Weather 9-15-21

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This morning, we have an upper level trough sliding into southcentral British Columbia and an associated jet stream pushing into Vancouver Island with a tight pressure gradient aligned with the Cascades. Breezy and gusty winds through the Cascade Gaps into the Columbia Basin will be likely through the day today. Northcentral Washington weather forecast today will be partly cloudy, cooler and breezy at times with afternoon highs in the lower 70’s. 

Thursday to early Friday our main weather event begins to take shape for the Pacific Northwest. The cooling trend also continues as we head into late in the week. Thursday’s weather will feature increasing clouds, light winds and seasonably cool temperatures with highs near 70 degrees. 

On Friday, a large area of low pressure pushes a plume of moisture into the state brining us a 50% chance of daytime rain showers going up to a 90% chance on Friday night, highs in the mid 60’s. The orientation and track of the moisture plume is such that the Cascade rain shadow effect may not play as big a role in this atmospheric river event meaning central and eastern Washington should fare well with rainfall amounts. 

A cold front passes through early Saturday morning will bring some breezy conditions and a 70% chance of rain with highs still cool into the upper 60’s. 

Another saturated shortwave of low pressure will arrive on Sunday which means the Inland Northwest can expect another round of widespread showers. Northcentral Washington weather on Sunday will be cloudy with a 70% chance of rain, highs in the mid 60’s. 

A ridge builds of high pressure builds off the coast on Monday and Tuesday and stops the moisture flow into the region. Both days will be mostly sunny and seasonably cool with afternoon high temperatures right around 70 degrees.