As you can see, there was actually plenty of rain in the forecast, so allow me to explain the paradoxical title for this post. Used to be that NWS included the expected amounts of rain (in inches) in the details below their graphic, as well as the percent chance of rain, which is part of their graphic. But I’ve noticed over the last few months that the amounts have been missing. Not always, but frequently.
So I looked into why that was happening and, bottom line, it comes down to lack of data. In order to predict the amount of rain you need to measure how much water the air holds. This is done by measuring the air’s humidity directly, using both ground-based and balloon-lofted instruments. It can also be done by NOAA weather satellites that measure the microwave emissions of water molecules.
Fortunately, the satellites are still up there and functioning fine. But they can only measure the humidity in what is known as the effective layer — the top-most layer of clouds in most cases. How much water vapor, if any, lies below is not completely visible and must be estimated.
Balloons provide higher resolution data than satellites — critical for accurate local forecasts. Unlike a satellite, they measure humidity all the way from the ground up to around 100,000 feet where they typically burst.
The NWS releases approximately 76,600 balloons annually (an average of around 210 per day) from 100 sites across the country. Each site typically launches 2 per day, but they sometimes launch more if severe weather is expected. The cost of a weather balloon is roughly $200 but it’s money well spent.
FYI, if you’re curious about how these things actually float, see my 2023 post: How Weather Balloons Work
Weather balloons carry radiosondes that send back a variety of atmospheric data to support weather forecasts: temperature, dew point, relative humidity, barometric pressure, wind speed and direction, and GPS location. Here’s one “parked” after inflation and waiting for launch:
Of course, as this balloon ascends into lower pressure air, it’ll get a lot bigger. By the time the balloon reaches 100,000 feet it will have expanded by 3–4X in volume.
Alas, at least 10 balloon launch sites (as of this writing) have suspended or limited launches because of a reduction in funding and staffing. That happened in March of 2025, and we’re now starting to see the effects of that reduction. It’s not so much the cost of the hardware, it’s the staffing cuts. People are needed to launch balloons, as you’ll clearly see in these videos:
Calm Day: https://youtu.be/u4R0l_HuS5s
Windy Day: https://youtu.be/bNJwRSmLs-4
With fewer weather balloons forecasts will be less accurate. Given the documented increasing frequency of extreme weather (drought, heatwaves, heavy rainfall, hurricanes, tornadoes) meteorologists need all the data they can get.
The fact that I’m not getting rainfall amounts in the forecast may seem a trivial inconvenience. And it probably is. But it led me to do the research for this post, and made me aware of how much NWS has been damaged by funding and staffing cuts. I felt it was worth sharing what I learned with my readers.
Next Week in Sky Lights ⇒ Why Mirrors Reverse Left-Right and Not Up-Down