Edward Plumb: Well, good morning, everyone, and welcome to the Alaska Spring Breakup Outlook. This event is being held in the International Arctic Research Center on the University of Alaska Fairbanks Troth Yeddha campus. The Alaska Center for Climate Assessment and Preparedness, we're also known as ACCAP, Is hosting this event. ACCAP is part of the Regional Integrated Sciences and Assessments, which is funded by the NOAA Climate Program Office. ACCAP has been working here in Alaska for over 17 years to improve the ability of Alaskans to adapt To a changing climate. A few logistics before we get started. Your video, Has been turned off, and you have been muted. And at the end of the presentation, we'll have about 10 minutes or so for a Q&A, and at that time, I'll allow you to unmute yourself and turn on your video if you want to ask a question directly to our speakers today. Otherwise, feel free to put questions in the chat as they're talking. I will try to answer as many as I can, and any that we can't get to, or I don't know the answer to. I will bring those up to the presenters during the Q&A session as well. We will have a recording of the presentation on our website in a few days, and so the webinar is being recorded. Additionally, something new we're doing is, at the end of the Zoom, when you get ready to log out, you will be prompted for a brief survey at the end of the webinar, and if you're using Zoom in the browser, please hit Leave Meeting rather than closing the tab, the browser tab. in order to get prompted for the survey, and we really appreciate you taking a few moments to answer the survey questions. There's just 3 quick questions, and a fourth one that's optional. So, I would go ahead and get started here. So, my name's Ed Plumb, and I'm the Weather and Flood Hazard Specialist here at ACCAP. And it's my pleasure to introduce today's speakers. We've got two folks today. We've got Kyle Van Peursen, is the Service Coordination Hydrologist with the River Forecast Center. Down in Anchorage, which is part of the National Weather Service. He has many years forecasting river breakup in Alaska, and has flown hundreds of miles of river and ice jams, reconnaissance along the Yukon and Kuskokwim rivers. Our second speaker, well, actually, Rick's talking first, is Rick Thoman, is the Alaska Climate Specialist with ACCAP, and has many years of experience producing reliable Alaska climate information and graphics describing Alaska's changing environment. His work spans the bridge between climate modeling, Alaska communities, and the media. So, well, thanks, guys, for joining this annual webinar that we do every spring. So, I'm going to hand it off to you. Looks like you're going to be speaking, Rick. The floor is yours. Richard Thoman: All right, well, thanks very much, Ed, and Thanks, everyone. As said... as Ed said, this is an annual, presentation. This is either the 10th or 11th, spring in a row that we've done, the ACCAP, National Weather Service, river breakup, outlook. So, I'm going to... I'm going to take, two parts of the timeline here, just a quick review of what's happened in the past, past winter, to kind of set the stage, and then I'm going to review, what we have for the climate, sub-seasonal, outlooks in the future here, and then I'm gonna hand it off to Kyle, and he's gonna drill down into the specifics of what all this means for the 2026 spring breakup. Let's go ahead and jump right in. And this, this is just, first up is what's happened since autumn. So, graphics here, courtesy, National Weather Service, Brian Brettschneider, and these are the climate analysis model, based, looks at precipitation on the left and snowfall on the right for the October through March time period. And, And you can see in the... in both of these, the scale here is the percent of the 1991 to 2020 normal. So, concentrating on... on mainland Alaska here, overall, generally less precipitation than normal across most of south central and southwest Alaska, generally near to above normal precipitation. for the 6 months across, the interior. More of a mixed bag across, say, western Alaska up to the Seward Peninsula. and northwest Arctic. Now, on the left-hand side, that's precipitation, so that includes both rain and the liquid equivalent of snow that fell in the models of view of things. So you can see, particularly the eastern interior, Fairbanks northeastward, as well as portions of the upper Tanana Valley, into the Yukon, more than 150% of normal precipitation, for the winter, noticeably less in the Koyukuk Valley, the northwest interior. And the Kuskokwim, more of a mixed bag with above normal precipitation, kind of northeast of McGrath. But generally, near to below normal downriver, from McGrath there. In the, Susitna Basin, they're generally near to below normal. Parts of the Susitna Basin, significantly below normal precipitation for the sixth month. On the... On the right-hand side is the snowfall, different percentage difference from normal. This looks similar, but it's not identical to the... to the, precipitation. Some of that is, because of rain that would have fallen, particularly early in the cold season, even inland. But overall, you can see here now, above normal snowfall. Again, the water equivalent of the snowfall, for much of the eastern interior. But now, that snow deficit shows up more cleanly in the Koyukuk Basin there, below normal, battles all the way, down to, the, the, Yukon River, as well as across much of, southwest Alaska and western Alaska, really only out towards Bering Strait, did we see above normal snowfall out there. Generally in South Central, including nearly all of the all of the Susitna Valley below normal snowfall in the model's estimation here. So, that's the precipitation side of the house. The cold season, of course, is, was really quite dramatic. Now, I know it's a long time ago, it's hard to remember, but the 2025-26 cold season started out really warm across Alaska, and that's shown on the left-hand side. That's the temperature departure, from the 1990... or 1991 to 2020 average. across Alaska, and you can see virtually everywhere, warmer than normal, and some areas by quite a bit. Those