Why It's Hard To Predict Whether Vermont Will Have Spring Flooding This Year

Motorists slog through spring floodwaters near Enosburg, Vermont
in April, 2011. 

We here in Vermont are getting toward the start of the spring flood season, so it's only natural to start wondering if this year will be bad for that kind of nastiness.

At the moment, there are plenty of mixed signals on what kind of spring flooding, if any, the Green Mountain State sees this year.

First, some background. Flooding can and does occur at any time of year in Vermont. Ice jams during rainy, very warm January thaws can trigger floods, as they did in 2018.

Late spring and summer torrential thunderstorms can set off big local flash floods, as they have in many years, like in 2013.  Tropical storms heading north into New England we know can cause serious floods, as we remember from Irene in 2011.

Large autumn storms can sweep through and cause floods, as we saw big time last Halloween.  And of course, rain and melting snow can cause spring flooding in March and April.

Quite frankly, Vermont doesn't need any more flooding.  Last April, the kind of spring flood I'm talking about hit parts of central, southern and eastern Vermont, prompting a federal disaster declaration.

Then that even worse Halloween storm a few months back triggered serious flooding across the northern half of Vermont, prompting another federal disaster declaration. Yep, two such declarations within about seven months.

So, on to this spring. We might as well talk about it today, Sunday, since the outdoors does have a mild, spring-like feel.

Today's weather signals that we are now entering our first good thaw of late winter and early spring.  The first chance of any late winter or spring flooding comes late this week, but that is decidedly iffy. The chances that an expected pretty big storm late this week are pretty low.

That's because at this point, the storm looks like it will bring us a mix of stuff. It will probably include rain, but that rain will likely mostly just soak into the existing snowpack. Plus the storm will probably bring other types of precipitation, like wet snow, sleet and/or freezing rain.  If the storm ends up being mostly snow or mixed precipitation, that would actually add slightly to the risk of flooding later.

That's because there will be even more snow and ice locked up on the ground, waiting to melt.

Even if that happens, the amount of snow on the ground, and the amount of water locked up in that snow, is roughly normal for this time of year, says the National Weather Service South Burlington.

That NWS office issues a winter/spring flood outlook every other week this time of year, so that's where I'm getting this information.  A normal late winter snowpack implies a normal spring flooding season, if you ignore all other possible factors, which of course you can't do.

Moisture in the soil is near to just a little above normal, which is largely a legacy of last year's very wet autumn. River flows currently are also near or a little above normal.  There's ice in the rivers which could cause ice jams, but it's not a huge amount of ice. We've had a warm winter.

Lake Champlain also has a near normal level heading into the spring flood season.

All this means is it's a tossup as to whether you should think about any spring flooding in Vermont this year.

Spring flooding is a major concern for much of the nation this year.  

Last spring brought widespread, disastrous and in some places unprecedented flooding to much of the central United States, especially in places like South Dakota, Nebraska, Iowa and Missouri.

The outlook for this year is pretty grim, especially in the eastern Dakotas, the upper half of the Mississippi Valley, around the Great Lakes and other parts of the Midwest, as The Weather Channel reports.   Of course, we've already had super serious flooding in the South this month.

In the bigger river systems like the Missouri, Mississippi, Ohio and other large rivers, you can make an educated guess ahead of time as to how serious flooding might be a month or two down the road,

Vermont lacks those big rivers.  In the large river systems further west, floods are slow rolling disasters.  Vermont floods are like a mugging.  They hit you in an instant, and just as quickly, they're gone.  It's hard to predict a mugger, and it's hard to predict a Vermont flood well in advance.

In some years, when the snowpack and the soil moisture and the rivers are high in late February, you can safely anticipate at least some flooding later in the spring. In normal-ish years like this, it all depends on what March and early April does.

If we have a lot of very wet storms over the next two months - either rain or snow - that can make the flooding risk skyrocket.  If we have a March and early April full of perfect sugaring weather - mild thawing afternoons and freezing nights - the snow melt is slow and we have a low flood risk.  A big bout of super warm, record temperatures, especially if accompanied by heavy rain, you get floods.

Long range forecasts are tricky, but some of those forecasts do predict a relatively stormy first half of March. Beyond that, you might as well flip a coin.

Climate change adds an additional twist.  The risk of heavier individual rain storms is getting higher.  However, that overall risk is a big picture thing.  You really can't tell when those bigger, heavier storms might hit.  The next monster storm could be next week, or it could wait five years or more. Who knows?

The only thing I can say is have your sump pumps ready, just in case. This year truly is a tossup.

Weird, Challenging Nor'easter Snowstorm Continues To Keep Forecasters On Toes

Extremely heavy snow falling in Bucks
County, Pennsylvania today. There were
widespread reports of thundersnow and
snowfall rates of at least two inches per hour

The long-promised nor'easter is now well underway in the Northeast, and it's continuing to frustrate the heck of out many meteorologists.

