With Poa annua it seems there is no normal or expected behavior. PA as an annual should only last one season, dying after it seeds in the spring. Unfortunately there are hundreds of varieties of this weed. Some varieties are perennials, and don't die in the summer. Here's a good link:

http://msuturfweeds.net/details/_/annual_bluegrass_47/

I think my only hope to get rid of them is to pull them. Ive heard there is no post emergent that wont kill the cool season grass i have. So pull them and over seed here in a few weeks. Then use a pre emergent next fall. Its either that or let them live. any thoughts?

There are some people out there that are having success with Tenacity. Ethofumasate (Prograss) is a selective herbicide that targets poa annua. Velocity is another one, but that one might be restricted to professionals only, and it can cause temporary harm to KBG. A good anti-poa annua strategy involves regular preemergent applications, especially in late summer, and late winter/early spring. Controlled round-up application will obviously kill poa annua, but if you don't have a spreading grass like KBG, those areas will remain bare, but you can always plant some grass in pots to fill in the bare areas since you will have a preemergent barrier down.

Thanks for info. I found quite a few discussions on some of these Post emergents.Supposedly there are a couple brands called Poa Constictor and Norton SC that are less expensive than Prograss.($500 2.5 gallons!!!) However I cant seem to find anywhere to buy them. Are these commerical grade products that only licensed guys can get?

Most of the products you and I mentioned are geared towards professionals, so they come in gallon sizes because they have a lot of area to treat. A gallon or two of Prograss will last the average homeowner a lifetime. Tenacity is available for $50 dollars for 8 oz., and that will last a long time, but you also need to mix it with a surfactant. Most of the heavier duty stuff you mentioned are sold at EH Griffith's and Lesco/John Deere. There is probably a Lesco near where you live.

thanks for Info. It seems that Tenacity is the way to go and was recently approved for home use. Now if I can just get two or three days of no rain.

Oregonandre...I am curious as to how well the Tenacity worked for you. I am in Hillsboro and I am seeing poa come up...unfortunately, I mowed and didn't bag :(