EF1 tornado, Gultonville to Marienville, Pennsylvania, May 1, 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

May 1, 2017

Touchdown

3:35 PM EDT (19:35 UTC)

Lifted

3:36 PM EDT (19:36 UTC)

On the ground

1 minutes

Path length

0.8 miles (1.3 km)

Path width

150 yards (137 m)

Deaths

0

Injuries

0

County

Forest County

Touchdown point

41.378, -79.177

Lift-off point

41.387, -79.168

Record number

1705011335-01

34 damage points were recorded along this path by NWS PBZ, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 107 mph.

• several dozen trees snapped/uprooted with a width of about 25 yds

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

A large low pressure system tracked across the Great Lakes during the late afternoon and early evening, dragging a cold front across the region. Ahead of the front, shortwaves embedded in strong southerly flow supported showers and thunderstorms, some of which became severe during the afternoon. Convection organized into a squall line that produced wind damage. While instability was not excessive, high levels of wind shear and low level helicity produced several rotating storms in the main line. These storms produced 6 confirmed tornadoes including 2 EF-0s across Butler county, and 3 EF-0s and 1 EF-1 in Clarion county in Pennsylvania. Most damage was done to trees or structures from falling/snapped trees.

The National Weather Service in Pittsburgh has confirmed a |tornado near Newmansville in Clarion and Forest Counties in Pennsylvania.||Two distinct, tornadic damage swaths seemingly associated with |one parent mesocyclone were discovered beginning along Pine Hollow|Road in northern Clarion County.||A survey team examined damage along Red Pine Circle and Pine |Hollow Road in northern Clarion County. The team discovered a |coherent, convergent track of tree damage that began in a field to|the west of Red Pine Circle and carved a focused swath through |trees at the northwestern corner of the Red Pine Circle loop. |Hardwood and softwood trees were snapped and uprooted in this |area, with damage sustained to several cabins from falling trees. |Nearly every tree within the 100 yd-wide swath sustained some |degree of damage.||To the south of the tornado track, additional tree damage was |discovered that is consistent with a broader swath of non-tornadic|wind. Sporadic, snapped large limbs and a few uproots were found |along the southern stretch of Red Pine Circle and the southern |portion of Pine Hollow Road.||A distinct track within the same parent mesocyclone crossed Pine |Hollow Road near Kerr Drive and continued to show sporadic damage |to trees into southern Forest County before weakening along |Guitonville Road in Green Township. Direct damage along the |entirety of the track appears to be predominantly to trees, with |extensive tree devastation encountered along Pine Hollow Road. In |this area, a section of forest was leveled/snapped, representing |the most-intense wind damage encountered in all surveys conducted |for this storm system. Clarion County officials informed the team |that the road had been closed for a prolonged period following the|storm.||Tree damage along this track's extension on Kerr Drive and across|Carll Drive continued into the wooded area to the north. Damage |with some degree of concentration also was encountered along |Guitonville Road at the geographical northward extension of this |track. While the survey team was unable to traverse the wooded |area between these two damage points to confirm their continuity, |it appears most probable that an at-least discontinuous track of |tree damage connects the two points.

A narrow, convergent path of damage was documented via aerial imagery after being discovered and documented by Forest Service personnel. Damage consisted of uprooted and snapped hardwood and softwood trees.

A narrow, convergent path of damage was documented via aerial imagery after being discovered and documented by Forest Service personnel. Damage consisted of uprooted and snapped hardwood and softwood trees.

An initially narrow tornado grew in scale rapidly with several embedded subvortices, causing considerable and widespread damage to hardwood and softwood trees over a nearly mile-long path. This path was documented via aerial imagery after being discovered and documented by Forest Service personnel.

A narrow, convergent path of intense damage was documented via aerial imagery after being discovered and documented by Forest Service personnel. Damage consisted entirely of uprooted and snapped hardwood and softwood trees. This is segment one of a county-crossing track into Elk County, PA.

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

16 minutes of warning. NWS PBZ issued a tornado warning for this county at 19:19 UTC, 16 minutes before the tornado touched down, in force until 19:45 UTC.

The county was under a tornado watch, issued at 16:32 UTC and running to 20:27 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 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 16:16 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), 110 km away, was scanning. The volume nearest the touchdown began at 19:34 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

14 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.