Tornadoes · United States · Montana · 2020
EF0 tornado, Nashua to Glasgow, Montana, May 20, 2020
From Nashua to Glasgow, this EF0 tornado ran 0.8 miles across Valley County on May 20, 2020, touching down at 9:17 PM MDT and reaching 50 yards wide. It killed nobody.
The rating scale
Tracks are drawn in the color of the rating. The Enhanced Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.
EF065 to 85 mphthis tornado
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
EF186 to 110 mph
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
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.
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.
EF4166 to 200 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
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.
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.
The record
- Rating
- EF0
- Date
- May 20, 2020
- Touchdown
- 9:17 PM MDT (03:17 UTC)
- Lifted
- 9:22 PM MDT (03:22 UTC)
- On the ground
- 5 minutes
- Path length
- 0.8 miles (1.3 km)
- Path width
- 50 yards (46 m)
- Deaths
- 0
- Injuries
- 0
- County
- Valley County
- Touchdown point
- 48.160, -106.490
- Lift-off point
- 48.171, -106.496
- Record number
- 2005202117-01
What the Weather Service recorded
An expansive surface low pressure area and plentiful moisture shifted into eastern Montana and directed multiple and persistent severe thunderstorms from south to north through the region from mid-afternoon through then late night hours of the 20th. One of these stronger storms produced a brief weak tornado in Valley County.
NWS employees conducted a storm survey, which showed evidence of a brief tornado near the town of Whatley, traveling north across US Highway 2. Damage included: the doors blown in and part of the roof blown off of a metal barn with metal roofing scattered around for 100 yards, a cottonwood tree was snapped, the metal roof of a house was peeled back, a carport roof was completely ripped off, and an aluminum boat was blown 100 feet. Peak winds speeds were estimated at 80 mph. Tornado was rated an EF-0.
From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.
The warnings
0 minutes of warning. NWS GGW issued a tornado warning for this county at 03:17 UTC, 0 minutes before the tornado touched down, in force until 03:30 UTC.
The county was under a severe thunderstorm watch, issued at 23:53 UTC and running to 05:00 UTC.
| Issued (UTC) | Expired | Product | Office |
|---|---|---|---|
| 23:53 UTC | 05:00 UTC | Severe Thunderstorm Watch | GGW |
| 02:18 UTC | 03:15 UTC | Severe Thunderstorm Warning | GGW |
| 02:44 UTC | 04:00 UTC | Severe Thunderstorm Warning | GGW |
| 03:17 UTC | 03:30 UTC | Tornado Warning | GGW |
| 03:33 UTC | 04:30 UTC | Severe Thunderstorm Warning | GGW |
| 04:02 UTC | 07:00 UTC | Flood Advisory | GGW |
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 forecast that day
The Storm Prediction Center had this point in a Slight Risk, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 01:00 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 air that afternoon
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.
Glasgow Intl Airport, MT (KGGW), 00:00Z
3.3 hours before the tornado, 10 km from the path. May 21, 2020.
- Mixed-layer CAPE
- 975 J/kg
- Mixed-layer CIN
- -43 J/kg
- Surface CAPE
- 2631 J/kg
- Mixed-layer LCL
- 1692 m above ground
- 0-6 km bulk shear
- 30 kt
- 0-1 km bulk shear
- 3 kt
- 0-1 km storm-relative helicity
- 2 m²/s²
- 0-3 km storm-relative helicity
- 35 m²/s²
- Significant tornado parameter
- -0.0
- Supercell composite
- -0.4
- 0-3 km lapse rate
- 7.8 K/km
Glasgow Intl Airport, MT (KGGW), 12:00Z
8.7 hours after it, 10 km from the path. May 21, 2020.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- -89442 J/kg
- Surface CAPE
- 0 J/kg
- Mixed-layer LCL
- 1319 m above ground
- 0-6 km bulk shear
- 59 kt
- 0-1 km bulk shear
- 23 kt
- 0-1 km storm-relative helicity
- -100 m²/s²
- 0-3 km storm-relative helicity
- -80 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
- 0-3 km lapse rate
- 4.8 K/km
The surface observations
Glasgow International Airport (GGW), 11 km from the path, in the two hours either side.
