Plant closing and notice period questions after 15 years as an office manager

My employer announced that the site will close and gave us written notice. It has been a long 18 weeks. I do not know if I should start looking now or wait for severance news. Should I stay for the bonus?

Thanks for writing this out. I went through something close to it 5 months ago, and it got easier once I kept a simple log of every call and form.

Write down key dates and keep copies of the notice. Mine helped when a question came up later.