Question:
I was driving back from McPherson KS yesterday. Weather front moving through temp dropped over the hour from 80 ish high humid to 60’s or 50’s. Tornado Watch i believe. i was driving back on Hwy 150, about 50 minutes out of town heading back to Kansas City when all of a sudden all 4 windows exterior including back “fogged out” in an instant, like a quick WAVE..looked down temp said 53 on my truck. ran my wipers it was as thick as rain and looked almost like very thick wet frost. It happened again a couple miles down the road. i have been all over the world but never experienced this “instant” frost well above freezing that was like someone throwing it on all my windows at once? Microburst of cold air? Pressure drop?
Answer:
As a meteorologist who stormchases (these days only when storms are nearby), I’ve experienced this phenomena several times in my life – including when a ton of hail fell, turning the ground white, and quickly cooling the ground after a storm. I grew up in the Kansas City metro area, so I’ve seen this around both Kansas and Missouri – the local topography and plant life can also affect how cold some microclimates (tiny areas that differ from the overall main climate type of an area) can be after a storm.
What you encountered was likely the result of a rapid temperature drop combined with high humidity. Here’s a breakdown of why it happened so suddenly and dramatically:
1. Temperature and Humidity Factors
- When warm, humid air comes into contact with a surface that’s significantly cooler (like your windows), the moisture in the air quickly condenses into tiny droplets. This is similar to what happens when you breathe on a cold window and see it fog up.
- The sudden temperature drop you noticed—around 80°F down to the 50s—likely meant the exterior surface of your truck windows got cooler than the surrounding warm air, encouraging quick condensation.
2. Why It Was So Sudden
- Weather fronts often bring rapid temperature, pressure, and wind speed changes. The drop to 53°F and the presence of high humidity created an almost “instantaneous” fogging effect on your windows. When the temperature difference and humidity levels reach a certain point, the effect can be very sudden and look like frost or thick fog.
- As you drove, you moved through areas where the temperature, pressure, and humidity shifted quickly. Strong winds or microbursts (short, intense downdrafts of air) may have also contributed by pushing cooler air over your vehicle. I’d need access to archived weather data to confirm whether there was a microburst at that time and date.
3. Appearance of Frost-Like Condensation
- The condensation likely appeared dense and “frosty” because of how quickly it formed on your windows. It was too warm for actual frost, but the thickness of the fogging effect combined with dusty windows could easily look like frost or frozen moisture, as I can attest from personal experience.
4. Why the Effect Isn’t Consistent
- In a storm environment, temperature and moisture vary greatly over a short distance, especially when you factor in local hills, trees, crops, etc. Additional humidity can come from the evapotranspiration from plants, especially growing crops, in fields. Temperature changes over a short distance often occur – sun-warmed road patches contrast with cold areas where maybe hail or cooled rain recently fell, for example. I’ve also seen dips in the road where fog gathered and no fog appeared when we hit the hill peaks, thanks to microclimate (very small-scale) effects.