darkest red areas, more than 9 degrees above normal for those two months. But of course, about, December, third or fourth, we flipped the switch and turned into a really cold pattern across virtually all of Alaska, except for portions of the North Slope and southeast, as well as the central and western Aleutians. But most of Alaska, especially for the Yukon and Kuskokwim drainages, significantly below normal. Notice the temperature scales on both of those graphics are the same, so that you can see the really amazing flip there that occurred in December and persisted through March. Of course, both the December and January cold snap, and then the, in many places, record cold March are really highlighting. And that, of course, I'm gonna, as Kyle's gonna be showing, impacts portions of the hydro system, particularly, in many areas, river ice thickness here as we, head towards breakup. And just to bring us up to date here, here are the temperature departures at individual stations for April. This is through The 19th, so through Sunday here. Not a lot to write home about here. This graphic from the High Plains Regional Climate Center, kind of big bins for temperature departures from normal, but the yellows are kind of 0 to 5 above normal. The greens are 0 to 5 below normal. So nothing dramatically different from normal. Given that, fairly wide range. One interesting feature is across northern Alaska, but especially in the, in the Tanana Valley. On up into the Yukon. We've had a number of... Of days during the month where high temperatures are actually running significantly below normal, but low temperatures have been above normal. And so, not quite balancing out, but if we just did high temperatures, this would look different. Than the average is because of the cloudy skies frequently, and even some precipitation, unusual for, for April, which is often a very dry month. But all in all, kind of a mixed bag, but probably more below normal than above normal across mainland Alaska during the start of April. Okay, so that's the... that's kind of the climate, review. Now we're going to take a look at the temperature outlooks for, for the rest of the breakup season. Now, I want to start out here, this is... I don't usually show this, but I think it's important because we are setting up for a significant pattern change across mainland Alaska. On the left-hand side, we have the kind of the mid-atmosphere, the steering flow, for the... this is the, for the 5 days from the 16th. to the 20th, cold low pressure across-centered on average in that time across northwest Alaska, and generally, a cold pattern aloft across most of mainland Alaska. And, the result has been, in some places, snow. In most areas, as I said, significantly below normal, especially high temperatures. That is going to change, in the coming days as low pressure becomes more solidly established across the the Bering Sea, ridging, building across the, southeast Alaska and eastern Pacific, and so we're going to get more southerly flow across, from the Gulf of Alaska into mainland Alaska. It's gonna be a big change. Now, this is not a particularly hot pattern for, much of inland Alaska, but, particularly, compared to what, the month has brought so far, especially in regards to high temperatures, gonna go from mostly below normal to at least near, or maybe only a little below normal. And remember, across the interior, normals are rising at about 2 degrees every 3 days now. So, even normal or a couple degrees below normal is going to be a big change, and importantly for breakup, that means high temperatures now going to be at low elevations, sustained significantly. Above freezing in the coming days in and through next week. So, the... here we have now the Climate Prediction Center's outlook. These are from yesterday. Be advised. Of course, these are updated every day and may... may change, but as of yesterday, for the last days of April on the left-hand side, Climate Prediction Center generally forecasting significantly above normal. It's more likely than near normal or below normal for most of Alaska. Alaska ranged northward, with, and the same in there in southeast, near normal being the forecast for southwest Alaska, south central, and the, the northeast Gulf of Alaska coast. For the week 2 outlook, so April 28th to May 4th. From yesterday, same basic pattern, north of the Alaska Range, tilting to favor significantly above normal temperatures. Alaska Range south, including southwest Alaska, and south of the Kuskokwim River. Near normal was the best, bet by the CPC as of yesterday. Now, for week 3-4, So, this is a... this is a forecast issued by the Climate Prediction Center once a week, every Friday, so the most recent is for May 2nd to 15th, so the first half of May, effectively. And you can see here the outlook favoring significantly below normal across southwest Alaska. That's a reflection of the continued sea ice, and when that melts for a while below average sea surface temperatures in the southeast Bering Sea. Fairly large area there, with equal chances for above or below. normal temperatures for the three... for the two weeks as a whole, and then favoring above normal northern interior, but also, arcing down into the easternmost interior, as well as, most... all of southeast Alaska there. Now, another tool that we have from our colleagues at the World Climate Service, this is a multi-model composite here of two different models, the U.S climate forecast system and the European climate system. And here we see the... the forecast, for week, for week 3 there on the left-hand side, so this is May 4 to 10, and now the World Climate Service also provides this at... for week 4, explicitly, so a little finer resolution in this product than the CPC week, week, 3-4 outlook. And you can see, generally, near to above normal favored for week, 3 there, so May 4 to 10th. Less of a signal there as we get into mid-May, although across Mainland Alaska, except for the Bristol Bay, Alaska Peninsula region, generally near. No tilt, or maybe slightly favoring above normal temperatures. And the last piece of the puzzle that we have here is at the monthly scale, so these are from the Copernicus