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Public Information Statement
National Weather Service Spokane WA
251 PM PDT Mon Mar 24 2025

Wednesday night and Thursday: The upper level ridge will begin its breakdown Wednesday evening as a deep upper level low offshore begins to move inland. Following the warm, moist start to the day on Wednesday, models are showing MUCAPE by the afternoon of 500-1500 J/kg across eastern Washington and the Idaho Panhandle, and up to 1000 J/kg in central Washington. Strong southerly to southwesterly flow aloft and light surface winds ahead of a slow moving frontal boundary will also result in 30 to 50 knots of 0-6km shear. While this raises flags for the potential of stronger to severe thunderstorms and definitely needs to be monitored over the next day and a half, there is little lift and a large amount of convective inhibition (CIN) during the later afternoon and early evening. Some deterministic models show strong enough impulses moving into central and eastern Washington during the afternoon that could potentially overcome the amount of CIN in the atmosphere, but the stronger lift is currently projected to arrive after sunset while the surface instability begins to wane. This would lessen the overall ingredients for severe thunderstorms, but continued elevated CAPE overnight would still support nocturnal thunderstorms.

By early Thursday morning, a front will slowly shift into eastern Washington and bring a 10 to 20 degree drop in temperatures and widespread precipitation to the region. Drier air will filter in behind the front, but weak instability continues in the afternoon with shower and thunderstorm potential remerging Thursday afternoon for far eastern Washington and north Idaho. Snow levels will decrease to pass level with snow showers for Stevens and Lookout Pass. Winds will also be breezy on Thursday with gusts 25-35 mph in the unsheltered areas. Locally higher gusts possible in the lee of the Blues and near the Upper Columbia Basin and Waterville Plateau.

Impacts: If stronger to severe storms develop Wednesday afternoon and evening, wind gusts up to 60 mph and heavy rain look to be the primary impacts. Winds could result in tree damage along with isolated power outages. If heavy rain from thunderstorms occurs over sensitive locations such as smaller creeks and streams or snow-free slopes and burnscars, and then is combined with additional precipitation with the front, impacts from rises on the creeks and debris flows or rockslides will be a concern. Currently, the burnscars without snow are the Swawilla burnscar on the Colville Reservation and the Gwen burnscar in Nez Perce County.

Friday through Sunday: Weather will remain cool and unsettled through Saturday as weak waves move through and bring potential for mountain snow showers and lowland rain. Ensembles then show a quick break from weather as weak and transient upper level ridge shifts into the Inland Northwest on Sunday. /vmt