For the second day in a row, the convection and thunderstorms developed over the Cascades and rolled into the western lowlands…in this case hitting southwest Washington, Portland, and the northern Willamette Valley.   Mark Albright, past WA state climatologist, reported that an observer in downtown Vancouver just W of I-5  reported 0.40 inches of rain in 5-minutes from 19:29 to 19:34 PDT 26 May 2012.  The highest hourly amount from the Portland Hydra network (46 sites) seemed to be the 1.34 inches over one hour from 19:00 to 20:00 PDT reported at Hayden Island just west of I-5.

Take a look at the Portland radar at 7:26 PM Saturday….see those reds?…that is torrential rain.

Here is the storm total precipitation from the radar…you can see the track of the heavier rainfall.