Much of Wyoming in under a Flash Flood Warning today and it won't be surprising to see warnings and advisories issued today for parts of Montana. Here are the details for Wyoming as of Noon today.

According to the National Weather Service:

Flash Flood Watch remains in effect through this evening... 

* portions of WY and Wyoming... including the following areas...  
  in WY... Bighorn Mountains southeast... Bighorn Mountains west... 
   Casper Mountain and Owl Creek and Bridger Mountains. In 
  Wyoming... Absaroka Mountains... Cody foothills... Green 
  Mountains and rattlesnake range... Lander foothills... Natrona 
  County lower elevations... north Big Horn basin... northeast 
  Johnson County... southeast Big Horn basin... southeast Johnson 
  County... southwest Big Horn basin... upper Wind River basin...  
  Wind River basin and Wind River mountains east. 

* Through this evening

* another upper level weather disturbance will override a frontal
  boundary today with ample low level moisture. This will lead to
  some strong thunderstorms with heavy rainfall in some areas
  along and east of the Continental Divide this afternoon through
  this evening. Locally heavy rainfall may fall over areas that
  already have saturated soils from monday's rains... as well over
  near bankfull rivers to potentially create flash flooding.

* Rock or mud slides will be possible in steeply sloped areas...  
  especially around mountain passes and canyons including Wind 
  River Canyon. 

Precautionary/preparedness actions... 

A Flash Flood Watch means that conditions may develop that lead
to flash flooding. Flash flooding is a very dangerous situation.