Cloud Cover

Today and tomorrows temperatures will depend on many things but one of which is cloud cover. This time of the year it is pretty difficult to determine cloud cover for a few reasons; an excess in low level moisture due to snow cover, a large inversion layer, and over mixing of the atmosphere. Well, here are a couple of the models we can look at to determine cloud cover. These pictures are from two different models that simulate cloud cover for noon tomorrow.Its pretty easy to see that the pictures are quite a bit different. This time of the year, the models will typically over do the clouds a bit so we can expect at least a little sunshine here and there on your Wednesday but don't expect a sunny day.

Tranquil Week... With Tranquil Snow?

We are watching as a couple of very weak storm systems make their way through the nation this week. We'll be seeing them flowing from the West to the East over the course of a couple of days.

The first one will be arriving Wednesday it looks like, and one thing to keep in mind is Cody's post from below - the jetstream is going to be right over us most of the week. That likely means at least a slim chance of flurries to a dusting of snow Wednesday through Friday. But, ripples in the jetstream will be the main cause of our snow chances - ripples are what we call "short waves" in the meteorological community. Small swirls of energy that make their way in. Regardless of what this one is, we will likely see some snow out of it.

This is still far away, keep in mind... but the following maps are what two different computer models think we'll be seeing as far as snow is concerned:

1) A Shorter Range Forecast Model (known as the NAM)


This model has some more snow in the forecast than the longer range forecast model. This one has a little bump farther toward the South and East, with maybe 1 or 2 inches in select locations.

2) A Longer Range Forecast Model (known as the GFS)

This is a model that I typically tend to side with, with decent results (you might argue differently, haha, but hopefully we have been nearly right-on for most storms this winter). It gives what looks like a 1-3" range for mostly the Missouri River Valley, and slightly farther to the East.

We'll see what happens over the next couple of days. If I had to do a forecast right now for Sioux Falls I'd probably go with up to an inch, or up to 1/2 of an inch.

Have a great Monday night!

~KDLT Meteorologist Aaron Shaffer

Tranquil.....Finally

Looks like we are headed for a pretty quiet week across South Dakota as there are no signs of any major systems right through next weekend. Mild today and tomorrow but then a little cooler as we get to the end of the week. We will see a couple of very weak systems move through Wednesday through Friday and that has a lot to do with the jet stream location. The jet stream is the river of air thousands of feet above the surface that steers all of the weather systems in the atmosphere. Well, typically the closer you are to the jet stream the more active your weather is. So, the maps below show the jet stream location. The first map is for this evening and the second map is for Wednesday night.The jet stream tonight will be well south of us, giving much of the upper Midwest a quiet night. But then by Wednesday, the jet stream pushes back north and invades us once again. We can expect a few ripples to fly through the area that may bring a few flurries or some light snow to some of us by weeks end but nothing major is in the forecast. Enjoy the tranquility!!

KDLT Meteorologist Cody Matz

Snow Pack - How much is in your city?

Well with the return of the sunshine and not a cloud in sight . . . I could take this picture of our area with the satellite. When there are clouds, we'd pick those up on here, but since it's pure blue skies today - we can actually have a good idea of what the snow pack looks like. The brighter the white, the more snow, the closer to black, the less snow. With the help of the National Weather Service, I put in some contours of how much snow is piled up in our region. Of course there are some places with locally higher amounts, but this gives a general idea of how much snow is stacked on the ground. In those darker areas, the snow doesn't have the most affect on our temperatures, so where there is less snow, it's going to be easier for temperatures to climb around Sioux Falls, Yankton, Vermillion, Lake Andes, etc. Where there is more snow pack is where you can expect temperatures to stay colder, sorry Wilmont... that 15 inches of snow will really make climbing out of below freezing temperatures hard. But hey - that snow pack could be a lifesaver... check out this interesting story of a woman in Canada who stayed alive because of the snow pack!

~KDLT Meteorologist Jesse Ritka

How Much Snow Tomorrow?

In most cases, we tend to have a pretty good idea how much snow we are expecting. But unfortunately, there are those few times in which its kind of a crap shoot. Here is what I mean. The two graphics below really help explain what I'm talking about. The first graphic is the snowfall forecast from the National Weather Service (NWS) in Sioux Falls and the second one is from the NWS office in Aberdeen.
Even with a quick glance at these you can see that there is a BIG difference in their forecasts. Snow storms are very complex and is one of the hardest things to forecast. So what makes this particular storm so difficult. The main reason for the level of difficulty of this storm is that no model seems to be real accurate with the current location of the low pressure. That means that none of the models really have an idea of what's happening now so how can we expect them to understand what's going to happen down the road. The other major difficulty is the components of the system are not expected to come together until the storm is right overhead. This basically means that a couple of hours can make or break your forecast. So if the components come together a couple hours earlier, it will start snowing earlier, and therefore many areas could end up with more snow than originally thought. This could also happen the other way and we could get little if any snow at all. So these are just a few of the complications plaguing the forecast of the incoming snow. However, under the circumstances, I believe that my forecast might be the most accurate because it is right in the middle of the two that I showed you earlier. I guess only time will tell.

