USGS/Cascades Volcano Observatory Report:

Since about 2 am PDT on the morning of 09/23 an earthquake swam has been occurring at Mount St. Helens. Through 5 P.M. PDT about 200 small (less than magnitude 1) earthquakes have been recorded at MSH. The earthquakes are occurring at shallow depths (less than 1 kilometer, or 1/2 mile) mostly under the lava dome that formed between 1980 and 1986. Such earthquakes are common at St. Helens, but a swarm with this many earthquakes has not been recorded for several years, most recently on November 3-4, 2001. The cause of such shallow swarms is uncertain, but may reflect increased ground water levels with the onset of autumn rain. Any eruption is unlikely to occur without significant additional precursory activity.

I grew up in the Seattle area and May 18, 1980 is one of those dates that just sticks in your memory. I'm sure it sticks even better in the minds of those who lived on the east side of the state and who were buried in ash.