May 17, 2022: Aftercasting

We’re not forecasting any more, but Sean always finalizes his graphs to see how close the predictions came.

Short version: the thaw went better than expected.

Before we examine the final version, let’s go back and look at this spring’s first forecast, from late April.

You can click on these to see larger, sharper versions.

Early in the spring, Sean estimated that we’d need to reach a target thaw index of 190 points. That’s the horizontal yellow line. That value of 190 was based on the severity of the winter. Last winter’s freezing index was close to 1900 points, and a ratio of ten to one is his starting point for predicting the thaw.

April Thaw Forecast Graph.

The blue line is formed by plotting this year’s daily temperatures (Mean Daily Temperatures, to be specific). In the early spring, he sketches in the blue line using the weather forecasts, and then as time passes, he replaces the forecast line with actual data.

Now here’s the post-season analysis version.

Final Thaw Graph.

As you can see, the blue line plotted from actual weather reports rose more steeply than the early version based on weather forecasts.

Also, the ice melted at a slightly better rate than the base ratio of ten to one predicted, so the thaw was complete (marked with a yellow star) at a lower thaw index than the target of 190. It happens. Temperature is a big factor in the thaw, but it’s not the only one. Some of the other factors aren’t included in weather forecasts, especially long-term ones.

Perhaps you’d like to see how this spring’s temperature profile compares to other years in our records. Sean has a graph for that, too.

Spring Temperature Trend After Inflection.

In this graph, the timeline across the bottom is synchronized to each year’s Inflection Date, not the calendar date. Also, the lines for previous years continue to plot the rising cumulative index even after the ice is gone. We’re just comparing spring temperature trends, not trying to factor in ice thickness or anything like that.

This year’s data is shown in a dotted line, and it’s the second highest track on the graph. On both this graph and the previous one, that red line that we didn’t quite equal represents 2007, a very warm spring, so we did quite well this year. As Sean commented, once we finally got Mean Daily Temperatures above freezing*, they were often in double digits.

*When the Mean Daily Temperature goes above freezing and stays there, we call that the Inflection Date, and that’s what Sean bases his graphs on.

Lastly, the Shark-fin graph.

There’s really only one change to this. This year’s ice-out date of May 16 has been marked with a red dot, bringing the thaw phase to a close.

Shark-fin Graph.

Sean will continue to plot the summer numbers on here so that we can see how much summer heat we accumulate, which will affect water temperature and the inevitable freeze next winter.

In the meantime, here’s hoping that he can plot a summer fin that is tall and wide, because that would be the sign of a season that is both warm and long.

Signs of spring: The trees are leafing out, and I saw daffodils blooming in someone’s garden today!

Fun tidbit: Sean did some internet sleuthing, and as far as he can tell, Lake of the Woods Ice Patrol is the only website of its kind anywhere in the world.

I think that’s about if for this year. I’d like to thank everyone that helped.

Sean, of course, for the graphs and predictions.

The pilots and drone operators, and everyone who sent in photos. They made Ice Patrol possible this year.

The donors, who alleviated the stress of trying to do this on a shoestring budget. Having enough money to book flights meant I didn’t have to worry about going without aerial photos in the critical weeks.

The people who participated via email or the comments form. I received a lot of very helpful information from those sources, and it’s growing as a way to pool our knowledge.

And lastly, the followers and visitors. Ice Patrol had a busy spring this year, racking up nearly 75,000 views in under five months. Traffic peaked at over 2400 views a day. That keeps me going, and I’m tickled that people check in from all over the world.

Thank you all.

Ice Patrol will now go (mostly) dormant until next spring.

Talk to you then!


May 16, 2022: All Clear

There was still some ice on the south end of the lake yesterday, in the vicinity of Oak Island. It may have been wiped out later in the day, but I don’t know for sure, and it might not have been the only patch left, so I’m using May 16th as our official ice-free date for Lake of the Woods this year. I believe Shoal Lake is also clear.

So let’s see how that stacks up.

The 2022 Brick Graph.

This year’s brick goes in the previously empty May 16th-20th slot, and shows 2022 as the second latest thaw in my records. It certainly feels like it.

Now let’s see how it looks on the Pancake Graph.

You can click on these to see larger versions with sharper text.

2022 Pancake Graph.

The rapidity of this year’s thaw is not quite as exceptional as I thought. 2020 was two days faster, and 2013 was a match, at nineteen days from Inflection Date to Ice-free and just one day earlier. Something that turned out to be not so similar was 2014. I drew a lot of comparisons this spring between this years melt and the one in 2014, because the thaws then and now both started late, ran to cold weather and featured high water levels. Despite having all those things in common, the ice went much faster this year.

