By Cedar Attanasio Officials on Tuesday urged residents in some parts of Juneau to evacuate ahead of what could be a record surge of floodwater after a huge upstream basin of rainwater and snowmelt dammed by Alaska’s Mendenhall Glacier started to release. Officials in recent days have been warning people in the flood zone to be ready to evacuate. On Tuesday morning they confirmed water had started escaping the ice dam and flowing downstream, with flooding expected late Tuesday and on Wednesday. They advised people in the city’s flood zone to leave while saying there was no need to rush. The Mendenhall Glacier is about 12 miles (19 kilometers) from Juneau and is a popular tourist attraction due to its proximity to Alaska’s capital city and easy access on walking…