Suggest a route for me — late October, near Denver

I should add, I *do* understand that "winter" starts at different times every year, some winters are snowier than others, and so forth. Just looking for some trends and predictions, if you were in my shoes.

Also, another concern that I didn't think of … are we still going to be able to collect water from streams, or is there a chance that they'll be iced over already? Having spent most of my life, and most of my backpacking, in basically 1-season locations, I'm not used to planning for that sort of thing :-)

Keep in mind that is deer/elk hunting season here. If that concerns you, you might want to consider RMNP where there's no hunting allowed. I've only been backpacking there a few times (kind of hassle with permits and rules on where you can camp, etc) so I'm not of much of a help with route suggestions. Water won't be a problem in October. I'm good going out with 20 degree bag in October. But there are few places you can have a fire so I wouldn't count on that.

http://www.nps.gov/romo/planyourvisit/backcntry_guide.htm

The Flatirons are right nest to The People's Republic of Boulder and may not permit camping but you can stealth camp off trail.

A better place is the Indian Peaks trailhead just outside of Nederland, past the turnoff for the ski area. I like the trails there and the views are great BUT at 10,000 to 11,000 ft. it may snow like hell and be cold. Ya can't tell. "Mountains make their own weather".
Check forecasts closely.

No one can tell you what the weather is going to be like in the mountains in late October. This has been a different type of year with respect to weather: lots of very late spring-early summer snow and rain, drying out now, but anyone's guess as to when winter will kick in this year.

If weather is holding and forecasts look good, then the Indian Peaks Wilderness Area and adjacent James Peak Wilderness offer some great opportunities for loop hikes up and over the continental divide, and no permits are necessary in late fall. Rocky Mountain Nat'l Park is deeply mired in bureaucracy so start your permit process now if you want to do that – as mentioned, no hunting allowed there and usage drops way off after the elk rut ends. Nice loop potential in the Park, but bear canisters are required for backcountry camping below treeline. That is a hassle.

Grab a copy of the Trails Illustrated map for Rocky Mtn Nat'l Park (#200) and/or the Sky Terrain map for Southern RMNP and Indian Peaks Wilderness, if you are a map person. Excellent trail info on both of those, and easy to spread them out and do some planning.

If the weather has turned, you might have a Plan B in your back pocket. The western part of the State offers some amazing lower-elevation fall camping opportunities around the Grand Junction area. But that is a 5 hour drive from Denver. And even if some mountain areas have gotten snow, others may not have. Weather patterns can vary broadly across the state.

Be aware that there. Is. No. Camping. In the immediate vicinity of Boulder, including the Flatirons. For anyone to suggest that it's OK to "stealth camp" is misinformed at best and terribly disrespectful of this special, heavily used place.

I'll echo all the comments about RMNP. As a federal facility, it's of course succumbed by all sorts of procedural demands. Yet, its trails are quite exciting, and hiking them removes you from the deer/elk hunters. And, if you remain below treeline, the odds of anowfall are lesser.

If I remember correctly, snow tends to fall heavily in the lower elevations on the Western Slope, tapers off as its storm cells reach higher elevations, and then takes on new life (and more power) as the cells descend the steep, eastern-facing Front Range. The snow then tapers off at lower elevations.

A fair choice, IMO, is P-Mag's Twin Owls Loop:
http://www.pmags.com/backpacking-loops-mags-favorites

I love to go backpacking in late October…I just go to the Colorado Plateau. :)
(parts of CO near Grand Junction as mentioned earlier and of course parts of Utah, NM and AZ)

If you are absolutely 100% gung-ho for something in the Colorado mountains, the Wet Mountains are not far from Pueblo, CO and may be a bit more mild. (EDIT: And wear blaze orange..) Still a fair drive from DIA.

But, again, esp in late October, I would personally go elsewhere than the mountains in the Denver area. I've been known to do lower elevation trips in the Denver foothills for a quick weekend, but I'm a local. Probably not worth flying into from Denver for that type of backpacking.

If you are willing to drive a little bit from DIA (5-6 hrs), your options are going to be better.

Well, hell, if you're going to recommend stuff as far south as the Wet Mountains, how about the Sangres or Great Sand Dunes National Park? But it's much better to fly into COS for these.