Climate Change Service. The May outlook that was issued the beginning of April is on the left, and the June outlook for the issued beginning of April is on the right. Now, CPC also provides a May outlook, but they don't provide a monthly outlook beyond the first month, so we'll use the multi-model, of... forecast here from the Copernicus Climate Change Service. The big bull, cold bullseye there in the Southeast Bering Sea, again, reflecting the sea ice and continuing below normal sea surface temperatures there. But otherwise, you can see for May, outside of Southwest Alaska, at least a bit of a tilt to favor significantly below... significantly above average temperatures for the month. In June, still have that cold air in Bristol Bay, Alaska Peninsula, but a larger area with tilt to favor significantly above normal, and And although the tilts are larger, south of the... south of the Brooks Range for June, we're mostly talking about breakup on the North Slope, and there, it's only... it is a modest tilt to favor significantly above normal. Presumably, breakup will be through most other areas by the time we get to June. That is what I have for ya, And I think at this point, I am going to stop sharing and hand it over to the person you really want to hear from in this presentation, Kyle, with the Breakup Outlook. Kyle Van Peursem: Oh, but Thanks, Rick. I don't know about that. Hopefully I have good news for folks, but, can I get a quick audio and screen check? Make sure I'm good. Edward Plumb: Hear you loud and clear, Kyle. Kyle Van Peursem: Are you seeing my screen? Edward Plumb: Yep, we see. Kyle Van Peursem: Alright, I'll... Good to know. Alright, we'll start. Alright, well, thanks for that, Rick. Yeah, it's gonna be interesting to see how the temperature pattern plays out and how it drives breakup this year. It's always the trickiest part. So, as Ed said, my name's Kyle Van Persen, I work for the Alaska Pacific River Forecast Center, based out of Anchorage here. I've been flying Riverwatch since 2022 was my first year, and, typically I've been on the cusp of one the last couple years. This year, I'm gonna be flying, the Middle Yukon section, based out of Galena this year. So, let's go over, what I'm gonna talk about. Alright, first thing I want to do is first talk about the breakup process. Just educate folks in case you're not super familiar with how it works, talk about what happened last year. And then we'll go into the outlook, the flood threat for this year, and talk about our schedule as we head into breakup. Alright why do we care so much about breakup this time of year? I think for folks in, let's say, Anchorage. Breakup to them means it's... Snow is melting, there's a lot of road spray, you're cleaning up all the, you know, the dog poop on the ground that's left over, there's a lot of trash, it's more of an inconvenience. For folks that live in the interior, especially in those big rivers, like the Kuskokwim, the Yukon, Tanana, Koyukuk Rivers, breakup has a whole different meaning to them, because it's... The times when you... when they experience the worst flooding that they've seen. Maybe they've lived there for a while. Breakup means they're... They've seen houses, their whole village, get washed out, or ice, jams in front of their village and destroys buildings, and... they're left without power, it's... it can bring back bad memories. So, flooding, or ice jam flooding, is one of the leading causes for moderate to major flooding in Alaska, and documented, history for the state. So... That's why we put so much effort during this time of year to prepare folks and provide outlooks and let them know what to expect, especially as you go into Breakup and we fly Riverwatch, providing that aerial reconnaissance, real-time updates on what's happening. Let folks know to get ready if something bad is coming their way. Now, coastal flooding is beginning to creep up, especially the last couple years. For now. Ice jams are still the predominant cause of major, to moderate flooding in the state. Let's take a look at some of the historic floods in recent memory. Eagle, 2009, it was a bad year, had their worst recorded flood in history. For their, for their location, and it caused a kind of a cascading effect downstream. A lot of other places flooded on the Yukon that year that year. It was a rapid warm-up at the end of April, which really triggered, the breakup that year. Galena, I'm sure Ed has memories, good memories of this. In fact, he took this picture, he was flying Riverwatch. When this happened at the end of May in 2013, I believe it was one of the, if not the latest, breakup, for many locations recorded on the state that day. It was a very, very cold, delayed, breakup, cold May. So. And it warmed up rapidly in May, end of May, and caused a massive ice jam. at Bishop Rock, downstream of Galena, and caused their worst flooding on record. And then, more recently, 2023 was probably one of the worst, if not the worst year in terms of total severity of breakup in the state, in recent memory. We had Circle. had their record high, flood of record, or their worst flood of record in May 13th, 2023, on literally the exact same day Crooked Creek also had their record high flood of, On May 13th. Unfortunately, I was flying this segment when this occurred, and it was, pretty devastating to see. So, when you think about breakup, breakup happens, or it's kind of split up into two different regimes. So, on the right here, we have what was called a thermal breakup. Thermal breakup are typically viewed as, like, good breakup, good breakup years. So, during these years, we tend to have lower snowpack, warmer winter, ice is thinner. The ice becomes rotten or candled, kind of breaks apart easier. We typically have warmer Aprils that tends to start to melt earlier, melts that snow, weakens the ice sooner. Don't have a lot of snowmelt push coming down all at once, and tend to not have many sniffing ice jams. If you go to the left side of the scale, dynamic breakups are the bad years. Here's some examples. I said 2009, 2013, 2023. These are years where the ice remains hard, it's typically thick, it's resistant to breaking up. The... we usually