Final answer:
Using the alternate static source causes the airspeed to be overindicated and the altimeter to show a higher altitude due to the shift in static pressure the instruments experience.
Step-by-step explanation:
When using the alternate static source, airspeed indications will typically increase, and pressure altimeter indications will increase as well. Due to the change in the static pressure that the instruments are exposed to, variations occur because the alternate static source is normally located in a place within the aircraft where the pressure is slightly higher than the outside air. This results in the airspeed indicator overreading and the altimeter showing a higher altitude than actual because the instruments sense a lower static pressure than is present outside the aircraft, which is normally the case when the normal static source is used.