[Geysers] Thermal Basin-Induced Weather?

[Pat Snyder]

I have driven through shoulder-season hail-and-graupel loaded thunderstorms many times, and also have been caught in them on the Upper Geyser Basin, most often in the Giant Cage, at Beehive or at Fan and Mortar (of course). Most springtime gazers can attest to these storms being nasty and numerous. See attached photos.

I am not exactly sure what produces the isolated patches of hail/graupel. Wikipedia has an explanation here:
http://en.wikipedia.org/wiki/Graupel

I am fairly sure, since I have also encountered the same phenomena near Ennis, Montana, and other places outside the park, that the thermal steam doesn't affect it, but I might be wrong.

It makes for very dangerous driving as well.

Pat Snyder
 
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On Oct 9, 2012, at 9:17 PM, Jacob Young wrote:

> On September 25, 2012, I was on a bicycle ride with my dad in the Old Faithful area.  Around 3pm, a thunderstorm with steady to hard rain and sub-50F degree temperatures forced us to take cover in the trees off the main road a mile north of Biscuit Basin for about 45 minutes.  Eventually, we started seeing southbound cars with what looked like snow on windshields.  One car had several inches of snow on top and we wondered where in the park it was snowing during this storm.
> 
> Around 6pm, while driving past Midway Geyser Basin, I was astonished to see significant accumulation of hail/graupel along the roadway.  The slopes around the Midway parking area still had an inch+ of the stuff on the ground.  The area of hail deposit was so small and highly concentrated at Midway (perhaps only within 100 yards North or South of the parking area) that I wondered if significant amounts of steam (natural or man-made) have been known to affect the type of precipitation that falls on an area.  Or was it just happenstance that the hail only fell there?  Any thoughts?
> 
> Either way, it must have been awful for those that were caught out on the Midway boardwalk when this storm came through!  Absolutely nowhere to hide!
> 
> Jake Young
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