have above-average snowpack across a good portion of the interior. And the biggest, I guess, driver of dynamic breakup years is what happens in April and May in terms of temperatures. Typically, we have cold Aprils. That just delays melt. It kicks it down the road. And then it warms up rapidly as you get into May, and all that does is it compresses the time that we have to melt off all that snowpack. It melts it off all at once, instead of over a whole month or so. And this is when we are most likely to see ice shams flooding. So last year, it was more on the thermal side, didn't have a whole lot of impacts. And this year, We're trending towards dynamic. So, I made this graph to kind of give an idea of how... of what it looks like in terms of a dynamic and a thermal breakup. So, let's say we have a typical year. We have... we're starting off in early April, the ice has a certain amount of resistance, strength, or force. And we, and in April, we don't have any snowmelt yet, so there's no... we call it hydrodynamic drive that's... That snowmelt entering the water system and putting force on... up against the ice. And then as we go into May, or April, the snow begins to melt. At the same time, the ice begins to weaken. Now, when these forces meet, the drive of the snowmelt coming down the river versus the strength of that ice resisting the drive, when those forces meet and overcome, that's typically when we have breakup. And where this happens on the breakup severity scale on the right, where this happens simply determines how bad breakup is. So this year, you know, a normal year normal breakup severity. Might have some flooding, some ice jams, but nothing too bad. Let's talk about a thermal year. Let's say... We didn't have a whole lot of snow, it was a warm year, warm winter. The ice isn't strong, it's thin. We don't have a whole lot of snowpack at the same time. As you go into April, I'd say it warms up. We have warm temperatures in April. That ice begins to weaken pretty quickly because there's not a lot of snow on top of it, so the sun and the warm temperatures begin to weaken the ice, and the bonds between the ice. And it can fall apart easier. At the same time, we don't have a whole lot of drive coming down the snow... down the river from snowmelt. So when those horses meet, it's low on the severity scale, and we don't have a lot of impacts. People are happy. So this is an example of what a... the river looks like during a thermal year. I think this is on the Cusco, 2015 or 2016. Very warm, low snowpack. That winter, ice is dark here it's candled, so it just kind of breaks apart, and it doesn't put up a lot of resistance when the snow melt comes down the river. It just breaks apart, and breaks up without any incident. Let's talk about dynamic year. Let's say we had a really cold first half of winter, kind of like this year. The ice is thick, it's strong, we have a... and then we go into maybe second half of winter, and we put a ton of snow on that. So we got 3, 4, 5 feet of snow on top of 3, 4, to 5 feet of thick ice. But then we go into April, -oh, it stays cold. Nothing's melting yet. The ice doesn't... hasn't weakened yet. No water has really entered the river system yet from snowmelt. But then all of a sudden, we get into early to mid-May, we have a big ridge that forms over the interior, temperatures go into the 60s and 70s all of a sudden, we have a rapid influx of snowmelt that hits the river, but the problem is the ice hasn't really had a chance to weaken. So, we have a ton of snowmelt, and it has a lot of force behind it, and the ice also has a lot of force. And when these two meet, they meet higher up on this brick-up severity scale, and we have bad years. We have years where we have tons of ice jams and flooding behind, where the breakup front is on the river. This is what a dynamic breakup looks like. 2023. You can literally see where the river is transitioning from solid, in-place ice to that broken chunk ice. This is called the breakup front, and it's, like, just moving downstream in a linear fashion. And then on the right here is the Taylor Highway Bridge on the 40 Mile River. In 2023, you can see a big ice jam formed at the bridge with a lot of debris in it. So, when you have an ice jam, this is typically what you... kind of a diagram you would see as the breakup front is moving downstream. So, on the right, you have that strong, intact, ice, and it has a certain amount of force. And then the ice... Where the breakup front is, is beginning to begin to break up and get chewed up, and that line moves downstream as you have more snowmelt and more water entering the river system. I think of this as, like, a dam in the river. It's, in a sense, impounding water that's moving down from upstream, downstream. And that brick up front, it... let's say it runs into an area of stronger ice, or a constriction, or a bend in the river, and that breakup front stops. The problem is, you have tons of water still coming down behind it, and the water has no place to go, so it has to back up, and it moves up and out, and causes flooding behind it enough force finally builds up behind that breakup front, and it's able to continue downstream until it jams up again, and then it floods again. So you can think of it as, like, a dam with water impounding behind it, and that's why, the worst flooding, or typically all the flooding that we see during breakup, is Behind the breakup front. So, this is a drone video that I took during that record flood event in May of 2013 at Crooked Creek. And where this is, this is actually after it had crested, still very high, but this is behind the breakup front. We have all the trailing chunk ice Still flowing downstream. The river, that evening, or that prior day, had jammed up. About 5 miles downstream of this, around the bench here, at a place called Rabbit Island. It's a constriction, or the river has to go around the island in two places, and as the breakup front came through, it got stuck there, jammed, all the water piled up behind it, and flooded the... almost the entire village of Crooked Creek, besides the high points. And that... you kind of get an idea of what it looks like afterwards. Water's