One to three inches of rainfall expected in next 18-24 hours

At 8:45 a.m., radar showed a large area of moderate to heavy rainfall moving into western Connecticut.  This area is part of a large complex of showers and thunderstorms covering most of New York, Pennsylvania and the Washington, D.C., area.  This area is moving to the East at 30 mph and rain should overspread all of Connecticut by 10 a.m. Thursday, according to state emergency officials.

The latest GFS and NAM computer models are forecasting a general one to three inches of rainfall during the next 18-24 hours for most of the state. A few locally higher amounts are possible in any thunderstorm activity however severe thunderstorms are not expected at this time.

This rainfall is expected to result in minor to borderline moderate flooding of the Housatonic and Farmington Rivers and minor flooding along the Connecticut River. For the mid-sized rivers minor to pockets of moderate flooding are possible especially along the Still River, Quinnipiac River and Yantic River. For the smaller rivers flooding will be dependent on the track of individual showers and thunderstorms and is generally expected to be minor to moderate. Urban flooding can be expected if rainfall rates reach one inch per hour during this event. Towns are advised to closely monitor their local rivers and streams.

Here is the detailed forecast based on current radar and the GFS and NAM computer models:

Thursday: Rain entering the state from west to east between 8-10 a.m. The rain is expected to fall moderate to occasionally heavy at times for a six-hour period through mid afternoon. Some urban flooding is expected from late morning into early this afternoon. A break in the rainfall may occur for several hours late this afternoon and early this evening.

Thursday night: Rain redeveloping and becoming heavy at times for six to 10 hours. Urban and small stream flooding can be expected tonight with the medium sized rivers also approaching and going into minor flooding overnight. Some gusty winds along the coast up to 40 mph at times may down a few tree limbs or whole trees resulting in a minor number of power outages. The rain is expected to end before daybreak on Friday.

Friday: Rain showers are forecast to end completely by noon. Urban flooding is expected to subside around daybreak. However the mid-sized rivers are forecast to continue to rise for a few hours Friday morning before cresting around noontime. The larger rivers are expected to continue rising through the day cresting either Friday night or during the day on Saturday.

Overall this is expected to be a minor to moderate flooding event with a minor number of power outages, according to the state Department of Emergency Management and Homeland Security.