Through the close of trading Wednesday, the Russell 2000 has been up nine days in a row. If it can hold on to its midday Thursday gains, that would be 10 days in a row. That might seem like a rare feat, but it's happened 19 times since the late 1980s.
Whether or not the small-cap index closes up Thursday or falls to start a new down streak, basic probability tells us that we will get this kind of streak every once in a while. It's like the illusion of a "hot hand" in basketball: Even a totally average player will have a long scoring streak on occasion.
In the case of the stock market, we can show that its streaks aren't too far off from flipping a coin. When we run a simulated coin flip thousands of times, we get a very similar pattern of "up" streaks. The big-cap S&P 500 is nearly identical to our coin flips. The Russell 2000 is made up of small-cap stocks and is more momentum based, so we see a few more long streaks than you'd expect at random.