Montana Severe Weather Hazards

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Montana Severe Weather Hazards

• Disaster Mitigation Stakeholders Meeting April
  19th, 2007

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National Statistics
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Montana Statistics
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MT Average Severe Thunderstorm Reports by Month
Source SPC
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Lightning Hazard Northwest portion of the state
with relatively few maximum occurrence SE
MT. Montana ranks in top 10 nationally as far as
deaths per capita
Thunderstorm Flash Density (Bernhardt)
Graphics courtesy Vasaila
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Tornados reported over 53 year period
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Greater than 2 inch hail reported over 53 year
period
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Very strong wind events (red due to
thunderstorms, blue not) Note Chinook zone
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Chinook Winds felt in the lee of the Rockies from
Alberta south into Montana strongest near Rocky
Mountain Front (e.g. Glacier County)
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Flooding

• Can be due to
• Heavy rain and/or snowmelt
• Ice jams
• Dam failure (especially dangerous)
• Most common problem people attempting to cross
  flooded roadways and getting carried away

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Dams near high population areas
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Wintertime Severe Weather

• Snow/ice and slippery roadways (car accidents)
• Combination of snow and blowing snow creating
  blizzard conditions (mainly near and east of the
  divide)
• Extreme cold/low wind chills (risk for people and
  livestock)
• Avalanches

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Montana Ranks 5th in avalanche fatalities had
more this year
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Drought have had wet and dry periods over the
past century currently in a dry period
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Annual Departure from Mean StreamflowMissouri
River at Fort Benton
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Summary Severe Weather Hazards

• Severe thunderstorms (Hail, Wind, Tornadoes)
• Lightning
• Flooding due to heavy rain, ice jams, snowmelt,
  dam failure
• Winter Weather (snow, ice, slick roads, extreme
  cold)
• Mitigation Educational outreach on
  preparedness public alert radios in public
  buildings and in more homes
• Stormready program

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• Towns and Counties can become Stormready.
• Elements
• 24 hour warning point
• Public alert systems (sirens, NOAA weather
  radios, etc)
• Periodic weather safety and spotter talks
• Written hazardous weather action plan
• Good information flow to and from the weather
  service