F0 tornado, Roy, Montana, April 25, 2003

1. F040 to 72 mphthis tornado

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. F173 to 112 mph

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

3. F2113 to 157 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. F3158 to 206 mph

   Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

5. F4207 to 260 mph

   Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

6. F5261 to 318 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

F0

Date

April 25, 2003

Touchdown

3:10 PM MDT (21:10 UTC)

Path length

2.0 miles (3.2 km)

Path width

25 yards (23 m)

Deaths

0

Injuries

0

County

Fergus County

Touchdown point

47.330, -108.930

Lift-off point

47.330, -108.930

Record number

55

A strong thunderstorm moving through Fergus County during the mid afternoon hours on the 25th, produced a tornado 15 miles North of Roy. The tornado began at 1410 MST and was on the ground for 7 minutes. No damage was reported with this tornado.

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

27 minutes of warning. NWS TFX issued a tornado warning for this county at 20:43 UTC, 27 minutes before the tornado touched down, in force until 21:15 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 20:23 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.

NWS Great Falls, MT wrote its last area forecast discussion before the tornado touched down at Apr 25, 2:30 PM MDT, 40 minutes earlier.

SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
230 PM MDT FRI APR 25 2003

.SHORT TERM...TONIGHT AN UPPER LEVEL DISTURBANCE WILL MOVE NORTH
FROM SOUTHWEST TO NORTH CENTRAL MONTANA. THIS WILL ALLOW FOR A BAND
OF PRECIPITATION TO MOVE NORTH ACROSS THE AREA. SOME AREAS MAY SEE
UP TO A QUARTER OF AN INCH OF PRECIP AS IT MOVES THROUGH. THE PRECIP
WILL COME TO AN END AFTER MIDNIGHT...BUT THEN REDEVELOP TOWARDS DAY
BREAK OVER THE SOUTHWEST. EXPECT SNOW LEVELS TO LOWER TO 5000 FEET
OVER THE SOUTWEST...AS MUCH COOLER AIR MOVES IN. FOR SATURDAY...
RAIN AND MOUNTAIN SNOW WILL BE LIKELY ACROSS MUCH OF THE REGION...AS
AN UPPER LEVEL DISTURBANCE MOVES EAST ACROSS THE CWA. TEMPERATURES
WILL BE ABOUT 10 DEGREES COOLER THAN TODAY AS WELL. BRUSDA

ON SUNDAY THE SURFACE LOW TO THE NORTH OF CWA
CONTINUES TO PULL OFF TO THE EAST AS A SURFACE HIGH BUILDS IN
OVER THE SW. UPPER RIDGE BUILDS OVER CWA SO WILL DROP POPS OVER
MUCH OF THE AREA FOR EARLY SUNDAY AND SUNDAY AFTERNOON. EXPECT SW TO
S FLOW ALOFT TO START SO WENT WITH CHANCE OF SHOWERS SUNDAY
NIGHT. ATMOSPHERE BECOMES UNSTABLE IN SW FLOW ALOFT AND EXPECT
MORE SCATTERED SHOWERS/THUNDERSTORMS. TIMING AGAIN WILL BE THE
PROBLEM. LOOKS LIKE GFS CONTINUES TO BE THE FASTER OF THE MODELS SO
LEFT POPS IN GOING FORECAST AS WAS. LATEST GFS TEMPERATURES CONTINUE
TO BE COOLER THAN GRIDS. AM NOT BUYING INTO THEM AS YET. ANY SUN
DURING BREAKS IN THE CLOUDS WILL GET TEMPS INTO THE 50S QUITE EASILY.
OVERALL TREND IS FOR CLOUDINESS AND COOLER WITH SCATTERED SHOWERS.
CAMP

.EXTENDED...FOR THURSDAY AND FRIDAY...EXPECT SCATTERED SHOWERS AND
THUNDERSTORMS TO CONTINUE...AS AN UPPER LEVEL LOW MOVES INTO
SOUTHERN IDAHO. THE HIGHEST CHANCES WILL BE IN THE SOUTWEST...WITH
THE LOWEST CHANCES NEAR THE CANADIAN BORDER. EXPECT TEMPERATURES TO
BE NEAR TO SLIGHTLY BELOW NORMAL ON THURSDAY AND FRIDAY. BRUSDA

.CCF NUMBERS
GTF TW 035/051 033/056 030 17863
    BEEEE 053/034 056/034 058/033 056/036 059 22223333333
CTB TW 033/049 030/053 028 17663
    BEEEE 050/030 053/032 055/031 053/034 056 21113333333
HLN TW 035/051 034/055 031 17863
    EEEEE 056/036 059/036 059/035 057/038 060 23333333333
BZN TW 036/052 033/056 028 17863
    EEEEE 054/033 058/033 058/032 056/035 059 23333333333
WEY WO 026/039 022/043 018 17963
    EEEEE 045/025 048/025 048/024 046/027 049 24443344444
DLN WO 038/047 030/053 027 17963
    EEEEE 051/032 054/032 054/031 052/032 055 23333333333
HVR TW 037/054 032/052 030 17865
    BBEEE 055/030 061/032 062/031 060/034 062 21112222222
LWT TW 036/052 032/053 028 17863
    BEEEE 051/032 056/034 058/033 056/034 059 22223333333

.TFX...NONE.

MTZ008>015-044>055-260010-
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREAT FALLS MT
645 AM MDT FRI APR 25 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL AND SOUTHWEST MONTANA

.DAY ONE...TODAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

NO WATCHES, WARNINGS, OR ADVISORIES CURRENTLY IN EFFECT

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

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.

Lewistown Municipal (LWT), 51 km from the path, in the two hours either side.

From the Iowa Environmental Mesonet's archive of airport observations.

The Billings radar (KBLX), 166 km away, was scanning. The volume nearest the touchdown began at 21:08 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.

The live radar over the trackEvery 2003 tornado in MontanaEvery tornado in Montana since 1950Warnings in force in Montana 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.