One of my workmates stopped by the Storm Tracker 2 Weather Center to ask a question about a crazy thing that happened in Emmett Friday night Nov. 20, 2009. 

Coming out of a Bible study many encountered a strange site of mud covering their vehicles. It was obvious a shower had moved through and it perplexed them because it was clear this mud had fallen from the sky. So knowing he knew me they sent him to find out what happened.

First I should say that yes it did rain mud and to a degree it rains mud almost every time it rains. In order for raindrops to form they need tiny microscopic particles called CCN or Cloud Condensation Nuclei for water vapor to condense to liquid.  Once this process starts the water droplet will grow in size and eventually be big enough to fall to the earth. 

Dust and dirt are types of CCN and there were allot of them around Friday night.

Here's how it rained mud in Emmett and most likely in other southwest Idaho areas. Thursday night through Friday of Nov. 20, 2009 the winds were cranking at sustained speeds more than 20 and 30 miles per hour.

The colored map is showing wind speeds in knots and it's pretty clear that at 8:30 am MST it was windy over southwest Idaho. A cold front was approaching from the west and the wind direction was from an easterly direction.

A great tool in meteorology for seeing where the winds are coming and going is a streamline analysis. I've created one below for the 8 am MST time on Friday Nov. 20, 2009.

Weather observations are reported every hour at most airports and remote stations across the country allowing us to tap into hourly wind speed and direction information.  It is very clear that the main wind direction across southern Idaho was from the east.

With that type of wind and the terrain surrounding Emmett there was some serious turbulence going on! By that I mean the winds were churning from the valley floor to the mountain tops. The high mountains surrounding the area acted like a ramp for the wind to launch off of before rolling to the surface.

 The winds were probably bouncing off the north face mountains down to the south face mountains. The mountains on three sides were like a fence and trapped the dust in a concentrated area of the atmosphere surrounding Emmett. With sustained winds at the high speeds for so long many larger than normal particles of dust accumulated.

When the rains arrived in advance of the cold front the mud flinging stage was set.

At 8:30 pm MST Friday night the radar showed a strong shower over Emmett. The showers were convective like thundershowers in spring.  Some of the large dust particles were sucked into higher levels of the cloud. 

Large particles make for good ice formation so larger hail was most likely in the clouds.  When they started to fall and melt in the mild air large raindrops formed.

The end result was mud pie falling from the sky!  It was so thick they had to use the windshield wipers and wash just to see!