A strong spring storm dropped across the Great Basin, and then moved eastward across Colorado.  Isolated but strong thunderstorms preceded the system on the 17th with hail up to nickel size near Boulder Airport and Brighton.  Significant snow fell across the Front Range mountains and foothills over the next couple of days.  The heaviest snowfall occurred in Boulder and Larimer Counties.  Along the Interstate 25 Corridor, rain turned to snow on the morning of the 18th, heaviest from around Broomfield northward.  The heavy wet snow snapped the limbs of fully leaved trees and caused scattered power outages.  Eight hundred trees on the campus of Colorado State University were damaged.  Some trees in and around Fort Collins completely collapsed under the weight of the snow.
A couple of barns collapsed in Larimer County. One was a historic barn in Estes Park, with another in northeast Loveland.  Fifty-five head of cattle were inside the collapsed barn in Loveland; three were injured and later euthanized.  Numerous branches and trees snapped around Fort Collins and in the foothills.  Elsewhere, several scattered smaller power outages were reported.  Three to nearly 5 inches of liquid precipitation occurred, as rain or a mix of of rain and snow, fell around Greeley and 12 miles northwest of Briggsdale.
Storm totals in the Front Range mountains and foothills included:  42.0 inches near Allenspark, 41.5 inches near Ward, 36 inches at Estes Park, 32 inches near Pinecliffe, 30.5 inches northwest of Golden, 30 inches near Nederland, 26 inches near Breckenridge, 25 inches near Aspen Springs and Bear Lake State Park, 18.5 inches northwest of Rustic, 16 inches at Copper Mountain and Dillon, 15 inches at Drake, 14 inches at Aspen Springs and Deadman Hill, 13 inches at Tower, with 9.5 inches near Evergreen.  On the west side of the Interstate 25 Corridor, storm totals included:  10 inches near Superior and Louisville, 6 to 8 inches in and around Fort Collins, 6 inches in Lafayette, 5 inches in Broomfield and Loveland, and 4 inches near Niwot.

Hail in BOULDER, COLORADO
From 17-MAY-17 18:25:00 to 17-MAY-17 18:25:00 (MST-7)
Location: BOULDER ARPT
Magnitude: 0.75 
Reported by: CoCoRaHS

Hail in ADAMS, COLORADO
From 17-MAY-17 19:40:00 to 17-MAY-17 19:40:00 (MST-7)
Location: BRIGHTON
Magnitude: 0.88 
Reported by: Trained Spotter

Hail in ADAMS, COLORADO
From 17-MAY-17 19:42:00 to 17-MAY-17 19:42:00 (MST-7)
Location: BRIGHTON
Magnitude: 0.88 
Reported by: Trained Spotter

Heavy Snow in S & E JACKSON / LARIMER / N & NE GRAND / NW BOULDER COUNTIES ABOVE 9000 FEET, COLORADO
From 17-MAY-17 17:00:00 to 19-MAY-17 17:00:00 (MST-7)
Reported by: SNOTEL

Storm totals included:  25 inches at Bear Lake, 14 inches at Deadman Hill, 10 inches at Lake Irene and 9 inches at Joe Wright and Long Draw Reservoir.

Heavy Snow in S & SE GRAND / W CENTRAL & SW BOULDER / GILPIN / CLEAR CREEK / SUMMIT / N & W PARK COUNTIES ABOVE 9000 FEET, COLORADO
From 17-MAY-17 17:00:00 to 19-MAY-17 17:00:00 (MST-7)
Reported by: Trained Spotter

Storm totals included:  26 inches near Breckenridge, 16 inches at Cabin Creek and Copper Mountain Ski Area, 10.5 inches near Dillon and Jones Pass, with 9 inches in Winter Park Ski Area.

Heavy Snow in LARIMER & BOULDER COUNTIES BETWEEN 6000 & 9000 FEET, COLORADO
From 17-MAY-17 17:00:00 to 19-MAY-17 17:00:00 (MST-7)
Reported by: Trained Spotter

Storm totals included:  42.0 inches near Allenspark, 41.5 inches near Ward, 36 inches at Estes Park, 32 inches near Pinecliffe, 30 inches near Nederland, 25 inches near Aspen Springs, 19 inches northeast of Red Feather Lakes, with 15 inches near Drake.

Heavy Snow in LARIMER COUNTY BELOW 6000 FEET / NW WELD COUNTY, COLORADO
From 17-MAY-17 17:00:00 to 19-MAY-17 11:00:00 (MST-7)
Reported by: Trained Spotter

Storm totals included 8 inches around Ft. Collins, with 5 inches in Loveland.  Extensive tree damage was reported, with up to 800 trees impacted on the Colorado State Univieristy Campus alone.   Some of the trees completely toppled under the weight of the wet and heavy snow.

Heavy Snow in BOULDER & JEFFERSON COUNTIES BELOW 6000 FEET / W BROOMFIELD COUNTY, COLORADO
From 17-MAY-17 17:00:00 to 19-MAY-17 02:45:00 (MST-7)
Reported by: Trained Spotter

Storm totals included:  12 inches near Rocky Flats, 10 inches near Superior and Louisville, 6 inches in Lafayette with 5 inches in Broomfield.

Heavy Snow in JEFFERSON & W DOUGLAS COUNTIES ABOVE 6000 FEET / GILPIN / CLEAR CREEK / NE PARK COUNTIES BELOW 9000 FEET, COLORADO
From 17-MAY-17 17:00:00 to 19-MAY-17 17:00:00 (MST-7)
Reported by: Trained Spotter

Storm totals included:  14 inches in Aspen Springs, 12 inches near Rocky Flats, with 7.5 inches in Georgetown.