This may have been partly due to the wet weather. Something I learned from meteorologists this year is that high humidity has a powerful melting effect on ice.

I’m curious to see how Sean Cockrem’s graphs look this spring. They’re more sophisticated than mine, and will reveal how this year’s temperature profile compares to those other years. It’s worth mentioning that some of Sean’s earlier predictions turned out to be pessimistic, but that’s because they were modeled on weather forecasts that also turned out to be pessimistic. If you tell Sean it’s going to be cold, he’s bound to respond that it will be a later melt.

Now that the May Long weekend is not overshadowed by the possibility of ice on the lake, we’re all set to start our summers, right?

Not so fast.

As I write this, the weather forecast is calling for gloomy conditions, with cloud, rain and below-normal temperatures for the next week. We could see near-freezing temperatures Friday and Saturday night, and it doesn’t currently look like the long weekend’s Saturday will be warm at all.  The Weather Networks says a high of just 7°C with showers of rain, perhaps mixed with snow! and Environment Canada is just a little more optimistic, suggesting partly cloudy and 10°C. For Sunday, they trade positions, calling for 15 and 12 respectively. An average high for the 21st of May is close to 19°C.

Even the 14-day outlook doesn’t suggest any temperatures above 18°C before the end of May. Let’s hope they’re being pessimistic again.




May 13, 2022: Forecast Friday

Soon, the ice-out date will be history, and not a matter for forecasts.

But while we still have a little ice left, here’s Sean’s last take on it for this year.

Remember, you can click on this graph to see it large and sharp.

Lake of the Woods Thaw Forecast.

This year’s temperature profile (the blue line) runs parallel to the best case example from 2007 (the red line). Since last week, Sean has updated the path of the blue line to replace forecast temperatures with actual ones up to the present.

His conclusion? Based on temperatures, the lake should be entirely ice-free in the evening of May 17th.

Temperatures are not the only factor in play, though, so there’s still some wiggle room for wind and high humidity to get rid of the ice even faster. Certainly it is very windy today. I think it’s possible that the ice might be gone a day or so earlier than the temperatures suggest.

In the meantime, although there is still ice present, many people will be able to reach their cottages by boat already. For those who cannot, yet, it is only a matter of days.

Satellite imagery is a bit of a tease lately, because of cloud. Yesterday, Terra satellite was able to see only the south west corner of the lake. Today, Aqua got a look at only the east side. In both cases, there was no significant ice visible, but we’re reaching the stage where it would be hard to spot from space.

Lake levels continue to rise. Water is flowing into Lake of the Woods faster than it can be let out. Sean calculates that the surplus amounts to an olympic-sized swimming pool’s worth of water every second and a half. That would raise the lake by an inch and a quarter every day. If that continued for a week, it would come to another fifteen inches, but nobody knows exactly how long the inflow will remain so high.

As mentioned on Ice Patrol yesterday, the water level of the Winnipeg River is so high that it’s raising the water level in and around the Black Sturgeon Lakes. That’s washed out a number of roads, and resulted in an evacuation order for a lot of people that live north of the Kenora Bypass. The evacuees will have a narrow window to get out. The City of Kenora Works Department is attempting to re-open one route with heavy equipment, and they think they can keep that road passable for four hours this afternoon. After that, the floodwaters will close off all the ways out.

You can read more–and see a map of the affected area–at Kenora Online.




May 6, 2022: Forecast Friday

First off, I made mistakes with the previous post. Dated May 5, I forgot to hit the PUBLISH button until this morning. Secondly, the version that went out by email was incomplete. A drone panorama from Paul Leischow was omitted from the version I hastily put out, and the email version will not be updated to show the corrected version.

To see the full May 5 post, click here or visit the Ice Patrol home page and scroll down.

Now, on to the latest. Sean has been tracking how the weather we’re actually getting compares to the weather forecasts he bases his predictions on. You may recall that we put more trust in the seven day weather forecast than the fourteen day outlook.

This time around, that has worked out well. In the week since Sean released his first prediction, the weather was very close to what was forecast. The second week of that fourteen day outlook is now our coming week, and the new seven day forecast for it is more optimistic.

To be clear, the weather forecasts are updated all the time, and new seven and fourteen day forecasts come out every day. But because Sean does his graph on one particular day, the forecast line on the graph reflects the forecast available at that time.

Sean has revised his graph with the new information, and with more confidence.

Remember, you can click on this graph to see a larger version. You should zoom in on that to see it at it’s largest and sharpest.

