Ben's Weather Blog

Rain and thunderstorms will move through the area over the next 60ish hours. Accumulation will vary, but is expected to reach 10+ mm.

Starting off today, we may see some possibly severe thunderstorms this afternoon or evening. A low is currently developing over south-central Alberta, and will bring some slow-moving thunderstorms. Tonight, some rain will position itself near Hwy 16 west of Vegreville. This rain will be moderately heavy, and will continue through tomorrow morning. Overnight tonight, we can’t rule out a surprise thunderstorm. During the day tomorrow, it seems the precipitation will arrange into some wrap-around, as the low causing all this moves into central Saskatchewan. This wrap-around precipitation will stem from near Battleford, go up to Slave Lake, then down around to Drayton Valley or Rocky Mountain House. This does seem it will slow down rain here a bit, meaning we may only see a few showers tomorrow night. On Friday as the low continues eastward, we will see the wrap-around rain come to us, with some possible imbedded thunderstorms. The precipitation is expected to be over by Saturday morning.

So, how much accumulation are we talking? I would say we’ll have a baseline of ~10 mm. That is from the rain after tonight. How much we actually get though heavily depends on if we get hit by storms. If we don’t, 8-15 mm it is. If we instead get hit by a severe thunderstorm today, and another storm on Friday, then we could see well above 50 mm. It really depends on where the storms are.

One more thing; temperatures. Today is 27 (probably), tomorrow near to slightly below 20, and Friday a few degrees above that. After that, we are expected to return to mid 20 highs for the weekend and early next week.

At the moment, the jet stream is kind of all over the place. Roughly though, it’s overhead-ish.

As we look into the week, we can see lots of storm potential. In fact, every single day for the rest of this week probably has an >30% chance of us getting a thunderstorm. This is because of the same reasons of all other stormy days we’ve had in the last month or two. We have warm and cold air mixing together and creating instability, a close jet stream, and no blocking patterns.

A thing that will be paired with the storms this week is more low 20 highs, like a lot of what has happened so far this summer. The ridge will move eastward, and a through will come in its wake. It has already appeared in northern BC, and will dig its way down all the way to Montana this week, and will likely cool temperature down by about 5 degrees, starting Wednesday. The low will also bring clouds, so the second half of the week, mainly Thursday and Friday, will see semi-overcast skies.

Now what about precipitation? Just like what we had over the weekend, most of it is going to be from storms. This means precipitation will be very variable, just like how in the last 48 hours Stony Plain got over 20 mm, while my house probably got about 1.

That is it for today. If you want more details, just wait for my email forecast this evening. If I end up busy, then maybe tomorrow evening.

Back on Wednesday, I said that there was a possible larger heat wave coming this week into next week. So, this week is this week, meaning it’s time for an update.

For the next few days, not much has changed since then. We still have the low sneaking its way into the Gulf of Alaska. We still have a blocking high in the southern US which is ridging up to here. The main thing that has changed is what happens after Thursday.

First of all, let’s look at Thursday evening, which is the first picture. I have laid out where the polar jet stream and subtropical jet streams are. You can see the classic omega block pattern. At this time we have not one, but two blocking highs below the subtropical jet stream, which are collectively enforcing a ridge (zigzag line) up to Alberta. What I really want you to take notice to though is the Pacific high. That is the one on the left with the arrows pointing to it. Now, look at the second picture. This one is for just 24 hours later. Notice anything different about the Pacific high? Yes, that’s right. It’s expanding to the west. If you go to the third image, this time on Sunday morning, you can see the jet stream has gone way south and we are now in a cold wave.

Next, let’s move to what the actual temperatures may look like during the heat wave.

Finally, precipitation. Besides today, the work week looks bone dry. Only when we get to Friday night there are some possible showers and/or storms.

If you want to know what next week and beyond will be like, then you won’t have to wait long! I will post an August outlook later this week.

This weekend because of low pressure and the western side of some zonal jet stream flow over the area will cause temperatures about 4 degrees below normal, partly cloudy to overcast skies, some scattered showers, and we can’t rule out some isolated thundershowers.

So, how much rain are we thinking? I would say probably something like 5-10 mm. Maybe more though. A lot of this is hit-or-miss showers, so it is possible we only get something like 3 mm, but also just as possible that someplace in the city gets 20. For the timing, I would say we’ll probably start with some showers or thundershowers in the afternoon/evening on Saturday, followed by some showers continuing into Sunday. Which should be over by Sunday evening.

The following material may contain many terms you are unfamiliar with. This time, I’ll just let you look it up.

We’ve been very lacking in the heat wave department so far this summer, but it looks like pretty late in the omega block season, we may actually get something. Let’s take a look at our upper air forecasts. Here I will supply a “gallery” of images for you, to reference as I explain what’s going on. If you want to see the images better, right click them, and then press “Open image in new tab”.

First image: This is the forecast for Sunday. You can see there is a long area of zonal flow (red line). If you didn’t know with zonal flow usually is it sunny near the eastern edge, but then as you slowly go west, it gets cloudier and cloudier to point where there is rain near the western edge. As you can see, we are going to be on the western edge, and this might bring some rain on Saturday night into Sunday. The main thing to look at here though is the low in the Gulf of Alaska. As I have mentioned many times, whatever is going on in the Gulf of Alaska really controls what happens here. A high, low temperatures. A low, high temperatures. This area has been dominated almost entirely by the Pacific high this month, which is why we’ve been so cold. But, as you can see, there is a low there on the map. This low is currently forming in Alaska, and is expected to move south, before stalling in the Gulf of Alaska. The orange line is the jet stream then, and the yellow is the jet stream now.

Second image: This one is for Tuesday. Now the low is almost a cut-off low. It has caused significant troughing, which has made way for a blocking high in the southern US to start to ridge up north. This could be the beginning of a heat wave.

Third image: Now we’re at the start of the first weekend of August. The jet stream made its way all the way down to the subtropical jet, the high has ridged up more, and some lows around Baffin Island and the southern tip of Greenland has also started to trough. This means we have a full omega block.

Now, we must ask, how long will this stay? Well, here’s the interesting thing: It seems the shortwave trough in the third image that is pushing southeast of the westerly low may actually push the blocking high far enough to displace it to be more centred around Florida, which may give the jet stream wiggle room to jump the Rockies at least temporarily. Forecasts have been suggesting a cooldown around the first or second day of the month, but aren’t really sure what’s going to happen after that. Some say the heat will return for another 5 days or so, but others say the omega block may move farther to the east and we’ll suddenly be in a cold pattern. Right now, it’s hard to say who’ll be correct.

For now, that’s where I’ll leave it. I’ll post a short-range forecast on probably Monday, explaining for about what next week could shape up to be.