Cloud clover can destroy a Milky Way photography trip fast. I had a conversation a couple of years ago with another photographer. During that conversation, I had an “aha” moment. We were discussing a trip he wanted to make, and he was worried about the cloud cover. Since he was 6 hours away from his target location and it was Oklahoma, he was kind of hesitant. He then told me about watching the weather models, particularly the average cloud cover forecast on the College of DuPage website.


I have a passion for weather photography and have spent a lot of time learning how to better my chances at catching a photogenic storm. My “aha” moment came when I realized that one of the same tools that I was using for weather photography I could use for chasing the Milky Way. In my series for beginning Milky Way photographers, I wrote about several apps and websites that I and many others use. This article is about how I use one of those websites.

There are several different locations on the Internet that host the weather models. One is the College of DuPage Meteorology website. College of DuPage is based in Illinois and has a meteorology program that is said to be one of the best in the nation, along with Oklahoma University. I came across this site a few years ago and used it extensively for not only weather photography, but for chasing the Milky Way. For a short time several years ago, they did have an IOS app, but it was removed from the App Store. Luckily, I was able to grab it before it disappeared.

The Average Cloud Cover Model can give you an idea of what you will face.


Just looking at the website can make you cross-eyed fast. Between the tabs, clicking on them, and the additional menu; it can lead to mental overload if you do not know what you are looking for. That’s where this article comes in. I break down how I use the website to my benefit for my Milky Way photography.


When you get to the main page of the COD numerical models, there are a total of 11 gray tabs with a bunch of initials. Out of those 11 tabs, I only use two which I will cover here and then mention a third.

The third, labeled GFS, stands for Global Forecast System. This particular model is run four times a day and forecasts 16 days into the future. As a layperson, the only use this model is good for is for social media attention getters. They tend to use this particular model to scream “snowmeggedon” in the middle of winter and getting people stirred up. The more responsible folks in the weather community will use these forecast models as a “heads up.” Unlike others, they will not try to induce panic for likes and shares.

The two tabs that I use are the NAM or North American Mesoscale Model and the HRRR High-Resolution Rapid Refresh. These are the go-to pages on the website.


Like the GFS, this particular model is run four times a day also. The NAM forecast goes out for 84 hours. The NAM is useful for coming up with a preliminary game plan, but there should be some room for flexibility. A 2-3 day forecast can have some reliability to it in some parts of the country. In other parts though, forget about it. Springtime on the High Plains can ruin a weather forecast real quick.


The HRRR is the go-to model as it is the most accurate. The HRRR is run every hour and covers just the next 18 hours. Again, depending on how far in the future you are looking, you might want to have a flexible plan in place. If you are looking at just the next 4-6 hours, then your success rate will be liable to pretty high. One disclaimer though, thunderstorms will trash an HRRR model fast. In my one storm chase bust from last year, I followed the HRRR radar forecast to try to catch a supercell. The supercell never materialized. But every other time I relied on it last year, either for weather or night skies, everything panned out as forecasted.


When you click on a tab, a menu will pop up on the left side of the screen. There will be different options such as “Select Model Run” “Select Sector View” and others. When you click on a tab, it will usually default to the latest model run.

The “Select Sector View” tab will allow you to zoom in on the part of the US that you are in, such as the Southwest, or Central Great Plains, etc. Once you select a sector, then a default weather model will pop up on the screen. You should also see a slider pop up under the gray tabs, along with a color meter. If this is red, that means that the model run is not complete. If it is green, then it is complete. There will be a button on the left side of this meter with 0 on it. This button will allow you to slide through the hours and see how the forecast plays out.

Next to the meter is LOOP and SAVE. If you click on LOOP, then player controls will pop up, and you can adjust the speed, rewind, pause and so one. There is also an option SAVE that will allow you to save a loop as an animated .gif.

Back to the menu, we want to look at the cloud cover forecast. To find that, go to “Precipitation Products” and then click on Average Cloud Cover.


In my research workflow, I will start looking at the cloud cover models a couple of days out, using the NAM models. Once I am within the 18-hour window, I will start looking at the HRRR models. For the most part, if I am chasing Milky Way not thunderstorms, I feel very comfortable making decisions within 6-8 hours of a forecast model run.


Honestly, out of all the apps and websites that I use, the COD website and the NEXLAB app is my go-to for research. The information is map-based; I can get a clear picture of what I should expect at a given location. Also, with the HRRR models running every hour, it is almost real time. Apps like Clear Outside and Clear Sky Charts do not do hourly updates, so I might not have updated information when I look at them. I will use these apps in conjunction with the weather models. In fact, I tend to look at them first. Because they are somewhat stripped down, I can find information faster. I can go to the COD website and confirm whether the information is accurate.

An animated loop of the HRRR Average Cloud Cover forecast model.

When you are reading the forecast models, be aware that they use GMT or Zulu Time. You can find out the difference here.


Now to be fair, there is another website, that is very similar to the COD website. I have not used it much because it has been difficult for me to work in the past. There have been times that I could not get anything to work on the site. As of this writing though, everything seems to be working for me. Pivotal Weather presents the models in a cleaner, more attractive layout. I will have to spend more time on it.

Screen capture from


The COD website is an excellent tool to put into your toolbox. At this point, the information I can pull up on the site will determine if I decided to greenlight a Milky Way trip, change location or cancel. I have that much faith in it. I do not rely on it entirely; it compliments everything else that I use. But I highly, highly recommend that people use it for their Milky Way trips. You will have the most up to date information using this website.


Please enter your comment!
Please enter your name here