If you want to refresh your memory, you can see the previous version by clicking here.

So, what’s different? The blue line is steeper. That’s good. It means that the weather forecast is better, and that means we’re likely to hit the target thaw index sooner. Sean is now saying it looks like the ice will be gone a day or two before the May long weekend, instead of just as it begins.

Graph Explanation:

The horizontal yellow line represents the thaw index we think we’ll need to reach to melt all the ice on the lake.

The blue line represents our thaw index this year, based on known temperatures so far, and forecast temperatures for the future.

The red line shows how fast the cumulative temperatures can rise in a very good year. It’s based on the fastest-warming spring in our records.

The green line represents a worst-case scenario based on the weakest, coolest spring we know of.

It’s worth noting that the revised graph now shows that our weather is tracking very close to the best-case scenario, roughly paralleling it. That would give us a thaw that’s very fast. That’s about right for one that happens this late in the year.

Now the fine print.

This graph and prediction is based solely on air temperatures and an assumed thickness of ice based on the winter’s severity. It does not take into account such factors as the strength of water currents, precipitation, humidity, the UV index, tornadoes, tsunamis, or comet impacts.

This graph may pose a choking hazard to pets and small children, especially on a smartphone. Wear sunblock if reading the graph outdoors. Do not attempt to use this graph while driving or operating heavy equipment. Follow regional and local safety regulations regarding eye protection and personal safety equipment. Always unplug the graph before putting your hands near the moving parts.




April 29, 2022: Sean’s Graphs

I know people have been waiting for Sean Cockrem’s graphs. Now that we’ve finally seen temperatures shift to mostly above freezing, he was able to set yesterday as Inflection Date, and start work on predicting how long the thaw might take.

Sean writes:

At long last Iast, I’m ready to declare [April 27th] as the 2022 inflection date. Usually I wait a few days after to make sure that the measured daily means are above zero, but based on how far into April we are and with the 14 day having consistent warm temperatures, I’m going to make the executive decision for this declaration.

This was the third coldest winter so far this millenium. Only the 2013/14 and 2008/09 winters were colder. This was also the latest inflection date we have had in the last 20 years of data collection.

For the forecast, I have set our target thawing index at 190 which is based on an average 1:10 thawing index:freezing index. I’ve entered the forecast data for the next month or so. Keep in mind everything after a week is a guess, and everything after two weeks is based on seasonal temperatures. This year has been anything but seasonal. Having said all that, there is a glimmer of hope that we will be ‘Ice Out’ right around May 20th, which is the Friday of the long weekend. If the temperatures stay below seasonal, it’s going to be a long shot for complete ice out, which is not to say that a good portion of the lake will be open by then.

As far as the season goes, this one will be down to the wire for the next 3 weeks closing in on the long weekend. A bit more interesting on our end than other winters where the ice is off in late April. Fingers crossed we get some sunny warm days.


I recommend clicking on these graphs to see a larger version. Then you should click on that to see the graph enlarged to it’s full resolution.

Let’s start with the updated shark-fin graph.

The Shark-fin graph plots the severity of each winter and marks the beginning and end of each thaw.

The key points to keep in mind:

The downward spikes plot the temperature trend of the winter. A long winter makes a wider spike, and a severe winter makes a deeper spike.

The thaw commences when the Mean Daily Temperature rises above freezing (on a lasting basis) and that date is marked with a blue X. This is the Inflection Date.

The thaw ends when the lake is entirely ice free. That date–when we reach it–is marked with a red dot.

What can we tell about the winter we just had? It was the second coldest on the graph, and as Sean said, this is the latest Inflection Date we’ve seen since we started keeping records. (2003 was the year I started taking pictures, so Sean hunted down the weather data back to that year. Before that, we don’t know when the ice was gone.)

Summary: It was a long cold winter, so we assume thick ice. It was a late start to the thaw, so that puts us behind.

On to the next graph.

The Cumulative Freezing Index compares the temperature path of each winter.

This graph takes some of the same data, but focuses strictly on the winter. Each winter’s Cumulative Freezing Index is shown as a separate line that ends on the Inflection Date, and this past winter is represented by the heavy dashed line.

Key points:

The years are synchronized to the calendar on this graph, so some years have already become colder than others at the starting line of December 1st.

We had a mild fall, so we got off to a good start.

This years line drops lower than most, because we had a lot of cold weather.

It extends further to the right than any other line because it took so long to get to Inflection.

Now comes the speculative graph: the Forecast.

This one takes some explaining. In the first two graphs, we gave the winter a “score”.