~KDLT Meteorologist Cody Matz

Cold This Weekend

First off, I just wanted to recap my post from yesterday, "The Art of Mixing." I told you about mixing and that it can play a huge role in high temperatures. Well, it turns out that even I drastically underestimated it. We hit 38 degrees yesterday! That's really warm for this time of the year and not to mention, I only forecasted 32. So you can see why there are times when even we get it wrong.

Now, on to the forecast. As Aaron mentioned, snow is on its way again. But I wanted to focus on the cold air behind the snow for right now. Forecast models appear to be horribly underestimating the shallow dense cold air that will make its way down from Canada on Sunday. Just a couple days ago, all of the models were showing highs in the low twenties on Sunday. But, as the system gets closer, they are finally adjusting to the very shallow arctic air. Now, the model you see below is forecasting a high in Sioux Falls of about ten degrees.

This seems a bit more reasonable then low twenties. However, will have to see how much mixing we will get on Sunday because that could mix some of that dense arctic air away from the surface causing our temperatures to be a few degrees warmer.

~KDLT Meteorologist Cody Matz

Snow For This Weekend? A December Recap As Well

You betcha! We are looking for some more potential accumulating snow - and this one might influence some travelers looking to watch the Vikings play this weekend, so if you fall into that category you might want to pay close attention to this post (I'm actually driving to Minneapolis for that game, so I've been paying close attention to this weekend's forecast).

Snow looks to develop - and most of it for the Sioux Empire should be toward NE South Dakota into west-central and western Minnesota. Unfortunately it doesn't just go away at that point. We're seeing some good potential for that snow to hit the Minneapolis area sometime near Saturday evening. A lot of people will wake up in the Minneapolis-St. Paul area with a few inches of snow.

This is one computer model's take on what might be on the ground come Sunday morning:

I would tend to agree with this one. It looks like a couple of inches in NE SD, along with the Minneapolis area. You can see the sharp drop-off in totals near Sioux Falls.

December Recap

So... in December it felt pretty cold, right? If that's what you thought, you were right. We can thank our two days with below zero highs for that. Here's a recap of what we saw in the Sioux Falls area:

If you look at that graphic, your suspicions of a snowy December will be confirmed as well. So far, we still don't have any major January storms in the works - but stay tuned, because there are a few lesser chances showing up (see above).

Have a great night!

~KDLT Meteorologist Aaron Shaffer

The Art of Mixing

Looks like the next couple of days are going to be reasonably warm in Sioux Falls. But, it's not going to be nearly as warm as it could be. The reason for this is poor atmospheric mixing. The ability for the air to mix with itself at different levels of the atmosphere is a key part in how much the temperature can warm during the day. The more mixing that occurs, usually the warmer it will get. On a typical day, the atmosphere is able to mix the bottom 1000-2000 feet. This means that the air 2000 feet above the surface can eventually find its way to the surface where you and I are standing. On windy days, air 7000 or 8000 feet above the ground can actually find its way to the surface. This is where wind gusts come from. When faster winds at the upper levels of the atmosphere are mixed down to the surface. Now, the reason why you get so much more mixing on a windy day is because the winds are traveling faster which in turn, they can travel greater distances. Well, to get this kind of mixing even on a windy day, you need a unidirectional wind. That means that you need your winds to be coming from the same direction. If you have wind coming in from opposite directions, then they just cancel each other out and you get very little mixing to occur.

So, in explaining all of that, we get to what's going to be happening over the next couple of days. Well, we will be seeing some breezy conditions, however, the winds will not be unidirectional. This will inhibit our mixing causing temperatures to stay cooler then their potential. The pictures below are a profile look at the atmosphere. The wind barbs are on the right and are circled. The first picture is a forecast for today at 4pm. The barbs are all facing the same direction which means more mixing and warmer temperatures.

The second picture is a forecast for tomorrow at . The barbs near the surface change drastically with height. This is not a good scenario for mixing and that's why temperatures will be cooler at 11 degrees.So, even though temperatures are going to be warmer then they have been, they aren't going to be as warm as they could be.

~KDLT Meteorologist Cody Matz