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Montana Severe Weather Awareness

Montana Severe Weather Awareness

NWS Watch and Warning Program

Severe Thunderstorm
Photo Courtesy of Sean Heavey - June 16, 2007; $35 Million Hailstorm Impacting Glasgow To Nashua.

Overview Watch / Warning Program Thunderstorm Climatology Severe Weather Safety Lightning Safety Weather Sources

Short You Tube video "Staying Aware of the Severe Weather Threat".

Ready, Set, Go: This is the mindset we want people to be in when it comes to being prepared for hazardous weather.

Ready: At this stage, the National Weather Service sees something on the horizon that may end up being a widespread severe weather event in the future. The Hazardous Weather Outlook issued by the local NWS offices will give you this information. Also, the Storm Prediction Center issues thunderstorm outlooks that give an idea of where severe thunderstorms may develop in the next 8 days.

Set: In this stage, we are confident that a hazardous weather event will occur, but are not sure of the exact timing, location, or impact of the event. For severe thunderstorms and tornadoes, a Watch is issued to give the public a heads up that they need to be prepared for the possibility of severe weather within the next 8 hours.

Go: When we hit this stage, we are confident that a thunderstorm is producing severe weather and we issue a Warning. The lead time can be just precious minutes out to an hour. At this stage, you should take action by seeking shelter.


Funnel Cloud: A funnel-shaped cloud, extended outward or downward from a thunderstorm, that corresponds to a rotating column of air. If the rotation is violent and reaches the ground, the funnel cloud is associated with a tornado.

Tornado: A violently rotating column of air, in contact with the ground, that extends from the base of a thunderstorm to the ground. This is often visible as a funnel cloud with swirling dust or debris near the surface.

Severe Thunderstorm: A thunderstorm that produces hail of 1 inch or larger (quarter size) and/or a wind gust to 58 mph or higher.

Microburst: A convective downdraft with an affected outflow area of less than 2.5 miles wide and peak winds lasting less than 5 minutes. Microbursts may induce dangerous horizontal/vertical wind shears, which can adversely affect aircraft performance and cause property damage.

Straight-line Winds: Generally, any wind that is not associated with rotation, used mainly to differentiate them from tornadic winds.

Flash Flood: A sudden inundation of water in low-lying areas, usually brought on by heavy rain, dam break, rapid snowmelt or ice jams.

Watch: The potential exists for severe weather to occur within the next 8 hours but the exact location and timing is not known. Action can be taken to protect property such as putting your vehicle in the garage, putting away patio furniture, etc.

Warning: Severe weather either is occurring or will be shortly. Immediate action should be taken to protect yourself by going to the lowest portion of a sturdy building, or into a closet, hallway or room without windows.

Severe Thunderstorm
Photo Courtesy of Sean Heavey - West of Glasgow, July 28, 2010.

US Dept of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
Great Falls Weather Forecast Office
5324 Tri-Hill Frontage Rd
Great Falls, MT 59404-4933

Tel: (406) 453-2081

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