Why NOW could be the perfect time to sell Antofagasta plc, 88 Energy Limited and WM Morrison Supermarkets plc

Today I'm looking at three stocks in peril of fresh share price weakness.

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Copper calamity

With copper prices heading south again, I believe now is the time for investors to sell out of Antofagasta(LSE: ANTO).

Three-month futures at the London Metal Exchange have slipped to their cheapest since February, hitting less than $4,600 per tonne today as fears over chronic oversupply grow. Indeed, Bank of America-Merrill Lynch estimates that 670,000 worth of mine supply losses are required to balance the market this year.

And this gross imbalance threatens to persist well beyond this year, in my opinion. With monster projects like BHP Billiton's Escondida and Rio Tinto's Oyu Tolgoi in the throes of expansion, and China's economy expected to keep on decelerating, concerns are rising over who exactly will suck up this excess material.

And with Antofagasta dealing on a mega-high prospective P/E ratio of 57.7 times, I reckon this leaves plenty of room for a correction should -- as I expect -- newsflow across the copper segment fail to improve.

Driller in danger?

Oil explorer 88 Energy's(LSE: 88E) share price has trended lower again in recent months as previously-bubbly investor appetite has failed to recover.

There's no doubt that the company's Icewine asset in Alaska offers terrific potential. 88 Energy advised in February that exploratory work had revealed an asset with "world class resource prize potential," news that sent share pickers piling-in.

And in April 88 Energy successfully raised A$25m via an oversubscribed share placing to continue work at the project.

Still, the nature of dragging raw materials out of the ground is always an unpredictable business, where operational setbacks -- or indeed downward revisions to potential payloads -- can have a significant impact on future revenues. And for small, cash-tight operators like 88 Energy, this is a particularly risky business.

With the company also facing the impact of weak crude prices once, or indeed if, maiden oil is struck, I reckon 88 Energy is a risk too far for cautious investors.

Supermarket strain

With the fragmentation of the British grocery space set to intensify, I reckon Morrisons (LSE: MRW) is a sure-fire sell for shrewd investors.

The Bradford chain has seen earnings slide during each of the past four years as rising competition -- and in particular the breakneck progress of Aldi and Lidl -- has dragged shoppers away from its doors.

The City expects Morrisons to kick back in the year to January 2017, however, with a 31% bottom-line rise. But I reckon a subsequent P/E rating of 19.4 times fails to reflect the risks of such forecasts being met, not to mention the firm's lukewarm long-term growth prospects.

Latest data from Kantar Worldpanel showed Morrisons' market share slip again during the 12 weeks to May 24th, to 10.7% from 10.9% a year earlier.

And with the discounters investing heavily in their in-store and online operations, I expect Morrisons' customer base to keep on toppling. And at current share prices, I reckon now is the time for shareholders to cash in.

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Royston Wild has no position in any shares mentioned. The Motley Fool UK has recommended Rio Tinto. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.