A River Runs Through Us

Today we are experiencing the unusual:  a relatively potent June atmospheric river, in which moisture from the subtropics is heading directly into our region.  

Substantial precipitation has fallen, helping to mitigate previously dry conditions from northern California to coastal Brtish Columbia. 

The radar image tonight says it all.....rain, some of it moderate to heavy, extending over western Oregon and Washington:


And a recent satellite image of atmospheric water vapor content shows an impressive moisture "river" extending from north of Hawaii to southern Oregon. 


Precipitation has been bountiful....and the event is not over by any means.  The event-total through 4 PM indicates about a half-inch over Puget Sound but 1-3 inches on the south side of the Olympics and 1-1.5 inches over SW Washington.  Very welcome, indeed, after a dry spring along the coast.


But if you really want to be impressed with the precipitation, head to southern Oregon and northern CA, where some locations have enjoyed over three inches (see below). That is serious rain.


Many locations will get around 50% more before this is all over tomorrow morning.

Several of you have emailed me about the humidity.   A number of locations in our region have had dew points jump into the lower 60s, which is very high for this time of the year.  In fact, we are almost certain to break a few monthly dew point records.  With high dew points, our relative humidities have hovered above 90% for the last few hours, including 100% at SeaTac Airport (see  5 PM plot below).  But if you want much drier conditions, head to eastern Washington, where values drop into the 20s!


The murk of the saturated air and accompanying fog is evident in a recent KING-5 weather cam (below).  


This multi-day event is hardly over, and rain will push over the Cascades and across the eastern slopes of the barrier;  the precipitation is very, very welcome since it will put the "damper" on wildfires for a while.

Here is the latest European Center model forecast for the total precipitation over the next 48 hours. Substantial rain over the Cascades and far eastern Washington.  Expect some thunderstorms in the mix during the next few days---more on that in my next blog.


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