The Cumulative Freezing Index is a single number that sums up how much cold weather we had over the course of the winter. This winter’s number was -1887.* That’s nasty.

*Refresher: Sean derives this number by using a simple technique. Once the Mean Daily Temperature drops below freezing in the autumn, he takes note of it every day. If the MDT is -3°C one day, the line drops three points. If the MDT is -5°C the next day, the line drops a further five points.

Sean tracks the rising temperatures after Inflection Day, too. Then, using my dates for ice-out, he looked for a relationship between the freezing index and the thawing index. This got him a rule of thumb: for every ten points on the freezing index, you need one point on the thawing index to get rid of the ice.* That’s a starting point.

There are other factors that can hasten or delay the thaw. Sunshine is always helpful. Rain and wind can speed the thaw along, especially if the timing is right.  Strong currents are a plus. On the negative side, snow is the worst, but clear nights and cloudy days don’t help either. This forecast doesn’t try to predict any of those things. They’ll be wild cards that may mess with this simple prediction, or they might balance out.

*does that seem strangely unbalanced to you? For the purposes of Ice Patrol, there are only two seasons: the one where it’s below freezing, and the one where it’s above. Generally speaking, we have more summer than winter here: the summer spikes on the shark-fin graph are bigger than the winter ones. But the thaw is just a few weeks out of the year. If the thawing index had to equal the freezing index to melt the ice, it would take nearly all summer to thaw the lake. Also, the lake is not frozen to the bottom, because water is weird stuff, but that’s a whole other story.

In any case, this forecast is an estimate. Sean figures that we’ll need to accumulate roughly 190 points to get rid of the amount of ice this winter should have created.

So he goes to the weather forecast to see how long that might take, and you know how those are. As Sean suggested above, the seven day forecast is broadly reliable. (When it’s off, it’s usually in the timing.) After that, the fourteen day forecast is more of an educated guess, and the really long-term stuff basically just goes, “I don’t know… normal, I guess?”

The forecast graph tracks how long it might take for the weather to melt the ice.

So here’s how it looks for now. The horizontal yellow line is set at 190 points. That’s our target. The vertical grey line is the start of the May Long Weekend. That’s not a deadline, it’s more of a  wish. The smooth blue line is the weather forecast. It hits the target on Friday of the May Long.

There are two other lines. The red one shows how the Thawing Index racked up in the best year, and the green one represents the worst spring we know of.

The red line is the easier one to understand. 2007 was a lovely spring. If we could have those sorts of temperatures this year, the thaw would go a little faster. But as far as our records go, that’s a best-case scenario, and a long shot.

The green line is confusing. 2004 was a dreadful spring, and in fact the whole summer was exceptionally cool. The temperature trend that spring was feeble. So how did the thaw go? Not bad. It had been a middling kind of winter (~1500 points), so the target that year was lower. Despite the chilly spring, the lake was clear of ice by mid-May, significantly better than the ten-to-one rule of thumb would have predicted. In terms of modelling, 2004’s data made it an outlier.

In conclusion: Lake of the Woods is on track to be clear of ice right around the long weekend. If the weather forecast is right, and if the rule of thumb holds true this year.

Thanks, Sean!

Keep in mind that we should see steady progress between now and then. Marinas will open. Many islands will be accessible a week or more before the lake is entirely ice-free. That may also be true of Falcon Lake and West Hawk.

Shoal Lake plays by it’s own rules, and often lags a few days behind Lake of the Woods.

Further north, the long weekend and the opening of fishing season may face problems.

April 9, 2022: Satellite Saturday

A few Saturdays have gone by without the regular Satellite Saturday feature. There are a couple of reasons for this. Most worrisome, one of my two favourite satellites is offline at the moment. NASA’s Aqua satellite–which carries one of the MODIS cameras–has gone into Secure Mode. Maybe this has to do with solar activity, or perhaps it’s a technical problem of a different sort. At any rate, it hasn’t delivered any pictures since the end of March. NASA technicians are trying to get it functioning again.

The other reason is cloud cover. We’ve had a ton of it. So poor Terra, working without its twin, has had few chances to image Lake of the Woods. We finally had clear skies for a while yesterday, and Terra was able to capture this.

April 8th MODIS false-colour image from NASA’s Terra satellite.

If you click on this image, it won’t get bigger. But you will see a version with some location tags.

Remember, in the false-colour images, ice is pale blue and open water is black. Aside from the Winnipeg River, flowing towards the top of the picture, the only open water of note is the bit near town, and some at Big Narrows, just left of the center of the frame. There might be something over at Whitefish Bay, to the right of center in this picture. Significantly, there’s no water showing at south end of the lake, not even at the mouth of the Rainy River.