still high, still hasn't receded all the way down. It took about a day, day and a half for it to finally recede down. So ice jams occur, as you can imagine, in places where, there's constrictions in the river. Maybe where, there's sharp meanders, or the slope of the river, goes from steep to shallow, anything that can restrict and impede the flow of the breakup front, that's typically where we have jams. This is a infamous jam point downstream of Galena, this is Bishop Rock. And you can see it has kind of all... everything that you would want in an ice jam point, with a constriction and a sharp bend. And unfortunately, it's right... it's downstream of Galena. And this is what it looks like here. I think Ed, I think he took both these pictures? Correct me if I'm wrong, but... The picture on the left, you can see May 27th, The ice sheet kind of got... almost turned horizontally, and got stuck at the bend, and then all the ice jam... all the ice behind, this ice sheet just piled up behind it, and it couldn't push through the jam, and it got stuck for 3 days and caused Really bad floating in Galena. You can see on the right how backed up the river was, how much chunk ice there was, and overflowed. We tend to have, two different types of... flooding during breakup. The first, and this is typically the worst, is during ice jams. During ice jams, the river stage, like, their actual river level, is the highest, during, breakup. That's because the ice tends to constrict, the riverbed, and the water has to move... go up and out, and causes the highest river levels during that period of time. Now, snowmelt comes typically after that, when you have more melt coming down from up high, and that's typically where we have the highest flow moving downriver. But that doesn't necessarily mean you're gonna have the highest river stage, or how high the water is. It tends to be actually lower than, during ice jams. So let's talk about what happened last year. So last year, again, I said it was more on the thermal side. We didn't have a whole lot of impacts, at least For most of the breakup season through May. We had a few minor floods on the Cusco and up at Fort Yukon, on the Yukon River. Those were just kind of low-flow scenarios where there wasn't a lot of snowmelt coming down. I actually got just stranded, and... Kinda got stuck. Just caused some minor flooding in Kalskag, and very minor in Antioch. But we did have a delayed melt, for the north slope. And... Sorry about that. And that caused, actually, most of our issues last year was on the North Slope. During breakup. So here's an animation of our breakup map. If you... I have the link below that map if you want to follow it through the breakup season this year. We update this daily, if not hourly, during breakup, and it... we update it based on satellite imagery, based on reports on the ground and photos that we get on the river status once it goes from ice to open. We also label villages when they're under a flood watch, warning, or advisory. So you can see how that breakup... I'll break up... progressed last year. And really, the... again, as I said, the biggest impacts were on the North Slope. You can see how late the North Slope broke up last year, and I'll go into that, into why that happened. So, last year was kind of a year... from the south, it was, like, textbook dynamic breakup year. You can see this is Tulik Lake, on the left, their temperature plot for this April through, June period. The bars represent the daily temperature range, the blue bars, and then in between that are the... Record high temp for the day, low... record low temp for the day, and then kind of the brown... area in the middle is the average temperature for the day. So you can see, as we were in May, this location on our slope had record low temperatures, pretty much through most of the month, well below average. And then all of a sudden, June comes around, a big flip, and they go record high with temperatures into the 70s. On the right is the snowpack plot from last year, and you can see we were averaged above average snowpack, but then it stayed... snowpack stayed around through the first week of June, and then melted off within 5 days, 2 feet of snow and melted off in 5 days. So, as you can imagine, that led to some... Some bad flooding. So on North Slope, this was what it looked like, satellite imagery on June 12th. Looks like midwinter. When I go to the next slide, I want you to look at the rivers here. Compare them to how they look in this image. Five days later, it melted off all the snow, and the rivers were completely swollen. So we had the Colville River. Way out of its banks. This park and the Sag River, also way out of its banks, caused a lot of flooding in that area. Here's some images from the Dalton Highway. On the On the North Slope, a frozen culvert blew out. Some flooding, general flooding in the area along the Dalton Highway. The Colville River at Umiat recorded its record high crust. And, you can see how high it went up and how... how rapidly it came up. It flooded, Umiat camp for several days. So yeah, that's a very textbook example of what a dynamic breakup looks like, and that was driven primarily just by that rapid Transition from record cold temps to record high temps. So, how we looking this year? The things that we look at for breakup, there's kind of 4 major things that go into our outlook. First one is snowpack. Are we above average? Snowpack, below average. Where is the snowpack above and below average? Ice thickness? Plays a part, though not as much as you would think. Another thing that we look at is, how did the river freeze up? Were there any jams that... That kind of happened during freeze-up stage. Did the river freeze up at a really high level? Or did it freeze up low? And then, probably the most important factor are April spring temperatures. So, Rick already mentioned, What we're looking at for, the outlook for spring temperatures, going from... tend to be a little bit below average in April to potentially above average, especially for the eastern interior. That'll definitely play a role in how things pan out this year. So, this is the NRCS April 1st Snow Survey on the