using System;
using System.Text.RegularExpressions;
 
class Program
{
  static void Main()
  {
    string modify = "KLAX 032109Z 26014KT 10SM FEW070 SCT120 BKN220 21/17 A2986 RMK AO2";
 
    modify = Regex.Replace(modify, "FEW([0-9]{3})", "few clouds at $1");
 
    Console.WriteLine(modify); 
 
    modify = Regex.Replace(modify, @"(?s)(?<=[0-9]{2}SM)(.+?)0([0-9]{1})0.+?(?=[0-9]{2}/[0-9]{2})", "$1$2 thousand.");
 
    Console.WriteLine(modify);
  }
}
 

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