It's been a weird week of weather here in Central PA and this weekend I wanted to take a moment to "investigate" a few "meteorological crime scenes" that happened locally on Wednesday, when we had the following bizarre weather:

- Heavy snow overnight - Precip changed to sleet and then rain - Thunderstorms followed in the afternoon with lightning and hail - Included a gust front producing sleet - Storms followed up by two rainbows

Today's blog will be part one, covering three questions and I'll add two more on Sunday.

Question #1: People witnessed a rare rainbow over snow. Why is this so unusual?

Answer: A rare set of weather conditions came together for this. I took my first photo of a rainbow over snowpack on Wednesday, as did Stormchaser Ron down in Johnstown (he actually got two rainbows - photos here). Here's one at AccuWeather HQ (featuring AccuWeather.com's Ken Reeves):

Consider these factors about Central PA winters:

A. Snow won't make a rainbow. When we get fresh snow on the ground, it generally isn't immediately followed rain, but rather cold and snow flurries. When we get warm enough for it to rain again, the snow is generally melted.

B. Even more rare is for a fresh snow to be followed by fast-moving, convective, cellular thunderstorms (which make for good rainbows) -- but that happened Wednesday.

C. Rainbows in the winter certainly aren't unprecedented and I took some amazing pictures of a rainbow last January at AccuWeather HQ -- but there was no snow on the ground.

D. And let's not forget that capturing rainbows depends on how much time you spend outside -- It is generally too cold to be chasing rainbows here in Central PA during the winter and residents (including myself) spend much of their time indoors.

Here are some more pictures I took Wednesday including a couple of Meteo Madness Man himself (click here to see all):

Question #2: How was it raining out of the blue sky?

Answer: Fast moving storms and high winds are to blame. What Ken is gesturing at in the photo above is actually the rain that was falling on us, not the rainbow. I would estimate that for 10 minutes after the clouds disappeared overhead, it continued to rain. You see this with snow a lot in the winter but not usually rain (because it's heavier and falls faster). But this storm was moving quickly, effectively "dragging" the rain behind it, and high winds in the lower atmosphere may have contributed as well.

Question #3: Was that sleet or hail falling Wednesday afternoon?

Answer: Probably both. It's really hard to tell when temperatures are in the 30s or 40s but I think what I photographed above (which came from a small shower before the main line of storms hit on Wednesday) was hail. Note that it is larger and whiter than sleet (which is usually smaller than a BB and clear). But as Henry and I watched the line of storms come in (it had lost its lightning before it got here though over 1,000 strikes were observed near the PA border), the gust front actually started with sleet which was something that I had never seen before. It was just too cold (mid 30s) for the rain from the beginning of the gust front to make it to the ground in a liquid form.

Tune in tomorrow for Part Two where I answer why my wife heard a big boom outside our house Thursday night that wasn't the winds, and why co-worker Michelle and her husband experienced sudden sinus congestion on Wednesday.

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