The whole Lent-to-Easter thing has a very definite flow to it. Moving from Ash Wednesday through the Sundays of Lent, from Palm Sunday to Triduum and finally Easter, there’s a definite progression to what’s happening at Mass.
But there are breaks in that flow at daily Mass. Last week it was St. Joseph, today it’s the Annunciation. Why?
Because there are people and things that are also on the calendar this time of year that are too important to lose sight of during Lent, like St. Joseph. And in the case of today’s solemnity, the Annunciation, those things are closely connected to the whole Lent-to-Easter thing.
When you hear today’s Gospel, listen to what is said about the child that Mary will give birth to. If you think about all that the angel says this child will do and will be, it makes sense that Jesus’ entry into Jerusalem would turn into the royal reception found in Sunday’s (pre-Mass) Gospel. This is the backstory for Palm Sunday.
Readings for the Annunciation: http://www.usccb.org/bible/readings/032515.cfm