Heavy Rain and the Beginning of Autumn

Autumn began at 6:30 AM this morning and the atmosphere is clearly watching the calendar.

Tomorrow will bring the first of a series of wet weather systems,  each associated with a potent atmospheric river,  that will bring as much as TEN inches of precipitation to the northern Cascades and Olympics.   

As a result, wildfire season in Washington State will be coming to an abrupt close.

Precipitation will be heaviest during two periods, one tomorrow and the other on Saturday, when atmospheric rivers--narrow currents of large water vapor values--will make landfall on our coast.  

Here is the forecast atmospheric moisture content at 8 AM tomorrow (Wednesday), with the blue and white colors indicating the largest water vapor values.  When the water vapor current rises on our local terrain it is forced to condense, resulting in bountiful precipitation.

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