Homes in Seattle. D.Fajio / Flickr

Seattle and Portland have seen the biggest increase in home prices among 20 of the largest metropolitan areas nationwide.

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According to data from S&P CoreLogic Case-Shiller, Seattle has seen a 12.3 percent increase in home prices year-over-year in March, the highest of all 20 metro areas.

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Seattle was followed by Portland, where home prices increased 9.2 percent year-over-year. Home prices in Dallas increased 8.6 percent.

That's compared to cities like San Francisco, the epicenter of an infamous housing affordability crisis. San Francisco saw a 5.1 percent year-over-year increase in home prices.

According to the new data, an unusually low inventory of homes for sale accounts for the rise in prices.

Seattle has seen a 1.79 percent monthly change in its home price NSA index. That index indicates the changes in the total value of all existing single-family housing stock.

Portland, meanwhile, has seen a 1.26 percent monthly change. Nationally, that number is 0.98 percent.

The analysis adds there is no telling when rising prices and mortgage rates will force a housing slowdown. Seattle and Portland were also compared to cities like Las Vegas, San Diego, New York, Miami, Atlanta and Chicago.