Natural gasoline at Mont Belvieu, Texas, last week posted its highest price since June 2015—a 28-month stretch—as the hub’s composite NGL barrel (bbl) extended its stay above $30 to five weeks.

While last week’s price of $31.76/bbl was only the third-highest for the year, the five-week rally represented the longest maintenance of the $30-plus price level since late November 2014, when the lowering tide of the down-cycle was sinking all NGL boats. At Conway, Kan., the barrel remained above $30 for two consecutive weeks for the first time since February.

In its quarterly report, Jefferies credited the after-effects of Hurricane Harvey for third-quarter NGL price spikes and contemplated the potential of a price surge for propane if forecasts for a chillier winter come through in the Northeast and mid-Atlantic states.

Jefferies focused on propane supply, which was the shortest in inventory days during July since at least 2000. July stockpiles of 64.1 million barrels, Jefferies said, were about 34% below the five-year average. The July figure was significantly above the July 2013 stockpile of 55.3 million barrels, but the analysts noted that sharply higher domestic consumption and exports brought the inventory days down to only 38.4.

Propane had little price movement at either hub in the last week but still registered among the highest weekly averages of the year, and was 61% above the year-ago price at Mont Belvieu and 62.5% higher at Conway.

Ethane remains the most oversupplied NGL, Jefferies said, with a 34.6-day July inventory that was 31% above the five-year average. The analysts noted that butane and C5+ were also oversupplied, but below historical norms.

Ethane’s price has been stagnant since Harvey damaged numerous ethylene plants. Despite last week’s increase, the price at Conway was still 21.7% below the pre-Harvey August peak. Ethane returned to its pre-Harvey price in September but has slipped for three straight weeks.

The Plastics Exchange reported that markets were sluggish, with ethylene trading down 2 cents per pound. En*Vantage said it expects ethane to remain in its current trading range until damaged plants are able to return to operations in November. Compared to a year ago, ethane was a touch above at Mont Belvieu and 19.2% below at Conway.

Domestic demand for butane, Jefferies said, is slightly behind year-to-date demand in 2016. The price, of course, is way ahead (38.4% last week at Mont Belvieu and 41.8% at Conway). That is because exports have ramped up—an all-time average high of 180,000 bbl/d was set in March and substantial monthly year-over-year increases were recorded in June and July.

“...[W]e forecast butane prices in 2018 to average 90 cents/gal as exports continue to provide incremental demand and crude oil prices modestly recover,” Jefferies said.

Storage of natural gas in the Lower 48 increased by 51 billion cubic feet (Bcf) in the week ended Oct. 13, the U.S. Energy Information Administration reported, below the Bloomberg consensus of 54 Bcf and the 2016 increase of 77 Bcf. It is also below the five-year average increase of 78 Bcf and resulted in a total of 3.646 trillion cubic feet (Tcf). The figure is 4.7% below the 3.825 Tcf figure at the same time in 2016 and 1% below the five-year average of 3.681 Tcf.

Joseph Markman can be reached at and @JHMarkman.