The March E-mini S&P 500 future (ES) has rallied aggressively off the February 11 low of 1802.50, trading near 1993 at 10:40 AM on March 4. Despite the rally, this is still a bear market. The price is well below the July peak of 2110, as well as a series of peaks that occurred during November and December. Those latter peaks form a strong resistance area, which this rally--if it continues--will likely be halted by.
Since mid-2015 the bars around each peak have formed a barrier for the next peak. These areas are marked by grey boxes on the chart. If the price continues to rally it will eventually hit major resistance between 2047.5 and 2075--a wide range due to the wide-ranging bars that formed the most recent top.
Figure 1. March S&P 500 Futures, Daily Chart
Until that resistance area, the S&P 500 has some room to move. Unfortunately, strong resistance up near 2050 doesn't mean the market will go there. It could start falling before then. Currently the price is in another minor resistance area between 1983 and 1995 (blue box), where the price broke below support in early January. If the price stalls in this minor resistance region--moves sideways for a couple sessions and then starts to drop--short-term momentum will likely shift back to the downside.
If the price continues to drift higher, the next major shorting opportunity is near 2050, as the price enters resistance from the former highs. If the price does reach those highs, it will have run a long way and buyers will likely be exhausted.
Short-term momentum is up, but this is still a bear market. That could change eventually if the price starts making higher highs and higher lows again, but for now, odds favor picking good trade spots on the short side.