Short Term or Localized Events (Move to hotel, friend or family for a couple of days):
Tornado destroys your house or makes neighborhood unsafe for a while (destroyed infrastructure)
Chemical spill (I live very close to the loop, a downwind tanker overturning could result in an evac for several days)
Damaged distribution gas line (similar to above)
Meth or bomb lab being found in close vicinity
House burns down, flooded, or otherwise made unlivable
Mid-term or less localized (Loss of house and job for most of city, evacuate area or hunker down)
Wildfires - not likely to penetrate far into the city... but if we had a perfect storm of windy, extreme drought and a damaged water main that kills water pressure like we had a few years ago who knows.
Super Flu or some other highly contagious, fast spreading disease with a medium mortality rate (5-10% ,)not likely to collapse society, but pretty good reason to isolate yourself for a while.
Serious economic problems resulting in massive rioting, undependable utilities, gas shortages or food shortages but short of a total societal collapse
Very Bad Stuff (you're probably screwed, but chance favors the prepared)
Anything leading to a complete collapse of society..
Epidemic with High mortality rate (20%+) (Historically small pox has killed more humans than anything else)
Complete economic collapse, hyper-inflation, extreme depression
Civil war or nuclear war
Of course the smaller events are much more likely than the big events to occur, and thus seem less far-fetched, but if you don't believe the items in the third category are possible, you either ignore human history or the old saying "history repeats itself". However, that being said I personally only prep for the first two categories, because I don't see a realistic way to seriously prep for the third category without removing ones self from society and moving to some rural place, which is not a sacrifice I am willing to make "just in case".
I actually live closer to the town of Slide than to Lubbock.. have thought about most of those scenarios and would have to do a lot more work if we lived in town. Truthfully if I lived in Lubbock, our house would be a viable near-term BOL - there's really not much beyond a house fire that would force us to truly "bug out" without warning.
Other things like wildfires and whatnot would force evacuation, but with enough warning to get the INCH box into the truck. Tornado would also hit quickly but would force us into the basement, where we have a "bug-in" box with supplies and clothes (and self-extrication tools) stashed under the assumption that we'd be sprinting down in the middle of the night in pajamas.
It's really the "collapse of utilities" scenario I'm doing most of my prepping for. The stuff stashed in the basement, coupled with the stuff stashed in the INCH box in the garage, plus a pantry full of canned food and a vegetable garden will let us comfortably bug in for a long time. A gas-fired generator, or a wind-turbine, or some solar panels would go a long way toward keeping the frozens cold and allow the well pressure tank to fill every few days - that's definitely on the to-do list. A number of effective firearms and a few thousand stockpiled rounds for all of them will keep the squatters out and some feral pigs on the grill if it goes on too long.
I haven't yet decided what to do about the middle of the night house fire, though. We're friendly with our neighbors and they're less than about a 1/4-mile away, I have no doubt they'd offer help and shelter in the case of a simple house-fire, but again I'd hate to be schlepping down the road in my sooty underwear. Need to think of a way to keep some supplies and a change of clothes nearby but outside the structure of the house.
Dang -- this wound up being a big unstructured brain dump.. sorry. I guess it illustrates the stage I'm in with regard to the prep.. Lots of thought, some action, not much refinement yet. Comments welcomed!