WASHINGTON (AP) — The average rate on the 30-year fixed mortgage jumped after standing pat for three straight weeks at record lows. But the rate stayed below 4 percent for the 12th straight week, keeping home-buying and refinancing attractive for those who can qualify.

Mortgage buyer Freddie Mac said Thursday the rate on the 30-year loan rose to 3.95 percent. That's up from last week's rate of 3.87 percent, the lowest since long-term mortgages began in the 1950s.

The average on the 15-year fixed mortgage rose to 3.19 percent from 3.16 percent. It hit a record low of 3.14 percent three weeks ago.

So far, low rates have done little to help the housing market, which is slowly improving. Few people can qualify for the rates and many who can have already done so.

But the housing market is flashing signs of health ahead of the spring-buying season. Sales of previously occupied homes are at their highest level since May 2010. More first-time buyers are making purchases. And the supply of homes fell last month to its lowest point in nearly seven years, which could push home prices higher.

The job market is also improving, which is critical to a housing rebound. In January, employers added 243,000 net jobs — the most in nine months — and the unemployment rate fell to 8.3 percent, the lowest level in nearly three years.

Frank Nothaft, Freddie Mac's chief economist, said the housing market is gradually starting to pick up. Still, home sales remain weak and it could take years for the market to fully return to health.

To calculate the average rates, Freddie Mac surveys lenders across the country Monday through Wednesday of each week.

The average rates don't include extra fees, known as points, which most borrowers must pay to get the lowest rates. One point equals 1 percent of the loan amount.

The average fees for the 30-year and 15-year loans were unchanged at 0.8.

For the five-year adjustable loan, the average rate fell to 2.80 percent from 2.82 percent, and the average fee fell to 0.7 from 0.8.

The average on the one-year adjustable loan fell to 2.73 percent from 2.84 percent, and the average fee was unchanged at 0.6.