Canada

Weather Underground Forecast for Tuesday, May 20, 2008.

A low pressure system in the Tennessee and Ohio Valleys will move east across the Mid-Atlantic Tuesday, with its cold front slowly sagging southeastward. This will result in widespread showers and thunderstorms along its path. Strong to severe thunderstorms are likely to develop especially along and ahead of the cold front from the Carolinas southwestward into parts of the Deep South, with the main threat of large hail and damaging wind gusts. Expect thunderstorm activity to decrease rapidly in the evening. As the cold front pushes offshore overnight, much of the precipitation should cease, except parts of the Southeast, where the southern end of the cold front lays beneath.

Farther north, scattered showers and thunderstorms will continue over the Northeast during the afternoon and evening hours as a broad trough of low pressure remains in place. In addition, well below normal temperatures are expected throughout the Northeast and Great Lakes for one more day.

Out West, another Pacific front will push ashore early Tuesday and sag southeastward. Expect coastal rain to continue in the Pacific Northwest Tuesday morning, gradually spreading across the Northern California as well as the northern Intermountain West and Northern Rockies throughout the day. This cold front will also bring cool and windy weather to portion of the interior West Tuesday, reliving the recent heat incursion. Strong winds will develop ahead of the cold front in the afternoon and evening, with gusts possible in excess of 45 mph. On the other hand, an excessive heat event continues over much of the Southwest Tuesday, as an unseasonably strong high pressure system remains in place. Near or above record high temperatures can be expected once again.

Elsewhere, scattered thunderstorms are expected in southern Florida. Moreover, light snow showers are possible in the Upper Peninsula of Michigan.

Temperatures in the Lower 48 states Monday ranged from a low of 14 degrees at Lolo Hot Springs, Mont. to a high of 120 degrees at Death Valley, Calif.