An abnormal weather pattern for September developed, triggering a significant downslope wind event. Based on climatology and previous case study findings, this type of event most commonly occurs during the winter months. Downslope wind events are often confined to areas near canyon mouths, and usually impact only isolated areas with extreme winds. This event broke the mold in terms of both the early fall timing and extensive spatial coverage of the damage. High winds were reported as far south as the Tooele Valley, with high wind reports all along the Interstate 15 corridor stretching north into the Cache Valley. With the trees having their full canopy, the tree damage all along the Wasatch Front was extreme, with an estimated 4,500 trees damaged in Salt Lake County alone. Current estimates put the cost at $8.9 million. The storm led to 1 fatality, 20 direct injuries, and 4 indirect injuries.

High Wind in CACHE VALLEY/UTAH, UTAH
From 08-SEP-20 02:00:00 to 08-SEP-20 03:33:00 (MST-7)
Magnitude: 59.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

A peak wind gust of 68 mph was recorded at the Logan-Cache Airport. Widespread power outages were reported, with Rocky Mountain Power reporting 13,000 customers lost power. Numerous large trees were downed, including a tree estimated at 140 years old.

High Wind in WASATCH MOUNTAIN VALLEYS, UTAH
From 08-SEP-20 06:00:00 to 08-SEP-20 10:00:00 (MST-7)
Magnitude: 51.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A weather station in Morgan recorded a peak wind gust of 59 mph. A large tree fell on a house in Morgan, and downed trees and blowing debris were reported in Midway.

High Wind in GREAT SALT LAKE DESERT AND MOUNTAINS, UTAH
From 07-SEP-20 18:10:00 to 08-SEP-20 16:40:00 (MST-7)
Magnitude: 70.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A peak wind gust of 81 mph was recorded by the U.S. Army Dugway Proving Ground Camel Back Mountain sensor.  Other notable peak wind gusts included 70 mph at Upper Cedar Mountain, 64 mph at Promontory Point, 64 mph at Gunnison Island, 64 mph at I-80 @ mp 29, 61 mph at I-15 @ Tremonton, 61 mph at SR-30 @ Curlew, 60 mph at Rosebud, and 59 mph at I-80 at MP 71 East Delle.

High Wind in SALT LAKE AND TOOELE VALLEYS, UTAH
From 08-SEP-20 05:05:00 to 08-SEP-20 14:08:00 (MST-7)
Magnitude: 77.00 MG
Property damage: 4.30M
Crop damage: 0.00K
Reported by: Mesonet

A historic downslope wind event impacted the Salt Lake and Tooele Valleys, with the most extensive damage observed across the Salt Lake Valley. A peak wind gust of 89 mph was recorded at The University of Utah Browning Building. Other notable peak wind gusts recorded included 77 mph at Salt Lake City International Airport, 68 mph at the Great Salt Lake Marina, 68 mph in the Salt Lake City Avenues, 67 mph by the Baccus Highway sensor, 67 mph by the I-215 at Olympus Cove sensor, and 59 mph by the Foothill Dr at Mario Capecchi Dr. sensor.  Widespread wind damage, downed trees, and power outages were reported. The Salt Lake Forester estimated more than 1500 trees fell on public land alone, not including private property, during the event.  Many of the trees were 60 to 100 years old. Liberty Park lost 69 trees, and the City Cemetery lost 255 trees. Over 180,000 power outages were reported along the Wasatch Front, with some locations taking days to around a week to have power restored due to the extensive damage. Salt Lake City schools were closed Tuesday through Thursday. The Capitol Complex was closed due to extensive tree damage, as were numerous parks, golf courses and recreation areas. Many COVID-19 testing sites were damaged and had to close, including all University of Utah testing sites. The only know fatality for the event occurred in South Salt Lake, when a 61-year-old truck driver unloading his truck was blown over by the wind, striking his head. In addition, Intermountain Healthcare  reported that 12 patients were treated for wind-related injuries. Damage and cleanup costs for the event tallied $4.3 million.

