It’s not a crash, but it sort of smells like one. Housing starts and newly issued residential building permits dropped sharply in January, the Census Bureau reported this morning. The declines, which came in well below expectations, follow a pattern of late: disappointing economic news for the US. But once again there’s also the routine of analysts telling us that the unusually harsh winter weather is temporarily weighing on the data and so better numbers are just around the corner. Perhaps, but for the moment there’s a new dose of ugly numbers to review.

New-home construction slumped to a seasonally adjusted annual rate of 880,000 last month—16% below the revised December total of 1.048 million. Permits fell too, although the carnage was comparatively mild: a decline of 5.4% in January vs. the previous month.

By some accounts, the weak data came as no surprise. The Wall Street Journal, for instance, advised that

Jed Kolko, chief economist at Trulia, predicted Tuesday that weather would shave 1.1% from the pace of January’s housing starts and 1.4% from construction permits. He described those effects as fairly small.

The real concern is the downward trend in the year-over-year figures for starts and permits–a trend that’s been around for some time and one that’s starting to bite. For the first time in nearly three years, new residential construction activity last month was below the level from a year ago. Permits are still higher on a 12-month basis, but just barely. It would be a lot easier to dismiss all this as noise if the trend was enjoying a degree of stability, but that’s not true either. Instead, there’s a conspicuous downward bias in the year-over-year comparisons in recent history for these leading indicators.

Momentum, in short, is clearly negative for the housing industry. The only hope is that the weather is the problem rather than a fundamental change for the worse in the business cycle. The problem, as I noted earlier today: it’s going to take a couple of months at the least to figure out if weather really is a factor or if there’s a deeper problem brewing in the macro data.

Meantime, it’s hard to overlook the fact that today’s weak housing report follows similarly downbeat news this month for nonfarm payrolls, industrial production, personal income and the ISM Manaufacturing Index. If weather isn’t the culprit, the economy’s in trouble.

Unfortunately, reality will remain shrouded in a fog of uncertainty till at least April, when the post-winter economic data will begin to emerge. In the interim, every economic release deserves close attention as we struggle to figure out what’s truly happening.

On that note, keep a close eye on tomorrow’s jobless claims data and PMI Manufacturing Index report. The consensus view on both counts anticipates minimal drama. But if recent history is a guide, forecasts are far less valuable than usual these days.