Seattle-area home prices climbed again in April, with one of the highest monthly gains among 20 metro areas in the nation, according to the S&P/Case-Shiller index released Tuesday.

The average price of existing single-family homes in King, Snohomish and Pierce counties soared 2.3 percent over March, when the average price jumped 1.9 percent, on an unadjusted basis. Seasonally adjusted, the monthly gain in April was 0.8 percent.

Over the past 12 months, area home prices rose 11.2 percent. The Seattle metro area has posted double-digit annual gains now for 14 consecutive months, though the market is still about 14 percent below its July 2007 peak.

Nationally, home prices posted 1.1 percent growth over the month and 10.8 percent over the year.

“Although home prices rose in April, the annual gains weakened,” David M. Blitzer, chairman of the Index Committee at S&P Dow Jones Indexes, said in a statement. “Overall, prices are rising month-to-month but at a slower rate.”

However, Blitzer cautioned, “housing is not back to normal: prices are being supported by cash sales, low inventories and declining foreclosure and REO sales (sales of real-estate owned, or bank-owned, property). First-time homebuyers are not back in force and qualifying for a mortgage remains challenging. The question is whether housing will bounce back before the Fed begins to tighten sometime next year.”

Home-price gains in the Seattle metro area have been rising faster than gains in the 20-city index: April’s monthly gain was twice as large as that of the 20-city index on an unadjusted basis. Seasonally adjusted, Seattle’s gain was four times larger than the gain in the 20-city index.

Fewer foreclosures and delinquencies are helping home prices gain ground lost during the recession.

The rate of foreclosures among homes with mortgages in King and Snohomish counties was about 1.4 percent in April, down from about 2.1 percent a year ago, according to data provider CoreLogic. Mortgage delinquencies — payments that are 90 days or more past due — fell to about 3.4 percent of mortgages in April, compared with about 5.2 percent a year ago.

First-time homebuyers are competing fiercely with each other and with investors for a shrinking pool of lower-priced homes.

This trend shows up in Case-Shiller’s home-price index, which tracks price changes of individual homes sold in the past three months by comparing the latest sale with the previous sale price.

In the Seattle metro area in April, average sales prices of homes in the lowest tier — those that sold more than six months ago for under $275,217 — were up 16.6 percent over the year. That compared with 11 percent appreciation in the highest tier — homes that sold more than six months ago for more than $443,041.

Sanjay Bhatt: 206-464-3103 or sbhatt@seattletimes.com On Twitter @sbhatt