One of the best runs for small stocks in 20 years

The small-cap Russell 2000 is continuing its impressive run Friday despite broader weakness. If it holds up, this will be its 33rd consecutive day trading above its 10-day average.

It's rare to see runs this long above such a short-term moving average. Because it's a shorter time frame, it hugs prices more closely, so it's easier for an index to gyrate above and below it. A run of 33 days is among the longest in 20 years.

Momentum doesn't die easily, and that was the case here. The next 2-4 weeks tended to be good for the index, but over the next 3 months it settled back quite a few times.

If the run coincided with a 52-week high, like now, then it was undefeated over the next couple of weeks.

By the time the Russell has (almost) doubled off of a low, it fell back over the next few months every time. Based on its current momentum, we might have a wait a bit to see if that tendency is going to come to fruition this time.