So, I've got this job now where my off time varies daily. As such, I want to put together an adventure bag, something that I can just head out for a day hike or other outdoor outing, without having to stop at home. Something that has a change of clothes, some snacks, outdoor gear. Any suggestions as to what I should keep in it? I do want to keep it light weight too. I like having gear, but I hate packing it!

Sounds like oh just need to have a second go bag, for your recreation. From your states summer weather, keeping food and drinks in hot car might be problematic.  But if you can keep in your workplace, you won't have any issues.

Really depends on where you're going to be. I keep a Kifaru Scout packed so that I can just throw it in the vehicle for a day hike. I keep a small first aid kit, tarp, fire starter kit, rain jacket, GPS, compass, zip ties 550 cord, two Nalgene bottles and snacks. If I know I'm going to be out more than a couple of hours, I'll throw in a jetboil, some mountain house and a waterfilter.

This is what I do, although I have my bladder out to dry and seem to always forget it and have to go back in the house.

So, I’ve done something very similar.  My go-to, day-hiking pack is an Osprey Manta 30 (roughly 30 liters).  It does have a dedicated hydration pocket and I keep the hydration bladder empty and will fill up just before hitting the trail.

This is the perfect size for a multitude of activities from hiking, bouldering and even mountain biking.  My only recommendation is I would have separate small gym bag dedicated to your change of clothing and footwear.  This is something that will likely change seasonally.  The only clothing I keep in my Osprey are a pair of socks, a rain jacket, fleece hat and gloves.

It’s a pretty light kit, but still capable of sustaining me as a 72-hour kit.  My favored day-hiking shelter is an Exped Poncho-Bivy that can serve as an emergency tarp shelter or regular poncho.  I don’t always pack a cook kit, but I have been carrying a smaller BOT (700ml) pot/mug with a small brew kit and alcohol stove with 4-6 ounces of fuel.  

If I get a chance this afternoon between work and my son’s soccer match, I’ll snap a couple pictures.  I know Osprey changed the feature of their Manta pack (I have their first model), it’s really the perfect size for my needs.

ROCK6

You can use a gym bag or a colored stuff sack. That way it's easy to take out and easy to identify.

I have actually been brainstorming putting some gear like this together lately...  Stand alone Jeep dedicated gear.  I have been watching a few YouTube Vids by CoyoteWorks and it has really been getting me thinking outside the box.  He does several mock vehicle bug out scenarios under different parameters and circumstances but I think its a good idea, really makes you think, could easily be converted to impromptu outings etc (which is what he is doing in reality.)

I have plenty of gear and packs but one thing that is always in my mind is keeping expensive gear in my Jeep.  I just can't bring myself to do it as of yet.

I think the best alternative is to have an outing "BOB" or gear rig that sits in your man cave ready for general adventure.  Could even have a modular kit depending on mode of travel (KLR650 in my case) adaptable to vehicle camping, hiking, paddling etc...

These are great "exercises".  I've done this a couple times and need to do it more.  I have my truck GHB or my minimalist day-hike bag and when I've had a Friday off, I leave work as usual on Thursday, but detour to hit a local state park.  I do a few hours of hiking or at least until about 30 minutes to sun down and then setup a camp for the night.  Nothing complicated, but just a routine "shake-out" of gear to simulate a number of situations.  Granted, this isn't any of my bug-home routes, but it still provides reinforcement of other skills.

ROCK6

So, this is my grab-and-go bag for day-hikes or overnight hikes in more moderate weather (typically not below 40 degree lows).  This particular load was for a single overnight trip, but an extra pound or two of food could extend that to two or three days.  This load here is 14 pounds even; no water weight, but it does have a dinner meal and breakfast; some snacks and drink mixes along with enough fuel to boil 4-5 pots of water.

Osprey Manta 30 pack with a 3L Osprey hydration bladder
JRB Stealth Sierra quilt/sleeping bag/worn-insulation; this is a 40-degree quilt and with the extra ounce of down, it's pretty much spot on for me when it comes to comfort.
Exped Bivy/Poncho/Tarp shelter with four mini groundhog stakes and suspension line.
AMK Bivy; bulky but pretty durable as a bivy or ground cover.
Klymit Recon (3/4 length) inflatable pad
Eno Sub7 hammock and whoopee-sling suspension
Folding CCF seat pad

Spare merino wool socks
Merino wool skullcap
Synthetic buff
Glove liners
Leather work gloves
OR Helium rain jacket
Sawyer water filter with two 1L squeeze pouches
Evernew 2L collapsible water bag
Nalgene 16oz water bottle with 300ml nesting titanium cup
Toaks 550ml pot with lid, nesting bowl
Folding spork
Collapsible silicone cup
Trangia alcohol stove with pot stands
Four-ounce fuel bottle
Mora 510 (actually 511 with the finger guard removed) with firesteel
SAK Rucksack with tweezers and mini-firesteel
Small FAK
100mph tape
Bic with protective cap
Zebra AA headlamp
Compass
U-Dig-It trowel
TP
Hand sanitizer
Bug repellant
Bug headnet
Microfiber wash cloth
550 cord
Extra batteries (need to replace with a single battery as I don't need all four)
10K mAh battery charger
Tinder/tea-light candle



















Now this type of bag relies on plenty of water sources, but I do have a couple gallons of water stored in my truck.  Additionally, I need to ensure my clothing is packed and layered properly for the full spectrum of temperature conditions of the current season.  Now, I don't have any sleeping clothes or a change of clothing (evident by the size of the pack).  This forces me to avoid getting too muddy or wet if temperatures are in 40's.  I also use my HPG Kit Bag which has a layer of redundancy in some area:



Looking at my layout, I know I could really trim this down. For a ground cover, I may just add a length of Tyvek folded up and stashed with my hydration pouch.  I have a much lighter trowel (do I even need one?); I don't need that 550-cord or at least replace with Dyneema cord; I could use my mini alcohol stove which is about 1/5th the weight of the Trangia stove; I really don't need the SAK as I always have a folder or multitool on me; I could drop that extra Ti bowl, I really don't need that AMK bivy, and I already mentioned I am going to cut down the battery pack to a single AA...just some observations of my own  Oh, and the only item I left out on accident was my small Silky saw!

So, for the OP's definition, this is my "Adventure Go-Bag" that covers close to three seasons in my AO for day-hikes and up to two nights based on my food plan.

ROCK6