Harsh winter weather may have hurt sales of Ford's all-important F-Series pickups, which declined slightly in January, but the Blue Oval's SUVs continued to show strength. Image source: Ford Motor Company.

Ford Motor Company (NYSE:F) said on February 2 that its U.S. sales in January declined 3% from a year ago.

The decline wasn't a huge surprise, given weather-related challenges in many parts of the country, and given that January of 2016 had just four "selling weekends," versus five a year earlier. 

While Ford's SUV sales remained very strong despite the challenges, its all-important F-Series line posted a year-over-year drop in sales. 

Strong pricing and good SUV sales, but a dip for Ford's biggest profit driver
We'll start with the troubling news: Sales of Ford's F-Series pickups totaled just 51,540, down 5% from a year ago. But that drop followed a blowout month in December in which Ford sold over 85,000 F-Series pickups, a huge number. 

Despite Ford's decline, there's no reason to think the overall U.S. market for full-sized pickups is cooling off just yet: Arch-rival General Motors' (NYSE:GM) full-sized pickups posted a 7% year-over-year increase in sales last month, and Fiat Chrysler Automobiles' (NYSE:FCAU) Ram pickups gained 5%.

The good news behind the F-Series' sales drop is that average transaction prices on the F-Series were up about $2,500 year over year, while Ford's incentive spending on the pickups was down $500 versus January of 2015.

That gain in average transaction prices helped Ford to an overall gain of $1,800 year over year, but the ongoing shift in buyer preferences away from sedans and toward crossover SUVs probably also helped boost Ford's pricing.

Sales of Ford's midsize Edge crossover rose 26% in January. Its upscale sibling, the Lincoln MKX, posted a 51% year-over-year sales gain. The two were all-new last year, both are significantly improved over their predecessors, and both are in red-hot "sweet spots" of the current market.

The all-new 2016 Lincoln MKX is hitting its stride in the market. U.S. sales rose 51% last month. Image source: Ford Motor Company.

Ford's smaller Escape and larger Explorer crossovers both posted slight year-over-year sales declines in January. But the company said overall sales of Ford-brand SUVs were its best for January since 2004. 

The shift from cars to SUVs showed up on the other side of Ford's showrooms, with the small Fiesta and compact Focus sedans both posting double-digit year-over-year sales declines. The midsize Fusion eked out a slight 0.9% sales gain, while the upscale Lincoln MKZ had a 6.3% sales increase.

Does this mean Ford's U.S. sales have peaked?
It's too early to tell. The fact that GM and FCA both managed overall year-over-year sales increases suggests the overall market still has some room to run. Between the weather and the calendar, it's not unreasonable for Ford to say that its small sales decline in January was more of a fluke than a worrisome new trend.

Auto sales (and automakers' profits) are cyclical, moving up and down with the rhythms of regional economic conditions. Right now, the U.S. auto-sales cycle is probably near its peak: Not many people expect that U.S. auto sales in 2016 will grow much from 2015's record levels. 

But as Ford executives emphasized on Tuesday, the company's improved pricing and continued restraint on incentives will help the most (from a profit perspective) of the sales it is getting in this still-very-strong market. 

Long story short: It's not quite time to be worried about Ford's ability to generate big profits in North America, but it might be time to start keeping a closer eye on sales trends as the year unfolds. 

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.