Help!

I've signed up for a half-marathon in 16 weeks from now (Feb. 21st) and I have designed a lovely training plan for myself that includes two short-ish runs (one easy run and some speedwork) and a long-run on the weekend.

I cycle to work almost everyday, roughly 130 km/week with lots of hills, so my cardio fitness is pretty good. I ran a 50-minute 10K recently without much prior training (I was pretty sore after tho'!!) However, I need to rebuild the specific strength needed for the half-marathon. I want to enjoy the race, and the post-race too.

Problem: When to run? I'm fine with the long run, it's the shorter, week-day runs that are the problem.

Constraints: I leave for work around 6:30 a.m. on my bike and I'm seldom back home before 6 p.m. I could in theory run over lunch at work but I'm not so keen on having to take yet another shower at work. When I get to work at 7:15 a.m. it's really still quite dark (winter months), and it's an area where I will not go for a run on my own in the dark due to safety concerns.

Do any of you have suggestions? What do you all do to juggle bike-commuting, a busy professional life requiring reasonable clothing, and running?

Help! I miss running and I want to make this work. Thanks in advance.