A series of troughs and cold fronts will pass across southern Australia this week, with the troughs bringing unseasonable heat followed by cold fronts dragging the mercury back down. A cold front crossing Tasmania today is a prelude to what is in store for much of southern Australia this week. This cold front is further south than those to follow, so only parts of Tasmania are feeling the direct effects of the brisk winds and showers today. A trough is currently moving across the south, and the northwesterly winds associated with it are responsible for dragging heat from the interior over southern parts of the country. Parts of SA, including Adelaide, are actually in the midst of a late season low-intensity heatwave. The heat will make its way to eastern New South Wales by Monday, including Sydney which just recorded its warmest first week of April since 1977 at Observation Hill. A cold front is following the trough, this one much further north than that impacting Tasmania today. However, it looks to weaken and be forced south after clipping southern WA on Monday. So heat will remain for many parts of southern Australia, in particular SA, NSW and the ACT well into this coming week. Yet another trough looks to move across southern Australia later in the week, however it should be be kept a bit further north than its predecessor. This means the heat will be restricted to areas away from the coast in SA and VIC, but should reach eastern NSW. The cold front following this trough may be the strongest so far this season, and should blast away the lingering summer-like heat from most areas. Despite this front, parts of eastern NSW look like staying warmer than average for this time of year for at least a couple of weeks yet.