Damaging Winds in Montana, May 21, 2002

Name: Damaging Winds in Montana, May 21, 2002
Start: 2002-05-21T17:30
End: 2002-05-21T19:45
Location: Montana

May 21, 2002 · NWS GGW · 4 events in 2 counties and zones

4 thunderstorm wind, as filed by the National Weather Service.

Where it happened

Every event with a place to put it. Tap one for its entry below.

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Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
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The toll

Deaths: 0
Injuries: 0
Property damage: $75,000
Crop damage: None recorded
Events: 4

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Glasgow, MT wrote its last area forecast discussion before the first event at May 21, 1:30 PM MST, 4 hours earlier.

Area forecast discussion, May 21, 1:30 PM MST, 4 hours before

NORTHEAST MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
230 PM MDT TUE MAY 21 2002

.SHORT TERM...WATER VAPOR IMAGERY SHOWS HIGHLY AMPLIFIED FLOW WITH
VIGOROUS TROUGH LIFTING NORTHEAST OVER THE GREAT BASIN REGION. THE
SURFACE REFLECTION OF THIS TROUGH IS A LOW THAT WILL TRACK EAST
ACROSS EASTERN MONTANA TONIGHT AND TOMORROW. HOWEVER EACH MODEL
DEVELOP DIFFERENT TRACKS WITH THE AVN TAKING A NORTHERN ROUTE ALONG
THE CANADIAN BORDER WHILE THE ETA TAKES THE LOW EAST INTO
SOUTHWESTERN NORTH DAKOTA. BOTH MODELS PRODUCE HIGHEST QPF AMOUNTS
ACROSS SOUTHERN SASKATCHEWAN WITH MAIN SYSTEM. MAIN PROBLEM FOR
PRECIP WILL BE HOW MUCH MOISTURE IS AVAILABLE...SINCE OMEGA VALUES
WILL BE DECENT WITH PASSAGE OF FRONT. WILL HOLD OFF PRECIP
DEVELOPING UNTIL MIDNIGHT TONIGHT AND INCREASE POP VALUES FOR
TOMORROW NIGHT WHEN A WEAK VORTMAX MAY CONTINUE TO PRODUCE RAIN
ACROSS THE CWA. OTHERWISE POPS LOOK REASONABLE.

THERE WILL BE A COOL DOWN OF 15 TO 20 DEGREES FOR TOMORROW AFTER
FRONT/LOW HAVE PASSED. HOWEVER BELIEVE INHERITED TEMPERATURES FOR
TONIGHT AND TOMORROW ARE TOO LOW AND WILL INCREASE THEM AND GO MORE
IN LINE WITH GUIDANCE. COOLEST DAY WILL BE THURSDAY WITH A CANADIAN
HIGH CENTERED OVER EASTERN MONTANA. THIS HIGH MOVES OFF TO THE EAST
FOR FRIDAY STARTING A WARMING TREND.

WINDS ARE MAJOR DIFFERENCE BETWEEN MODELS BECAUSE OF MODEL TRACKS.
ETA TAKES WINDS EAST TO NORTHEAST TO NORTHWEST WHILE THE AVN GOES
SOUTHEAST TO SOUTHWEST TO NORTHWEST. RIGHT NOW WINDS ARE NORTH
NORTHEAST IN WINNETT AND LEWISTOWN AND CURRENT SURFACE ANALYSIS GOES
ALONG BETTER WITH ETA. SO WILL FAVOR THE ETA SOLUTION. OVERALL WIND
SPEEDS WILL CONTINUE TO BE BREEZY UNTIL THURSDAY AFTERNOON INTO
THURSDAY NIGHT WHEN HIGH SETTLE IN OVER REGION.

.LONG TERM...SOUTHERN BRANCH OF SPLIT JET CONTINUES TO SET UP OVER
NEMONT FOR THE EXTENDED PERIOD WITH ZONAL FLOW ALOFT. WEAK RIDGE
KEEPS SATURDAY DRY HOWEVER BY SUNDAY...A TROUGH DIGS SOUTHEAST
ACROSS THE PACNW. THIS TURNS THE FLOW SOUTHWEST BRINGING WEAK
SHORTWAVES ACROSS THE MONTANA. WILL INCREASE POPS SLIGHTLY BEYOND
DAY 4 HOWEVER WILL NOT MAKE ANY MAJOR CHANGES. BERDES

KGGW RWB 046/055 034/053 040/058 77665322
     BEEE 040/062 042/066 044/068 044/070 7711222222
KGDV WRB 046/060 036/053 039/058 77335322
     BEEE 040/062 042/067 045/071 045/073 7711222222

.GGW...FIRE WEATHER WATCH FOR ALL ZONES UNTIL 03Z.

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

4 thunderstorm wind. Local standard time, as filed.

Thunderstorm Wind, Petroleum

When: May 21, 5:30 PM MST
Where: Petroleum County, Flatwillow
Measured: 55 kt (63 mph)
Reported by: TRAINED SPOTTER
Coordinates: 46.833, -108.400

Thunderstorm Wind, Petroleum

When: May 21, 5:44 PM MST
Where: Petroleum County, Winnett
Measured: 50 kt (58 mph)
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 47.000, -108.350

Thunderstorm Wind, Petroleum

When: May 21, 6:45 PM MST
Where: Petroleum County, 25 mi N of Winnett
Measured: 53 kt (61 mph)
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 47.367, -108.350

Thunderstorm Wind, Phillips

When: May 21, 7:20 PM MST to 7:45 PM MST
Where: Phillips County, 18 mi S of Zortman
Measured: 62 kt (71 mph)
Property damage: $75,000
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 47.650, -108.533

A line of thunderstorms produced severe winds across southern Phillips County. The damaging winds were generally less than 70 mph, but one RAWS site at Zortman did measure a 74 mph gust. A group of researchers just north of the UL Bend had significant damage to trailer they were using to stay in while conducting research. Three trailers were completely toppled, and another had the side caved in.

What these are

Thunderstorm Wind: Winds from a thunderstorm of 50 knots (58 mph) or more, or lower winds that caused damage or casualties. Measured gusts are marked MG, estimated EG.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Montana in 2002 Every state in 2002 This day in weather history Warnings in Montana, May 2002

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 5295732, 5295733, 5295734, 5295735.