left for Alaska, and then the Environment Canada, their snow survey for Yukon, on the right. Generally, we have well above average snowpack for the Upper Yukon, the headwaters of the Yukon Basin. Some spots, in the headwaters of the Yukon, like near Whitehorse in that area, had record high snowpack for April 1st. So, we're definitely very concerned about that. And then other places where there are measurements that we're concerned about are gonna be, Tanana River Valley, definitely above average snowpack, and I'm sure folks in Fairbanks can attest to that. Surprisingly, though, the Koyakuk River didn't really have low, low snowpack, and South Central overall, and even though if you're in Anchorage, it seems like snowpack was above average, especially at the end of the year. Everywhere else was below average for South Central. And then we use this Arrow 5 reanalysis to kind of fill in the gaps where there's not data, and this provides more of a general spatial view of the snowpack anomaly. So this is the snowpack anomaly for April 11th, and it pretty much matches what we see from the Yukon and the NRCS snow surveys. We have above average in the headwaters of Yukon, and scanning into the upper Yukon portion of the U.S. And then the 10 river above average. We had to have an area of above average for the North Slope, even more than last year. And then, right along the mouth of the Cusco, kind of the lower Cusco, has above average snowpack. The Koyukuk, Buckland, and middle to lower portions of the Yukon have averaged to below average snowpack. And the good news is for the Cusco, the headwaters of a lot of the major river drainages that feed into the Cusco, like the Tatlawiksuk, the Swift, Aniak River, those are all well below average snowpack, so that's gonna help them out this year. But there are some other things that are gonna play not in their favor, which I'll go over in a second. So, we like to compare how things looked in previous years. So, on the top here, we have what this snowpack anomaly looked like on April 1st for 25, and then on the right for 24. And then we also, below that, show the difference from this year to those years. So, bottom left shows that for... Compared to 2025, red means that we have less snow This year than last year. So we have less snow in the Koyukuk and kind of northwest part of the state compared to last year. And more snow in the Upper Yukon. Than... than last year. And definitely more snow along the lower Cuscoquin, than last year. 2024 saw, a lot of flooding along the lower Kuskokwim, and you can see they had a lot of snowpack that year. Along the west coast of the state. The good news is, for them is, for a majority of that area, we... this year, we have less snow than that... than that year. 23, again, that was one of the worst years, you know, if you look at the... at the Upper Yukon, Canadian Yukon. It's a little concerning because it's kind of mixed, but it looks like it's about the same if you average it out, than we had compared to 23. So, that's why we are definitely concerned about the upper this year, and 23 had, again. Circle had its worst flooding on record. And then, for the mouth of the... of the Cusco, the lower Cusco has more snow than 2023, but for the most part mainland Alaska has less snow this year than 23, especially 22. 22 was a huge snow year for the interior. We had really bad flooding on the Tanana River at Manly Hot Springs that year. We had a massive ice jam that formed, upstream of Grayling that spilled water into the Innoko River and flooded Shageluk. Luckily, that jam happened kind of in an area where there's not a lot of infrastructure. Could have been a lot worse if it happened further down the river or closer to Galena. Galena had some minor flooding that year, as well, and McGrath had some moderate flooding that year. So the good news is, for those areas, it's definitely looking, there's less snowpack in, this year compared to 2022. We also look at thawing degree days, how has our melt, how does it look compared to normal? So, in terms of, like, how far along we are in Melt, we're below... we're... we're definitely, late. You can see we're below average for 9 degree days across the state. I'm pulling a few plots here. I compared this year to previous bad years, and the major thing that you see is fine degree days during these years are always delayed and below average in April, and that's... we're kind of on the same track this year. Now, if we were to take the CPC guidance that Rick talked about and said that's gonna verify, we would... we should start seeing fawn degree days pick up here, as we get towards the end of April. So... The question is, how rapidly are those... are those temperatures gonna jump up? If we get... you know, if the CPC guidance is even less than what occurs in terms of temperatures, and we jump up into the 50s or 60s, or even worse, 70s in the eastern interior, we could definitely see, some... some major issues happening in... as we go into May. So hopefully we can kind of just... slowly warm up, as we go into May. Our river ice is, as you can imagine, cold deer. on the whole, it's above average. There are some spots that kind of jump out that are below average, but if you look at it at the whole, we're definitely above average. Some key spots are, like, the Nenana Ice Classic. one of the highest ice thicknesses ever measured there during that period of record back to 1989, I believe, and they recorded over 50 inches of... of ice, in April, in early April. So that's... I mean, that's definitely concerning, definitely... Folks downstream need to be aware of that. You have thick ice, and it's going to be hard to break that up. Eagle also has above average ice thickness. Luckily, the river froze up below average up there, which will work in their... in their favor. So, some other areas that we're concerned about in terms of how the river froze up, it's going to be at the mouth of the Yukon. We heard reports from our observers out there that they're concerned about breakup this year. They said the river froze up, high, and in fact, at the USGS gauge at Pilot Station. froze up at, record high stage. So, it just means when things break