Residents in South Australia should prepare now for dangerous weather during the second half of the week, beginning Wednesday. An intense low pressure system and cold front will cause around 48 hours of severe weather from tomorrow. Heavy rain, flooding, damaging winds and severe thunderstorms are all likely in populated areas. The cold front will arrive first, producing rain and thunderstorms across the state on Wednesday. The most intense showers and storms will occur near the front itself, which is due to cross Spencer Gulf during the early afternoon, reach Adelaide around 5-6pm and cross the state's eastern border at night. These storms will be capable of producing damaging to destructive wind gusts, heavy rain leading to flash flooding, large hail and lightning strikes numbering in the tens of thousands. While the front leaves South Australia on Wednesday night, the low will arrive next and cause further showers, storms and the strongest winds of the event. Winds blowing from the west will strengthen significantly on Thursday morning as the low moves towards the state from the Bight. Damaging winds are a risk in all districts, although the strongest gusts will be in the south near the low. Wind gusts could exceed 130km/h along exposed coasts and peninsulas, which are capable of uprooting trees and causing considerable structural damage. At this stage Adelaide's strongest winds will occur from the afternoon, with gusts exceeding 100km/h in the metro area and stronger about the Hills and Mount Lofty Ranges. Total accumulated rainfall during Wednesday and Thursday is expected to be in the 30-60mm range from about the Mid North district down to the Mount Lofty Ranges, including Adelaide. Locally heavier falls of 100mm are possible about the ranges, which will trigger flash flooding. Large waves of over eight metres are expected to cause coastal erosion and localised flooding on Thursday, mainly to the west of Kangaroo Island. Blustery showers and large waves will continue in the state's south on Friday morning, although conditions will ease during the day as the low moves east towards the Tasman Sea. This weather system is likely to produce widespread damage and power outages that could last for days. It is a good idea to prepare now and if you need assistance during the event, contact the State Emergency Service on 132 500.