May 14, 2019: All Clear

I believe Lake of the Woods is 100% ice-free today. So here’s a look at how the spring went, in graphs. You can click on the graphs to see a full-screen, zoomable version.

First, the Brick Graph. Each year gets a brick, and I stack them according to when the ice went out. For simplicity, I divide April and May into five-day periods.

2019 was not an early thaw. Of the last sixteen years, only 2014 was significantly worse, and that was a dismal spring after a brutal winter.

Here’s a slightly more complex graph, that shows not just the date the lake was clear of ice, but the length of time from when it started melting to when it finished. More specifically, each horizontal bar spans the calendar from the Inflection Date, when the mean daily temperature rose above freezing on a lasting basis, to the Thaw Date, when the lake was entirely free of ice.

2019 is at the top, 2018 just below, and so on, down to 2008, the earliest year Sean worked out an inflection date for.

Some fun trivia from this graph: Our inflection date was April 13th this year. 2016 shared the same inflection date, but the lake cleared by May 4th, a full ten days earlier. The ice was probably a lot thinner that spring, because the winter had been mild. 2010 was an extraordinary year: the lake was completely clear by mid-April!

Here’s a graph from Sean that shows how our spring temperature profile compares to other years.

On this graph, all the springs are lined up with Inflection as Day Zero at the left regardless of the calendar date. Each year gets dots in a different colour, and day by day, the mean temperature is added to the rising total. A spring with a string of hot days will produce a steep rise, a cooler spring will show a flatter line. The solid red line is the average for all the years since 2003. 2019 is the thin blue line, and Sean points out that although we did better than average at first, we fell behind about halfway along and never quite caught up.

Anyway, that’s the kind of spring it was, but the lake’s open now. I won’t be doing regular updates any more until next year. I expect I’ll fire up the Ice Patrol again on the first day of spring, or the inflection date, whichever comes first.

Thanks to everyone who came by to visit the website and shared word of it with friends, and a special thanks to my guest photographers and my co-workers at MAG Canada who made it possible for me to offer updates on days when I didn’t fly.

Talk to you next year,


May 13, 2019: The Last Ice

Today I went looking to see if any ice remains on Lake of the Woods. I did find some, south of the Barrier Islands, but it’s just little patches of loose, candled ice.

The photo above is from around 10:00 this morning, and looks south over Allie Island towards the Alneau Peninsula. I’ve circled the area of interest so you’ll know where to zoom in for a better look. At full resolution, that’s clearly ice.

I thought a little patch of weak ice like that wouldn’t last long, so I was looking forward to checking on it on my return in the afternoon.

We came back at about 5:00 and after checking to see that Big Sand Lake, north of Minaki was open, (too far away to photograph, but it is open) I started with a picture of Shoal Lake.

As far as I can tell, Shoal Lake is wide open. Because it’s deep, It often clears about three days later than Lake of the Woods, but this year it cleared earlier.

Next shot, Big Narrows.

Looking south. Left of centre is Wiley Point, with Big Narrows above the middle of the picture. In the distance, is that ice on Little Traverse? It was so hazy I wasn’t sure, but there was ice there the other day.

Next, I checked on that ice south of Allie Island.

In the centre of the picture, you can see it’s falling apart, but it’s not gone.

There was a lot of discussion about Bigstone Bay over the weekend, so I wanted to get a bird’s eye view.

This picture is centred on Scotty Island, with Middle Island and Hay Island stretching away to the right. Bigstone Bay appears to be entirely clear.

Next, a closer look at Bare Point and Pine Portage Bay.

Bare Point Marina and Northern Harbour, on Pine Portage Bay, are key access points for Bigstone Bay and Hay Island. Both are wide open now. I counted about twenty boats in the water at Northern Harbour this afternoon. There might be more, but the bigger boats are easier to see.

So although a small amount of ice persists, the lake is essentially open for boating.

Let’s go to the satellite imagery, Bob.

Aqua‘s image was spoiled by cloud today, but Terra got a pretty good shot. The white circle encompasses Rabbit Lake, Round Lake and Laurenson’s Lake, which are good markers for picking out Kenora. The small red circle is the surviving ice south of Allie Island. The large red circle indicates the area of possible ice on Little Traverse, but the satellite image shows nothing except a streak of cloud.