up, there's not a lot of room left for the river to rise before it starts flooding things. It was reported rough ice at Emmonak, and then the big thing is the shore fast ice from the sea ice is really strong this year due to the cold winter that we had, and that impedes the brick up front as it hits the mouth. So, those are all things that we're concerned about for the lower Yukon this year, and has us Increase their breakup flood potential. There's also a freeze-up jam that was reported That happened downstream Cooker Creek, right up Five Mile Island, where it jammed up in 23 and 20... and 2011, which was the previous record crest for them. Bethel Search and Rescue said, yeah, this is exactly what happened in 2011, even though the snowpack seems to be lower, overall in the headwaters. you know, it still is of concern. If the brick up front can't get through that ice, it's gonna back up and cause some flooding upstream of them, so we have them at high, as increased threat. And then, generally, there's this really rough ice from Antioch down to Bethel on the lower portion of the Yukon, or sorry, of the Kuskokwim, that is just gonna increase the threat for ice jams in that section of the river. In terms of timing, because spring is delayed, everything in terms of breakup is likely going to be delayed, too. So this is our current, best guess, if you want to call it. The dates labeled there in black are the median date, and then in red are... you can add on to those median dates, for our expected breakup. So, 3 to 5 days late for the eastern interior, that's gonna be Upper Yukon, Tanana, and then 1 to 4 days late on the southwest portion of the state. So, lower Yukon to Kuskokwim is what we're looking at. And later, breakup... Tend to be more impactful on the whole. So this is kind of an overall... where we're most concerned about this year. Areas in red, gonna be the Upper Yukon, Lower Tanana, where Manley Hot Springs is. Those are areas we're concerned about, as well as Crooked Creek, due to that localized, threat from the breakup, or the, frees up jam that happened downstream of them. Other areas that were also... have elevated concern that we're concerned about, it's gonna be the, the rest of the Yukon down to, say, Galena, the Tanana River, and then, as I mentioned before, the lower Yukon with that just rough and high freeze-up. North Slope has more snow than they did last year, so, we put them as elevated concern as well. If they warm up next, More gradually than they did last year, and they shouldn't have many issues. And in terms of specific villages, we use a village's, historic flood threat during breakup to come up with this, and then we adjust it up or down based on the four factors that I've talked about previously. So our areas of greatest concern are going to be, again, Circle, because it's naturally... it's just a vulnerable location due to this location. Crooked Creek, as well. And then other spots on the Upper Yukon, including Eagle, down the Fort Yukon. And then Tanana, Manley Hot Springs are gonna be areas of concern with that thick ice. And then the rest, most of the, lower Kuskokwim are gonna have areas of elevated concern. And as I said again, Alakanuk and Emmonak, we're definitely gonna be paying close attention to them this year. Alright, so for the rest of the breakup, kind of, here's what to expect from the River Forecast Center. Every Friday, we send out, update our weekly breakup outlook, kind of what we're expecting for breakup, the severity, the timing, and we'll mention any changes from the previous week. We do community calls that started this week with the Yukon and Kuskokwim folks, and they provide just kind of their anecdotal on-the-ground observations, and that really helps us kind of ground truth what we see on our side. Riverwatch will likely begin the end of the first week of May this year, based on the later timing that we're expecting, and that'll go probably through the last week of May, all the way down to the mouth of the Lower Yukon. We do 4 segments. It's Upper Yukon, which covers, kind of, the border all the way up to, Stevens Village. The middle covers, say, from Koyakuk up to Tanana. the lower Yukon goes, Russian mission down to the mouth, and the Kuskokwim, obviously, is, most of the river from Slint Mute down to the Nepaskiak, Napakiak. And then during breakup, we send out, daily breakup summaries, kind of like what has happened over the last 24 hours. And then, we also provide end-of-day river watch updates after the field crews have landed for the day. Alright, so here's some photos from last year's River Watch. Luckily, it was a pretty benign year, but it was a really good, really love getting out and going to these communities and talking with people. We'd land, let them know what we expect and hear what their concerns are. Fly a lot of miles, a lot of hours. We get on the radio, just brief folks what's going on. But yeah, it's a really good way to engage within the community, and folks really are... Coming to trust us and rely upon our reports, so it's such a valuable tool for everyone in the region, and we'll continue to do it as long as we can. Alright, that's all I have. I'll, take any questions. For Rick and I. Edward Plumb: Great. Thanks, Kyle. I will allow everyone to unmute themselves or start your video if you have any questions, but first, there's just... there's a couple questions, I didn't get to in the chat. I'll go ahead and ask you those two first, Kyle. Yeah, somebody had a question. Last year, such a sudden and dynamic breakup was not predicted for the North Slope. Are there any lessons learned on improving predictions? Kyle Van Peursem: It wasn't predicted in the mid to long term, because that's the hardest thing to predict, is temperatures that far out, but we actually, about a week out, that signal of really rapid warming was predicted, and we were having, calls with partners on the North Slope, and they were actually pretty well, I guess, up to speed on what was going to happen. So we had flood... flood watches out days in advance of this happening. We had models of doing pretty well in kind of predicting that. So, it wasn't predicted in terms of the... in