The Bureau of Meteorology is warning of heavy rainfall and possible flash flooding across much of south east Tasmania. Hobart saw about 33mm of rainfall between 4pm and 7.30pm, and the Bureau reissued a severe thunderstorm warning for the Midlands, upper Derwent Valley, south east, East Coast, central North and Central Plateau districts just after 7pm. The Bureau said rainfall rates of up to 20mm an hour were possible. Locations which may be affected include Swansea, New Norfolk and Hobart. The intersection of Davey St and Sandy Bay Rd was underwater earlier in the evening, as police warned motorists to avoid Risdon Rd in New Town and Bowden Rd in Glenorchy. Meteorologist Alex Melitsis said an unstable atmosphere, moist air mass and light winds had led to slow moving thunderstorms over Hobart. He said the situation was uncertain, and that the Bureau would leave the severe thunderstorm warning in place until "the coast was clear." A Taste of Tasmania spokeswoman said the twilight cinema had been cancelled and buskers had moved inside for the evening. A harness racing meet at Elwick was also called off. Police are warning people to drive sensibly and to the conditions and said some low lying intersections near the city were under water.