Early runs of computer models a few days before this storm were remarkably consistent in forecasting what this thing would do. Those same models have been all over the place - not knowing what to predict - as the storm got underway.

That's the opposite of how it usually works out. Forecasts usually get more accurate as we get closer to the storm. Not this time, really.

Broad brush: The latest trends suggest northwest Vermont will get a little less snow than we were thinking last night. As I say that, parts of New Jersey, southern New York and inland southern New England are getting blasted even more than many forecasters thought.

The bad news is this worst of the storm seems to be hitting New Jersey, the New York City metro area and on up into the lower Hudson Valley and Connecticut right at rush hour today.

Things weren't too bad earlier today in that neck of the woods, so a lot of people went to work. Now that it's time to go home, YIKES!

Snow late this afternoon is coming down at a rate of two to three inches per hour, which is amazing. Visibility sucks. And since temperatures are near 32, that wet snow compacts under car tires to create slick ice, then deep accumulations pile up on top of that. And throw in some lightning and thunder to make things really dramatic.

By the way, there's LOTS of thundersnow in New Jersey, southern New York and Connecticut. More than I've seen in a nor'easter in a long time.

Yeah, just try driving in that crap.

Additionally, this is very wet, heavy snow down there. A lot of trees and power lines are coming down.

Those bands of heavy snow are, as expected, moving north into northern New England, but the question is, how intense will the snow be tonight, given the latest computer guidance that the storm will go a little further east than earlier anticipated?

One band of snow moved northward through Vermont this morning and early afternoon, laying down a half inch ot an inch and a half of snow. But it's March, and when a weak sun temporarily struggled through the clouds, most of that melted.

The bigger band will come through tonight, so there's no snow to cause any melting

An initial band of snow with the current nor'easter dropped
0.7 inches of snow on my property in St. Albans, Vermont
late this morning and early this afternoon, but the
higher sun angle in March meant that a lot of it
melted when the sun struggled to come through the clouds

So the latest thought is that anything in Vermont east of a line from Middlebury to Newport can still expect at least six inches of snow by the end of the day Thursday. In the Champlain Valley, it may - or may not - end up being a little less than that.

It depends upon how the northward moving snow bands hold together.

The National Weather Service office in South Burlington, Vermont has a fairly doubtful outlook on this, so they've downgraded winter storm warnings in the Champlain Valley to winter weather advisories. 

They're saying four to six inches - total - in the Champlain Valley. They're probably right, but this storm has held so many surprises that I'm not counting on that forecast, even though we're right at the cusp of the storm starting, when we're supposed to know what's going on.

I guess just expect lousy travel conditions overnight and on Thursday morning as we deal with this snow.

It still looks like whatever snow we get will get lighter during the day Thursday, but it will continue off and on into Saturday. There will be light additional accumulations each day through Saturday up here in Vermont, but nothing spectacular.

In the warmer valleys, there will also probably be a small amount of melting as temperatures rise just above freezing, and the stronger solar radiation in March will get through the clouds.

Speaking of computer forecasting models not knowing what's next: Nobody has any idea what the frig the weather will be like early next week. I guess we'll have to wait to find out.

Vermont Weather Like A Moody Teenager

The weather this weekend in Vermont and surrounding areas is behaving like a bored teenager. The teenager might be listening to One Direction, but is certainly not motivated to move one way or the other.

A towering shower cloud boils
up through the hazy, humid air  Friday
evening northwest of St. Albans, Vermont  

The same with the weather. We're caught in that sticky airmass just sitting here, not being much use at all. (Kind of like our teenager sometimes behavies)

There's subtle wind shifts, boundaries, patches of sun, patches of clouds that could trigger showers or thunderstorms at any time, but nothing striking or definitive to help forecasters tell us what will happen and when.

The result has been a guessing game of when and where any showers or storms will form. And if they do form, how heavy will they get?  Whatever forms isn't moving very fast, so a few spots could get minor flooding.

But where? There's a subtle stationary front over northern Vermont. Will it move a bit north? Or a bit south? Will other dynamics come into play to encourage more showers and storms?

It's anybody's guess, but the consensus is there's a lesser chance of rain Sunday as a patch of somewhat drier air moves in aloft. But not down here. It will still be humid as heck.

It's hard to rely on weather forecasts in this type of weather situation. To be on the safe side between now and say, noon Monday, go ahead with your outdoor plans but be ready to move inside at the drop of a hat because a random downpour, shower or thunder bumper could arrive at any time.

Like most teenagers, the weather will eventualy get motivated and moving again. A cold front is still expected to come in Monday or Monday night with a more definite batch of showers and storms. Then it will turn cooler and more invigorating by the end of the week.

Just like our teenager when she comes out of her funk.