Thunderstorms are firing up in South Australia this morning at the beginning of a multi-day and multi-state severe weather event. A strong cold front and complex low pressure system will generate severe thunderstorms, heavy rain and damaging winds across a large part of the country between now and Friday. South Australia is first in line. Thunderstorms building over the North West Pastoral District this morning will spread across the state with the cold front today, reaching central areas by the afternoon and the eastern border by tonight. These storms have the potential to produce large hail, damaging to destructive winds and heavy rainfall. After this initial round of severe weather, emergency services won't have time to relax. Westerly winds will strengthen rapidly over South Australia later today as the complex low intensifies over the Bight. Damaging winds are possible across most of the state tonight and on Thursday, although the strongest winds will be in the west where gusts may reach 120km/h along the coast this evening. These winds are capable of considerable structural damage. Gales are possibly through central areas from tonight, possibly gusting to around 90km/h in Adelaide and higher about the coasts and ranges. Rainfall accompanying the front and low will cause an accumulated total of 30–60mm over South Australia's Mid North, Mount Lofty Ranges and parts of Adelaide over the next 48 hours. This rain is likely to cause both flash and riverine flooding. Conditions will ease in South Australia on Friday afternoon as the low moves away to the east. In Victoria, damaging winds and heavy rain are also likely during the days ahead. Wind gusts of 90-100km/h are likely near the front as it moves through the state's west this evening and central and northeastern districts overnight into Thursday morning. Gusts may exceed 110km/h on elevated terrain. Flash flooding and river flooding are both likely as well. Rain and storms during the next 24 hours could cause 10-20mm within a few hours. Further showers on Thursday and Friday with the passage of the low will be falling onto saturated ground. Flood watches are in place for a number of river basins across state. The main threats for New South Wales will be damaging winds, heavy rain and severe thunderstorms accompanying the front on Thursday. The strongest winds will be on the ranges during the afternoon, where gusts could reach 90km/h. Moderate to heavy rain is likely to exacerbate existing flooding over the state's Central West and South West Slopes on Thursday morning. Further showers, storms and potentially damaging winds will develop in the southwest on Thursday near the low. Queensland can expect to see potentially severe thunderstorms accompanying the front through western districts tonight, then central and eastern areas on Thursday. Damaging winds, heavy rain and hail are all possible with these storms. Rain will spread over Tasmania on Thursday and Friday, bringing another 50-80mm of rain across recently flood-affected areas of the state. This may lead to renewed river level rises at the end of the week. The latest warnings throughout this event are available here: http://www.weatherzone.com.au/warnings.jsp