Fun with Clouds, Part Two: at the top left, our friends the fair-weather cumulus. At the right, in blue, high altitude clouds made of ice crystals. In the lower part of the picture, clouds of vertical development: towering cumulus or nascent thunderclouds, with watery bases and icy tops. When clouds like this become full-grown thunderheads, the vertical movement of water droplets up and down through the freezing level forms hailstones.

Summary: only one tiny patch of weak ice remains on Lake of the Woods today, and it will be gone tomorrow.

That means we’ll be ice free on exactly the same date as last year, which kind of makes sense given how the winters were similar in both duration and coldness.

I say kind of, because although the winters had a lot in common, the springs were quite different. 2018 was a late, cold spring that turned really warm at the end of April. 2019 was a slow, cool spring with few warm days.

Here’s Sean’s updated graph of our temperature progress this spring.

Overall, you can see we had moderate thawing this year, with the blue dots showing that mean daily temperatures added up slowly, especially in late April. When Sean and I first modelled this year’s forecast, we chose a thaw index of 240, because that’s how much heat it took to melt last  year’s ice, and the two winters were similar. In the end, although the predicted date for ice-out came close, the actual amount of heat it took to do it was less than we thought, and this graph shows a revised forecast with the expected thaw index reduced to 190.

Basically, we assume that a long cold winter makes lots of ice, and it will take lots of warm days to melt it all. That’s simplifying, and we know it. The brutal winter of 2014 thawed with an index of 194, so 190 is not unreasonable. Perhaps last year’s 240 points was an oddity.

In any event, we didn’t need as many thaw days as we first thought. Sean offers these technical insights:

Sources of error are plenty in this high level statistical analysis. Wind, direct sunlight, rain, ice thickness, snow thickness etc are all variables that the analysis does not take into account.

Our ratio of freezing index to thawing index was right around 10 this year, which is the average for the last 15 years or so. Our initial prediction this year was conservative based off of last years data and went with 7.5 freezing index to thawing index ratio.

If we had ignored last year’s unusual thaw, we would have used a ratio of 10 and gone with an index of 200. That would have been close.

That’s basically it for this year. I’ll do a wrap up post when I can confirm that last patch of ice is gone, and I’ll update the different graphs that show how this spring compares to recent years.

Now that boats are hitting the water, it’s time for my annual reminder that the stretch of Safety Bay from Bush Island west to Norman is a licensed Water Aerodrome: an airport for float planes. Please watch out for them when boating in this area. Think of it as a runway. For safety reasons, float planes have the right of way when taking off or landing. When taxiing, they are supposed to be like any other watercraft, but from experience, I can tell you that they cannot decelerate quickly or turn sharply. Do be careful around them.

May 1, 2019: Marinas, Aerials and a Graph

Lots of stuff today. I’ll start with some contributor photos, move on to a handful of fresh aerial photographs, and finish with a look at Sean’s Thaw Graph and the weather outlook.

You can click on any of the images to see them full-screen. Some will be higher resolution than others.

I got photographs from three contributors today that follow up on my marina report from yesterday. Here they are in the order I received them.

Al Smith sent me this picture of the docks at Smith Camps on Thunder Bay.

Smith Camps on Thunder Bay.

This shot looks out from Thunder Bay at Bigstone Bay.

Then Ian Bruce sent me this look at Bigstone from a different vantage point.

Ian says: Taken from mainland on Branch road 6A, looking south to Hay Island. Boulder Island middle distance to the east side touching flag pole. Still lots of ice, shorelines thinning to a bit open.

A little later, Brian Finnegan sent me a picture  of Henderson’s Marina on Route Bay.

Henderson’s Marina, Route Bay.

Looks like things are coming along there.

In a separate email, Brian attached this shot of the docks at Northern Harbour.

Docks at Northern Harbour, Pine Portage Bay.

Brian mentioned that marina operator Gary Hall said he hopes to be putting boats in the water next week.

Thanks to Al, Ian and Brian for taking the time to send me their pictures to share with you.

Okay, on to aerial photographs. Today wasn’t great weather for taking pictures. Luckily, I grabbed a few shots in the morning, just in case the afternoon was poor. This turned out to be the right choice: although we had low cloud in the morning, we had lower cloud in the afternoon, with showers as well.

So, I’ll start with the standard view of downtown Kenora I get after we lift off from Runway 26 and climb to the west.

