The National Weather Service has confirmed that a tornado crossed Montgomery County on Thursday afternoon from North Potomac to Burtonsville. Another tornado, also on Thursday, was confirmed in the Coltons Point area of St. Mary’s County, the Weather Service said Friday.

The two tornadoes brought to six the number confirmed in the Washington area this week. All of them appeared to be of minimal intensity, ranking at EF-0 on the Enhanced Fujita scale.

Although witnesses and residents appeared to have little doubt that they had seen tornadoes, formal classification requires a Weather Service investigation.

The Montgomery tornado, with winds of up to 70 mph, appeared just before 4 p.m. Thursday, traveled 17.3 miles and had a maximum width of 150 yards, the Weather Service said.