Predict my marathon time

What race are you running. You have to factor in terrain, heat, and humidity before making a prediction. That said, in ideal race conditions I would put you around 3:25. I'll give you my exact prediction when you tell me what race you're doing

It will be very tough. You need to double the distance and increase pace from a very recent race.

I ran my last marathon in 3:11 and the first 13 miles felt extremely relaxed at a 7:00 pace, about 1:31. I kept that pace till the last 10k, then it all started slipping away. If that 1:36 HM felt tough at all, I would suggest shooting for a 3:20. After all, we both now have another 11 months to get a BQ for 2014.

Santa Clarita Marathon on 11/04 - here's the map

http://scmarathon.org/course-information/#course-map

Looks pretty flat. The weather is usually dry, in the mid/high 60s. Last year it poured though, so who knows...

I think a 3:25 is a pretty reasonable goal.

http://www.mcmillanrunning.com/calculator gets you a pretty close estimate, assuming solid training.

Everybody is different but for some perspective, I ran a 1:34 HM and a 3:22 Marathon. 

How do you know that?  Long run data?  Asking because your 2-week-old HM time is 1:36 (7:20 mpm).  Something seems off.

Unless you have been doing a lot of cycling mixed with that mileage I'd imagine you go a little under 3:30.  Not enough mileage.  Those calculators assume proper mileage and endurance as well.  

June wasn't that long ago.  Conservative or not.  A 3:42 is easy jogging compared to a 3:10.

I just know based on my own abilities being not too far away from yours that I was capable of around a 1:30 heading into one last year and ended up a bit over 3:20 and there is no possible way I could have ran a 3:10 without an epic blow up.  I was also running a lot more, but you might be better at the longer stuff.  I just think those lack of miles catch up the last 10k.

It'd be cool if you can do it though.  Good luck. 

3:28:44

Unless your HM was only an "ok" race.

The jump from 3:42 to 3:10 is a significant jump of 1:13 minutes per mile (7:15 pace vs 8:28 pace) and IMO would take at least a year with considerably higher mileage than you are logging.

Two years ago I ran a 3:23 marathon after running a 1:36 HM.  However I was averaging around 60 mpw.  

My guess is that you will run around 3:25.

The HM was 6 days after doing the LA tri (my A race for fall) and 3 days after doing a hard 10 mile run. I've ran a 20 miler this summer at about 7:22 per mile, however I had to stop after that.  I think that I got stronger in the last 3 months, but who knows...

+1! But that's still a long time ago that you've done a 20 miler and low miles.  I think the last 6 miles for you are really going to hurt.  If you can suffer inhumanly, you'll hit 3:20. But, I think if you try to go 7:15 early you may end up doing a walk/run the last 10k.  Good luck though.  I too will be jealous if you hit 3:20ish even on that mileage!! I'll adjust to 3:28:50 on new info.

We have similar times on 5K and 10K (though my 5K and 10K were both done as the run leg of a triathlon vs just an open run).  My last HM late last year when I was just coming of injury was 1:40 and I hadn't done any marathon training then.  Run volume is also higher (25mpw over the last 7 months on average and 30mpw avg over last 2+ months).  I asked for advise from this forum on what pace to run and strategy (specifically for NYC marathon) since it's my first one and don't know how to pace.  Most recommended that I stay around 8:00-8:15/mile or even slower based on my lack of mileage.  Something around 3:40-4+ hrs seem to be what the consensus looks like.

You're shooting for 3:10 and seems that there are a lot of 3:25's predicted.   I'm curious on how this turns out as it would be good to compare results with similar prep (major assumption on my part as your logs aren't filled out so don't know how much cross-training you've been doing). 

Good luck with your BQ attempt!

I really want you to pull this off, and I'll check back with you in a couple weeks to see how you did, but I think it's going to be really tough!! 

I think if you are Boston or Bust for this race, then go for it. But your best chance is to maintain a 7:15m/mile pace for the entire race.

However, with your recent HM time and your low weekly training mileage the odds are not in your favor. So, if you want to give yourself the best chance to have a great marathon time (and go for Boston when you have more training logged) I would go out at a 7:45m/mile pace and then bump it up for the last 10K if you have it in you. Just my .02¢, and probably not even worth that!!

3:34

Don't take the Yasso 800s workout to be a meaningful predictor. Somebody who cannot reach the 800 times is very unlikely indeed to make the associated marathon time (e.g., if you can't run 10 x 800 in 4:00 then forget about running a 4-hour marathon), but it doesn't work the other way. Doing the Yasso time doesn't mean that you have the fitness to run the corresponding marathon time. 

Since registration for Boston 2013 is closed, the next opportunity to run Boston would be 2014, entries presumably opening in Sept 2013. So why not try for a sensible improvement in your PR this time around, then if you're still motivated, put in higher mileage during the winter so that you can have a better stab at a BQ in the spring.