Monday, February 10, 2014

Deep Snow Pack = Big Flood Concerns

With so much snowfall this season and so much of that snow staying on the ground, the thought may have crossed your mind: "What happens when all this melts"!? That is something that hasn't strayed far from our mind in the Stormtrack weather center this winter. A look at current conditions and a historical context will reveal an uneasy outlook for area rivers the next few weeks.

First what does the current snow pack look like? Right now it is generally over 10" for northern Ohio and Southern Michigan.

And how much water does that snow currently have in it? Satellite analysis and actual samples reveal a widespread 1.5" to nearly 3" base for our entire area. A VERY 'healthy' amount...

So why the concern? This is where we turn to history in our area. At least 70% of the significant floods on our local rivers have come during a winter/spring thaw. On the Maumee river at Waterville that number is actually 100% for the top 10 crests.

It doesn't take much page turning in the history books to find a very recent example of this potential in 2008. That season recorded the 7th most snowfall in a season in Toledo's history. In early February, when there was around 1" of water locked up by snowfall on the ground, a warm-up and heavy rainfall released it quickly into waterways. Temperatures spiked into the 50's and over 2" of rainfall fell. Adding the water already on the ground, frozen ground and ice on the rivers/creeks already made for historic flooding. The Sandusky, Maumee and Blanchard all recorded top 10 crests during that warm-up.

And while the deep snow pack certainly plays a big role in flooding it isn't the entire equation. Thick ice can slow and even block water flow on waterways, a frozen ground that can expedite runoff and additional rainfall are also important factors. Significant ice at the mouth of the Maumee river also could slow any water from running down the waterway into Lake Erie. 

The bottom line is we need a slow, gradual warm-up that would allow this snow to be released gently into area creeks and rivers. Given the very active weather pattern we have been in this winter and look to continue a slow warm-up may be a tall order. Forecast models are already hinting a potential quick hitting warm-up around February 21-25th. We will need to watch this closely.