The answer is yes, and so far as I know Walla-Walla is the one for long-day zones. I planted some also this year but the germination was terrible.

The storage onions will bolt, most likely.

I have onions that I miss digging every year. They survive just fine up here in Minnesota with no cover. However, they run to seed as soon as they are up the next year and are pretty worthless as storage onions. I use the seeds for scallions.

Start onions from seed as EARLY as possible. I'll probably start mine in January this year. The earlier, the bigger the bulb i think. I've heard of people starting them around Christmas (the long day types). I grow mine in containers and get some pretty massive bulbs (softball size). I harvested about 20-25 bulbs this past season that are sitting in the basement. I don't use a lot of onion, but they are fun to grow.

I generally agree with those who say starting onion from seed is a waste of time. I am aware of some who do it successfully, but those who wish to get good sized bulbs in the first year from seed really need to start very early. Probably around the time you are opening Christmas presents early. They take a long time. Also, you need good artificial lighting as natural sunlight is weak and day length short at this time of year. If you have a heated greenhouse maybe you don't need artifical lights, I dunno. I grew my onion from seed under 400 watts of HID lighting and that didn't seem to be enough to get them to transplant size when starting in February.

The most reliable method I know of is to purchase onion plants from a reliable supplier like dixondale farms. A cheap option, particularly if you don't care about variety distinctions beyond red, yellow and white are onion sets.

If you want a perennial onion that will go on forever look into the multiplying onions. They tend to be fairly strong rather than sweet, but you will have onions all year. You can even chisel them out of frozen ground if so inclined. If you like the greens, you will always have that except during the sub freezing period.

Start your seed onions the day after Christmas, or at least by January 1st. Transplant them outside in the spring if they are as big as a piece of spaghetti. You'll end up with a lot of really good onions. Seed onions will get bigger than sets every time. I don't use supplemental lighting but do grow in a heated greenhouse.
I plant them outdoors in early spring, or at least by May here, in a double row about 4" apart X 4" between the rows and run a soaker hose straight down the center between the rows.Sprinkle a little 10-10-10 down the center. Mulch with shredded leaves. That keeps the water in and the weeds out. Water when needed by hooking up the hose.
We had lots of onions that weighed a pound and more using Utah Sweet Spanish seeds.
and you're good to go!