At times like this, I get curious to see how the situation compares to past years.

Here’s a mosaic I made up for today’s presentation at Common Ground. I had fun, by the way.

Common Ground – Volume III was released today. It contains all the stories of the Lake of the Woods Area from the last five Common Ground storytelling events. Copies are available at the Kenora Public Library and the Lake of the Woods Museum.

If you click on this picture you’ll see it full-screen. The resolution of the mosaic is 1920×1200.

Comparable false-colour images from 2012, 2014, 2017, 2018, 2021 and 2022.

These pictures are all from the end of March in recent years.

2012 was one of our earliest melts, as you can clearly see here. 2014 was the year Ice Patrol became a website, and it was dreadful: there’s so much snow in the woods that you can barely distinguish the lake. 2017 shows open water at Rainy River, Big Narrows and the Winnipeg River. There’s bare farmland on the American side, too. 2018 wasn’t ice free until May 14, and it was still very icy in late March. 2021 shows much less snow in the forest, and the thaw was over by April 24th. This year most closely resembles 2018. We shall see.

Also worth mentioning: there’s been very little change between March 27 and April 8. That’s almost a fortnight without visible progress.

The future of NASA’s Terra and Aqua satellites is limited. They were designed to operate until “the early 2020’s”. Terra is low on fuel, and cannot correct it’s orbit like before. Aqua is having a time-out.

So I am exploring a new portal that offers satellite imagery from the European Space Agency’s Sentinel satellites, as well as Landsat satellites from NASA / USGS* and some others. I haven’t got the full hang of it yet, but I have made a start. I have learned that Sentinel 2 (there are 8 or 9 Sentinel satellites, and they are not identical) offers a Short-wave Infrared view that is similar to the images above. The good news is, the resolution is much higher. The bad news is, quite often the satellite only images narrow strips of Lake of the Woods. It’s a trade-off, you see: because the camera zooms in for good detail, it cannot easily cover huge swathes of ground. Or lake, in our case.

But here’s one recent success. You can click on this image to see a full-screen version. 

Sentinel 2 Short-wave infrared image of Lake of the Woods. March 28, 2022.

You might want to compare this image to the picture at the lower right of the mosaic above. That MODIS picture was taken just one day earlier, so you can get an idea of how the colour scheme compares. It seems clear that open water is black, but I’m not sure about the medium blues. Thin ice, slush, or surface water over ice?

I look forward to getting more familiar with this resource.

*The nine LandSat satellites are a joint project of the National Aeronautics and Space Administration (NASA) and the United States Geological Service (USGS).

The weather: we are having another warm spell, but the forecast is for significant snowfall next week, and cold temperatures into the Easter weekend. We have not yet reached the Inflection Point, because although we’ve had some above-freezing days, we keep sliding back to colder (and below normal) temperatures. An average high for today’s date is 7°C, and an average overnight low is about -4°C. That would put us on the right side of the Inflection Point, but we continue to fall short.

So we’re off to a late start. Other years with late Inflection Dates have run to fairly rapid thaws, because April weather tends to be pretty warm.

Here’s the Pancake Graph so you can see how this spring fits into that pattern.

You can click on this graph to make it larger and clearer.

Inflection to Thaw Calendar for 2003 to 2021.

We had a nasty cold winter, so if we don’t hit Inflection until after Easter, we’re going to need some good warm weather to stay on track for my first guess, which was that we’d be ice-free around May 11-15.

Signs of spring: I saw Mallards today, and the gulls are squawking. I have not yet seen a skunk or a bear. The bear part worries me a bit. We had a lot of bear activity in town last year because the berry crop was poor. That hard winter may have been too much for underfed hibernators. I fear there may have been a significant die-off. The snowdrift on my deck that was once the size of my Tucson is now down to just a couple of meagre* snow-shovels worth. Will it be able to hold on until next week’s reinforcements arrive?

I use mostly Canadian spellings: colour, favourite, meagre, and so on. I once had a short story rejected by an American magazine’s slush reader for “spelling mistakes.” This is my revenge.




March 23, 2022: Colin Napper

We have our first aerial photos of the year. Colin Napper went flying with Connor Ward in Connor’s Grumman Cheetah on Sunday. He had some trouble sending the pictures (uploading full-size pictures often causes a smart-phone to time out or give up.) so I didn’t get them until today.

Anyway, here’s what the lake looks like near town, as of Sunday, March 20th.

Looking west over Rat Portage Bay, with Kenora in the foreground and Safety Bay and Keewatin at the right.

