Save for Title Page

Table 57: Summer Storms Risk by City in Valley County

Data from the State Hazard Mitigation Plan for Montana from 2013 was available which included the dollar loss for counties broken up by district throughout the state. This data indicated Valley County had a total of 4injuries, 0 fatalities, $20,586,921 in property losses and $39,413,337 in crop losses from severe summer weather from 1960-2012. However, information provided by Valley County officials indicated the damage from the storm was near $30 million.

4.7.2 Severe Summer Weather History in Valley County

Thunderstorms can occur anywhere in the world and at any time of the day; however, in Valley County they are most likely to occur between the months of May and August. All thunderstorms produce lightning and thunder. Some have the potential to produce damaging straight-line winds, large hail, heavy rain, flooding, and tornadoes. A thunderstorm is classified as “severe” when it contains either singly, or a combination of, hail 1" or greater, winds gusting in excess of 50 knots (58 mph), and/or tornado. The history of thunderstorm events in Valley County was provided by National Oceanic Atmospheric Administration (NOAA). From 2009 to 2014, there have been 156 recorded events of severe summer weather in Valley County, including excessive heat, heavy rain, high wind, lightning and thunderstorm wind. During this time there was a total of $86,000 in property damage and $1.5 million in crop damages for Valley County. However, Valley County officials indicated the damage was near $30 million. There have not been any reported deaths or injuries from severe summer weather during this time period. A comprehensive list of the last 50 years of data can be found in Appendix B.
In 2014, Valley County experienced a severe summer storm event. The August 21-25 event was extremely unusual in its scope (heavy rain and significant flooding) for the time of year. This is only the second time in recorded history of significant flooding after the spring/early summer time frame. October 1986 was the only other time a flood of this magnitude has occurred after June.

Figure 20: Rainfall Event Totals for Northeast Montana from August 21-25, 2014

Hailstorms are also common during the summer months because hail are ice crystals that form within a low-pressure front due to warm air rising rapidly into the upper atmosphere and the subsequent cooling of the air mass.  National Oceanic Atmospheric Administration (NOAA) provided the history of hail events in Valley County. From 2009 to 2014, there have been 118 recorded events of hail events in Valley County. Of these 118 hail events, Glasgow is the city which has had the most occurrences from 2009-2014. A comprehensive list of the last 50 years of data can be found in Appendix B.This list of events indicates the location, date, thesize of hail, deaths/injuries and damage incurred from these hail events.
Of the summer storms, there have been five severe summer weather events in the last 50 years in Valley County that have been declared a major disaster by FEMA. All of these disasters were major declared disasters, which is when the event is clearly more than state or local governments can handle alone. The beginning and end date of the incident are included for these declared disasters, as well as information on the type of assistance program which was provided.

Table 58: Major Declared Disasters for Summer Storms for Valley County

IH Program Declared	IA Program Declared	PA Program Declared	HM Program Declared	Declaration Date	Incident Type	Title	Incident Begin Date	Incident End Date	Disaster Close Out Date	Place Code
No	No	Yes	Yes	10/9/2014	Severe Storm(s)	FLOODING	8/21/2014	8/25/2014		99105
Yes	No	Yes	Yes	6/17/2011	Severe Storm(s)	SEVERE STORMS AND FLOODING	4/4/2011	7/22/2011		99105
No	No	Yes	No	7/25/1997	Severe Storm(s)	SEVERE STORMS,ICE JAMS, SNOW MELT, FLOODING	3/1/1997	8/6/1997	3/13/2006	99105
No	Yes	Yes	Yes	10/14/1986	Flood	SEVERE STORMS & FLOODING	9/25/1986	10/28/1986	10/30/1992	99105
No	No	Yes	Yes	3/15/1986	Flood	HEAVY RAINS, LANDSLIDES & FLOODING	2/24/1986	3/7/1986	10/30/1992	99105

4.7.3 Mitigation Actions in the Past Five Years

Several mitigation actions have been completed in past five years.
One mitigation action was to promote the use of multi-hazard mitigation measures and this was to be accomplished by purchasing NOAA Weather Radios and enhancing weather radio coverage in Opheim. The siren systems in Glasgow, Fort Peck, Richland, Opheim, Nashua, and Hinsdale were updated, the emergency advisory equipment at the radio station in Glasgow. The county received Storm Ready designation from the National Weather Service.
The functionality of critical and special needs facilities and infrastructure during disasters was accomplished by purchasing and installing generators, protecting electric infrastructure, and by creating and enforcing ordinances that prevent the railroad from blocking emergency access routes. Lastly, the county improved the public’s ability to protect themselves during hazardous events by providing public education and creating tornado safe rooms.
A critical focus of this iteration of the mitigation plan updateincludes severe summer storms. Beyond carrying the most pertinent actions from the previous plan, several cities, and the county included several long terms and short term projects to include building in power redundancies and or enhancing sheltering opportunities.

4.7.4 Vulnerability in Valley County

All residents within Valley County are potentially vulnerable to summer storms, especially those who live in manufactured homes, and who are in areas without shelter. Summer storms happen each year in Valley County and have the potential to produce high winds, tornadoes, hail, and lightning.
The 2013 Update to the State of Montana Multi-Hazard Mitigation Plan included the vulnerability of state property and buildings that are considered to be highly vulnerable to severe summer weather. Valley County was included in the counties that have a high frequency of the combined events. The state buildings located in Valley County had a total of $3,911,669 in building value, $2,244,606 in contents value for a $6,156,218 in total value deemed highly vulnerable to severe summer weather.

4.7.5 Summer Storms and Climate Change

The 2013National Climate Assessment (NCA) indicated that future climate change projections include more precipitation in the Northern Great Plains and less in the Southern Great Plains. In 2011 this pattern was strongly manifested with exceptional drought and recording-setting temperatures in Texas and Oklahoma and flooding in the Northern Great Plains.
According to the Federal Advisory Committee Draft NCA, other trends in severe storms, including the numbers of hurricanes, the intensity and frequency of tornadoes, hail, and damaging thunderstorm winds are uncertain. Since the impact of more frequent or intense storms can be larger than the impact of average temperature, climate scientists are actively researching the connections between climate change and severe storms (National Climate Assessment Development Advisory Committee, 2013).

4.7.6 Relationship to Other Hazards

Summer storms have a relationship to other hazards including fires, flooding, and tornadoes.

Structural fires have the potential to be related to summer storms because lighting strikes may ignite a structure. Flood, tornado, and high winds may also cause structural fires in their aftermath. Downed power lines, natural gas leaks or other sources of ignition initiated by natural hazards may spark afire in structures. Routes to structures may be restricted due to flooding or debris from storms.
Flooding also can be related, because heavy rain from summer storms can cause flooding from frequent storms or storms causing high levels of rainfall during a short period of time.
Tornadoes develop out of thunderstorms, where there's already a steady, upward flow of warm, low-pressure air to get things started.Hail can also occur as part of thunderstorms and can cause damage depending on the size and duration of the hail.

Download 4.32 Mb.

Share with your friends: