MISO Midwest entered emergency status June 23 during the RTO’s first serious heat wave of the summer.

MISO declared a maximum generation event for 4-10 p.m. ET, when it estimated that all available resources would be in use. The Step 1 declaration allows the RTO to commit emergency resources and curtail export schedules.

The grid operator said a combination of wide-ranging heat, higher-than-forecasted load, forced outages and restricted transfer capabilities necessitated escalating its earlier emergency warning to an emergency event.

Based on forecasts made in the morning, MISO foresaw the most pressing problem occurring about 7 p.m. ET, when its approximately 121 GW of available capacity would come a few megawatts shy of its load forecast. By afternoon, however, it no longer predicted a deficit.

MISO also issued a maximum generation warning for June 24.

The RTO originally forecast 122.8 GW of demand for June 23. At 1 p.m. ET, its members were serving almost 114 GW of load at a marginal cost of $324.77/MWh. Indianapolis, Detroit and St. Louis were forecasted to hit 95 degrees Fahrenheit or higher June 23. At midday, solar generation was contributing about 12.5 GW and wind 13 GW.

By 6 p.m., MISO was meeting about 119 GW of demand with the help of 5.2 GW of imports priced at about $139/MWh. By then, it had recalibrated its peak demand forecast down to about 120.7 GW.

MISO has been preparing for a sweltering summer. In an outlook issued in May, it estimated it could see a June peak load of nearly 122 GW in a high-demand scenario but expected the peak more likely would top out at 115 GW. The RTO’s July forecast called for a 122.6 GW peak under normal conditions and a high-demand scenario of 129.3 GW. (See MISO Braces for Hot Summer, Potential 130-GW Peak.)

MISO also initiated a capacity advisory for the South region June 21 due to forced generation outages.