Intense winds developed as a vigorous cold front, accompanied by a line of thunderstorms, spilled over the Cheyenne Ridge and moved rapidly across the Urban Corridor and Northeast Plains. Peak wind gusts to 83 mph (72 kts) downed trees and power lines.
Every event with a place to put it; 10 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
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.
The episode as NWS BOU wrote it up.
Intense winds developed as a vigorous cold front, accompanied by a line of thunderstorms, spilled over the Cheyenne Ridge and moved rapidly across the Urban Corridor and Northeast Plains. Peak wind gusts to 83 mph (72 kts) downed trees and power lines. Approximately 32,000 Xcel customers in Weld, Boulder, Lafayette, Littleton, central Denver and Aurora were without electricity for up to two hours. Zero visibilities were reported due to blowing dust, dirt and other flying debris. As a result, a multi-vehicle accident occured along U.S. Highway 85, between Greeley and Fort Lupton. Six people were treated for minor injuries. Several vehicles, including semi trailers, were reportedly blown off Interstate 70, west of Limon and along Interstate 76, in Morgan County. In Lyons, the roof of the new post office under construction was blown off the building. The Regional Electric Association estimated the damage to power lines and poles, as well as the cost to run backup generators during the outages, was approximately $3.4 million.Strong winds gusting to 58 mph (50 kts) at Denver International Airport caused at least a dozen incoming flights to be diverted to Grand Junction and Colorado Springs. Departing flights were grounded for at least an hour. At Southwest Plaza in Littleton, shoppers were evacuated as rocks holding a tarp on a portion roof under repair, toppled into the mall. Temperatures in one hour dropped from the mid 70s into the mid 30s.Peak wind reports included: 83 mph (72 kts) at Greeley Airport, 71 mph (61 kts) at Fort Collins, 70 mph (60 kts) at Lyons, 68 mph (59 kts) at Fort Morgan and 15 miles east of Parker, 66 mph (57 kts) at Merino, 64 mph (56 kts), 4 miles east of Haxtun, 64 mph (54 kts) at Severance, 63 mph (55 kts), 5 miles southwest of Sedalia, 61 mph (53 kts), 15 miles west northwest of Sterling and 6 miles southwest of Wellington, 60 mph (52 kts), 2 miles north of Johnstown and 58 mph (50 kts) at Denver International Airport.
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 Denver/Boulder, CO wrote its last area forecast discussion before the first event at May 20, 1:45 PM MST, 1 hour earlier.
NORTHEAST AND NORTH CENTRAL COLORADO AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER COLORADO
245 PM MDT SUN MAY 20 2001
SHORT TERM DISCUSSION: A VERY POTENT STORM FOR THIS LATE IN THE
SEASON WL MOVE OVR THE FCST AREA TONITE. STG CDFNT WAS MOVG THRU
KCYS AT 20Z WITH THEIR RADAR SHOWING 35 KT WINDS BEHIND IT. MSAS
3HR PRES CHANGE CHART SHOWS A PLUS 6 BULLSEYE OVR KRIW.
POST-FRONTAL TEMPS IN CENTRAL WY DROPPED TO FREEZING DURING THE AFTN
WITH PERIODS OF MOD SNOW. CDFNT SHUD REACH DEN BTWN 4 AND 6 PM WITH
STRONG N WINDS AND RAPIDLY FALLING TEMPS. THE SHOWER ACTIVITY ALG
AND BEHIND THE FRONT HAS BEEN QUICK TO CHANGE OVR TO SNOW BECAUSE OF
THE STRONG COLD ADVECTION WITH THE SYSTEM. RADARS IN WY HAVE ALSO
BEEN SHOWING SNOW ECHOES IN THE 30-40 DBZ RANGE...INDICATIVE OF 1-2
INCH/HR SNOW INTENSITIES. 700-500MB OMEGA FIELDS FM THE MODELS SHOW
VALUES OVR NE CO IN EXCESS OF 12 MICROBARS/SEC...SO LOTS OF VERTICAL
MOTION TO GENERATE HEAVY PCPN THIS EVENING. BY MIDNIGHT...THINGS
SHUD BEGIN WINDING DOWN AS MODELS SHOW THE MAIN AREA OF LIFT
DROPPING INTO SERN CO. WARM GROUND SHUD HELP TO MELT MOST OF THE
SNOW THAT FALLS...BUT IN ZONES 35...36 AND 41...ENHANCED UPSLOPE
FORCING AND HIGHER ELEVATIONS COULD ALLOW A FEW INCHES OF SNOW TO
ACCUMULATE. THE STRONGEST WINDS WILL BE RIGHT ALONG THE FRONT...AND
WHEN HEAVIER SNOW DVLPS THE WINDS SHOULD SLACK OFF. SINCE IT IS SO
LATE IN THE SEASON...AND CONDS CUD GET BAD FOR A FEW HOURS...WL
ISSUE A S/BS ADVISORY FOR TONITE.
