The weather over the Inland Northwest today will be influenced by two features; a broad area of low pressure ejecting northeast through the Intermountain West and a second will be a shortwave approaching from the north. The combination of these will result in an upward trend of afternoon instability, and increasing risk for showers and possible thunderstorms. Confidence is highest over the Northern Cascades and Okanogan Highlands where weather models have been most consistent. A few weather models suggest some storms will survive the trip into the lower terrain along the Highway 97 corridor between Omak and Wenatchee and around Grand Coulee and Wilbur. While brief downpours will be possible with this activity, today carries a low threat for flooding with storms expected to be moving southward at 15-20 mph.
Wenatchee Valley weather today calling for sunny skies and light northwest winds with afternoon highs in the lower 80’s.
Friday will be quite unsettled across Northcentral Washington as low pressure deepens while dropping south through Central Washington. This event will get going early Friday morning with showers expected to blossom across much of Eastern Washington as a cold front swings inland around the base of the low. Cannot rule out a few rumbles of thunder during the early morning hours given modest lift and steep lapse rates but the focus for slow moving thunderstorms capable of heavy rainfall will during the afternoon following a few hours of heating. Just about every location will stand a shot for showers and thunderstorms during the afternoon hours with a 50% chance in the Wenatchee Valley, highs in the mid 70’s. The greatest risk of heavy thunderstorms will focus north of a line from Chelan to Ritzville to Pullman but cloud cover is likely to create a chaotic environment for pockets of better instability. The concern however, will be the slow movement of the weather cells and if sun breaks are ample, cells will be capable of a quick half to three quarters of an inch before collapsing. Gusty west to southwest winds will develop on the southern periphery of the low impacting Wenatchee, Ritzville, Pomeroy and Pullman. These winds will be associated with the strong cold advection and feature speeds of 15-20 mph with gusts near 35 mph.
Unsettled weather in the forecast for Saturday as well as a trough of low-pressure drops south along the British Columbia coast. There is a 40% chance of rain with much cooler temperatures behind the cold front with afternoon highs in the lower 70’s. Moisture remains quite deep and this will bring the potential for another round of localized heavy rain.
On Sunday, high pressure takes over our weather pattern with partly cloudy skies and high temperatures in the upper 70’s. For Memorial Day on Monday the forecast couldn’t be better with mostly sunny skies, light wind and afternoon high temperatures in the lower 80’s.
For Tuesday and Wednesday, the Inland northwest will be caught between a deep low pressure system in the Gulf of Alaska and another up by Hudson Bay in Canada. That puts Northcentral Washington in a rather dry west-northwest flow. Under mostly sunny skies each day, afternoon high temperatures will reach the mid 80’s, around 5-7 degrees above normal for this time of year.