Riding the momentum from rallying futures prices as the natural gas market begins to look optimistically toward summer, forwards firmed by the double digits throughout much of the Lower 48 during the April 22-28 trading week, NGI Forward Look data show.

With continued strength in export volumes — via liquefied natural gas (LNG) and pipeline to Mexico — providing the fuel and a maintenance-related drop in production creating the spark, May Nymex Henry Hub futures surged nearly 20 cents in the three days leading up to Wednesday’s contract expiration.

The June contract pulled back on its first day as the prompt month Thursday, and then remained range bound on Friday. But the bullish run for May prices established a foundation for widespread gains in forwards trading at...