Late today our weather will change to a more fall-like pattern. Northcentral Washington can expect increasing clouds throughout the day as a large area of low pressure starts to move inland from the pacific. The Columbia Basin and Wenatchee Valley will see mostly cloudy skies by afternoon with high temperatures in the mid to upper 70’s.
Wednesday is the part of the forecast that turns much wetter and a bit windy. There will be a virtual river of moisture directed at the Northwest, albeit a fairly narrow stream. Cloudy skies for Wednesday and a 50% chance of daytime showers going up to a 100% chance of rain by tomorrow night, highs in the mid to upper 60’s. There should be enough frontal dynamics with a slow enough progression of the front that communities such as Omak to Wenatchee to Ephrata and Moses Lake won`t be skunked with between 0.05 inches to around a quarter of an inch of rainfall expected by Thursday morning. Rain amounts will be much higher where upslope will be favorable including right at the Cascade crest, where between 1.5-3 inches is possible, and over the higher terrain from the Okanogan Highlands to the Idaho Panhandle where between 0.50 to 1.0 inches of total rainfall is expected. Winds also look to increase starting Wednesday with southerly pre-frontal winds to westerly post-frontal winds on Thursday. Winds on Wednesday will generally gust to between 20-30 mph and will be aligned up the Okanogan Valley.
As the weather system passes Thursday, Northcentral Washington will see breezy conditions, a 50% chance of showers with afternoon high temperatures in the mid to upper 60’s.
On Friday, weather models continue to show a mid-level wave tracking through for another round of showers. Expect mostly cloudy skies Friday with a 50% chance of widely scattered showers early with highs in the mid to upper 60’s.
Over the weekend the upper level jet stream begins to lift north as a flat ridge of high pressure develops. We will see just a slight chance for isolated showers Saturday and warmer temperatures with highs around 70 degrees.
Then on Sunday and Monday, the ridge of high pressure will bring a warming trend to Northcentral Washington with partly cloudy skies Sunday, mostly sunny skies Monday with afternoon high temperatures in the upper 70’s Sunday and around 80 degrees on Monday.