Laurenson’s Lake is open now, and so is Round Lake (not shown in this pic) Rat Portage Bay still has some ice, but it looks very weak.

As we start to swinging south to head east to Dryden, we get a look at the area south of Devil’s Gap.

In brief: Matheson Bay at the left, Gordon and Galt Islands near the middle, Rogers and Treaty Islands at the right. The ice looks soft here, too. The channel into Devil’s Gap is open at the lower left, partly blurred out by a propeller blade.

Next, as we continue to turn from south to east, we look at Bald Indian Bay.

Sultana Island dominates the middle of the frame, Pine Portage Bay is behind that, and Heenan Point extends almost to the right edge of the picture. Thunder Bay lies behind it.

Okay, remember how I said it was a good thing I snapped a few pictures on the way out this morning? Here’s what it looked like in the afternoon. I had to grab this shot through the side window; it’s impossible to shoot through the windshield with our high-speed wipers going.

Anyway, this looks south west at part of Bigstone Bay with Heenan Point at the right and Hay Island emerging from the rain in the distance.

Now, on to the weather situation.

I had to email Sean to ask him to update the Thaw Graph. As you can imagine, it’s not good news, and he didn’t want to depress everyone. Even so, I think it’s a useful way to picture the temperature trends and their significance.

Click on the graph to more easily read the fine print. The blue line with dots represents how our daily mean temperature is adding up towards our goal. (Set to 240 points based on similar ice-making conditions last winter.) With recent temperatures barely squeaking above freezing, that upward progress has levelled off lately. That means a delay in accumulating enough warm weather to melt the presumed amount of ice.

Which brings us to the forecast. A normal daytime high this time of year is around 15ºC. The current  Weather Network forecast doesn’t call for a temperature that warm until mid-May. Forecasts can be wrong, of course, and they’re most certainly subject to change. But it seems likely that we’ll be spending the next two weeks struggling, (and mostly failing) to reach double-digit highs. At night, we’ll be close to freezing.

If there’s a bright side, it’s a peculiar one: miserable weather can also remove ice. Rain and wind are not as nice as sunshine, but they do transfer energy that can melt and break up ice. As we head into May, I’ll take any help we can get.


April 23, 2019: Graphs

I didn’t fly today, so I’m catching up on some graphs and predictions.

First, an updated graph from Sean C. You can click on it to see it full-screen.

To recap:

The blue line with the plot points tracks our actual daily mean temperatures so far.

The yellow line is based on weather forecasts. In theory, this is the path that the blue line will follow, but it gets less reliable the further into the future you look.

The solid red line represents a warm spring that racked up lots of high daily mean temperatures in a short time. It’s sort of a best-case line.

The solid green line represents a cool spring that took a long time to deliver a decent amount of heat. This is more of a worst-case scenario.

The horizontal dotted red line represents our goal for this year, a thaw index of 240. As each day’s mean temperature gets added to the blue line, we rise towards that goal.

The target index of 240 points is based on last year because the winter conditions were very similar as to both the length of the winter and the depth of the cold.

The vertical dotted red line indicates a date we might make it by. It was set to May 17th when this graph was first created, but we’ve already started to improve on that.

We might have an easier thaw if last winter’s frequent snowfalls degraded the quality of the ice compared to 2018. Soft ice wouldn’t require as many warm days to melt, so we could do it with less than 240 points.

Here’s a graph I made, using data provided by Sean, but presented in a different way. It’s wide, so you should probably click on this one to see it clearly.

I’ve given each year a horizontal bar that starts on the inflection date (when the mean daily temperature rose above freezing on a lasting basis) and ends on the day Lake of the Woods was ice-free. The most recent year is at the top, and the oldest year (2008) is at the bottom. Rather than line up all the inflection dates at the left edge, I displayed them on a calendar base, because a May thaw is apt to apt to get more hot days than a March one. You can see this: the lines that start really early run longer than the ones that start late.

Now it happens that our inflection date this year was April 13th, the same as 2016. I’m confident that this thaw will take at least as long as 2016’s, which ended on May 4th, so this year’s bar is solid blue up to that date. Realistically, there’s little chance of getting off that easy. The winter of 2015/2016 was a mild one, and the ice didn’t put up much of a fight.

I’ve tentatively shown a longer period of uncertainty in pale blue. I ran that out to as late as May 17th. That’s to match the prediction from Sean’s graph. I’m really hoping that’s on the pessimistic side. I didn’t have the heart to project anything worse.

