The strong upper level ridge which has been parked over the Inland Northwest for the past week will slightly weakened today by the passing of a weak upper level disturbance tracking through central British Columbia. This will briefly interrupt the recent warming trend, although the impacts will be quite subtle. The light southerly mid-level winds of yesterday will turn more westerly and increasing slightly in response to the passage of this system but only to around 5-10 mph. Temperatures today will be similar to yesterday, with afternoon high temperatures mainly in the mid-60’s. We should also see some passing high clouds today, although they could be thin and fairly high up in the atmosphere. For Friday, the ridge is expected to strengthen over the region in response to a deepening trough off the coast in the Gulf of Alaska. This will revive the warming trend across the area, although weaker winds and stronger inversions will inhibit efficient mixing and could lead to increasing pollution levels over many valley locations.
Beginning today through next Tuesday, the Wenatchee Valley will be under an air stagnation advisory. People with breathing problems may feel the effects. High temperature on Friday under Sunny skies will wartm a bit into the upper 60’s.
Saturday through Tuesday, Weather models continue to show the stubborn upper ridge over the area through Monday for a continuation of mostly clear skies, light winds, cool mornings, and mild afternoons with highs mainly in mid to upper 60’s. This pattern will continue to produce strong temperature inversions at night with limited afternoon mixing.
The ridge moves east on Tuesday allowing for a pattern change for the middle to end of next week as an upper level low pressure system passes Tuesday night into Wednesday. We have a 20% chance of showers on Tuesday and that goes up to a 30% percent chance of rain on Tuesday night and Wednesday. Afternoon high temperatures will also cool back to normal at around 60 degrees.