Could be a number of factors. Prices are generally composed of generation, loss, and congestion terms. The generation term is driven by the marginal cost of energy (i.e. what's the cheapest generator that still has capacity). The losses term is fairly self explanatory. The congestion term factors in the thermal ratings on equipment based on what can be delivered to a location.

Someone else speculated that this is due to a rise in Natural Gas costs. This would make some sense given that the rise is uniform across the region.

Disclaimer: I work in the energy space. I know nothing about what is happening here and these are personal opinions.