Natural-gas prices briefly dipped to their lowest point since November as heavy supply and tepid demand keep causing a steady retreat. Weather forecasts show no winter chill likely before late October, meaning there is no demand for home heating large enough to absorb the record supply coming from the country’s shale-gas boom. That has pushed buyers out of the market and pushed prices down 6.8% during the past two weeks. The front-month contract finished Friday on a four-session losing streak, with closing prices below $3.80 a million British thermal units for the first time in a month.