An upper level ridge of high pressure remains the dominant weather feature across the Inland Northwest today. At the same time, a weak shortwave trough is passing through Southern British Columbia, which has aided in enhancing south to west winds a bit across the Northcentral Washington, but is otherwise only spreading high cloudiness. Warm and dry weather will persist across the forecast area today, under mostly cloudy skies; temperatures will generally be a few degrees cooler than yesterday. Highs this afternoon will be in the upper 70s to lower 80s, which is still around 10 degrees warmer than normal for this time of year.
Our next storm system is currently situated over the eastern Pacific, and is expected to begin spreading precipitation across the Cascades around midday Tuesday. Precipitation might be spotty initially with the best chances remaining over higher terrain, with this system weakening as it nudges into the upstream ridge. At this stage, instability on Tuesday looks to be limited across much of the region with only a 20% chance of showers in the Wenatchee Valley tomorrow with highs cooling back into the lower 70’s.
By Wednesday, a deep and sprawling upper level trough visible on satellite this morning encompassing most of the Gulf of Alaska will send its initial cold front through the forecast area by Tuesday evening. We can expect a 30 % chance of rain Wednesday and a 50% chance on Thursday with afternoon high temperatures in the lower 70’s.
Several weak impulses of moisture will move through Northcentral Washington Friday, Saturday and Sunday bringing mostly cloudy skies and anywhere from a 20%-40% chance of scattered showers with afternoon high temperatures staying around 70 degrees with overnight lows in the upper 40’s.