It is the perfect storm: Rising home prices, rising mortgage rates, and rising demand are colliding with a critical shortage of homes for sale.

And all of that is slamming housing affordability, which is causing more of today's buyers to overstretch their budgets. This year, affordability—a metric based solely on the amount of the monthly mortgage payment—will weaken at the fastest pace in a quarter-century, according to researchers at Arch Mortgage Insurance.

The average mortgage payment, based on the median-priced home, increased by 5 percent in the first quarter of 2018 nationally and could go up another 10 to 15 percent by the end of the year, according to their report.

Researchers looked at the median-priced home, now $250,000, and estimated price gains this year of 5 percent in addition to mortgage rates going from 4 percent to 5 percent on the 30-year fixed. Other studies that factor in median income also show decreasing affordability because home prices are rising far faster than income growth.

Read more in CNBC.