LONG TERM DISCUSSION: A COOL DAY IS IN STORE FOR MONDAY BUT AMS
SHUD BEGIN STABILIZING AS THE STRONG TROF MOVES EWD AND HIGH PRES
BUILDS IN FM THE W. WX WL BE DRY...BUT THIS AFTNS SATELLITE
PICTURES SHOW QUITE A BIT OF CLD COVER IN MT FOR NOW. WL GO WITH A
PARTLY CLOUDY DAY AS SUBSIDENCE WL CAP MOST CONVECTION THRU THE
AFTN. AMS SHUD MODERATE ENOUGH ON MON AND MON NITE TO END THE
THREAT OF FREEZING TEMPS AT LOWER ELEVS TUES MRNG. BY MID-WEEK WE
WL BE UNDER A STRONG HIGH-AMPLITUDE RIDGE AXIS... ALLOWING FOR WARM
TEMPS AND DRY WX. BY THE END OF THE WEEK...SOME LOW LVL MSTR WL
RETURN FM THE GULF WHILE THE UPR RIDGE REMAINS IN PLACE. WL KEEP
THE EXTENDED FCST DRY AND SEASONAL THRU FRI...THEN INTRODUCE A
CHANCE OF AFTN THUNDERSTORMS FOR MEMORIAL DAY WEEKEND.
KDRBY
.DEN...S/BS ADVSY TONITE FNT RANGE FTHLS AND PALMER DIVIDE...ZNS
35..36..41.COZ030>051-202000- SIGNIFICANT WEATHER OUTLOOK FOR NORTHEAST AND NORTH CENTRAL COLORADO NATIONAL WEATHER SERVICE DENVER CO 1110 AM MDT SUN MAY 20 2001 THIS OUTLOOK PERTAINS TO THE FOLLOWING COLORADO COUNTIES ADAMS ARAPAHOE BOULDER CLEAR CREEK DENVER DOUGLAS ELBERT GILPIN GRAND JACKSON JEFFERSON LARIMER LINCOLN LOGAN MORGAN PARK PHILLIPS SEDGWICK SUMMIT WASHINGTON WELD SYNOPSIS: AN INITIAL COLD FRONT PUSHED THROUGH MOST OF NORTHEAST COLORADO THIS MORNING...BRINGING SLIGHTLY COOLER TEMPERATURES TO THE AREA. HOWEVER...A MUCH STRONGER COLD FRONT WILL RACE SOUTHWARD ACROSS THE NORTHEAST PLAINS THIS AFTERNOON. THE FRONT IS EXPECTED TO REACH THE COLORADO AND WYOMING BORDER BY 1 PM...AND THEN REACH DENVER...BENNETT...AND LIMON BY 4 PM. THE AIRMASS ALONG THIS COLD FRONT WILL BECOME MORE UNSTABLE DURING THE AFTERNOON...WITH SCATTERED SHOWERS AND THUNDERSTORMS DEVELOPING AFTER 3 PM. A COUPLE STORMS SOUTH OF A DENVER TO LIMON LINE MAY APPROACH SEVERE LIMITS WITH HAIL AND STRONG GUSTY WINDS...BUT SPOTTER ACTIVATION IS NOT ANTICIPATED. THE MAIN FEATURE FROM THIS STRONG COLD FRONT WILL BE UNSEASONABLY COLD TEMPERATURES AND SOME SNOWFALL. AFTER THE FRONT MOVES THROUGH...MOISTURE WILL QUICKLY INCREASE WITH RAIN SHOWERS BECOMING MORE WIDESPREAD. AS TEMPERATURES QUICKLY DROP INTO THE 30S THIS EVENING...THE RAIN WILL CHANGE TO SNOW IN MOST AREAS. AT THIS TIME...AN INCH OR TWO OF SNOW IS EXPECTED TO ACCUMULATE ON GRASSY AREAS IN THE DENVER METRO AREA...WITH 3 TO 6 INCHES OF SNOWFALL EXPECTED IN THE SOUTHERN FRONT RANGE FOOTHILLS AND DOUGLAS COUNTY. ELSEWHERE...LITTLE IF ANY ACCUMULATION WILL OCCUR. THE SNOW IS EXPECTED TO END AFTER MIDNIGHT WITH CLEARING SKIES AND TEMPERATURES DROPPING CLOSE TO FREEZING ON THE PLAINS. MONDAY WILL FEATURE MOSTLY SUNNY SKIES BUT COOL WEATHER WITH HIGH TEMPERATURES ONLY IN THE LOWER TO MID 50S. BARJENBRUCH
The national radar mosaic for the moment the first event began.
10 high wind. Local standard time, as filed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2001Every state in 2001This day in weather historyWarnings in Colorado, May 2001
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: 5250134, 5250135, 5250136, 5250137, 5250138, 5250139, 5250140, 5250141, 5250142, 5250143.