An afternoon riddled with severe weather was found over Northern Wyoming on Saturday June 16th. Showers and isolated thunderstorms were found across the area during the morning hours... which continued throughout the day. Stability took a sharp downswing during the late afternoon hours, and more widespread thunderstorm activity was found across Northern Wyoming, including the areas of Yellowstone and Grand Tetons, the Absaroka Mountains, the Big Horn Basin, and Johnson county. In addition, an isolated thunderstorm or two was found over Sweetwater county in Southern Wyoming.
Around 4 pm MDT, the Storm Prediction Center issued a Tornado Watch over Johnson county, which was slated to last into the early morning hours. At this time, dewpoints across the Johnson county were in the upper-50s/low-60s, and storm activity was beginning to move off of the Big Horn mountains into the lower elevations of Johnson county. A strong cell moved off of the Big Horn Mountains around 5pm MDT, and continued to move across Northern Johnson County. As it moved, the storm greatly increased in strength, and began showing signs of rotation on radar. The first tornado warning was issued around 515pm, and included an area north of I90, east of Buffalo and encompassed an area extending to the Johnson/Campbell county border. As of the time of this story, no direct confirmation of a tornado has been received at the Riverton Forecast Office. If you, or someone you know saw a tornado moving north of I90 (around exits 82-95, or 30 miles east of Buffalo) between 515 and 545pm, please contact the NWS Riverton at 1-800-211-1448.
A second supercell storm moved off the southern Big Horn mountains to impact the area around Kaycee, WY around 520-530pm. Around 525pm the NWS in Riverton issued a Severe Thunderstorm warning in efforts to protect residents from the threats of large hail and dangerous lightning, with the potential for strong winds. This storm passed over Interstate 25 around 540pm, and into Kaycee around 545 pm. A secondary cell developed behind the initial storm, which began to dive slightly south below Kaycee. As the storm further progressed, it turned tornadic in nature, and a second Tornado Warning was issued around 530pm. The storm moved further south and impacted the cities of Sussex and Linch around 550-6pm, producing 1 inch hail (Quarter-size) around the city of Linch in south-central Johnson County. Around 555pm, law enforcement noted a funnel cloud around 4 miles south of the city of Linch. Again, if residents of Sussex or Linch saw a tornado, please notify the NWS at the above phone number.
Stronger thunderstorms continued across the Big Horn Basin, and west of there throughout the evening as well, with numerous reports of pea-sized hail, and frequent lightning with heavy rains. A severe thunderstorm moved into central Park county around 550-6pm. This storm produced nickel and quarter-sized hail around 35 miles west of Cody between 6 and 615pm MDT, before weakening.
Severe thunderstorm activity ceased around 630-7pm across the area, though strong winds were present around the city of Byron around 740pm MDT. These winds did snap some tree limbs, and uprooted some trees as they moved through. Below are the Local Storm Reports (LSRs) from the severe thunderstorm / tornadic supercells across Northern Wyoming, as well as a couple pictures of the wind damage found across Byron. Again, if you have additional information on any of these events, please contact the NWS in Riverton at 1-800-211-1448.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE RIVERTON WY
649 PM MDT SAT JUN 16 2007
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
0600 PM HAIL 39 W CODY 44.52N 109.85W
06/16/2007 E0.88 INCH PARK WY UNKNOWN
PUBLIC REPORTED NICKEL SIZED HAIL.
0615 PM HAIL 34 W CODY 44.52N 109.74W 06/16/2007 E1.00 INCH PARK WY UNKNOWN PUBLIC REPORTED QUARTER SIZED HAIL.
0600 PM HAIL LINCH 43.61N 106.20W
06/16/2007 E1.00 INCH JOHNSON WY UNKNOWN
PUBLIC REPORTED QUARTER SIZED HAIL FELL FROM 600 UNTIL
0555 PM FUNNEL CLOUD 4 SW LINCH 43.57N 106.26W
06/16/2007 JOHNSON WY LAW ENFORCEMENT
LAW ENFORCEMENT REPORTED A FUNNEL CLOUD AND ROTATING