Porterfield - 69.
Middlesex drew their LV County Championship Division Two match at Lord's after yet another rain-affected day with Gloucestershire leading by 66 runs after reaching 161 for four from 54.3 overs in their second innings.
The hosts had declared on 313 for seven, taking a first-innings lead of 95.
Resuming today on 30, Gloucestershire lost their first wicket when Alan Richardson uprooted Kadeer Ali's leg stump. It was an excellent ball that came in sharply, deceiving the batsman who did not make an attempt to play the ball as he expected it to miss off-stump.
The first bowling change of the morning came after 10 overs - the 21st over of the innings - with Steven Finn replacing Tim Murtagh and being square cut for four, in his second over, by Hamish Marshall.
The first stoppage for rain came during the 28th over, just over an hour after play began. The disruption was brief, lasting just 10 minutes.
Six overs after resumption the visitors lost their second wicket on 92. Marshall, on 22, got an outside edge to a rising ball from Finn and was caught behind the stumps.
William Porterfield went on to bring up his fifth half-century in the championship this season from 108 balls having batted cautiously for nearly two-and-a-half hours.
Middlesex made a double bowling change shortly before lunch, putting on left-arm spinner Murali Kartik and off-spinner Shaun Udal.
The morning session ended on 105 for two and intermittent drizzle meant play was not resumed until 3.20pm, but within 15 minutes Finn claimed another wicket.
Once again he swung the ball in and knocked out Alex Gidman's middle stump to reduce Gloucestershire to 110 for three. Gidman's three runs had come in half an hour at the crease.
Porterfield's fine innings of 69 from 162 balls with six fours came to an end when Dawid Malan beat him with a leg break, trapping him in front of the stumps to make it 151 for four.
Chris Taylor, who had played a fine innings which included three boundaries in one over off Finn, remained not out with 38 from 42 balls when rain brought an end to the match an hour before the scheduled close of play. Finn finished with two wickets for 41 runs.