An atmospheric pattern that remains stagnant for days on end is known as a "blocking pattern." One example of this is a "Rex Block."
A Rex Block happens when high pressure is located north of low pressure, as seen in the image below.
That flow results in a transfer of energy from north to south, but very little from west to east. The blue arrows in the following image show the "normal" west-to-east flow across the United States.
During a Rex Block, though, that normal west-to-east flow is not possible.