A flood watch has been issued by the National Weather Service for the entire state until Wednesday evening, with significant rain forecast on top of rapidly melting snow and ice.

The NWS said Monday that rain will spread across the state early Tuesday morning with the first rains arriving in central Maine after midnight and becoming heavy at times throughout Tuesday afternoon and evening.

With rain predictions from 1 to 2 inches, with higher amounts in the mountains, NWS said it is likely already swelling rivers will overflow their banks.

NWS maps Monday night forecast minor flooding in Lewiston and Rumford.

Mild temperatures are expected to drop as a cold front sweeps in behind the storm Tuesday night. Forecasts are calling for rain, wet snow and sleet possible as the storm ends after midnight.

Meteorologist Mike Ekster of the National Weather Service in Gray said that between snow melt and incoming rain, the Androscoggin River is expected to rise to flood stage midday Wednesday.

Ekster said he expects river levels to remain elevated another 48 hours until midday Friday.

However, flooding is expected to be minor, Ekster said, with flood level for the Androscoggin River in Auburn at 13 feet and anticipated levels to crest only 3 feet above that at 16 feet.

According to forecast maps at the National Weather Service, Route 136 in Auburn begins to flood at 13½ feet. No significant impacts were forecast for the Rumford area.

To put things in perspective, Ekster said the Androscoggin River in Auburn reached 27½ feet March 20, 1936.