High Wind in NORTHERN WASATCH FRONT, UTAH
From 08-SEP-20 02:10:00 to 09-SEP-20 01:30:00 (MST-7)
Magnitude: 86.00 MG
Property damage: 4.30M
Crop damage: 0.00K
Reported by: Mesonet

A historic downslope wind event unfolded along the Northern Wasatch Front. The peak wind gust for the event, not only in this zone, but across the state, was a 99 mph peak wind gust recorded by the US-89 at Park Lane sensor.   Other notable peak wind gusts included 97 mph at Farmington, 84 mph at Hill Air Force Base, 82 mph in North Brigham City, 75 mph at Brigham City Regional Airport, 75 mph at Centerville, and 64 mph at Ogden-Hinckley Airport. Extensive wind damage was reported along the entire Wasatch Front, with widespread downed trees, damaged roofs and power outages. Transportation was heavily impacted with all major north-south (Interstate 15, Interstate 84, and U.S. Highway 89) routes closed or restricted at times through the event.  At least 50 semitrailers were overturned, with four truck drivers with injuries taken to  hospitals. Over 180,000 power outages were reported along the Wasatch Front, with some locations taking days to around a week to have power restored due to the extensive damage. All school districts were closed Tuesday, with some closures continuing into Wednesday. Two Ogden hospitals reported significant damaged, and an Intermountain Life Flight helicopter was severely damaged. At least 20 manufactured homes were heavily damaged in Box Elder County, requiring residents to be transferred to shelters.  Damage and cleanup costs for the event tallied $4.3 million.

High Wind in WASATCH MOUNTAINS I-80 NORTH, UTAH
From 08-SEP-20 00:00:00 to 08-SEP-20 10:00:00 (MST-7)
Magnitude: 84.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A peak wind gust of 97 mph was recorded by the Logan Peak sensor. Other notable peak wind gusts include, 78 mph at Snowbasin - Ogden Peak, 75 mph at Powder Mountain, 74 mph at Big Mountain Pass, 69 mph at SR-16 @ MP1, and 63 mph at SR-30 at MP 124 Laketown. In addition, widespread downed trees were reported at Powder Mountain, on private property along UT-39 north of Causey Reservoir, and at Snowbasin Resort.

High Wind in WASATCH MOUNTAINS SOUTH OF I-80, UTAH
From 08-SEP-20 06:30:00 to 08-SEP-20 16:15:00 (MST-7)
Magnitude: 56.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Widespread downed trees were reported along the entire Park City ridgeline from above Canyons Village to Guardsman Pass at Deer Valley. Downed trees continued over the top of Guardsman Pass at Blood Lake and into the upper portion of Big Cottonwood Canyon, where the Redman Campground was closed for a couple days due to removal of downed trees. The Mountain Trails Foundation, that maintains hiking and biking trails in the Park City area, reported a record number of blowdowns, with 80 plus trees reportedly cleared from trails in this area.  A peak wind gust of 65 was recorded by the Alta - MT Baldy sensor.

High Wind in UTAHS DIXIE AND ZION NATIONAL PARK, UTAH
From 08-SEP-20 04:50:00 to 08-SEP-20 12:10:00 (MST-7)
Magnitude: 56.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A Washington County gap wind event produced a peak wind gust of 64 mph at the I-15 at MP 29 Tripod sensor location, and a peak wind gust of 59 mph was recorded by the White Reef sensor.

Heavy Snow in WESTERN UINTA MOUNTAINS, UTAH
From 08-SEP-20 00:00:00 to 09-SEP-20 10:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: SNOTEL

Heavy snow occurred on the north slope of the Uinta mountains. Spirit Lake SNOTEL recorded 1.5 inches of liquid equivalent precipitation, or approximately 22 inches of snow, Hickerson Park SNOTEL recorded 1.2 inches of liquid equivalent precipitation, or approximately 18 inches of snow, and the Hole-in-Rock SNOTEL recorded 0.8 inches of liquid equivalent precipitation, or approximately 12 inches of snow.