I’ve been seeing pictures of some great bucks killed all over the country this past week. Deer hunting season is officially here and I couldn’t be more excited. The only dilemma for me is responsibilities are going to keep me out of the woods for at least the next few days. I’m hoping I can get out towards the end of the week or on the weekend. I’ve been cyber-scouting some new public spots here in southern Wisconsin that I’m pretty excited about.
As far as the weather goes? First let me say that I’m introducing a new format for how I’m going to write this up. I’m going to break it into sections, which could change over time depending on new ideas I may have. But for now I’m going to do a section on temperature, precipitation, and long range outlook. I’m still debating on doing a wind discussion. This is extremely important for hunting purposes but the main issue with it is wind is a very local variable, whereas temperature and precipitation can be talked about on a broad sense. I could be here for hours detailing the wind in every section of the country and I’m not sure that it would even do you much good. For now, I will talk about how wind on a broad sense will evolve according to fronts and such. I will leave the fine details up to you. If you want to look at wind forecasts on a very local scale, I suggest going to either pivotalweather.com or weather.cod.edu and looking at the ‘HRRR’ model or the NAM 3km. These are very high resolution models that are great for looking at things in the short term. With that out of the way let’s get into this week’s weather.
We’ve got a front moving through the country right now that’s going to do almost everybody a service except for those in southeastern and far eastern parts of the country. You can see it well on this color temperature map from the National Weather Service page:
If we roll this forward in time on the NAM model we can see that it will cool things down at least marginally all the way up to maybe just east of the Mississippi valley or a bit further by Thursday morning:
Interestingly the midwest is already starting to warm up again by this time. This is due to another low pressure system making its way across southern Canada that’s beginning to draw warm Gulf air northward again. If you look closely you can start to see the wind direction begin to shift northward again shortly after the front passes. The good news? Another low pressure system is expected to form east of the Rockies that will again bring another push from the north. Since this is a bit farther into the future we need to switch to the GFS model to look farther out (>84 hours):
The GFS tells pretty much the same story as the NAM out to 84 hours so we can be fairly confident about how far the first front will go. But if we look beyond 84 hours (you can see the hour of the model next to the F in the top right, so 84 hours would be F084), you can start to see another low pressure system develop near Iowa around hour 132. This is overnight on Sunday. This system will again draw cooler air from the north and bring it southward, and as long as we don’t get another tropical storm in the gulf this front has the potential to go all the way to the Atlantic. This front still isn’t particularly strong, so the farther you go south and east the less impact you will see from it. But I think this second front should be farther reaching than the one currently making its way in. The dates and times that are being shown on this model need to be taken with a grain of salt. Use them as a ballpark reference more than an absolute at these longer ranges. In the previous image you can be more confident in things happening relatively close to when the model says they will.
I think this is going to be the story temperature-wise for the next couple weeks. Several cold fronts with some areas farther north and west seeing more significant temperature drops with folks in the south and east getting generally more subtle effects. We are getting close to the time of year climatologically where the jet stream gets stronger and we start seeing bigger, stronger cold fronts. They will come, we just have to be patient for a few more weeks. Until then I think these more “run of the mill” fronts will still make for some great hunting.
As with wind precipitation is a very local variable but it is more easily talked about in a broad sense than the wind at someone’s exact location. I don’t plan to give “percent chances” of rain or any sort of probabilities of precipitation because again, I’m talking in a more general sense here. However, I think it will still be useful to have an overall idea of what areas will see rain/snow/etc. in the coming days. I will leave the specific point forecasting up to you.
Precipitation can be a very challenging thing to forecast, especially winter weather precipitation because there are an incredible amount of factors involved. When snow and other forms of winter precipitation become a factor in the forecast I think you will find it interesting to learn about the different atmospheric condition that can lead to all the different forms of winter weather. For now we are only dealing with rain in most areas, which is a somewhat less difficult thing to forecast. For our purposes I think it can be simplified quite nicely.
The driving force behind precipitation, especially large scale rainfall and thunderstorm events is rising motion in the atmosphere. Rising motion is most commonly created by low pressure systems such as the one moving across the country right now. Here is a water vapor satellite image of current conditions (from you guessed it, Satsquatch.com):
You can see counter-clockwise spinning over the Rockies near Colorado (our low pressure system) and clockwise spinning over the easter US (high pressure system). Rising motion occurs on the eastern portion of low-pressure systems. It’s not exactly obvious why this happens; it’s actually an entire year of meteorology school. However, the easiest way I can explain it is that a low pressure system can be seen like a bowl. Air goes down into the bowl on the west side, rides the wall of the bowl on the southern side, and goes upward out of the bowl on the east side.
Now don’t get in a debate with an atmospheric scientist using this logic, but I think it works for layman’s terms.
The reason this rising motion leads to precipitation is fairly simple: the atmosphere cools as you go up, and as air gets pushed upward the moisture in the air condenses and creates water droplets. If there is enough moisture present it will become heavy enough that the air can’t hold it and it falls as precipitation.
The eastern edge of this low pressure system is over the souther plains, and if you look at eastern Kansas you can see some white showing up within the yellow. These are storms forming within this corridor of rising motion. It’s convenient that this is currently happening so that I could give you this proof of concept. It’s not always that easy!
Now that you know a little bit about how this works, here’s a quick look at how this low pressure system will affect precipitation for the next few days:
As this low pressure system track east-northeast over the next few days it will kick up some thunderstorms in the eastern southern plains and some fairly significant showers in the midwest. Most of this will occur tonight and Tuesday, with some slight chances for rain on Wednesday. Some more general rain showers will also occur in the southeast and along the east coast during this same time frame. After these few days of rain it should remain dry for most areas into at least the first part of the weekend.
Long Range Outlook
I won’t say much for the long range outlook this week simply because it is pretty much the same as the last discussion. The CPC still shows above average temps for most of the central and eastern US for the month of October. We’re certainly observing that in many areas. Hopefully that will change in the coming outlooks.
By the next main forecast discussion the pre-rut will be upon us here in Wisconsin, and it won’t be long before the real thing is here.