Midwest and Northeast on Alert: As Snow Melts, Flooding and Ice Jams Are Possible

By: By Alan Raymond

Published: February 20,2014

 

 

 

 

It’s been a cold and snowy winter for the Midwest and Northeast. Some locations like New York, Chicago and Philadelphia are having winters that rank in the top five snowiest since record keeping began. That snow will eventually melt, releasing its locked up water - and it might happen sooner than you think.

Current Temperatures

Current Snow Depth

(VIDEO: Let it Rain, But Not Too Much)
With warming temperatures expected through the end of the week, snow will begin melting and ice could begin to break up on frozen rivers. What does that mean? Flooding from ice jams and melting snow is a distinct possibility.
Adding insult to injury, another powerful storm will bring heavy rain which could accelerate snowmelt, potentially enhancing flooding in some locations.
Here’s what you need to know:
Throughout the first half of this week, warmer temperatures have been streaming northward and the mild weather will be especially evident on Thursday. Highs in the Ohio Valley will be in the 50s and 60s and parts of the coastal Northeast could push near 50 degrees. 
(MORE: Prepare for Floods Now)
When you couple the effect of warm temperatures, melting snow and a ground that’s nearly impermeable because it’s frozen, you have a recipe for flash flooding.
This week, a potent low pressure system is forecast to bring heavy rain to parts of the Ohio Valley and Great Lakes, which will further exacerbate flooding concerns. The low is expected move through on Thursday before pushing into the Northeast on Friday. Rainfall amounts of 1 to 2 inches are possible within the next few days. Any rain that falls will only accelerate snowmelt, adding to the runoff from the rain.

Thursday Forecast

Thursday Night Forecast

Rainfall Forecast

According to the National Oceanic and Atmospheric Administration, the amount of snowpack that's still on the ground throughout the Midwest and most of the Northeast contains the equivalent of another two to six inches of liquid water.
Add the water from melting snow to the impending heavy rain, and you’ve got a lot of water that could accumulate all at once.
(MORE: Winter Storm Seneca)
Another concern will be ice jams on rivers. The warm temperatures and rainfall will cause ice sheets on the river to breakup and be carried downstream. Often, these pieces of ice will come together in a narrower part of the river and get stuck.
Water backs up behind the ice jam, causing the river to overflow its banks and flood surrounding areas.
Given the potential for flooding, some states in the Great Lakes region and the Midwest are currently under flood watches.
(ALERTS: Flood watches, warnings (in blue))
Bottom line: Flooding will be a serious concern through the end of the week. If you come upon a swollen river or creek, don’t drive through it. Two feet of water can sweep an SUV downstream.
(FORECAST: Indianapolis | Cincinnati | Cleveland | Buffalo)
MORE: 2013's Colorado Flooding

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Local resident Chad Obrien comforts his four year old son Elijah, as he works to remove waterlogged and contaminated floors and walls from his flooded basement, which was wrecked in recent flooding, in Longmont, Colo., Wednesday Sept. 18, 2013. (AP Photo/Brennan Linsley)