It might be possible to be ice-free around the middle of the range—May 10th or 11th—if we thaw as fast as last year. We’re doing well in that regard right now, but there’s cooler weather forecast for the weekend and next week that could slow things down again.

The final result may depend on two basic things: how much ice we can melt during our current warm spell, and how that forecast cooler weather plays out.

There are also two wild cards: rain and wind. Rain has an enormous capacity to deliver heat energy deep into ice if there are cracks. Wind can do violent damage to ice sheets once there’s open water in contact with them.


April 15, 2019: Sean’s Analysis

I didn’t do a Signs of Spring post yesterday, but if you’re interested, snow is retreating wherever the sun shines, but lingering in shadowy places. I’ve seen a pair of Mallards, my first ducks of the year. Also a pigeon and a pair of Whisky Jacks. I heard a second-hand report (hearsay!) of a robin. Cyclists are emerging from their winter dens.

And now onto the main topic.

Contributor Sean C. is finally confident that we’ve reached the inflection point, the date when our daily mean temperature rises above freezing on a lasting basis. He figures this took place on Saturday, April 13th.

That means that from now on, the ice will be melting steadily.

Here’s the first of his graphs, depicting the severity of the winter.

Each of the downward spikes represents a winter, ending on the date of the inflection point. The depth of the spike represents the severity of the winter, and the width of the spike represents the duration of the ice-making period. In a nutshell, the winter that just ended was not the worst, but it was a very close match for the previous winter, which was pretty bad.

You can click on these graphs to see them full-screen and a bit bigger.

Here’s Sean’s graph comparing the way some recent winters unfolded.

2019 Freezing Index

In this figure, each winter gets a line in a different colour, and tracks across the calendar until it ends on the inflection date. A short shallow line, like 2012’s medium blue one at the top, represents a mild winter that started to thaw early. The awful winter of 2014 (which was also the deepest downward spike on the first graph) is the grey line that slopes down and down, making ice until mid April. Above that are two lines that track together at the end. The dark blue one is from a year ago, and the dark red one is this year. These years look as closely matched on this graph as they do on the first.

Okay. We’ve established that it was a crummy winter that dragged on into the middle of April. Now what?

Well, now Sean uses some math to figure out how much heat we’ll need to melt the ice formed over such a winter. He works out a thaw index based on the severity of the winter. The index lets him make predictions based on the long-term forecast, and it works like this: If a day has a mean temperature of 5ºC, we add five points to the total. If a day has a mean temperature of 7º, we add seven, and so on*. Then he works out how many of those points we’re likely to need to thaw this winter’s ice.

2019 Preliminary Forecast

Sean’s first version of this graph used the same thawing index he forecast last year: 200. However, when I asked Sean if it might be better to use the actual index of 242 that came to pass, he reconsidered, and issued a new version of the graph using an index of 240.

The amended graph now replaces the earlier version on this post. The higher index adds another day to the estimated time until we’re ice-free.

On this graph, the red line represents a really warm spring (2007) that hit 200 points in early May and the green line depicts a cold spring (2004) that took much longer. Please note: this graph isn’t about the thaw in those years, it’s just about how rapidly we accumulated enough warm weather. The very short blue line hiding in the lower left corner is 2019, with data points marked by blue dots to show the actual daily mean temperature achieved. The yellow line is what the weather forecast says we’re likely to get. If the forecast is accurate, the blue line will grow along the yellow path, and Sean will extend the yellow line as new forecasts come into effect. (There are longer forecasts, but plotting them day by day at this point would be wishful thinking)

The horizontal dotted red line indicates the target thaw index of 240 estimated for this year, while the vertical dotted red line marks the date we might reach it, based on the trend in the longer-term forecasts.

*A sort of fun thing we learned about daily mean temperatures: you might suppose that if the daytime high was 10ºC, and the overnight low was 0ºC, then the mean daily temperature would be 5ºC. That turns out to be not quite right. Actually, such a day is likely to produce a mean temperature closer to 6ºC. We seem to spend more hours near the high than the low. Perhaps this is due to spring’s long days and short nights.

If you’ve been following along, you’ll have noticed that the predicted date for reaching the target of 240 points is May 87th. May 18th is bad. It’s even worse than last year, mainly because the temperatures forecast for the next weeks are not high.

