Yes, if the conditions are just right.
Large wildland fires can self-sustain themselves to a degree greater than anticipated by creating their own weather, using just one example. As long as the basics of the fire triangle remain intact (heat, oxygen, fuel) to allow the fire to create a micro-climate, that micro-climate can alter fire behavior to keep it self-sustaining longer than a break in the fire triangle would allow. In other words, the micro-climate can draw in more and more oxygen than ordinarily available. Simultaneously, that helps to sustain the higher heat levels. At the same time the increased oxygen and higher heat values may cause a poorer quality fuel supply to burn. And so on.
Portland, Oregon, may be one large city that can be devastated by such a fire. The topography, forest canopy and number of single/multi-family dwellings look to be sufficient to do the dirty work. Portland has a metro population in excess of two million. Add in the area’s strong conservation/environmental ethic, and the desire to bring as much “wildland” inside the city limits (Forest Park is a case in point) and the model for urban fire as you suggest is very, very strong. Yeah, downtown Portland is a concrete jungle, but there’s a hellofa lot of remaining in the city that is green and full of timber frame homes. picunurse is correct with respect to the Seattle metro area. I venture to state I think Portland has a more volatile mix than Seattle.
However, comparing Portland or Seattle to the 1991 Berkeley Hills / Oakland Firestorm offers a false comparison. The Berkeley Hills have an extensive introduced Eucalyptus tree problem. Australian eucalypts don’t really burn as much as the explode! The high oil content of eucalypts means a wildland fire causes the oil to vaporize in the air and set the stage for a natural BLEVE fire. The 1990s Canbera and Sydney fires were made worse because the eucalypt’s oil vaporizes before exploding in a BLEVE fire. In turn, they also generated huge fireballs that blew through neighborhoods with tremendous damage. That just does not happen at that level with native North American trees.
The Waldo Canyon Fire in Colorado is the fire in the news, and rightly so. But as of 530 am MDT today, there were 242 new fires reported in the previous 24 hours, 11 of them being large. In total there are 41 large fires burning across the country. Still, fire support is relatively low, and gearing up real fast. We got a callout request just today asking anyone with red cards who are unassigned of our availability status for the next two weeks. A callout request out like this, this early in the fire season (relatively speaking) is not unheard of, but ominous. The prognosticator national drought map should scare the crap out of everyone.