Facebook user Lisa Beighley shared this photo of clouds over Plum as the sun sets on Thursday, June 16, 2022.
Frank Carnevale | Tribune-Review
Clouds over Mt. Lebanon as the sun sets on Thursday, June 16, 2022.
John Hendrickson
John Hendrickson shared this photo of clouds over Butler County as the sun sets on Thursday, June 16, 2022.
Lilly Kubit | Tribune-Review
Clouds are pictured over Pittsburgh’s Mellon Park as the sun sets on Thursday, June 16, 2022.
Chaz Palla | Tribune-Review
Clouds are pictured north of Pittsburgh as the sun sets on Thursday, June 16, 2022.
Chaz Palla | Tribune-Review
Clouds are pictured north of Pittsburgh as the sun sets on Thursday, June 16, 2022.
Chris Pastrick | Tribune-Review
Clouds — mammatus clouds — seen over New Kensington in the early evening Thursday.
Chaz Palla | Tribune-Review
Clouds are pictured north of Pittsburgh as the sun sets on Thursday, June 16, 2022.
Lilly Kubit | Tribune-Review
Clouds are pictured over Pittsburgh’s Mellon Park as the sun sets on Thursday, June 16, 2022.
Megan Guza | Tribune-Review
Clouds over the Morningside neighborhood of Pittsburgh as the sun sets on Thursday, June 16, 2022.
Ron Martin
Clouds over the Greenfield neighborhood in Pittsburgh as the sun sets on Thursday, June 16, 2022.
Amanda Miller
Facebook user Amanda Miller shared this photo of clouds over Canonsburg as the sun sets on Thursday, June 16, 2022.
Amanda Miller
Facebook user Amanda Miller shared this photo of clouds over Canonsburg as the sun sets on Thursday, June 16, 2022.
Amanda Miller
Facebook user Amanda Miller shared this photo of clouds over Canonsburg as the sun sets on Thursday, June 16, 2022.
Beth Unger
Facebook user Beth Unger shared this photo of clouds over Plum Borough as the sun sets on Thursday, June 16, 2022.
Beth Unger
Facebook user Beth Unger shared this photo of clouds over Plum Borough as the sun sets on Thursday, June 16, 2022.
Beth Unger
Facebook user Beth Unger shared this photo of clouds over Plum Borough as the sun sets on Thursday, June 16, 2022.
Jennifer Jack Retter
Facebook user Jennifer Jack Retter shared this photo of clouds over Pine Township as the sun sets on Thursday, June 16, 2022.
Jennifer Jack Retter
Facebook user Jennifer Jack Retter shared this photo of clouds over Pine Township as the sun sets on Thursday, June 16, 2022.
Thomas Bachorski
Facebook user Thomas Bachorski shared this photo of clouds over North Huntingdon as the sun sets on Thursday, June 16, 2022.
Andrew Barclay
Facebook user Andrew Barclay shared this photo of clouds over Zelienople as the sun sets on Thursday, June 16, 2022.
Andrew Barclay
Facebook user Andrew Barclay shared this photo of clouds over Zelienople as the sun sets on Thursday, June 16, 2022.
Kathy Capozzoli
Facebook user Kathy Capozzoli shared this photo of clouds over National Cemetery of the Alleghenies in Cecil Township, Washington County, as the sun sets on Thursday, June 16, 2022.
Suzanne Vertosick
Facebook user Suzanne Vertosick shared this photo of clouds over Natrona Heights as the sun sets on Thursday, June 16, 2022.
Suzanne Vertosick
Facebook user Suzanne Vertosick shared this photo of clouds over Natrona Heights as the sun sets on Thursday, June 16, 2022.
Suzanne Vertosick
Facebook user Suzanne Vertosick shared this photo of clouds over Natrona Heights as the sun sets on Thursday, June 16, 2022.
Suzanne Vertosick
Facebook user Suzanne Vertosick shared this photo of clouds over Natrona Heights as the sun sets on Thursday, June 16, 2022.