| Time (UTC) | Temp (°F) | Dew point (°F) | Wind | Gust (kt) | Pressure (mb) | Weather |
|---|---|---|---|---|---|---|
| 01:20 UTC | 170° 5 kt | 998.6 | ||||
| 01:25 UTC | 170° 5 kt | 998.6 | ||||
| 01:30 UTC | 180° 5 kt | 998.3 | ||||
| 01:35 UTC | 200° 4 kt | 998.3 | ||||
| 01:40 UTC | 220° 4 kt | 998.3 | ||||
| 01:45 UTC | 250° 5 kt | 998.3 | ||||
| 01:53 UTC | 77 | 57 | 280° 7 kt | 998.3 | ||
| 01:55 UTC | 290° 7 kt | 998.3 | ||||
| 02:00 UTC | 310° 8 kt | 998.3 | ||||
| 02:05 UTC | 310° 8 kt | 998.3 | ||||
| 02:15 UTC | 320° 9 kt | 998 | ||||
| 02:20 UTC | 320° 7 kt | 997.6 | ||||
| 02:25 UTC | 330° 8 kt | 997.3 | ||||
| 02:30 UTC | 340° 9 kt | 997 | ||||
| 02:35 UTC | 340° 7 kt | 997.3 | ||||
| 02:40 UTC | 9 kt | 997 | ||||
| 02:45 UTC | 9 kt | 996.6 | ||||
| 02:50 UTC | 350° 9 kt | 996.6 | ||||
| 02:53 UTC | 74 | 59 | 350° 10 kt | 996.3 | VCTS | |
| 02:55 UTC | 11 kt | |||||
| 03:00 UTC | 330° 11 kt | |||||
| 03:05 UTC | 310° 21 kt | 995.6 | ||||
| 03:08 UTC | 71 | 58 | 310° 18 kt | 26 | 995.6 | -TSRA |
| 03:10 UTC | 300° 20 kt | 994.9 | RA | |||
| 03:15 UTC | 18 kt | 28 | RA | |||
| 03:20 UTC | 300° 24 kt | 995.6 | RA | |||
| 03:25 UTC | 210° 19 kt | 24 | 998.6 | +RA | ||
| 03:26 UTC | 65 | 58 | 190° 22 kt | 31 | 999.3 | +TSRA |
| 03:29 UTC | 64 | 59 | 180° 32 kt | 37 | 1000 | +TSRA |
| 03:30 UTC | 42 | 1000.3 | +RA | |||
| 03:31 UTC | 63 | 59 | 190° 35 kt | 44 | 1000.7 | +TSRA FG |
| 03:33 UTC | 63 | 59 | 190° 23 kt | 44 | 1000.7 | +TSRA FG |
| 03:35 UTC | 22 kt | 32 | 1000 | +RA FG | ||
| 03:37 UTC | 62 | 58 | 40° 17 kt | 44 | 998.3 | +TSRA FG |
| 03:40 UTC | 20° 11 kt | 998 | +RA | |||
| 03:43 UTC | 64 | 57 | 20° 11 kt | 36 | 997.6 | TSRA |
| 03:47 UTC | 64.4 | 59 | 60° 10 kt | 19 | 999.3 | TSRA |
| 03:50 UTC | 66.2 | 59 | 160° 16 kt | 22 | 999 | TSRA |
| 03:53 UTC | 64 | 59 | 170° 21 kt | 32 | 999.3 | +TSRA |
| 03:55 UTC | 20 kt | 999 | +RA BR | |||
| 03:59 UTC | 62 | 58 | 190° 25 kt | 32 | 999.7 | +TSRA BR |
| 04:00 UTC | 29 kt | 44 | 999.3 | +RA BR | ||
| 04:02 UTC | 62 | 58 | 220° 33 kt | 44 | 999.3 | +TSRA BR |
| 04:05 UTC | 61 | 58 | 230° 33 kt | 45 | 999 | VCTS +RA BR |
| 04:10 UTC | 240° 34 kt | 43 | 999.3 | +RA BR | ||
| 04:15 UTC | 240° 28 kt | 37 | 999.3 | +RA BR | ||
| 04:17 UTC | 61 | 58 | 240° 28 kt | 43 | 999.3 | VCTS +RA BR |
| 04:20 UTC | 240° 30 kt | 40 | 999.3 | +RA BR | ||
| 04:25 UTC | 230° | 40 | 1000 | +RA BR | ||
| 04:27 UTC | 60 | 57 | 230° 31 kt | 45 | 1000 | VCTS +RA BR |
