They should, although newly planted ones may take a season or so to adjust and settle in before putting on much of a flower show. They bloom consistently in my zone 8 and winter temperatures here can be quite mild - mostly in the 40's and up with just a couple of light frosts - and sometimes not so mild (dipping into the teens now and again) :-) BTW, witch hazels are just starting their bloom sequence right now in my area.

Mine is blooming like crazy right now, and our temps have been around 50s in the day, 40s at night... weather here is generally a lot like that of the PNW. I planted mine just last September. So I'd say you've got a good chance!

My Chinese witch hazel is pretty much full out. Yours may bloom fairly soon, too, just being a little later because you are a couple zones lower.

Oh! You better watch out,
You better not cry,
You better not pout,
I'm telling you why:

Hamamelis is coming to town!