The US National Weather Service issued a tropical storm warning and a flash flood watch for the central Gulf Coast June 18, prompting the Midcontinent Independent System Operator to declare a severe weather alert for the South Region effective through 11 pm ET June 19.

　　The affected power entities in the MISO region must review outage plans to identify whether any scheduled or current maintenance or testing can be deferred or canceled, the notice said.Potential Tropical Cyclone Three, which was expected to become a tropical storm late Friday, was forecast to bring storm surges, heavy rainfall and high winds, affecting parts of Louisiana, Mississippi and Alabama.

　　The system was forecast to move inland to the northeast over the weekend, according to the weather service.

　　Prices, demand trend bearishPower prices in MISO’s South Region weakened ahead of the storm as locations near the storm’s projected path felt the effects. Louisiana Hub real-time locational marginal prices trended around $32.75/MWh, and Mississippi Hub real-time LMP priced around $35.75/MWh, much lower than prices at Illinois Hub real-time LMP, which priced around $60.50/MWh as of 3:45 p.m. ET.

　　Overall MISO demand was forecast to slide 7.5% for June 19 to 81.7 GW, from 88.4 GW forecast for June 18. Demand for June 20 was predicted to see further declines, down to 81.5 GW.

　　Forecast day-ahead demand for June 21 was lower than for June 18, down about 4.2% to 84.7 GW, according to grid operator data.

　　ERCOT prices also slidePower prices at ERCOT also trended down on the Intercontinental Exchange, with North Hub day-ahead on-peak June 21 prices falling about $4.50 to trade at $43/MWh and the real time contract tumbling about $9.75 to trade around $42.25/MWh.

　　The North Hub real-time off-peak weekend strip for June 19-June 21 delivery slid about $2.50 to trade around $16/MWh as forecast demand for June 19 slid 2.2% to trend around 66.8 GW.

　　Houston Hub real-time on-peak for June 21 saw bid and offer activity between around $44/MWh and $49/MWh, lower than its previous settlement of $54.75/MWh.