Maybe not. Under both state and federal law, docking a salaried employee's pay for partial-day absences may result in destroying the exempt status of the employee. But there are several exemptions to this general rule. As just one example, if the absence fell within the FMLA or the Washington state equivalent, the employer could dock pay for the partial-day absence. In addition, if an employer intends to dock a leave bank rather than pay, the docking would probably be permitted. The rules regarding docking pay for partial-day absences differ form the rules regarding docking leave banks.
My comments are not intended to form an attorney-client relationship with the person who posed the question or any reader. Also, nothing stated is intended as, and should not be construed as, legal advice. If you seek legal advice concerning any matter, you should consult competent counsel.