You can click on these images to see them full-size and zoomable.

Note that there’s not a lot of open water, even in Safety Bay. In past years, I wouldn’t have started taking pictures until Safety Bay was open from shore to shore. If you’re wondering about the rest of the lake, fuggetaboutit. It’s ice.

This is Second Channel, looking northwest with Keewatin visible at the upper right.

And hello, what’s this?

A rare sighting of the elusive March Boater.

So a big thank-you to Colin and Connor for sending these along. I hope they’ll become regular contributors. Feel free to thank them in the comments.

Speaking of regulars, I have heard from some of my other flying friends.

Bruce White, who flies Boeing 777’s has said he’ll take pictures when he passes over. 

Josh Broten, who has been sending in pictures from his Cub for years now, has a fancy new plane. His Arion Lightning will let him travel over the lake faster.

Oh, and one last photo for fun. Sean Cockrem, the graph guy, had to snap this picture at a Winnipeg Jets game this winter. 

OHO! What’s that on that guy’s phone? The pancake graph!

Sean was amazed to see this in the audience. Someone explaining the Ice Patrol Pancake Graph to their friend. I’m delighted. Big shout out to these guys, whoever they are!

And now that the topic of graphs has come up, here’s a look at one of Sean’s. He’s been monitoring this winter closely because of how cold it was.

You can click on the graph, too, for a larger and sharper view.


This is a comparative graph that shows the Cumulative Freezing Index* for different years in different colours. By putting them together as an overlay, you can see how the winters since 2012 stack up. The fat dashed line represents this winter. Two things stand out. First, the only winter with worse numbers by this date was 2014, which was a brute. Second, the winter’s not over yet: in most years, we’re still making ice in March. One ray of hope, our recent warm temperatures clearly show as that uptick at the lower end of this year’s line.

*The Cumulative Freezing Index is a simple measure of how cold it’s been.

If the daily mean temperature was -5°C yesterday, the line grows downward by 5 points. If it’s +3°C today, the line swings up by 3 points.

Naturally, most years show steep drops in January, and start levelling off in March. This winter shows deep cold driving the line down in both January and February. If you were here, you’ll remember why.

I asked Sean if he thought we could have hit the Inflection Date** with our recent warm weather. He says it’s possible, but it’s quite common to see a warm spell give way to lingering cold weather. He’ll feel more confident when we see what kind of temperatures we get in the next week or two. They’re forecasting a cold weekend, with temperatures dropping as low as -17°C and highs of -9°C or thereabouts. After that, we’ll be getting close to April, and can hope for milder weather.

**Inflection Date is the date when the Daily Mean Temperature rises above freezing on a lasting basis. Right now, we’re waiting to see if it lasts. At Ice Patrol, we consider the inflection date to be the start of the lake’s thaw.

For perspective, average temperatures for this time of year are highs of around zero and lows of about -9°C. So when we were hitting highs of 10°, that was a bonus, and that’s why it stands out on the graph.

Okay, that’s all for now.

April 19, 2021: Compared to Last Year

We’re almost there. We’re stuck with a couple more days of shivery weather, but even if the remnants of ice hold out through those, Thursday’s warmth—currently expected to reach 14°C—will wipe them out. Of course, even while it’s cold, wind and wave action are working to destroy ice every hour.

In preparation for today’s radio chat with Ken O’Neil at Q-104, I was updating my graphs, and I noticed something.

Let’s say the ice holds out another day or two. The Brick Graph will look like this.

Brick Graph.

For this graph, I put the date the lake is 100% clear of ice into a five-day period (because sometimes I’m not sure of the exact date). So you can see we had a pretty early thaw this year, probably the third earliest of this century.

The Pancake Graph puts a slightly different spin on it.

You can click on this graph to enlarge it.

Pancake Graph.

This graph, more formally called the Inflection to Thaw Calendar, gives each year a bar that starts on the date of the Inflection Point* and ends when the lake is ice free. Two things jump out at me here:

First, despite starting early, this is the slowest thaw on the chart. We hit consistently above freezing temperatures early, but they were barely above freezing. As far as defining it by air temperature is concerned, the thaw looks set to drag on to about 48 days.

Second, look at last year’s bar: the thaw didn’t start until now!**

*The Inflection Point is when the Mean Daily Temperature rose above freezing for keeps.

**In terms of air temperature, anyway. On this graph, the 2020 thaw was fast, at 18 days. It does not take into account that water currents would have been thinning the ice from below while the air was still cold.

“Huh,” I said. “Do I have any photographs from late April last year in the archives?”

