April 25 (Reuters) - AvalonBay Communities forecast full-year funds from operations (FFO) marginally below Wall Street estimates on Thursday, as weakness in rental markets in Northern California offset strong performance in its suburban coastal markets.

The company expects full-year FFO, an important metric watched for real estate investment trusts (REITs), to be in the range of $10.63 to $11.03 per share. Analysts on average were expecting $10.86 per share, according to LSEG data.

AvalonBay's portfolio, which includes properties in cities such as Seattle and San Francisco, has seen some rental weakness due to flailing demand and strong supply. This offset steady rental growth in markets such as suburban New York, Southeast Florida and Washington D.C.

For the second quarter, the company expects projected FFO to be in the range of $2.59 to $2.69 per share. Analysts on average were anticipating $2.70 per share.

However, first quarter FFO per share of $2.73 beat estimates of $2.65.

Same-store rental revenue grew 4.3% in the quarter ended March from a year earlier. (Reporting by Rupali Chaudhary and Ananta Agarwal in Bengaluru; Editing by Sriraj Kalluvila)