OMEGA BLOCK sets up over North America

追加: 2026-05-30

[00:00:00]Thanks so much for joining me. We've got a lot of weather to talk about here in Western Canada as an omega block pattern sets up across the continent. So let's get straight into it here. Looking at this map from Animet, super handy site from Environment Canada, freely available Canadian weather model data that you can visualize here on this map.

[00:00:17]And this is the omega block. It's called an omega block because the jet stream shape here is kind of shaped like the Greek letter omega and this is later this week, kind of when this blocking pattern really reaches peak intensity.

[00:00:28]This is Saturday at noon. Very strong upper ridge here kind of flanked by two upper troughs. That's a textbook omega block pattern. Basically, what's happening in the atmosphere of the jet stream, when it's stronger, you still have these sort of migratory troughs and ridges, you know, weather systems carrying along in the flow.

[00:00:46]Sometimes the jet stream can slow down and uh it kind of become, you know, it becomes weaker, it becomes more wavy.

[00:00:51]Sometimes it can even stop, like like a an atmospheric traffic jam. In that case, uh you can see blocking patterns where you have these sort of highs and lows and deflecting the uh the weather systems around kind of a preferred path here. You're you know, you can't go through that high, you got to go around it. So that's why it's called a blocking high. It's blocking the prevailing weather systems here and forcing them to go around. Uh with these type of patterns, you can see extreme weather because this is stagnant weather and it can be highly impactful, highly amplified flow can bring, you know, significant heat waves, like we're expecting this week in the Canadian prairies. Uh you can see the onset or the worsening of droughts and fire weather. And in areas where it's more unsettled and there's uh the potential for heavy precipitation, you can see flooding. So um very impactful upper air pattern right now. In fact, if we look at the overall upper air pattern throughout the northern hemisphere, the uh North Pole is kind of right in the middle of the shot here. We can see it's very wavy throughout the northern hemisphere. So the jet stream's in that sort of weaker, wavier pattern across the globe and we're actually seeing an ongoing heat wave here in Western Europe. Uh Great Britain, France, monthly temperature records being set there. And we're likely going to be in a situation in which we're seeing two simultaneous heat waves ongoing across two different parts of the Northern Hemisphere. There is some research that suggested a certain wave number, uh you know, when you have five or seven in particular, five or seven of these long waves. We've got about five right now here.

[00:02:19]Uh you can actually have simultaneous heat waves in different breadbasket regions of the world. So, uh here in North America and in Western Europe, that's what we're seeing. So, this may be a factor this week, this wavy pattern in the jet stream.

[00:02:31]Simultaneous heat. Again, this map here is just displaying a height anomaly at 500 millibars, middle part of the atmosphere there. And it's just showing where the atmosphere is basically thicker or thinner than normal. Uh where it's thicker, uh warmer air occupies more volume, it's less dense. And so, you can see that's where the warmer air masses here and the colder air masses are where the heights are lower.

[00:02:53]So, again, very impactful weather is possible with these types of blocking setups, and we could see some uh significant weather this week here in North America with this omega block pattern.

[00:03:04]Uh you know, just to kind of get a sense of how unusual this is, this is from NAV's their situational awareness table.

[00:03:10]And we're looking at like we're reaching the peak values of the model climatology here, especially over Eastern Northwest Territories and sort of Kivalliq Nunavut there. Um the kind of peak magnitude there of the of the ridge is up in here in kind of Northern Canada. At no point in this model's climatology going back to 1979, I think 1979 to 2009, uh has there been forecast values, heights this this great here in this part of Canada uh during this 3-week period. Just gives you a sense of how strong this upper ridge is for about 3 days, uh Saturday, Sunday, Monday when that upper ridge peaks in in intensity.

[00:03:49]What that's It's to be uh bringing or being associated with here is of course uh likely record-breaking temperatures, temperatures getting into the low to mid-30s across the Prairie Provinces.

[00:03:59]We're talking Eastern Alberta, much of Southern and Central Saskatchewan, perhaps parts of Manitoba. Also well above normal getting north of 60 there.

[00:04:06]So likely record-breaking temperatures for several days and a bonafide heat wave across the Prairie Provinces. So important to stay cool out there.

[00:04:15]Uh to the west of that upper ridge though on the west side east of the upper trough, we've got kind of [snorts] a a low that cuts off here. We'll look at it in a second.

