Showers and thunderstorms forecast to develop Thursday and Friday may cause localized flooding in northeastern Washington, north Idaho and the Spokane area.
The rain event will be more widespread and “wetter” than the typical afternoon showers and thunderstorms that periodically blossom above the Inland Northwest in the summer months, according to National Weather Service meteorologist Charlotte Dewey.
“That is some of the difference. These thunderstorms will affect a larger portion of the region,” Dewey said. “We are going to see a large area that could see flooding impacts.”
The atmosphere above the Inland Northwest has more water vapor content than usual, meaning the storms that do develop are likely to produce heavy rain. And in contrast to typically summer storms, which fire up in heat of the day and diminish after sunset, the storms this week will have enough energy from an upper-level low pressure system to stay active longer.
“It’s a strong enough weather system that we will see those thunderstorms develop Thursday, and…the thunderstorms transition to rain showers Thursday night into Friday,” Dewey said.
In anticipation of the rain and potential flooding, the National Weather Service issued a flood watch for six counties in Washington and eight in Idaho, from Okanogan to Spokane to Shoshone. The watch runs through Friday morning.
Flooding is possible in urban areas, highways, low-lying areas and places with poor drainage. Burn scars in steep terrain will also be susceptible, the Weather Service said.
Less rain is expected in the Columbia Basin, Dewey said, so no flood watches were considered necessary as of Wednesday evening.
A preview came Wednesday afternoon, when showers over Shoshone County, Idaho, produced one to two inches of rain in a short time. The rain prompted a flood advisory for areas north of Pinehurst.
The rain is not expected to insulate the Inland Northwest from drought this summer. That kind of help depends on a sustained pattern of rain, Dewey said, and this week’s intense but short-lived rainfall will likely not provide much beyond short-term benefits. Dewey also noted that lightning generated by thunderstorms can ignite wildfires.
