noun
flower front; cherry blossom front
A line on a map showing the advance of flowering, especially cherry blossoms, across a region. Often used in weather forecasts and seasonal reports. Compare 開花前線 (same meaning).
See also: 開花前線
今年の桜の花前線は例年より早く北上している。
This year's cherry blossom front is moving north earlier than usual.
天気予報で花前線の予想図を見た。
I saw a forecast map of the flower front on the weather report.
Specifically the cherry blossom front. 花前線 can refer to other flowers as well, though it is most often used for cherry blossoms.
Compound of 花 (flower) and 前線 (front, as in weather front). The term is modeled after meteorological fronts, indicating the northward advance of blooming.