Ugh, very tired when I got home, which was later than I expected - I had to talk myself into going out at all.
(I have grown thoroughly acclimated to the cold, in fact I like it being in the mid-20s, but I had hoped to squeeze it in before dark, which proved a fantastically unlikely notion!)
It became clear to me, though, that I was so tired that I could do nothing else but lie on the couch and that it would be better to have a short run than to while away an hour doing nothing at all!
I have a 7pm appointment, that was the other constraint, and thus had no hope of fitting in the 8 miles on my schedule (shortage of vim and vigor as well as time), so I just did 3.5: over to Central Park, round the upper loop once and then home).
I feel slightly better now - will pop in the shower and get dressed in real clothes again and head back out.
NB it was the first spin for the new pair of fancy-pants tights I've ordered, they are very warm and good - in fact the description sort of makes you feel like they'd do the running for you if only you'd let 'em!