15.0 miles (24.1 km)

Path width

300 yards (274 m)

Deaths

0

Injuries

0

Counties

Weld and Laramie counties

Touchdown point

40.900, -104.335

Lift-off point

41.100, -104.380

Record number

1706121640-02

20 damage points were recorded along this path by NWS BOU and NWS CYS, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF2. The highest wind the damage implies is 115 mph.

• Recently (1-2 year old) constructed home with window and roof damage to west side. Semi-attached garage with garage opening to the west (connected by breezeway) completely swept clean. Construction type was different from home (metal roof material). Truck was moved east, then north from the garage and found about 100 yards away. Tire tracks along with minimal damage to truck cab suggests truck did not roll.
• Collapse of the barns roof and some of the exterior walls. Concrete interior wall still standing.
• Trailer was picked up and thrown into a tree about 20 yards away. Several other small trailers were moved. Shed had almost collapsed.
• Chicken coop completely collapsed. 2 grain bins were displaced, 1 still hasn't been found. Gas line was pulled out of the ground at the house.

Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.

Severe thunderstorm produced damaging hail, ranging from quarter to softball size across eastern Larimer and northwestern Weld Counties. The tornado was assigned a damage rating of EF-1. Areas of sporadic tornado damage were noted from 8 miles south-southwest of Hereford to north of Hereford near the Colorado-Wyoming border. In Weld County, the tornado was approximately 300 yards in width at one point and its path was 7.24 miles in length, it then crossed over into Wyoming. According County and City Emergency Management, hail damage occurred in the northwest part of Weld county including the towns of Pierce and Nunn. Several vehicles sustained broken windshields. The windshields of two patrol vehicles with Weld County Sheriff's Office were damaged. The officers were responding to unrelated calls when their vehicles were struck by golf ball size hail. Light damage to cars and general aviation aircraft was also reported at the Northern Colorado Regional Airport in Loveland.

One of the most significant severe weather episodes to affect southeast Wyoming and the western Nebraska Panhandle occurred on the afternoon and early evening of Monday 12 June 2017. Eleven confirmed tornadoes, hail to grapefruit size, and damaging winds were observed. Supercell thunderstorms developed during the early afternoon along Interstate 25 between Fort Collins, CO and Wheatland. Lifting northeast, these thunderstorms spread into the southeast Wyoming plains late in the afternoon and into the western Nebraska Panhandle during the evening. Two people suffered injuries with an EF-2 rated tornado north of Torrington near the Wyoming/Nebraska stateline.

A tornado touched down southwest of Hereford and continued to quickly move north northeast into Wyoming. Areas of sporadic tornado damage were noted from 8 miles south southwest of Hereford to north of Hereford near the Colorado-Wyoming border. The damage along the patch ranged from EF-0 to EF-1.

The tornado crossed into southern Laramie County, Wyoming from Weld County, Colorado approximately 4 miles southeast of Carpenter. It continued moving towards the north-northwest crossing mostly open farmland, paralleling County Road 151 where it impacted 4 residences. The most significant damage observed by the NWS assessment team was to 2 residences along County Road 151, where a semi-attached garage was completely destroyed (DI 1, DOD 3) by EF-2 intensity winds. Damage also was observed to single family roof structure. Additionally, numerous power poles were snapped along with a ruptured power line.

A short-lived tornado touched down just north of the Colorado state line to the southwest of Pine Bluffs along County Road 161. It was on the ground for approximately 4-7 minutes. A fifth-wheel horse trailer was lofted into the air for 50 yards sustaining significant damage. A small farm outbuilding was also destroyed (DI 1, DOD 7).

From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.

27 minutes of warning. NWS BOU issued a tornado warning for this county at 22:13 UTC, 27 minutes before the tornado touched down, in force until 22:45 UTC.

The county was under a tornado watch, issued at 19:11 UTC and running to 00:50 UTC.

Every warning and watch covering the touchdown point that day, from the Iowa Environmental Mesonet's archive of National Weather Service products. Lead time is measured from the issue of the warning in force to the touchdown time in the database, both of which were recorded to the minute by different people.

The Storm Prediction Center had this point in a Enhanced Risk, with a 0.10 chance of a tornado within 25 miles, in the hatched area where significant tornadoes were expected. The outlook in force was issued at 20:00 UTC.

SPC's Day 1 convective outlook as it stood when the tornado began, read at the touchdown point. The same archive is on the radar archive.

The radiosonde launches on either side of the tornado, from the nearest station that was launching then, drawn and analyzed the way Storm Lab does: the same diagram, the same parcel and shear definitions SPC's mesoanalysis uses.

The Cheyenne radar (KCYS), 41 km away, was scanning. The volume nearest the touchdown began at 22:40 UTC.

Open the radar archive at this moment, over the track

Reflectivity and velocity, decoded from the Level II archive in the browser. Volumes take a few seconds to open the first time.

Local storm reports within 60 km of the path, in the three hours either side.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

The live radar over the trackEvery 2017 tornado in ColoradoEvery tornado in Colorado since 1950Warnings in force in Colorado nowThe forecast where you are

20 more were confirmed in the United States that day.

Ratings are the survey's, read off the damage rather than measured; the rating scale is above. Tornado counts rise through the record as reporting improved, so a year in the 1950s is not comparable with one today except for the strongest tornadoes, which were always noticed.

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.