The 21-year-old, who will stay at Ewood Park until the end of the current campaign, hit form last month, bagging a brace against Portsmouth and further strikes against Oldham Athletic and Bury as Tony Mowbray’s high-fliers moved into pole position in the third tier.
Magpies forward Armstrong – who lifted the Under-20 World Cup with England last summer – also set up Elliott Bennett’s strike in Rovers’ 3-0 win over Wimbledon at the end of February.
Since joining Blackburn in January, Armstrong has netted five times in 11 outings, helping Mowbray’s men consolidate their promotion challenge.
He spent the first half of the season on loan at Championship side Bolton Wanderers, where he scored three goals in 23 games.
Armstrong has previously spent time on loan at Barnsley in the 2016/17 season and Coventry City, where he first worked under Mowbray, hitting 20 goals in 2015/16.