Jeffrey Weiss, chief technical analyst at Tejas Securities, says the benchmark S&P 500 index has been in a nearly 400-day bullish upside reversal pattern since November 2012.
"It's that pattern created then," said Weiss, "that I believe has been the fuse or the spark that helped ignite this market rally that has taken the S&P  from the mid-1,300s area to where it is now."
Weiss sees the pattern remaining for the time being. "I don't see enough evidence to tell me that the primary trend of this market has yet gone negative or that the bears have done enough to pierce the bull's primary trend armor," he said.
The first key level in the S&P 500 that Weiss is watching 1,920, the current level of a trend line in his short-term daily chart. That trend line previously had served as resistance until the end of last month, when the index crossed above it. He now sees it as support.
Should the S&P 500 break below the 1,920 level, there's a second line of support, according to Weiss' chart of weekly closes for the index going back to 2011. Like the shorter-term support line, it was once resistance—first in February 2011 and then again in August 2013. The line then became support when the S&P 500 crossed above it in October. It subsequently held after two tests in the last several months.
"That line next week should be in the 1,840s on a weekly close," said Weiss. "Despite the fact the market has gone a long way, these lines are holding. What concerns me is the fact that you never know what happens in this business."
To see the full interview with Jeffrey Weiss on what's next for the S&P 500, watch the above video.