| 04:30 UTC | 230° 29 kt | 1000.3 | +RA BR | |||
| 04:35 UTC | 230° 26 kt | 31 | 1000.3 | RA BR | ||
| 04:38 UTC | 58 | 55 | 230° 27 kt | 41 | 1000.7 | TSRA BR |
| 04:40 UTC | 230° 26 kt | 1000.3 | RA BR | |||
| 04:45 UTC | 240° 22 kt | 1000.7 | +RA | |||
| 04:50 UTC | 230° 19 kt | 29 | 1000.7 | RA | ||
| 04:53 UTC | 58 | 53 | 240° 19 kt | 29 | 1000.7 | TSRA |
| 05:00 UTC | 280° 18 kt | 998.6 | +RA BR | |||
| 05:05 UTC | 20 kt | 997.6 | +RA BR | |||
| 05:10 UTC | 17 kt | 998 | RA | |||
| 05:11 UTC | 58 | 53 | 300° 15 kt | 24 | 998.3 | TSRA |
| 05:15 UTC | 13 kt | 998.3 | -RA |
From the Iowa Environmental Mesonet's archive of airport observations.
The radar
The Glasgow radar (KGGW), 11 km away, was scanning. The volume nearest the touchdown began at 03:17 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.
What was reported nearby
Local storm reports within 60 km of the path, in the three hours either side.
| Time (UTC) | Report | Where | County | Remark |
|---|---|---|---|---|
| 02:00 UTC | LIGHTNING | 2 E Glasgow | Valley, MT | LIGHTNING HIT CHIMNEY AND KNOCKED OFF THE TOP FEW BRICKS. LIVING ROOM FIREPLACE DOORS FLEXED AND ASH BLEW INTO THE LIVING ROOM. |
| 02:17 UTC | TSTM WND GST 61 | 13 E Haxby | Mccone, MT | MEASURED ON A PWS AND POSTED ON FB. |
| 02:17 UTC | TSTM WND GST 61 | 34 Nw Circle | Mccone, MT | ALSO HAD 0.45 OF RAIN. FROM SOCIAL MEDIA. |
| 02:28 UTC | TSTM WND GST 61 | 13 E Haxby | Mccone, MT | CORRECTS PREVIOUS TSTM WND GST REPORT FROM 13 E HAXBY. UPDATED TO CORRECT TIME. MEASURED ON A PWS AND POSTED ON FB. |
| 03:01 UTC | TSTM WND GST 80 | 11 Ese Fort Peck | Mccone, MT | TRAINED SPOTTER ESTIMATED 80 MPH GUST SOUTH OF THE DAM ALONG HIGHWAY 24 SOUTH. |
| 03:04 UTC | TSTM WND DMG | 4 E Park Grove | Mccone, MT | TRAIN SPOTTER REPORTED LARGE BRANCHES DOWN BY THE FORT PECK DAM AND SPILLWAY. |
| 03:05 UTC | TSTM WND DMG | Nashua | Valley, MT | TREE DOWN ACROSS FENCE AND FENCE KNOCKED OVER. FROM SOCIAL MEDIA. TIME ESTIMATED FROM RADAR. |
| 03:05 UTC | TSTM WND GST 60 | Fort Peck | Valley, MT | NWS EMPLOYEE ESTIMATED WIND GUST OF AT LEAST 60 MPH IN THE TOWN OF FORT PECK. |
| 03:05 UTC | TSTM WND GST 67 | 2 E Fort Peck | Mccone, MT | MESONET STATION GGWFP 2.4 E FORT PECK (GGWWFO). TIME ESTIMATED. |
| 03:05 UTC | HAIL 1 | Ne Glasgow | Valley, MT | LASTED FOR 3 MINUTES |
| 03:05 UTC | HAIL 1 | Ne Glasgow | Valley, MT | LASTED FOR 3 MINUTES. |
| 03:11 UTC | TSTM WND DMG | 6 Se Nashua | Valley, MT | FB REPORT WITH PICTURES OF TREES DOWN. |
