Mt St Helens eruption, as photographed by NOAA GOES-3 satellite.
These videos provide a glimpse of what I (and other people in the area) experienced in the aftermath of the Mt St Helens explosion:
Ash that I collected off the hood of the neighbor's car:
A jar of Mt St Helens Ash from the 0832 eruption on 18 May 1980.
This explosive eruption sent ash 24,400 meters (80,000 feet) into the sky,
generated an earthquake of magnitude 5.2, made a sound that was heard
hundreds of miles away (I heard it in Spokane, 300 miles away), killing 57
people and thousands of birds and animals.
Image: GrrlScientist, photographed 14 April 2010 (this jar of ash was
produced by the 18 May 1980 explosion and was collected from the hood
of a car in Spokane, Washington).
I remember it was a hot and brilliantly sunny day. The sky was a perfect pale blue. In the early afternoon, a black cloud arrived, carried on strong, cold winds, and within half an hour of first seeing this cloud on the horizon, the entire city was engulfed in darkness and then ash began to fall. The ash looked like snow, but it was hot outside -- very confusing! The city was blacker than night for many days, and for many weeks (months?) after wards, the sun was only very weakly visible, always fuzzy and often looked orange or red due to the ash in the air which refracted the light into lovely colors. I never returned to Spokane again, although I explored the state for many years after wards in my many birdwatching trips. Depending upon your distance from the volcano, the ash is very different in size and character. There are still places in the state where the ash has formed drifts that are very tall. You can easily find this ash if you dig down below the plants and the thin layer of soil on top.
Being over on Vancouver Island I remember a deep bang that was apparently the eruption itself. And then, a couple of days later, the ash you mention began falling over everything (including over my dad's car, which I had to wash). A buddy of mine left a couple of vinyl LPs out that were ruined by the acid content of the dust.