[00:04:25]To the east of that low, it's a little bit more unsettled and so it looks like we're going to be getting several rounds of thunderstorms and rain through Alberta bringing above normal precipitation throughout the period. So it'll be warm and wet in parts of Alberta this coming week.

[00:04:40]Basically what's happening here is when we have that kind of southerly flow that sets up across North America, you get this low pressure system that forms like with this particular upper air pattern here with that western US trough and that southerly flow over Alberta, you get this surface low pressure here in Montana, counterclockwise flow in this direction and we have this kind of ridging over here to the east over the eastern prairies. This is going to be drawing like a large-scale southeasterly wind from kind of the central southern United States right back into Alberta and Saskatchewan. So we're tapping into some significant moisture with this system this week. This is a map of dew point temperature. Of course dew point is the temperature that you have to cool the air to at a constant pressure to reach saturation. And so it's a really good measure of absolute moisture content in the atmosphere.

[00:05:28]This is going through through Tuesday and look at these kind of high dew points, mid dew points kind of streaming back here from the central northern US back into Saskatchewan and Alberta through kind of Thursday and then there's another push later in the week where we might actually be seeing some sort of Gulf source air. Air that was originally over the Gulf kind of migrated its way north into the into the central US plains and kind of streaming back up northwest. So, for for late May, this is unusually humid. You'll feel the humidity at times in Alberta and Saskatchewan this week as we really pull that moisture northwestward. What's interesting to note though is we've got a lot of drought through western central United States, southeastern states.

[00:06:13]This is as of the end of April, but even like the last 30 days or so, well below normal precipitation through much of the continent. A very dry pattern right now. And so, it's it's incredible to think that we would actually be probably drawing significantly more moisture with this pattern back into Alberta.

[00:06:30]Had there been significant precipitation across much of the continent. You get that evapotranspiration into the atmosphere, you get more moisture. Nonetheless, we're still going to be seeing unusual moisture being drawn back into Alberta that's going to be influencing our weather here as well. In a way that we could be ending up with some significant precipitation totals. This is from the European and the Canadian ensembles and they're both kind of agreeing on an area of southern central southwestern Alberta seeing fairly heavy precipitation totals over the next 10-day period and portions of northern Alberta as well. So, that'll certainly slow down any any wildfire danger up north and add a lot of beneficial moisture here in in the southern central part of the province.

[00:07:11]Eastern prairies, they've been dealing with a sluggish start to spring until now.

[00:07:16]Major weather whiplash this week. So, they're behind in their planting in terms of agriculture. So, the dry weather in general, it's really hot, but the dry will help for getting getting caught up on the planting back here in Alberta. It's going to start to get a little wetter and more unsettled this week, but we are a little further ahead with our planting here. But, one thing we're going to want to watch here in the Rocky Mountains where we still have fairly substantial snowpack. If we look here, this is the Little Elbow Summit uh snow pillow. So, this is southwest of Calgary in the Elbow River headwaters.

[00:07:45]We can see that we've already kind of started trending into our spring fresh at period. There was the cold conditions over May long, a little bit of snow, but we've already started that down trend again as we start to melt. Still well above normal for precipitation or snow that's left out in the mountains. It's going to quickly melt though over the next couple days with this heat. Uh one thing we're going to watch for though is if there is heavy precipitation in the in the mountains of southwestern western Alberta, uh there could be uh kind of excess runoff with heavy rain falling on that much snow. So, we're going to have to watch at least for localized potential of uh you know, fast river flows, potentially some uh flood potential. So, we're going to watch out for that as we see the combination of warm temperatures and potential for heavy rains falling on snow in southwestern Alberta. Not a significant concern at the moment, but certainly something we are watching. Excuse me for a sec.

[00:08:35]>> [cough and clears throat] >> Okay, so the next map here, uh we're also considering the potential for thunderstorm activity with this setup this week. So, uh basically what's happening here, this is uh this is this evening's forecast. We're seeing an upper-level trough that kind of cuts off. We get this cut-off upper low that kind of sinks down into the western states as that ridging starts to really build here in the prairies. What this is going to be doing here is actually sending uh it's got that, you know, we've got that southerly flow coming north across Alberta, but it's sending a few kind of upper disturbances along in the flow that enhance the weather and uh increase the chances for thunderstorms.