Do I! Check this out:

Lake of the Woods on April 18, 2020.

This photo was sent to me by Bruce White, who works (or worked, perhaps, as the air transport industry is in terrible shape right now) for Air Canada, as his flight passed along the south shore of Lake of the Woods. It looks north, with Big Island at the bottom of the frame, and the Alneau Peninsula prominent in the middle. This time last year, the whole lake was frozen over.

Other photos taken at this time last year show the ice from lower altitudes, and it looks hard and white, with little snow cover. You can use the Archive Tool (located on this web page’s right hand sidebar) to visit the Ice Patrol posts from April of 2020, or any other spring month in recent years.

Also, you might recall that in 2014, the year Ice Patrol debuted as a fully fledged web site*, there was real concern that the lake might not be open for the May long weekend. We made it, but barely.

*Ice Patrol began in the nineties, as verbal reports to friends, and grew to an informal email thing before launching as a WordPress blog in 2014.

By the way, on this site, “ice free” means it’s all gone. 100%. Not enough ice left to make a Margarita! Why? Because although many lake dwellers can reach their camps when the lake is mostly open, not all can. In fact, this whole project started because I had friends who bought a camp by an ice road, and were frustrated that they couldn’t get there by boat when most other cottagers were happily cleaning up the mouse poop and putting out the patio furniture.

Okay, maybe happily isn’t the right word, but hey, we all have PPE now! It would be wise to wear your mask and gloves while cleaning your kitchen counters, and it is especially important if your property is gifted with raccoon droppings, because they pose a significant health hazard.

So, aside from the whole miserable Covid thing, we’re having a good spring. I have some friends flying this week, so I hope to get pictures of the last ice in the next few days, weather permitting.

April 5, 2021: Seems slow

I’ve been talking a lot about how favourable our conditions are this year. We had a mild winter that formed less ice than usual. We had an early start to the thaw, and we’ve had mostly higher than normal temperatures. Conditions seemed primed for a record-breaking early ice-out, but that’s not developing.

I’m not saying this year’s thaw is getting delayed, but I am pointing out that it’s gradual.  Gentle reminder that neither Sean or I predicted records would fall.

We’ve had years in the past, notably 2010 and 2012, where the thaw started almost as early as this year, and the ice was gone pretty quick. But I think we’ve begun to lag behind the progress of those years.

I’ll pop the pancake graph in here so you can see what I’m talking about.

You can click on it to see an enlarged, easier to read version.

Remember, each year since 2003 (at the bottom) gets a bar that starts on the inflection date* and ends when the lake is 100% ice-free. The first thing you might notice is that 2021’s line begins earlier than any other. And yet, it looks set to be one of the longest, representing a surprisingly drawn-out thaw for a warm spring following a mild winter.

*Inflection point or inflection date means the date when the air temperature started to average out at above freezing. More precisely, when the Mean Daily Temperature rose above zero Celsius on a lasting basis.

The two years that come closest to our starting point are 2010, at March 8, and 2012, at March 10. Both of those years had reasonably quick thaws, at less than 5½ weeks. [38 & 37 days, respectively, but who’s counting?] To match that, we’d want to be looking at a total thaw by April 10. So that’s where I began the pale blue of uncertainty on this year’s bar. But Sean Cockrem’s prediction, based on presumed ice thickness and air temperatures forecast, is April 20. Side note: this is his stated and preferred estimate, but his simplest formula, without intuitive insights, produced a date of April 25, so I ran the uncertainty zone out that far.

There are two things going on here. First, the earlier you start, the longer it can take, simply because March is apt to be cooler than April, even if temperatures are running above average. Second, air temperature is not the whole story when it comes to getting rid of lake ice. Sean’s model uses data from past years, and that data is all over the map. In other words, every thaw is different, which is why Sean has to make some educated guesses as to what kind of year we’re having.

Last year we got schooled. After air temperatures stayed depressingly low, the ice went in a hurry  (17 days!) There are many factors other than air temperature: snow cover, rain, wind, sunshine and so on. But I increasingly suspect that the biggest one is current.

Most years that I can recall, the water seemed to open up through the Keewatin Channel faster than this year. Sometimes the water spreads from Channel Island to Safety Bay quite quickly. This year it seems to be rather lethargic.

So I happened to be talking  with some friends on Zoom, and one who lives on Golf Course Bay remarked that this winter, the end of their dock iced in for the first time ever. Usually, the current swirling past the tip of their dock prevents ice from forming there, and the ice is notoriously thin in the whole area around the Coast Guard docks. This sparked a conversation about how—although the lake ice was generally thin—the low current allowed people to route some ice roads through usually untenable areas.