our breakup outlook. But it was... once we got closer to the event, we saw the signal popping up. And we knew, like, Snowpack hadn't even... began to melt yet. I mean, there's a good forecast of, like, temperatures are gonna get into the 60s and 70s, 7 days in advance, really. Edward Plumb: And then another... thanks, Kyle. Another question, let's see... Somebody had... you kind of mentioned Riverwatch starting in early May. Somebody was... I know you probably can't get to the details, but they were curious if you had an estimated time for when River Watch may start for the Cusco. Kyle Van Peursem: Yeah, right now... oh, I just had my spreadsheet up, I just lost it. I think we're aiming for the first full week of May, so likely... like, the 4th, possibly, starting that? We'll... we'll get a better idea in the next couple days, and that would go probably through... the second full week of May through, like, the 13th, 14th. So it's about 10 days, typically, from start to finish, based on how fast it goes. That answers your question? Edward Plumb: Great, thanks, Kyle. We had another question just pop in, into the chat. Before 2013, What were years of major flooding caused by Bishop Rock? Kyle Van Peursem: I'm gonna put that to you, because I don't know, you have more knowledge of me than me. Edward Plumb: I'd have to go back and look at this point, I don't remember the exact dates. Kyle Van Peursem: I don't know if anyone else is on here from... RFC, or has any idea, because I can't tell you offhand. Richard Thoman: So, certainly, 1947, Which was bad flooding, and I believe that was, one of the... one of the efforts by the, Air Force to... to bomb the, drop bombs on the ice jam at Bishop Rock. But obviously there are other events, after 1947, but that was a big one. That was a big flood year. Edward Plumb: Thanks, Rick. Yeah, I'm not remembering. I thought there was one in the early 70s, too. At Bishop Rock in Galena. I know, I know the River Forecast Center has... has that documented, especially after the 2013 flood, they were looking back at previous events that, On the flood record. Are there any questions from anybody out there that want to ask directly? You can unmute yourself if you have a question, or you can drop another question into the chat. Kyle Van Peursem: I see one from... asking about, is there information collected from the impacts of the flooding breakup on those river communities, anyone collecting info on how recovery efforts have gone, and think about female responses. That's going to be a question for the State Emergency Operations Center. We do document all the floods and their impacts, and it's in our flood database. But in terms of, like, FEMA responses, that would be, more for the state. Yeah, and actually, sorry, I do think you had already answered that, sorry about that. Edward Plumb: No, thanks, Kyle. The second part, yeah, with the recovery stuff, I didn't think that was a question for the Weather Service would know that, but... You addressed that, and... It looks like Daryl has a question. He's got his hand up. Go ahead, Daryl, you can unmute yourself if you'd like. Daryl Schaffer: Thank you, Ed. Kyle was just wondering, having seen some of the autonomous vehicles that... air vehicles that are being developed at UAF, in conjunction with everybody, ACCAP and IARC, But knowing that it's very human-intensive to have eyes in the sky, because the eye can see different things than a camera can. What are you looking at for the future as far as using autonomous vehicles for, some of the Riverwatch areas to be flying to different locations at one time, since you've got limited air capabilities with just your personnel? Kyle Van Peursem: Yeah, there's definitely... I could foresee in the future more UAVs being used. We use them as a supplement to... when we're on the ground, we want to pop up real fast and see what's going on. Instead of having that, you know, take off. It's just so much, so many limitations in terms of FAA stuff. Dot is actually using it, they have this program called Drone in the Box, they'll... they can activate them remotely. And from... they can kind of pop up and take aerial imagery from many different parts of the state. So that's definitely a possibility. I don't really see that happening for us anytime soon, we're just... we take them with us when we fly, and we use them as a supplement. But, I mean, yeah, for sure I could... the potential is definitely out there. I don't see manned... Riverwatch flights going away anytime soon. Edward Plumb: And, Daryl, Jessica. Commented to you in the chat there, if you want to reach out to her, get more information about that. Okay, any other questions? In the chat, anyone want to unmute themselves? Okay. All looks quiet, guys. All right, well, thank you everyone for, participating today. We appreciate you, joining the... the webinar, and like I mentioned, you will be prompted for just three questions when you exit out of The Zoom here, and if... if you're in the, web-based version, if you could click... Leave Meeting rather than just closing the tab that'll prompt you for the survey. And, if you guys have any final comments for anyone, we got a lot of thank yous coming in the chat here. Jessica Garron: Thank you to the ACCAP team for continuing to present this information with our weather service partners to the broad Alaskan neighborhood, so I appreciate you. Edward Plumb: Thanks, Jessica. Appreciate the kudos. Richard Thoman: Yeah, no, this is Rick. I did stick in the chat there. A couple years ago, I wrote up a little blog piece, with some of the history of some of the big breakups in Alaska. So, if you're interested in that history, some details there. Edward Plumb: And lastly, I will send out the link to the recording, I'll email it to everyone, but I'll also include some of the the links shared in the chat here as well, some of the resources from the River Forecast Center. All right. Well, thanks, thanks, guys. Appreciate you taking the time to, Do this again this year, and... Sure, we'll see you again next year. Kyle Van Peursem: Yep, thanks for having us. Edward Plumb: Alright, have a good day, everyone. Richard Thoman: Thanks, everyone.