Two valuable tells for a strong stock market: NYSE TICK stays positive through the day (top chart) and intermarket themes (from Barchart.com; bottom chart) favor commodities and a weak U.S. dollar.
Note how the moving average of NYSE TICK (blue line, top chart) consistently stays above the yellow zero line. That shows persistent buying pressure, as traders act on growth themes (demand for energy) and continue selling the U.S. dollar in favor of higher yielding currencies.
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