cls
$pattern_data = "(?<Дата>\d\d-\d\d-\d\d \d\d:\d\d:\d\d)"
$pattern_level = "(?<Уровень>INFO|ERROR|WARN)"
$tomcat = Get-Content "D:\tmp\tomcat.log"
$tomcat | where {$_  -match $pattern_data +",\d\d\d " + $pattern_level}| foreach {$Matches.Дата, $Matches.Уровень}

#Дата и уровень ошибки выводятся, осталось высветить расшифровку

(\n\s|[^\n])+

(\n\s|[^\n])+

(\n(?!\d\d-\d\d-\d\d)|[^\n])+

$text = Get-Content -path D:\tomcat.log
$pattern_yellow = "(\d\d-\d\d-\d\d \d\d:\d\d:\d\d)(,\d\d\d )(INFO|ERROR|WARN)([\s:]{2,3})(\n(?!\d\d-\d\d-\d\d)|[^\n])+"
$AllMatches1 = [regex]::matches($text,$pattern_yellow)
$AllMatches1 

string pattern_all = "(\\d\\d-\\d\\d-\\d\\d \\d\\d:\\d\\d:\\d\\d)(,\\d\\d\\d )(INFO|ERROR|WARN)([\\s:]{3})(\\n(?!\\d\\d-\\d\\d-\\d\\d)|[^\\n])+";
            string s = File.ReadAllText(@"D:\tomcat.log");            
            Regex regex = new Regex(pattern_all);
            MatchCollection matches = regex.Matches(s);
            if (matches.Count > 0)
            {
                foreach (Match match in matches)
                    Console.WriteLine("Дата = " + match.Groups[1] + " уровень = " + 
                        match.Groups[3] + " текст = " + match.Groups[5]);
                     //Console.WriteLine("Дата = " + match.Groups["Дата"] + " уровень = " + 
                    Console.ReadKey();
            }
            else
            {
                Console.WriteLine("Совпадений не найдено");
                Console.ReadKey();
            }