Thunderstorm Outlook for Canada and the United States for Tuesday, August 21st 2018

There will be Non-Severe storms in Northern and Central Manitoba, and Saskatchewan.  However, Severe thunderstorms are expected in Southern Ontario.   The main threats are Large hail, winds gusting to 100 km/h, and torrential downpours with 50 mm possible, and a few Tornadoes are possible. 

United States
Severe thunderstorms are expected in the Great Plains, SE States, the NE States, and the Ohio Valley.  The risk here will be, heavy localized downpours, large hail, and possible Tornadoes.  There will also be non-severe T-Storms in most of the USA on Tuesday.        

The thunderstorm forecast is issued daily from April 1 to September 30.
Definition of a Severe Thunderstorm 
In Canada, a rainfall rate greater than 50 millimetres (2 in) in one hour, or 75 millimetres (3 in) in three hours, is also used to indicate severe thunderstorms. Severe thunderstorms can occur from any type of storm cell. However, multicell, supercell, and squall lines represent the most common forms of thunderstorms that produce severe weather.

A thunderstorm is classed as severe if winds reach at least 90 km/h (58 mph), hail is 25 millimetres (1 in) in diameter or larger, or if funnel clouds or tornadoes are reported. Although a funnel cloud or tornado indicates a severe thunderstorm, a tornado warning is issued in place of a severe thunderstorm warning. A severe thunderstorm warning is issued if a thunderstorm becomes severe, or will soon turn severe.
Thunderstorm Safety Tips:
  • Move to a sturdy building or car.
  • Do Not take shelter under isolated trees.
  • Get out of boats and away from water.
  • Unplug appliances. Avoid using the telephone or any electrical appliances. 
  • Do not take a bath or shower.
  • Remember when thunder roars go indoors!

The Enhanced Fujita Scale (EF-Scale) rates the strength of tornadoes in Canada and the United States based on the damage that they cause. 

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