Thunderstorm Wind in Pend Oreille County, Washington

Thunderstorm winds knocked down trees which blocked State Route 211. Strong winds also led to numerous areas of tree damage between Newport and the Spokane County border along Highway 2.

A strong upper-level ridge during the end of July and beginning August helped fuel a moist and unstable air mass over the region. The ridge broke down on the 1st of August and was overrun by two weak midlevel impulses on August 2nd. As the second impulse passed over Central Washington during the late afternoon, strong to severe storms developed over the Waterville Plateau producing a combination of heavy rain and moderate size hail. Meanwhile, dewpoint depressions over Eastern Washington had grown between 40 and 50 degrees Fahrenheit. The rain and hail cooled outflow winds from storms over the Waterville Plateau spread east and gained momentum while tracking along the Highway 2 corridor across the Upper Columbia Basin. Additional storms fired along the gust front and continued to reinforce the cold pool and resultant winds. Gusty winds and blowing dust which originated over the Waterville Plateau traveled across Banks Lake and through much of Lincoln County but generally remained below severe speeds. It wasn't until the outflow boundary moved into Eastern Lincoln County and Lake Roosevelt near Seven Bays Marina when wind speeds ranged between 60 and 70 miles per hour. The winds led to numerous downed trees, waves four to six feet on Lake Roosevelt, widespread boat damage, power outages, and structural damage. The winds also fanned new wildfire starts from lightning. As the afternoon progressed, a combination of forcing from the shortwave and gust front continued to fuel additional storms over Northeastern Washington. Outflow winds from these storms generally moved north to south. As the north to south boundaries interacted with the westerly boundaries, some locations were spared experiencing wind gusts between 35 and 45 mph. In this absence, winds of 50 to 70 mph were observed coupled with widespread tree damage. A few storms briefly produced quarter size hail between Davenport and Northwest Spokane.