EF0 tornado, Forest Lake to Marine On St Croix, Minnesota, July 12, 2017

1. EF065 to 85 mphthis tornado

   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 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

EF0

Date

July 12, 2017

Touchdown

2:41 AM CDT (07:41 UTC)

Lifted

2:44 AM CDT (07:44 UTC)

On the ground

3 minutes

Path length

3.0 miles (4.9 km)

Path width

250 yards (229 m)

Deaths

0

Injuries

0

County

Washington County

Touchdown point

45.181, -92.858

Lift-off point

45.167, -92.799

Record number

1707120141-01

78 damage points were recorded along this path by NWS MPX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 90 mph.

• northern edge of damage. all pointed to the southeast.
• pointing se, but starting to see some toward the northeast
• garage doors closed. material blown ene.
• damage to the northeast. wind got inside and bowed out south wall

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

A complex of thunderstorms developed across west central Minnesota during the early morning of Wednesday, July 12th. These storms moved across the Alexandria area and produced damaging winds, with a measured wind gust of 59 knots at the airport. These storms moved across central Minnesota, and began to accelerate north of the Twin Cities metro area. Some of the storms produced tornadoes and damaging straight line winds as they moved quickly eastward into west central Wisconsin.

After exiting Anoka County just northeast of the junction of Interstates 35E and 35W in Columbus, the tornado continued across the far southwestern part of the city of Forest Lake, where it downed numerous trees and hit one farm. It dissipated about one mile east of Horseshoe Lake in the far northern portion of Hugo.

The tornado damaged over 1000 trees at the Warner Nature Center. Hundreds of trees were also damaged before it hit the Nature Center. The tornado dissipated shortly after exiting the Nature Center.

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

No tornado warning for this county appears in the archive as in force at the moment the tornado touched down.

The county was under a severe thunderstorm watch, issued at 03:00 UTC and running to 08:24 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 General Thunderstorms Risk. The outlook in force was issued at 05:30 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 Minneapolis radar (KMPX), 68 km away, was scanning. The volume nearest the touchdown began at 07:42 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 MinnesotaEvery tornado in Minnesota since 1950Warnings in force in Minnesota 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.