South–Houston real-time gap averaged +$13.40/MWh on Oct. 27 from 6 PM until 10 PM CDT

South’s real-time premium to Houston averaged $13.40/MWh in those four hours, versus only $0.50/MWh in day-ahead. Both sides contributed: South exceeded its own clearance by $6.55/MWh, while Houston fell $6.36/MWh below its clearance. West’s real-time average was also close to South’s, so this was not isolated South strength. System demand averaged 134 MW below forecast during the window, offering no support for a broad upside-load surprise as the explanation.

Today’s clearance is evidence against simply carrying that relationship forward: for Oct. 28 from 6 PM until 10 PM CDT, cleared South-minus-Houston averages −$1.22/MWh. Houston is priced above South, reversing yesterday’s realized ordering. That makes the pair worth monitoring, not an established persistent premium.

The common evening price level is nevertheless firmer. Hub Average clears at $46.09/MWh for Oct. 28 from 6 PM until 9 PM CDT, versus $40.04/MWh for yesterday’s matching hours. Metis 1 Preview, issued today at 6:55 AM CDT, averages $42.88/MWh—a $3.21/MWh discount that is small against its uncertainty. For the hour beginning 6 PM, its hourly-averaged p10–p90 interval bounds span $37.29–$67.18/MWh around a $51.26/MWh clearance. That is not a strong discount signal; the bounds do not give a probability of beating day-ahead.

For Oct. 28 from 6 PM until 10 PM CDT, watch whether South real time averages more than $10/MWh above Houston. A second sizeable premium despite the reversed cleared ordering would strengthen the case for treating this as recurring regional spread risk. Convergence toward the cleared Houston premium would weaken that case.