EF0 tornado, Bigfork, Montana, November 4, 2013

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

November 4, 2013

Touchdown

7:42 AM MST (14:42 UTC)

Lifted

7:46 AM MST (14:46 UTC)

On the ground

4 minutes

Path length

0.8 miles (1.2 km)

Path width

200 yards (183 m)

Deaths

0

Injuries

0

County

Flathead County

Touchdown point

47.971, -114.072

Lift-off point

47.978, -114.060

Record number

1311040842-01

A vigorous moist Pacific system brought snow to the higher elevations of western Montana impacting mountain passes including Lookout and Lost Trail. Impacts such as slick roads were reported at pass level by late evening Saturday November 2nd and continued through Monday the 4th. The frontal system brought heavy precipitation (up to 1.60) across the higher elevations of western Montana. Anywhere from 8 to 12 inches of snow were reported in the mountains while valley locations received a trace to 4 inches. A stalled out arctic front brought heavy snow to US-2 from Essex to Marias Pass between Nov. 3 & 4. A second cold-core upper level trough provided strong unstable conditions that helped to trigger winter waterspouts on Flathead Lake and intense valley-level snow showers on Nov. 4th.

A cold core upper level trough dropped out of British Columbia providing the necessary lift and instability to trigger showers across western Montana early on November 4th. The unstable atmosphere saw a 24 degree difference between Flathead Lake water temperatures(8.9 deg. C) and at 9,665 ft. MSL(700 millibars) -15 deg. C. A convergent boundary set up southwest of Wood's Bay with cool northerly winds coming out of the Flathead Valley and relatively mild southerly winds moving across the lake. This boundary provided the vertical lift to develop the band of graupel and snow showers. A waterspout was spotted by passers-by traveling on MT-83 near mile-marker 24. Viewing the photos and video that Mike and Dana Marchetti took, it appears that there could have been multiple vortices based on darkened shadows in the vicinity of the main vortex. The waterspout remained over Flathead Lake and no damage was reported.

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.

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 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 Missoula radar (KMSX), 104 km away, was scanning. The volume nearest the touchdown began at 14:38 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 2013 tornado in MontanaEvery tornado in Montana since 1950Warnings in force in Montana nowThe forecast where you are

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.