I think 能 might be misspelled, it might have been 熊, otherwise it doesn't make sense. But still "There is a tall bear ahead" is not good enough to get across, what does it really mean?
It is apparently a Japanese phrase commonly seen in Japanese anime.
"Front high-energy" is generally considered the earliest from the "Mobile Suit Gundam" series. Refers to the space battle ships (or mobile suits) travel in space, for safety reason, will always sweep for high energy reactions. If detected a high energy reaction, The pilot can decide to take evasive action or prepare to engage enemy.
In the videos from ACGN network. The message "前方高能" (High energy reaction detected in front) would often appear on screen. Whenever it does, the two enemies are in a collision course, intense battle will begin shortly.
Nowadays, they also use this phrase to announce upcoming exciting sequence of all kinds, not just for battle
It is Japanese Kanji, in China, it means the upcoming will be exciting/ shocking/ amazing/.
Another words is 高能预警: warn for upcoming.
When you watch an online video, you may see 弹幕 like this:
"前方高能" (The upcoming scene is amazing/ shocking)"
"高能预警, 非战斗人员速速撤退" (warning, the following scene is amazing, you don't want to miss it.)
The phrase is currently mainly used for warning that "something" special/shocking is about to happen.
前方: literally "ahead", here meaning "soon".
高能: literally "high energy", here meaning "great impact" and further into "something shocking", it could be either positive or negative.
Being put together makes it sounds more like "Warning: We are about to take great impact, please tighten your seat belts".
So the phrase is often used as a notification when you want yourself prepared for what's about to happen.
Note that the phrase "高能" is also used seperatly for "shocking"(as adjective).