THE OVERSEER of the New England power grid warned on Monday that the region is walking a tightrope this winter, flirting with emergency situations that could result in rolling blackouts.

Gordon van Welie, the president and chief executive officer of ISO-New England, said the power grid’s resource mix and fuel infrastructure are vulnerable when “extended severe weather conditions” combine with any one of several “contingencies” — the loss of a large nuclear power plant, the shutdown of several large generating units, the closure of a liquefied natural gas facility, or the cutoff of electricity imports from Quebec or New York.

“These are not hypotheticals, as all of these situations have occurred this winter, in the January 10 to 22 time frame,” van Welie wrote in his letter to industry officials and state energy leaders. “Thankfully, the region did not experience extended severe weather during this timeframe and we have been able to manage through them.”

Van Welie for years has been trying to raise alarms about the vulnerability of the region’s power grid over the next decade as New England shifts toward more renewable forms of energy. He has stepped up his warnings over the last year as the situation has deteriorated, trying to build consensus within the energy industry and among the region’s politicians on the scope of the problem and the possible solutions.

“We are not trying to alarm the region, but we would not be doing our job if we did not highlight the region’s vulnerabilities in certain circumstances,” van Welie said in his letter. “From our perspective, we are having the right conversation, although it’s a difficult one.”

The chief problem is natural gas. The region relies on that fuel for the bulk of its electricity production, but pipeline capacity into the region is constrained. During periods of extreme cold, more of the natural gas is directed to homes for heating and less to generators for electricity production. This winter the price of natural gas is also unusually high, so generators are using cheaper, dirtier fuels like oil and coal to produce power.

The situation has become even more concerning as renewable replacements have been slow to come online. The offshore wind industry stalled for several years during the Trump administration and is only now getting back on track. A transmission line, financed by Massachusetts ratepayers to bring additional Quebec hydro-electricity into the region, was shot down by Maine voters in November.

Importing liquefied natural gas from abroad is an option, but not a very good one in terms of cost and risk. “When I explain to state policymakers that the region has to depend on just-in-time imported gas from Trinidad, Qatar, and sometimes Russia, they shake their heads in disbelief,” he wrote.

Van Welie said in his letter that he supports the transition to renewable energy but it’s not happening fast enough. “The clean energy transition is a long journey and we cannot escape the reality that the region will be reliant on much of the existing fleet, and the fuels they utilize, for many years to come,” he wrote.

The grid operator said his organization is trying to address the demand for and supply of electricity. On the demand side, he said, he supports expanded state conservation efforts. “The only other tool we have is public conservation appeals, working closely with the governors and the local utilities,” he wrote. “This is a major reason we were speaking so publicly about the risks leading into the winter – so that the public would know they can help avoid more extreme emergency actions.”

On the supply side, van Welie said, he is hoping for technology breakthroughs in energy storage, long-duration batteries, modular nuclear reactors, and green hydrogen. “But I think these solutions are still years off,” he wrote.

He said the most realistic options are importing more hydroelectricity from Quebec, procuring more imports of liquefied natural gas, and incentivizing power generators to build more generating plants capable of shifting back and forth between natural gas and oil. He said the use of No. 2 oil should be prioritized.

None of these supply options would be easy. Importing more hydro-electricity from Quebec would require the construction of a new transmission line. Importing more liquefied natural gas, van Welie wrote, would probably require beefing up existing gas tanker terminals or developing the capacity to liquefy natural gas here in the region.

There are three liquefied natural gas terminals serving New England, one in New Brunswick, one in Everett, and one off of Cape Ann. Van Welie said in his letter that the New Brunswick facility is outside US jurisdiction, the Everett facility “is economically threatened,” and the Cape Ann facility can only accommodate a very specific type of ship.

Late on Tuesday, ISO-New England released a slide deck that tracked the power grid’s recent performance, including more information on some of the close calls cited in van Welie’s letter.

On January 11, according to the slide deck, the forecasted high temperature was 12 degrees in Boston and 11 degrees in Hartford. At 11 a.m., the New York power grid operator informed New England that it will not be able to provide as much power during peak demand periods “due to constraints on their system.” At 12:28 p.m., problems surface with a transmission line bringing electricity into New England from Quebec. At the same time, a number of generating plants go down, taking 1,100 megawatts offline. According to the slide deck, the unexpected loss of power was dealt with by bringing dormant plants online, which takes considerable time in some cases.

On January 12 at 2:45 p.m., the operator of the power grid in New Brunswick notified ISO-New England that the electric feed to the Canaport liquefied natural gas facility had shut down unexpectedly. Canaport takes imported liquefied natural gas and converts it for use on a pipeline feeding New England; the loss of power at the facility jeopardized delivery of natural gas to the region. Fortunately, power was restored at the facility by 4:24 p.m. and natural gas deliveries to New England resumed.