I was just a "childins" when Mt. Saint Helens blew up in Washington. I remember being so mad that we could not go out and play in all the "snow". Keep your mask on, and as others have said, start filling pots and pans, and the bathtub with water, you can use it for drinking and cooking if it comes to that (I would boil it first, and make sure you wash the tub out as well as possible, but if it is needed, you will be glad to have some water).
In my town, smack dab in the center of Washington, you could not really drive a car for 3 days +. We just had to live on the food we had in the house. My dad had to go up on the roof, and shovel all the ash off to keep it from collapsing under the weight. He actually shoveled it all off the lawns too, and moved it with a bunch of trips in a wheel barrow down into a gully. The neighbors just left it on their lawn, and it has never recovered, even decades later, their lawn still won't grow right.
Keep it safe. If there is a bunch of ash, you might not be able to run your car (can cause the car to overheat if your radiator gets blocked, and can plug up your air filter etc).
I keep a couple of months food supply, a water filter big enough to supply my family with water for many many months (easy to use one, put any water in it and gravity fills the 5 gallon container through the filters).
I don't have the money, or the space right now for a full 2 year supply, but I would definitely be ok for a few months if it came to that (ammo, guns, knives, axes, camp stove that runs on any liquid fuel, and emergency food supply).
I was raised thinking you should have a 2 year supply of food and water (essentials etc.....nudge and a wink to Alaskanativeson on the LDS thing).
It is kind of easier for me, as my parents give us kids emergency stuff for Christmas. How many people's parents give them a few months food supply, water filter, and bug out bags for everyone in the family? It is the kind of gift that gives you a sense of security, and stuff you would have a hard time paying for (or making your self spend the money on).