Weather forecasting -- changes in 24 hours

Yesterday, WRAL forecast the following for the rest of the week:

Tues: low 14, high 35,
Wed: low 17, high 45,
Thur: low 29, high 61,
Fri: low 40, high 69,
Sat: low 51, high 74,
Sun: low 53, high 72

Today, WRAL is forecasting the following:

Tues (today): actual (?) low 17, high 35, Once again WRAL forecast the Low below the actual low. No change in the forecast high.
Wed: low 15, high 47, Now forecasting both colder and warmer; each by 2 degrees.
Thur: low 29, high 61, Same.
Fri: low 40, high 71, Same low; high 2 degrees higher.
Sat: low 51, high 74, Same.
Sun: low 50, high 60, Low is 3 degrees lower than yesterday's forecast; high is a WHOPPING 14 degrees lower.

Why they forecast six to seven days out?
Why do we pay any attention six to seven ahead?

Will watch how this plays out through the week and into the weekend.