To talk about current, we need to check in with the Lake of the Woods Control Board, who strive to keep lake levels safe by altering the outflow through the Norman Dam. Spring is the season when that typically gets trickiest. It’s prudent to keep the lake levels on the low side in March, to allow for spring run-off and flooding. They call this the winter drawdown, and it’s part of their regular strategy. It’s usually followed by the spring refill. This year there wasn’t  much spring run-off, so lake levels have not risen as rapidly as some other years. So the outflow is being kept low, to give the lake levels a chance to rebound.

Here’s the latest bulletin from the Board.

The current level of Lake of the Woods is 322.42 m (1057.8 ft), a 40th percentile level for this time of year. The average lake level changed little over the past week and is expected to remain stable or slightly increase (less than 2 cm or 1 in) over the next week.

Lake of the Woods authorized outflow is 150 m³/s with no changes scheduled.

This time last year, when we had that very rapid thaw, the outflow was nearly four times as high. The current was probably eating away at the ice from below long before the air temperature rose above freezing.

From the air, this shows as open water in the narrows and channels, and ever since I started Ice Patrol, I’ve been paying close attention to those areas. It makes perfect sense that progress of that type is slow this year, despite the mild weather.

So while current is a big factor, its role this year will be passive. Which is one less wild card for Sean’s predictive model.

March 25, 2021: Sean’s first prediction

Sean Cockrem, the guy who contributes the fancy graphs, has come to some preliminary conclusions about when the ice might be gone. Here’s what he said:

Here’s my first crack at a forecast for this year.
A couple notes
  • in trying to figure out the required thaw index, I usually take the winter’s freezing index, which in this case was -1250, and divide it by 10 which is the average thaw ratio between the freezing index and the thaw index on the day the ice was out. In this case that would get us to a thaw index of 125.
  • when I plotted that line on the thaw forecast window, it pushed the ice out date to around April 25th.
  • back to that thaw ratio between the freezing index and the thawing index at ice out. It actually ranges from 4.37 to 17.77 over the last 18 spring thaws with the average being 9.98.  In the 5 winters with lower freezing indexes in the last 18 years, generally the thaw ratio is below 10(which means that it would push out the ice out date even longer…). I have provided a summary of the data in the table below:

So, here is where intuition and gut feeling plays a part in determining what that thaw ratio should be. I have assumed that it will be a bit higher than average and set it at 12.5. That’s not based on much more than the fact that your photos are showing open water, that the ice wasn’t that thick and that the snow cover is probably was thinner than average too. (I could be way off with this)
In the end, my forecast is based on some unknowns including the forecasted weather in the coming weeks as well. And right now with all the unknowns coupled together, it is suggesting that the Ice Out date is around April 20th.
Sean is picking March 4 as our Inflection Point this year, so I guess it’s time to update the “Pancake Graph.”  Inflection Point is when the mean daily temperature rises above 0°C. In other words, when we’re thawing more than we’re freezing. Sometimes I call it Inflection Day or Date.
You can click on this graph to see it full screen.


The Pancake Graph

This graph shows the time-span of the thaw in recent years, in order from oldest at the bottom to newest at the top. The blue bar for each year begins on the Inflection Point and ends when the lake is 100% ice free.

I’m not nailing down Sean’s predicted date as if it’s a sure thing. I’m showing a range of between April 10th and 25th for now. Two things jump out at me from graphing this. First, March 4th is the earliest Inflection Point Sean has determined yet. Second, even with the likelihood of an April ice-out, this is not a rapid thaw. In fact, it’s looking like one of the most drawn-out melts on the chart. That’s not crazy. The earlier we start, the longer it takes because of the cool March temperatures. The ice was not thick this year, so that’s part of the reason I allow for the chance of thawing by April 10. That would be extraordinary, but it makes for a time-span more in line with other early thaws.

You might be interested in this article on Kenora Online, about moderate drought conditions in the Lake of the Woods drainage basin.

The article refers to the Lake of the Woods Control Board, so I went to see what their latest news bulletin said. Here’s the part specifically about LotW.

The current level of Lake of the Woods is 322.42 m (1057.8 ft), a 40th percentile level for this time of year. The average lake level decreased by 1 cm over the past week and is expected to change little over the next week.

Lake of the Woods authorized outflow is scheduled to decrease to 175 m³/s on Monday, March 22.

That percentile may change in the next weeks. Usually, spring rains and floodwaters raise the lake levels in the coming weeks. With little run-off expected this year, the present levels are quite likely to look increasing low in comparison to seasonal norms.