| 03:14 UTC | TSTM WND GST 58 | 14 Nnw Hell Creek Rec A | Valley, MT | TIME RADAR ESTIMATED. MESONET STATION KIGM8 KING COULEE. |
| 03:15 UTC | HAIL 1 | Glasgow | Valley, MT | . |
| 03:15 UTC | HAIL 1 | Glasgow | Valley, MT | |
| 03:16 UTC | FUNNEL CLOUD | 2 E Whatley | Valley, MT | TRAINED WEATHER SPOTTER REPORTED FUNNEL CLOUD JUST EAST OF WHATLEY. |
| 03:17 UTC | TORNADO | 2 Ene Whatley | Valley, MT | A BRIEF TORNADO WITH PEAK WINDS OF 80 MPH TOUCHED DOWN NEAR WHATELY CAUSING MINOR DAMAGE TO TWO HOUSES. A CARPORT HAD ITS ROOF RIPPED OFF WITH MOST DEBRIS BEING LOFTED TO THE NORTH AND SOME TO THE EAST. A BOAT SITTING BE |
| 03:23 UTC | HAIL 0.5 | 1 E Glasgow | Valley, MT | REPORT FROM MPING: HALF-INCH (0.50 IN.). |
| 03:35 UTC | TSTM WND GST 72 | 6 W Larslan | Valley, MT | ROOF BLOWN OFF FARM BUILDING AND FENCE BLOWN OVER SOUTH OF FUHRMAN RD. FROM SOCIAL MEDIA. TIME ESTIMATED FROM RADAR. |
| 03:38 UTC | TSTM WND DMG | 15 S Opheim | Valley, MT | POWERLINES DOWN. SLIDING DOOR RIPPED FROM A 40 BY 90 SHOP. SEVERAL BIG BRANCHES DOWN. 500 GALLON PROPANE TANK KNOCKED OVER. FROM SOCIAL MEDIA. TIME ESTIMATED FROM RADAR. |
| 03:41 UTC | TSTM WND DMG | 18 S Richland | Valley, MT | FARM BUILDING DESTROYED. FROM SOCIAL MEDIA. TIME ESTIMATED FROM RADAR. |
| 03:45 UTC | LIGHTNING | 2 E Glasgow | Valley, MT | LIGHTNING HIT CHIMNEY AND KNOCKED OFF THE TOP FEW BRICKS. LIVING ROOM FIREPLACE DOORS FLEXED AND ASH BLEW INTO THE LIVING ROOM. |
| 03:48 UTC | TSTM WND GST 62 | 1 N Baylor | Valley, MT | TIME ESTIMATED FROM RADAR |
| 03:48 UTC | TSTM WND GST 62 | 1 N Baylor | Valley, MT | TIME ESTIMATED FROM RADAR. |
| 03:48 UTC | TSTM WND GST 63 | 1 N Baylor | Valley, MT | TIME ESTIMATED FROM RADAR |
| 03:48 UTC | TSTM WND GST 63 | 1 N Baylor | Valley, MT | TIME ESTIMATED FROM RADAR. |
| 05:00 UTC | HEAVY RAIN 2.05 | 8 Sse Glasgow | Valley, MT | |
| 05:00 UTC | HEAVY RAIN 2.3 | 1 S Glasgow | Valley, MT | |
| 05:30 UTC | HEAVY RAIN 1.94 | 2 Nne Glasgow | Valley, MT | STORM TOTAL PRECIPITATION OVER ABOUT TWO HOURS. |
From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.
This ground now
The live radar over the trackEvery 2020 tornado in MontanaEvery tornado in Montana since 1950Warnings in force in Montana nowThe forecast where you are
The other tornadoes of May 20, 2020
7 more were confirmed in the United States that day.
What this means
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.
Sources
NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.