It appears to me that when stocks go up based on some news or other, they do their climbing in the morning, soon after the markets open, and regularly spend the rest of the day giving back much of the gain.

Is this enough of a pattern to be useful?

There are sometimes buy the dip markets and sometimes sell the rip markets. If you can pick which is which (or when it's nothing, which is more common), or if the market you're on aligns with your personality, you'll do well.

The pattern you note will be perfectly useful/profitable until it unwinds and you go broke trying to keep applying it. Confirmation bias is a serious cognitive flaw that humans have and happens in as little as a few trades.

The better way is to think about the factors that go into making people scared or hopeful or greedy and noticing where things are in that regard. That's a part of the equation - another is realizing when large holders are shifting assets and why. For example, the recent turmoil in the markets started exactly when bonds took out 52 week lows two months ago and an asset reallocation began as bonds returns got on people's radar and risk models had to be reweighted.

Just make sure the stock that ripped isn't heavily shorted. It will often rip further or at least be very unpredictable with wild swings

buy the rumor, sell the news

I'd rather trade the opposite side buying the retrace from the rip since you can establish clear take-loss / take-profit points