The Quiet of a Storm Approaching
During a late summer afternoon 8366 ft (2550 m) high Grinnell Point was towering over sunny Swiftcurrent Lake in Waterton Glacier. Within minutes sinister clouds approached the Many Glacier area from the western horizon. Distant thunder filled the sky while the clouds turned sulphureous. The winds calmed down leaving the valley in total silence. The quiet of a storm approaching. One by one the distant peaks vanished from the skyline as the squall lines precipitation moved in. First drops reached the lake. Finally the thunderstorm crossed the lake leaving behind a thick layer of hail. Within 30 minutes the summertime landscape turn into a winter scenery with temperatures dropping significantly. This high impact weather event was triggered by an upper level cut off low moving in from Canada. The global upper-air flow pattern affects the weather at the surface. A trough brings cold air and low pressure to the south. A pinched off trough moves slowly eastward bringing severe weather where it comes in contact with the surrounding warm air mass.
Canon 20D, Canon EF-S 10-22mm, f/16, 1/2sec, ISO 100, tripod