May Nymex natural gas (NGK24) on Monday closed down by -0.079 (-4.46%). May nat gas prices Monday tumbled to a 3-week nearest-futures low and closed sharply lower. Forecasts for above-average US spring temperatures that will reduce heating demand for nat-gas are weighing on prices. On Monday, the Commodity Weather Group said forecasts are trending warmer across much of the southern and eastern US for April 20-24. Nat-gas prices have collapsed this year, with nearest-futures (NGJ24) posting a 3-3/4 year low last on March 26 as an unusually mild winter curbed heating consumption for nat-gas and …