There is almost NO problem whatsoever getting permits for GSDNP at the last minute in October- I did it once, long ago:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=24944

And have been back many times. And, yes, I did encounter hunters- I wore the fluorescent green/yellow jacket you see in the photos. Hell of a drive from Denver, though.

Hike-in-and-base-camp is probably more appropriate for GSDNP. You could base camp up at the top of the Sand Creek Drainage, if you want spectacular mountains: just below Music Pass, by the Sand Creek Lakes. That area is so beautiful it looks fake. If cold weather hits, just drop back down the drainage.

Or camp at the lower Sand Creek site and make a dayhike up Sand Creek to the pretty scenery. With a start earlier than mid-afternoon this is very do-able on your requested timescale, spending two nights at that site. I do, however, recommend a 4WD so that you can drive past Point Of No Return to the trailhead farther back.

Hard to make a loop, unless you want to connect Medano and Mosca passes via the Rainbow trail on the other side of the Sangres, or somesuch.

Another option, if you have a decent 4WD, is to drive to the Music Pass trailhead on the east side of the Sangres, and hike over the pass to the Sand Creek Lakes. The unusually rainy past two years have left the road to that trailhead in very poor condition, though. I just did it last month in my Tacoma.

Lost Creek Wilderness is the usual shoulder-season recommendation near Denver, but it isn't really classically "Colorado mountains."

I didn't give the suggestion of the Sangres proper or the sand dunes area for the reasons you listed as negatives! :)

The Sand dunes are lovely, but, IMO, make a better camping destination than a backpacking destination.

And late October in the high Sangres? Hmmmm……plus, not sure if the OP will have a rental vehicle that will be 4WD capable.

The Wet Mountains tend to be more mild and have less snow vs other Colorado areas.

But, and I'll say this again, the Colorado plateau is a better area for late October backpacking than the mountains proper IMO.

EDIT NOW THAT I'VE LOOKED AT GOOGLE MAPS: There's about a 30m difference between the lower greenhorn mountain trailhead and the Sand Dunes in terms of driving time from DIA.

Suggest you consider the Rough and Tumbling/Rich Creek Loop trail in the Buffalo Peaks Wilderness… 30 minutes SW of Fairplay, CO or 2+30 from DIA. The loop is only 12 miles but offers a number of side excursions to add time/distance/elevation. It doesn't have big mountains but terrific high meadows and lots of fishing opportunities. I hiked it in mid-October last year (just missed the Aspens) and had mild days with cool nights.
http://www.oriconline.org/what_to_do/trails_and_trips/backpacking_trips/x-rich_crk_and_rough_and_tumble_loop.pdf

Another area that is often overlooked is the Lost Creek Wilderness south of Bailey. Numerous loops to make a trip as long/short as you want. Check out a description here…http://www.summitpost.org/buffalo-peak-the-wigwam/153798

Maintained routes in the Sangres are almost all out-and-back hikes, so if conditions get bad just 'back' a bit. That's why I recommended base-camping at the Cold Creek or Sand Creek sites and day-hiking up into the mountains. But your point is taken.

I agree about the Colorado Plateau, but Grand Junction is a 4+ hour drive from DIA. And he did say that he wants mountains. In October. LATE October. That's the killer, right there. (Hey, Ian, how do you feel about snowshoes?) Might the weather cooperate? Yes, it might. But then again it might not, and in a very spectacular fashion. One option is to plan an optimistic trip, but also a less montane backup in case the weather is anything less than miraculous.

Maybe Grand Mesa? Or, what's Flat Tops like in October? Still pretty high- 11k or so- so I'd guess "miserable." Taking the California Zephyr to Glenwood Springs might be pleasant, though. Of course, you can take it all the way to Grand Junction, too.

Tough one. If he's flexible on mountains then there are other great options, as we have mentioned.

I now know why the ticket was so darn cheap… :)

Getting (possibly) too snowy for the mountains proper..not enough snow for skiing!

Late October/early November through ~mid-December is an odd time in Colorado for those reasons in terms of outdoor pursuits.

I went into the Sangres last year for a couple of nights in mid-October last year. You do have to contend with elk hunters. We saw quite a few of them and heard quite a few gunshots. We hiked from the Grape Creek Trailhead to Upper Sand Creek Lake, which was spectacular once we got there. But lots of mud below tree line and lots of wind up near the pass, so I would probably look elsewhere. I am actually going to try RMNP in early October this year. Already reserving sites . . .