The National Weather Service has issued a Severe Thunderstorm Watch for parts of Wyoming, Nebraska, and Colorado that includes the city of Cheyenne. The watch in effect until 8:00 PM Friday (May 17).

spc.noaa.gov
The NWS Storm Prediction Center has issued a

   * Severe Thunderstorm Watch for portions of 
     Northeast Colorado
     Southern Nebraska Panhandle
     Southeast Wyoming

   * Effective this Friday afternoon and evening from 1255 PM until
     800 PM MDT.

   * Primary threats include...
     Scattered large hail and isolated very large hail events to 2.5
       inches in diameter likely
     Scattered damaging wind gusts to 70 mph possible
     A tornado or two possible

   SUMMARY...Thunderstorms are expected to intensify over northeast
   Colorado and southeast Wyoming this afternoon, tracking across the
   watch area.  The strongest cells will likely pose a risk of large
   hail and perhaps damaging wind gusts.  A tornado cannot be ruled
   out.

   The severe thunderstorm watch area is approximately along and 75
   statute miles north and south of a line from 10 miles west southwest
   of Cheyenne WY to 20 miles east of Sidney NE. For a complete
   depiction of the watch see the associated watch outline update
   (WOUS64 KWNS WOU1).

   PRECAUTIONARY/PREPAREDNESS ACTIONS...

   REMEMBER...A Severe Thunderstorm Watch means conditions are
   favorable for severe thunderstorms in and close to the watch area.
   Persons in these areas should be on the lookout for threatening
   weather conditions and listen for later statements and possible
   warnings. Severe thunderstorms can and occasionally do produce
   tornadoes.