United States Just Had Its Wettest Winter On Record. Floods Next?

The United States had its wettest winter on record, says NOAA
All the states in blue were wetter than normal. Dark blue
represents a much wetter than normal winter. 

For the United States as a whole, this past winter was the wettest on record. Which means floods.

Yeah, we already had 'em, especially in places like Tennessee and California.

But since a lot of the precipitation came down as snow in parts of the country, the high water will spread to those northern areas that are snowy at the moment.

Climatologists use the period from December 1 to February 28 to define winter.  During that time, precipitation averaged across the United States amounted to 9.01 inches. That barely exceeds the old record of 8.99 inches during the winter of 1997-1998.

This past winter, the wetness was distributed over almost the entire nation. The only places that were not wetter than average were Washington State, parts of the northern Rockies and New Mexico. Even there, precipitation was near average for the winter.

As mentioned, Tennessee, which seemed to be having floods every time you turned around this winter, not surprisingly had its wettest winter on record. Eighteen states, mostly in Midwest and Ohio and Tennesse valleys had a winter that was in the top 10 wettest.

Here in Vermont, it was the 11th wettest out of the past 124 winters.

The predominant weather pattern featured storms entering the West Coast of the United States and then heading east, then northeast toward the Great Lakes. This ensured that most places in the nation got precipitation from this parade of storms.

The wet winter continued a trend that became well established last year. Many cities near and east of the Mississippi River all the way to the Atlantic coast had their wettest year on record in 2018.

Writing in the Category 6 blog, Bob Henson said:

"Despite periods of intense drought in recent years, especially toward the Southwest - with the impacts worsened by rising temperatures - the overall trend over the last century has been toward wetter U.S. conditions. The 48-state annual precipitation average is now around 31 inches, compared to 29 inches a century ago."

A two-inch increase over 100 years might not seem like a lot, but it is if you consider you have to average out all the dry and wet spots yearly in a vast nation like the United States.

Much of the winter precipitation came down as snow in the northern tier of states near the Canadian border from Washington to Wisconsin, the Upper Peninsula of Michigan and in far northern New England, especially northern Maine.

Snow depths are now great in many of these areas and the water content in the snow is high. That sets the stage for spring flooding.

California National Weather Service offices issued a statement Thursday saying that there's an elevated risk of spring flooding in much of the Golden State.

The snowpack in the Sierra Nevada is above average. If the spring is warm, or if there are unusual rains, the flooding could get pretty intense. There's already been quite a bit of flooding in California this winter from heavy rains, especially in the Russian River basin.

In Minnesota, where the deep snow has the equivalent of up to six inches of rain locked into it, National Weather Service forecasters are expecting the highest risk of flooding in years. In this state, a wet autumn made the soil soggy. Then a deep freeze at the end of January made the ground freeze to a pretty good depth, so runoff won't soak in easily.

Then February had record snows, and there's a good chance of two more really big snowfalls in the coming week. When it finally warms up in Minnesota, there's bound to be quite a bit of flooding.

Further south in Iowa, forecasters said snowmelt alone will probably be enough to cause flooding. If it's a rainy spring, it could turn disastrous.

It will be interesting to see what happens along the Mississippi River, especially if this spring is wet. It's already at flood stage in its lower half. Some areas along the river are at major flood stage.

Although that southern flood crest will start to head toward the Gulf of Mexico, will it recede enough once the snowmelt surge from the North, and crests from the Missouri and possibly the Ohio rivers move into the region.

Closer to home northern Maine, and to a slightly lesser extent northern New Hampshire, are at a pretty high risk of flooding this spring.

As of Thursday, Caribou, Maine had received 151 inches of snow this winter, and there was 45 inches - nearly four feet - on the ground. There's nine to 14 inches of rainfall equivalent in that northern Maine snowpack, so the flood risk there this spring is way above average.

Here in Vermont, the National Weather Service in South Burlington just issued its latest spring flood outlook on Thursday.

Spring flooding in Cambridge, Vermont in April, 2014. Depending
on weather patterns and precipitation, similar flooding could
hit the Green Mountain State later this spring. 

Vermont is on the edge of the deep snow in far northern New England.  That brings us to a bottom line above average flood threat in the Northeast Kingdom, north-central and much of eastern Vermont.

The rest of the state has a near average flood threat, but the risk of ice jam floods is pretty high on most rivers, since they have a lot of ice in them and there's lingering ice jams still in place from thaws earlier in the winter.

Storms in the forecast for the next week to ten days don't look like they will have huge amounts of precipitation, so we're probably safe in the short term.

Spring flooding in Vermont, if it happens, is most likely in late March or April, and how much high water comes depends on whether we get particularly heavy rain storms or sharp, strong spikes in temperature that would lead to rapid snow melt.

A slow snow melt with relatively dry weather will mean little if any flooding.

There's a great chance that Lake Champlain will reach the flood stage of 100 feet sometime this spring. The lake level is already above normal for this time of year, being at 96.73 feet as of this morning.

A minor lake flood is good for the ecosystem, but a larger one - perhaps a level of 101 feet or more - can really cause some damage. I'm doubting the lake will get that high this spring unless we get a TON of rain in the coming six weeks or so.  A repeat of the devastating 2011 Lake Champlain flood does not look like it's in the cards this year, which is a good thing.