Thunderstorm Outlook for Canada and the United States for Friday, April 19th, 2019. 

Canada

Non-severe thunderstorms are expected in southern, and eastern ON, as well as southern QC, SE Alberta, and SW Saskatchewan. The main risk(s) will be lightning, and localized downpours. 

United States

There is an enhanced risk of severe thunderstorms through Florida, Alabama, the Carolinas, up to the mid-Atlantic states. The MLCAPE will be strongest between Florida, and southern Virginia, and the wind shear values at 50+, as well as dew point values at 68 to 70 Fahrenheit, making this area the most prone to these severe storms. The main threats are:  hail 15%, damaging winds 30%, and a slight Tornado risk of  5%.  There will also be a chance for non-severe storms in northern California, and the NW part of the U.S. 

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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