ID flying insect (maybe giant yellow jackets?), Please!

I had 5 large noisy flying insects in my bedroom last night.  Here's a
description (sorry--I know nothing about flying insects, but I'll do my best
on the description).

These were slightly larger than a quarter from nose to end of abdomen (UW-M
website says yellow jackets are smaller than a penny).  These are hefty
beasts.  The made lots of buzzing noise as they flew and banged into walls
(probably didn't like being in there any more than I liked them being
there).  They have shiny abdomens.  If you look from the head end towards
the tail end of the abdomen, the first segment is black, the second segment
has three connecting  black "mountains" or triangles with the large one in
the middle, the third segment has three unconnected mountains (largest in
middle), and the next two have two unconnected mountains.  The mountains are
black, the rest is yellow.  I only see one set of wings.  They have a skinny
waist.  From the front, the face is yellow, but the eyes are brown and there
is a spot of black where the nose would be.

My questions:

What are these?  Why are they in my bedroom (this has never happened in the
four years we've been here).  The house has screens on all the windows.
Will they stay around this area long? Any advice on how to keep from
attracting these guys into the house?

Thanks!