I may have the story for the coldest and nastiest thunderstorm, but I'm not sure...here goes.
I was on a camping and hiking trip in Yosemite NP in the winter. There's a trail with 60 switchbacks that leads up to a vista point called "Oh My Gosh Rock". The reason it is called that, because when you see the view from there, you say "Oh My Gosh" it is just so beautiful. The view is probably one of the best views of the valley in the entire park, except from the air of course.
Well anyhoo, we're hiking through the area, and it had been snowing all day, and was a bit windy. We get to Oh-My-Gosh rock and the naturalist who was leading our hiking group told us that only three at a time could go off the main trail to the vista point at a time because the approximately 100 feet to it were very treacherous and icy. The viewpoint also has only a single bar about midwaist high to protect from falling.
So me and two of my buddies were the first ones to go down. Well, the view stunk because a big thunderstorm (we didn't yet realize how big it was yet) was moving down the valley, and with a lot of fog and snow falling, the view was practically non existent, visibility probably being about 1000 feet.
We came back up, and the next group went down with the naturalist. My buddies and I waited patiently on the main trail, when the lightning broke loose, and it was really, REALLY close. It was the thunder that claps so loud your eardrums hurt. It was the thunder that doesn't have any delay between the blinding flash and the deafening thunder. Next thing we see is the group who was down at the viewpoint come scrambling up the trail, with the naturalist close behind.
One of the guys is panting, "Oh my God! One of the lightning bolts must of struck about fifty feet in front of us, it scared the s*** out of me, the thunder was right there! Geez, lets get out of here". The naturalist says that she's not going to take down anymore groups to the viewpoint, which really didn't matter anymore because there was no more view.
The snow started falling really, really hard, to the point where there was almost no visibility. You could only see a couple heads in front of you in the hiking line. The wind really, really picked up so much that we started getting popcorn snow. Apparently this is snow that is picked up and circulated by the wind so much that it forms tiny little balls of snow, that look like little hail, but really is snow. The snow was whirling and going horizontally, and was really falling hard.
We hiked about fifty feet to this cave we had seen on the trail, it wasn't big, but we decided to wait out the storm in it. Well, we ended up sitting there for an hour. The wind picked up even more, and we heard a crashing noise, which we decided must have been a tree falling. It may have been an avalanche (yes, I've seen those at Yosemite). After it passed, I think it dumped almost a foot of snow in a little over an hour...it was just nuts.
Well, afterwards, the storm passed, but the skies didn't really clear. It snowed lightly for the rest of the day. Woa though, that was the most intense weather I had ever seen. I'm sorry this was so long, but it is such a vivid memory.
Anybody else have crazy weather stories? I have some more, I will put them later.