Weather 9-21-20

207

A couple of weak disturbances will push across the Inland Northwest over the next 36 hours or so. The first is still off the Northwest coastline. It`s expected to track across Northwest Washington and will spread mid to high level cloud cover, but lower levels will remain too dry for precipitation. What we will mainly see in Northcentral Washington will be some clouds today and mostly sunny skies on Tuesday with afternoon high temperatures mainly in the mid 70’s.

Weather models are all in good agreement for a moderate atmospheric river event settling over the Inland Northwest on Wednesday. As this large area of low pressure moves in on us, we will see cloudy skies Wednesday with a 70% chance of rain with highs in the mid to upper 60’s. By Wednesday night, much of the Inland Northwest will be within the target range of this weather system with widespread light to moderate rainfall. In Northcentral Washington Wednesday night, there is a 100% chance of rain with anywhere from .10 to .25 of an inch possible. This weather system is a sign of autumn and a transition out of the driest part of the year. Heaviest precipitation will be up at the Cascade crest with 2-3 inches of rainfall possible. There is some concern that moderate rainfall will result in mud flows off of recent burn scars across the region. However, much of the rain will come via stratiform precipitation and doesn`t look to contain the rain rates necessary for a significant flash flood threat.

Thursday through Saturday, the active pattern will continue as the upper level jet stream is aimed at the region with a mid-level weather system tracking through Thursday night into Friday for another round of showers and maybe breezy conditions. Under mostly cloudy skies, there is a 60% chance of rain on Thursday, a 50% chance Friday and a 30% chance of mainly scattered showers on Saturday, highs each day generally in the upper 60’s to lower 70’s.

Back to quiet and warmer weather on Sunday with sunny skies and afternoon high temperatures warming into the mid to upper 70’s.