Lisa Beighley
Facebook user Lisa Beighley shared this photo of clouds over Plum as the sun sets on Thursday, June 16, 2022.
Lisa Beighley
Facebook user Lisa Beighley shared this photo of clouds over Plum as the sun sets on Thursday, June 16, 2022.
Carol Bertrand
Facebook user Carol Bertrand shared this photo of clouds over Penn Hills as the sun sets on Thursday, June 16, 2022.
Jason Brandt
Facebook user Jason Brandt shared this photo of clouds over Unity Township as the sun sets on Thursday, June 16, 2022.
Jason Brandt
Facebook user Jason Brandt shared this photo of clouds over Unity Township as the sun sets on Thursday, June 16, 2022.
Ray Chobanian
Facebook user Ray Chobanian shared this photo of clouds over Bellevue as the sun sets on Thursday, June 16, 2022.
Ray Chobanian
Facebook user Ray Chobanian shared this photo of clouds over Bellevue as the sun sets on Thursday, June 16, 2022.
Debra Leasure Owens
Facebook user Debra Leasure Owens shared this photo of clouds over the Holiday Park Volunteer Fire Station as the sun sets on Thursday, June 16, 2022.
Debra Leasure Owens
Facebook user Debra Leasure Owens shared this photo of clouds over the Holiday Park Volunteer Fire Station as the sun sets on Thursday, June 16, 2022.
Debra Leasure Owens
Facebook user Debra Leasure Owens shared this photo of clouds over the Holiday Park Volunteer Fire Station as the sun sets on Thursday, June 16, 2022.
Karin Galligan
Facebook user Karin Galligan shared this photo of clouds over Washington County as the sun sets on Thursday, June 16, 2022.
Karin Galligan
Facebook user Karin Galligan shared this photo of clouds over Washington County as the sun sets on Thursday, June 16, 2022.
Karin Galligan
Facebook user Karin Galligan shared this photo of clouds over Washington County as the sun sets on Thursday, June 16, 2022.
Karin Galligan
Facebook user Karin Galligan shared this photo of clouds over Washington County as the sun sets on Thursday, June 16, 2022.
Karin Galligan
Facebook user Karin Galligan shared this photo of clouds over Washington County as the sun sets on Thursday, June 16, 2022.
Anika Keno Langgle
Facebook user Anika Keno Langgle shared this photo of clouds over Washington County as the sun sets on Thursday, June 16, 2022.
Anika Keno Langgle
Facebook user Anika Keno Langgle shared this photo of clouds over Washington County as the sun sets on Thursday, June 16, 2022.
Anika Keno Langgle
Facebook user Anika Keno Langgle shared this photo of clouds over Washington County as the sun sets on Thursday, June 16, 2022.
Anika Keno Langgle
Facebook user Anika Keno Langgle shared this photo of clouds over Washington County as the sun sets on Thursday, June 16, 2022.
People watching the skies above Allegheny County and surrounding areas Thursday evening for signs of potential thunderstorms instead were treated to vistas of clouds resembling fluffy cotton balls.
Known as mammatus clouds, they are a rare example of clouds that form in sinking air instead of rising air, according to the website earthsky.org.
Tinted by the setting sun, they provided a visual treat and great photo opportunities for many in the area, including meteorologist Shannon Hefferan and her colleagues at the National Weather Service office in Moon.
The mammatus cloud formation can be associated with severe weather, but that’s not always the case, Hefferan said.
While storms passed to the north and south of Allegheny County, she said, “There was no severe weather here at all.”
According to earthsky.org founder and science educator Deborah Byrd, mammatus clouds are pouch-like protrusions primarily composed of ice that extend from the underside of clouds. They can extend for hundreds of miles.
The clouds can be associated with severe weather, appearing in the vicinity of or before or after a storm, Byrd says, but she notes that it is a myth that the clouds can extend down to form tornadoes.
According to the Department of Atmospheric Sciences at the University of Illinois at Urbana-Champaign, the mammatus formation can occur with a high concentration of ice crystals and water droplets, resulting in saturated air that is heavier than the surrounding air and sinks toward the earth.
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