So just leaving Spences Bridge today I see an odd cloud of dust or mist up ahead. Around the corner about 300 metres I see that this "dust" is moving at a high rate of speed. I'm 2-up leaving the warm fuzzies of the Thomspon. This place is remowned for thunderstorms and I know there is a storm coming this night.
I round the bend and see to my horrow that I've driven right into a microburst. The sky is coming down at about 100 kmh. Dust and water vapour are crashing down outta nowhere. It hits the limestone face of teh rock wall/mountian to my left and creates a giant dust/sand "avalanche" headed straight for me. I hunker down, close the vents real quick on the helmet and squint. I hammer the throttle and punch a hole in this maelstrom. Sand everywhere. Feels like I'm riding through a sandblaster. Then in a rush it's gone. I look in my mirrors and see the people on the ground that were photographing the rapids scrambling. No later than 30 seconds later I pass Floman and Kittenwalk headed straight for it. I wave ecstatically to them amazed to run into yet another BCSB crew on the prowl in the twisties. I hope they didn't have to deal with the weird weather I rode through.
Source: The USA TODAY Weather Book by Jack Williams
Deadly winds from thunderstorms
Often wind damage that's blamed on tornadoes is actually done by winds coming down from a shower or thunderstorm. Such "microburst" winds can reach more than 150 mph. In a tornado, the air is rising as it swirls around the vortex. In addition to damaging buildings and blowing down trees, microbursts blasting down to the ground are a major aviation hazard and have caused several crashes. Today, pilots are trained in how to avoid microbursts and special Doppler radars to detect them are being installed at airports. Any strong winds coming down from showers and thunderstorms are known as "downbursts." If damaging winds are concentrated in an area extending 2.5 miles or less, it's called a "microburst." If the winds cover a larger area, it's a "macroburst." Microbursts are most common from the Rockies eastward in the USA because showers and thunderstorms are more common. In the humid East, "wet" microbursts are most likely while "dry" microbursts occur more often in the West. Lines of thunderstorms that cause one downburst after another are called derechoes.