A pair of upper lows became cut off over southern and eastern Montana  extending south and east into the Dakotas and Wyoming from a  negatively-tilted trough centered off the Pacific Northwest  coastline. This cut-off low spun in place through Thursday the 20th. The result was for significant accumulating snow in eastern portions of North-central Montana, with additional heavy snow across much of the rest of Southwest and Central MT.

Heavy Snow in SOUTHERN ROCKY MOUNTAIN FRONT, MONTANA
From 18-APR-23 08:00:00 to 19-APR-23 08:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: SNOTEL

Snotel equipment at Mount Lockhart and Dupuyer creek both estimated 11 inches of new snow.

Heavy Snow in SNOWY AND JUDITH MOUNTAINS, MONTANA
From 18-APR-23 20:00:00 to 20-APR-23 07:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

A co-op observer measured 14 inches new snow over 24 hours ending 7AM MDT 4/19. A public report of 24 inches was received southeast of Lewistown in the Snowy Mountains foothills. Additionally, the Crystal Lake Snotel estimated 33 inches new storm total snow for the event.

Heavy Snow in GALLATIN AND MADISON COUNTY MOUNTAINS AND CENTENNIAL MOUNTAINS, MONTANA
From 18-APR-23 06:00:00 to 19-APR-23 08:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: SNOTEL

Multiple Snotel sites in the zone estimated snow of 10 inches or greater. Clover Meadow snotel estimated 12 inches new snow over 14 hours ending 8 AM MDT 4/19.  Black Bear snotel estimated 10 inches storm total ending 3 AM 4/19 and Shower Falls snotel estimated 8 inches storm total snow ending 9 AM 4/19.

Heavy Snow in BIG BELT, BRIDGER AND CASTLE MOUNTAINS, MONTANA
From 18-APR-23 17:00:00 to 19-APR-23 16:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: SNOTEL

Four total SNOTEL sites estimated winter storm warning criteria storm total snowfall. The four are Brackett Creek (20 inches total), Sacajawea (23 inches), Boulder Mountain (10 inches), and Elk Peak (15 inches). Additionally, an automated alpine weather station at Bridger Bowl estimated 25.8 inches total snow.

Heavy Snow in JUDITH BASIN COUNTY AND JUDITH GAP, MONTANA
From 19-APR-23 00:00:00 to 20-APR-23 15:24:00 (MST-7)
Reported by: Trained Spotter

Spotter located about 3 miles south/southeast of Raynesford reported an event total snow amount of 24 inches.

Heavy Snow in ELKHORN AND BOULDER MOUNTAINS, MONTANA
From 18-APR-23 12:00:00 to 19-APR-23 00:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: SNOTEL

Snotel equipment at Tizer Basin estimated 11 inches new snow over 12 hours.

Winter Weather in EAST GLACIER PARK REGION, MONTANA
From 18-APR-23 14:00:00 to 19-APR-23 09:00:00 (MST-7)
Reported by: SNOTEL

Snotel station badger Pass estimated 14 inches storm total snow. High snowfall amounts were confined to uninhabited/high elevation areas.

Heavy Snow in EAST GLACIER PARK REGION, MONTANA
From 18-APR-23 14:00:00 to 19-APR-23 09:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: SNOTEL

Snotel station badger Pass estimated 14 inches storm total snow.

Heavy Snow in BEAVERHEAD AND WESTERN MADISON BELOW 6000FT, MONTANA
From 18-APR-23 16:30:00 to 19-APR-23 05:30:00 (MST-7)
Reported by: Public

Several reports from the public indicated snow in excess of 8 inches fell in the Dillon area over a relatively short period (Less than 12 hours, generally). A storm total report of 11 inches was received and a report of 10 inches over 5.5 hours was also received (5:30 to 10PM MDT). The COOP station at University of Montana - Western, in Dillon, had an event total amount of 9.5 inches.

Heavy Snow in FERGUS COUNTY BELOW 4500FT, MONTANA
From 18-APR-23 21:00:00 to 19-APR-23 17:00:00 (MST-7)
Reported by: Trained Spotter

Multiple trained spotters and public reports in the Lewistown area reported heavy snow. A trained spotter measured 20 inches new snow storm total 2 miles SE of Lewistown. A trained spotter near Hilger reported 7 inches storm total snow. Public reports of a foot and a half of new snow in Lewistown were also received. The COOP Observer in Grass Range reported an official snow amount of 9 inches for the event.

Heavy Snow in LITTLE BELT AND HIGHWOOD MOUNTAINS, MONTANA
From 18-APR-23 08:00:00 to 20-APR-23 06:00:00 (MST-7)
Reported by: COOP Observer

COOP observer located seven miles south of Shonkin had an event total snow amount of 33 inches. Multiple Snotel sites reported snow exceeding 10 inches, including snotel equipment at Stinger Creek which estimated 22 inches storm total. Snotels at Onion Park and Spur Peak also reported storm total snow in excess of 10 inches. A public report north of Monarch reported 10 inches from the evening of 4/18 into the morning of 4/19.

Heavy Snow in CASCADE COUNTY BELOW 5000FT, MONTANA
From 18-APR-23 17:00:00 to 20-APR-23 07:26:00 (MST-7)
Reported by: Official NWS Observations

Many observations of heavy snow were reported, including official NWS observations. Official NWS observations measured 6.5 inches new snow in 12 hours, and 9.3 inches storm total. The peak total was observed by a co-op observer 4 miles ese of Fort Shaw, who measured 13.4 inches over 24 hours ending 7 AM MDT the 19th. The co-op observer located three miles east/southeast of Sand Coulee had an event total amount of 14 inches. Co-op observer located about four miles south of Sun River reported an event total snow amount of 15.7 inches.

Heavy Snow in WESTERN AND CENTRAL CHOUTEAU COUNTY, MONTANA
From 18-APR-23 11:00:00 to 19-APR-23 09:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Two social media reports were submitted for the Highwood area. Both reports featured snow of 10 inches or more through the morning of 4/19. The report with the greatest total was 10.5 inches.

Heavy Snow in SOUTHERN HIGH PLAINS, MONTANA
From 19-APR-23 17:00:00 to 20-APR-23 09:30:00 (MST-7)
Reported by: Trained Spotter

Trained spotter two miles southwest of Augusta reported 11 inches new snow for an event total.

Heavy Snow in SOUTHERN ROCKY MOUNTAIN FRONT, MONTANA
From 19-APR-23 13:00:00 to 20-APR-23 01:00:00 (MST-7)
Reported by: SNOTEL

A persistent band of moderate to heavy snow resulted in high snow amounts. The Dupuyer Creek and Mount Lockhart Snotels both estimated 7 inches new snow over 12 hours or less. Mount Lockhart estimated 10 inches in 12 hours with Dupuyer Creek reporting 7 inches in 8 hours.

Heavy Snow in GATES OF THE MOUNTAINS, MONTANA
From 18-APR-23 17:25:00 to 20-APR-23 15:26:00 (MST-7)
Reported by: NWS Employee

NWS employee observed 7 inches new snow over 12 hours ending 625 AM MDT 4/19. Storm total snow for the employee was 10 inches. Additionally, a public report was received of 8 to 10 inches on the northeast side of the Missouri River in the Helena Valley area, just inside the Gates of the Mountain zone. A COOP Observer in the vicinity of Adel had an event total snow amount of 22 inches.