The weather pattern on August 10th featured a very moist and unstable air mass with a passing upper level low pressure. These elements promoted widespread thunderstorms with heavy rain which produced Flash Flooding over potions of eastern Washington. Local observations indicated some of these slow moving storms produced from 1 to locally in excess of 5 inches of rain. Particularly hard hit was the Wenatchee area where flash flooding was reported in gulches and canyons emptying into the city. These floods produced severe damage to at least three mobile homes in Wenatchee.
Elsewhere heavy rains flooded sections of Highway 2 on the Waterville Plateau and the area around Elk and Chatteroy north of Spokane received up to 5 inches of rain from a stationary thunderstorm which produced scattered flooding of streets and driveways, water in basements and washouts on hillsides. There were also isolated reports of hail with diameters of up to 1 inch with some of these storms.

Flash Flood in CHELAN, WASHINGTON
From 10-AUG-19 16:15:00 to 10-AUG-19 18:00:00 (PST-8)
Location: SOUTH WENATCHEE
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Heavy rain from a thunderstorm eroded a culvert and hillside above the Squilchuck Mobile Home Park resulting in three mobile homes being buried up to their roof lines with mud and rocks.  Residents in 16 other nearby homes were advised to evacuate until the hillside stabilized.

Flash Flood in CHELAN, WASHINGTON
From 10-AUG-19 16:15:00 to 10-AUG-19 18:00:00 (PST-8)
Location: SOUTH WENATCHEE
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Newspaper

Numerous streets in the southern portion of Wenatchee were reported as flooded and residents were advised to avoid travel in the area. Mud and debris flows in the Squilchuck, Pritcher and Halverson Canyons flowed down these canyons and into the city. In addition heavy rain in the city of Wenatchee backed up storm drains and sewers and contributed to the flooding.

Flash Flood in FERRY, WASHINGTON
From 10-AUG-19 17:50:00 to 10-AUG-19 18:25:00 (PST-8)
Location: KELLER
Flood cause: Heavy Rain / Burn Area
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Firefighters on the Williams Flats Wildfire reported numerous roads washed out due to heavy rain from a series of thunderstorms passing over the burn area. An estimated 2 inches of rain from persistent thunderstorms impacted the active fire site. Sixty four firefighters were stranded overnight when their access road was washed out by a flash flood during the evening of the 10th. They were successfully extracted the next morning using an alternate route.

Flash Flood in CHELAN, WASHINGTON
From 10-AUG-19 14:00:00 to 10-AUG-19 16:00:00 (PST-8)
Location: WENATCHEE HGTS
Flood cause: Heavy Rain
Property damage: 0.50K
Crop damage: 0.00K
Reported by: Law Enforcement

Water was reported flooding across Squilchuck Road near Halverson Canyon Road due to heavy rain from a thunderstorm.

Flash Flood in DOUGLAS, WASHINGTON
From 10-AUG-19 18:00:00 to 10-AUG-19 19:00:00 (PST-8)
Location: DOUGLAS
Flood cause: Heavy Rain
Property damage: 0.50K
Crop damage: 0.00K
Reported by: Law Enforcement

Mud and debris from thunderstorm heavy rain blocked State Route 3 miles east of Douglas.

Flash Flood in DOUGLAS, WASHINGTON
From 10-AUG-19 18:00:00 to 10-AUG-19 19:00:00 (PST-8)
Location: WATERVILLE
Flood cause: Heavy Rain
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Water was reported over State Route 2 and flooding into an adjacent house east of Waterville due to thunderstorm heavy rain.

Hail in GARFIELD, WASHINGTON
From 10-AUG-19 15:30:00 to 10-AUG-19 15:35:00 (PST-8)
Location: POMEROY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A member of the public reported hail with a diameter of 1 inch from a thunderstorms near Pomeroy.

Hail in DOUGLAS, WASHINGTON
From 10-AUG-19 14:10:00 to 10-AUG-19 14:20:00 (PST-8)
Location: WITHROW
Magnitude: 0.77 
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Public

Dime sized hail from a thunderstorm near Withrow produced crop damage.