Still, there are other factors to consider.

The index itself is not precise; it’s an educated guess based on turning a limited set of  past data into a mathematical formula.

A more positive influence might be ice quality. All that snow this winter made for some poor ice. If it’s weaker and softer, it should melt faster.

Then there are the usual wild cards: rain, wind and sunshine.

In summary, this year looks a lot like last year. Rosy forecasts haven’t panned out, and a normal ice-free date in early May looks unlikely.

Plan on the middle of May and cross your fingers.



March 19, 2019: Graphs

Yesterday I talked briefly about Sean’s method for analyzing the winter temperatures to see how much ice we were likely to have. Here’s his first graph for 2019, an update that shows how this winter compares to the last few.

Each spike above the center represents a summer, with the rising line showing the degree days above freezing. When the mean daily temperature falls below zero in the autumn, the line drops vertically and the downward spikes show the degree days below freezing.

A spring day with a mean temperature of 10ºC would be ten degree days.

Based on the severity of the winter Sean estimates how many degree days it will take to thaw the lake, and then looks at the forecast to see how long that might take.

It doesn’t matter much whether we have eight weeks of barely above freezing temperatures, or three weeks of exceptional heat: the numbers come out about right either way. Once enough heat energy is delivered, the ice is gone.

Freeze Thaw Index Graph

So what can we see from this updated graph? The last point on the graph shows that right now, we’re still below freezing most of the time. On the day that the mean temperature goes from below freezing to above*, Sean will draw the vertical upward line that marks the end of winter and place a blue cross on the chart.

Once we reach that point, he’ll be able to estimate our Thaw Index: the number of degree days it might take to melt that much ice.

*For the long term, that is. A single above freezing day does not mark the change of seasons.

But we can already see that this has been a long cold winter. With a freezing index of -1756 degree days, we’re in the same ballpark as last winter. The two winters before that were a lot milder, and you’d have to go back to 2014 to see one that was much worse. That was an ugly winter.

Sean sent along another graph that compares the recent winters in a different way.

Winter Severity Graph

On this plot, each winter gets a different coloured line. Each line ends on the date the mean temperature rose above freezing. This (2019) winter is the dark red line. It goes horizontally after today’s date because we don’t have the whole story yet. We don’t quite know when we’ll switch to thawing and end the line.

That brutal 2014 winter is the grey line at the bottom. We made a lot of ice that winter.

Sean made an interesting point about last winter, represented by the dark blue line. It was leveling off nicely, looked like it was all over, and then things turned cold for three more weeks, which you can see as a late dip in the line that extended it into April.

In summary, this winter was cold enough to make a lot of ice.

There are two things that might tip the balance in favour of an earlier thaw: reports that the ice is not very solid because of frequent snowfalls, and a long-range forecast for warm spring weather.

I’ll start on aerial photography when I have a flight on a  clear day.


November 15, 2018: We’re Making Ice

We’ve changed seasons. The average daily temperature has dropped below freezing, and it looks like the actual inflection date was November 7th. Effectively, that’s when freezing became the fashion, rather than the fad. In the week before that, average temps were right around 0°C, except for a mild Sunday on November 4.

Sunday, November 4. The pond by the Scenic Nook trail on Tunnel Island had mostly frozen over.

On Wednesday the 7th, the daily average dropped to -4°C, and in the following week it went as low as -9.5°C.

Same pond a few days later

The forecast calls for fairly consistent low temperatures in the next weeks, and let’s face it, we’re not going to start any serious melting in December. Remember, we’re talking about daily averages here, not daytime highs.

In summary, we’re making ice now. North of Red Lake, small lakes have been frozen since about the beginning of November, and on yesterday’s training flight, I saw small bays on Lake of the Woods were icing over. Strong winds were keeping larger areas from freezing, for now.

This time of year, I always see an upsurge in emails and comments asking if I’ll be reporting on ice thickness. Ice fishers want to know! Sorry, I will not. I cannot judge the thickness of ice from an airplane, and I worry that if I report that a certain bay has frozen, people will take that to mean the ice is thick enough to support them safely.

Someone sent this graphic my way. It doesn’t say which Department of Natural Resources, but I think the credit goes to Minnesota. Note the caveat that these guidelines should only be applied to new clear ice.

Have a safe winter.