Monitoring Tsunami Impacts Across the Pacific; Air Quality Concerns; Dangerous Heat; Critical Fire Weather for the West

Tsunami impacts continue for portions of the Pacific basin. Wildfire smoke causes unhealthy air in Midwest to Great Lakes. Heat dome spans Mississippi Valley to Mid-Atlantic with excessive heat warnings and advisories. Critical fire weather in Great Basin to Pacific Northwest (dry thunderstorms). Cold front spawns severe storms/heavy rain in Central U.S. today, shifts to East Coast Thursday. Read More >

May 21, 2010
Tornadoes & Flash Flooding

An area of upper level low pressure moved across the Great Lakes, with a trough extending into the Ohio Valley. The airmass had become unstable, and shear in the low levels of the atmosphere became favorable for the formation of tornadoes. In addition, thunderstorms tended to rebuild over the same areas, and rainfall was very heavy. This led to flash flooding across the region as well.