EF1 tornado, Mc Alisterville to Maze, Pennsylvania, August 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 mphthis tornado

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

3. EF2111 to 135 mph

   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

EF1

Date

August 12, 2017

Touchdown

3:12 PM EDT (19:12 UTC)

Lifted

3:20 PM EDT (19:20 UTC)

On the ground

8 minutes

Path length

5.5 miles (8.9 km)

Path width

200 yards (183 m)

Deaths

0

Injuries

0

Property damage

$500,000

Crop damage

$1,000

County

Juniata County

Touchdown point

40.646, -77.274

Lift-off point

40.600, -77.188

Record number

1708121312-01

An EF1 tornado touched down in Juniata County near Mcalisterville during the afternoon of August 12, 2017.

The tornado touched down on the northeast side of Mcalisterville, PA, near the Juniata Mennonite School. Damage included a flipped tractor trailer, snapped pine trees, and a long swatch of snapped and uprooted trees. The main school building roof was lifted off its base. There was sporadic tree damage all the way to Dunn Valley Road. Along Dunn Valley Road there was a flipped travel trailer, damaged trees, and a damaged house. Farther along the track, it damaged a bus shed and a tool shed. There was also sporadic tree damage in this area. Further to the south and east, along Maze and Blackdog Roads, there was focused swaths of tree damage along the north side of the road. Near the end of the road the tree damage became less evident. Peak winds were estimated at 105 mph, giving it an EF1 rating. There were no injuries or fatalities.

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

9 minutes of warning. NWS CTP issued a tornado warning for this county at 19:03 UTC, 9 minutes before the tornado touched down, in force until 20:00 UTC.

The county was under a severe thunderstorm watch, issued at 18:45 UTC and running to 22:31 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 Slight Risk. The outlook in force was issued at 16:33 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 State College radar (KCCX), 73 km away, was scanning. The volume nearest the touchdown began at 19:09 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 PennsylvaniaEvery tornado in Pennsylvania since 1950Warnings in force in Pennsylvania nowThe forecast where you are

4 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.