I wonder if the unexpected snow storm in the US with massive power outages will have an effect on the overall hashrate (and perhaps new difficulty?
Not, there are lots of people mining outside US.
I think that the impact on difficulty was minimal.
The difficulty is lowering because mining is not profitable, and is not a good idea to spend money on mining unless you have a great interest in BTC (It's not a good idea to mine BTC to earn $). Also, there are miners interested in BTC, that slow down their rigs to reduce the cost of mining.