On a day when most bank stocks are down, investors in Wells Fargo (NYSE:WFC) will be happy to hear that the California-based lender is bucking the trend -- at least for the time being. Roughly halfway through the trading session, shares of the nation's fourth largest bank by assets are up by $0.24, or 0.59%. By comparison, the KBW Bank Index (DJINDICES:^BKX) is lower by 0.13%.

The impetus for today's climb is admittedly hard to pin down, as much of the news coming out of the sector over the last few days would seem to weigh on bank stocks in general and Wells Fargo more particularly. Yesterday, for example, the Mortgage Banks Association released the results of its latest survey of weekly mortgage applications. According to its estimate, after adjusting for seasonality, mortgage applications decreased last week by 11.5% compared to the week prior. Excluding the seasonal adjustment, they fell by 20% over the same time period.

What's driving mortgage application volumes down? The answer is higher mortgage rates. According to Freddie Mac's Primary Mortgage Market Survey, the average rate on a conventional 30-year fixed-rate mortgage shot up this week to 3.91%. That's the highest rate in over a year, and nearly 60 basis points up from the trough at the end of 2012. This uptick is reducing the incentive of current mortgagees to refinance, as the MBA also reported yesterday that the refinance share of mortgage activity decreased to 68% of total applications down from 71% the previous week.

To get back to Wells Fargo, in turn, anything that happens in the mortgage market is of primary concern to the bank because it underwrites roughly a third of all home loans in the United States. But the flip side of the coin -- and this may go a long way toward explaining why Wells Fargo is bucking today's downtrend -- is that any negative impact of higher interest rates on mortgage applications volumes will be at least partially offset by a higher yield on earning assets.

John Maxfield has no position in any stocks mentioned. The Motley Fool recommends Wells Fargo. The Motley Fool owns shares of Wells Fargo. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.