The Bureau of Meteorology has upgraded its advice on Severe Tropical Cyclone Jasper, saying the highest risk of impact now lies somewhere along the 1000km stretch between Cooktown and Mackay. Previously, BOM forecast the impact area as being in the Mackay region, but has now upgraded its warning to include the major population centres of Cairns and Townsville. Modelling shows impact is likely to be mid-next week, probably about Tuesday morning. BOM said Jasper was situated 1320km east-north east of Cairns and was still classified as a category 3 cyclone at 10am AEST on Thursday. The bureau says Jasper is expected to strengthen further to a high end category 4 cyclone on Thursday night and possibly a category 5 cyclone on Friday. Jasper is being tracked slowly moving south to south west towards the far north east of the Coral Sea. Over the weekend, BOM says Jasper is likely to weaken and move west towards the Queensland coast. "While the timing and severity of a coastal impact remains highly uncertain, the highest risk of a cyclone impact lies between Cooktown and Mackay, including Cairns and Townsville mid next week," BOM says.