morning; forenoon
Refers to the time from morning until just before noon. Often used as a time reference in schedules or descriptions.
The rain will probably stop by late morning.
I'll head to Tokyo on a late-morning flight.
just before noon
Specifically the period immediately before noon, often implying the late morning hours around 11 a.m. to noon.
Please give me a call just before noon.
I finished my homework before noon.
It started raining from late morning.