[00:09:11]We're probably going to be seeing several rounds of thunderstorms uh through the western prairies with this setup, perhaps eastern parts of the BC interior at times, uh perhaps getting into parts of western Saskatchewan at times. But, nonetheless, uh this jet stream pattern is favorable for thunderstorm activity here in Alberta with uh with some heavy rain potential as well. So, again, uh this is uh lightning flash density for for every 6 hours here. This is getting into Tuesday, Wednesday, Thursday, Friday, Saturday, and Sunday. It looks like we've got 6 days, just days of thunderstorm activity here out on the prairies. Looks like the first real action's going to pick up Tuesday evening. Uh for us here in Southern Alberta, Calgary, I'm thinking there might be a chance we could get some nocturnal thunderstorms, uh 9:00 10:00 here in Calgary. If not, uh likely a lot of action out toward the mountains to the southwest. So, watch for lightning tomorrow evening. And then over the next few days as that moisture really starts to build in our region.

[00:10:08]We will see the increased an increased risk of of severe thunderstorms. I would expect uh the potential for some intense lightning with some of these storms. And with the amount of moisture, this is precipitable water anomaly. So, basically, it's just the amount of water vapor in the entire atmosphere column from top to bottom. How much is available to be precipitated out? And we can see as that moist air mass really gets established and deepens over the province this week. Highly anomalous.

[00:10:32]We're talking like 200% or more of normal here.

[00:10:37]With moisture just persisting over our region for several days and fueling that uh you know, the unstable air, the fuel for thunderstorms. So, we could see thunderstorms that are severe at times.

[00:10:48]And with that amount of moisture, uh if storms are slow-moving in particular, we could see some very heavy downpours with these storms. Would also not rule out the potential for some isolated tornado activity because we do have that moisture building throughout the week.

[00:11:01]We have the instability. We have some stronger winds in the mid-levels of the atmosphere at times that can help organize these storms into more sort of organized structures. And so, we're going to watch for the potential for severe weather uh west of that upper ridge uh this week as well. So, yeah, a very very interesting to see that much moisture uh really early to see that much moisture in the atmosphere here in this part of the world in the western prairie provinces. Now, finally, excuse [clears throat] me.

[00:11:27]I just finished having uh dinner, so I have a little bit of a frog in my throat. Uh looking at the wildfire situation here, we can see very quiet, very, very quiet start to the season uh, with very few out of control fires. There was one that really took off uh, a couple days ago there just west of Fort Smith uh, Northwest Territories, but in general, very quiet, but I would expect again, you're you're seeing this strong upper level ridging here, sinking air on the large scale, clear skies, hot temperatures.

[00:11:54]Inevitably going to be seeing fire danger developing across parts of the country. So, if we look here at our forecast from again, this is from the Canadian Wildland uh, Fire Information System website, super handy. They've just redone this site, highly recommend visiting it. Uh, as we get into Tuesday's fire uh, danger forecast and Wednesday, actually let's go back to Tuesday here.

[00:12:14]Taking a moment to load, there you go.

[00:12:16]Uh, extreme fire danger developing across uh, the grassland regions of the prairies, Alberta, Saskatchewan uh, over the next few days here and uh, you know, starting to spread east as we see, you know, east side of that upper ridge again, you'll really start to see that fire danger building in through northwestern and then across northern Ontario as we go through this week with dry, hot conditions.

[00:12:38]Um, with our fire danger forecast going up to this weekend. So, I would expect, you know, dry areas, dry grassland areas of the prairies still seeing that fire danger.

[00:12:46]Starting to cool off a bit out the out west here though, like I say, with that uh, you know, gradually increasing rainfall, thunderstorm activity. Um, thunderstorms of course come with lightning strikes, so there is the possibility that some of these strikes could start wildfires, but again, it's pretty wet. It's going to be round after round of precipitation, so it doesn't look like a huge fire flap to me out west. It looks like our concerns are sort of building eastward with this ridge throughout the week. So, keep that in mind, wildfire danger could develop through uh, you know, continue through parts of the prairie provinces and eastward across northern Ontario this week. Active pattern back to the west here in Alberta with rounds of showers, thunderstorms, some of which may be severe and the potential for some heavy rain across the province and very hot temperatures in between here. We're seeing record-breaking highs likely as highs climb into the low to mid-30s in parts of the Prairie provinces.

[00:13:36]So, stay tuned this week. Uh we'll talk to you next time. Thanks for joining.