About the FTB

Below are some frequently asked questions regarding the Colorado Flood Threat Bulletin website (www.coloradofloodthreat.com).

What is the Colorado Flood Threat Bulletin?

The FTB is a service provided to the residents of the State of Colorado by the Colorado Water Conservation Board. It is meant to provide an overview of the potential flood threat facing the State on a daily basis from May 1 through September 30. It consists of three different products:

  • Daily Flood Threat Bulletin – This product is issued daily before 11:00 am and is used to identify areas of the state that are at risk of flooding. Updates can be issued as needed by weather situation.
  • Flood Threat Outlook – This product is an outlook of the flood threat and precipitation amount/probabilities in the state over the next 15 days. It is presented in an event-based format that focuses on periods of potentially wet weather, and a precipitation map is included when the forecast precipitation exceeds 0.5 inches for any area during an event duration. The Outlook is updated on Mondays and Thursdays by 3PM.
  • State Precipitation Map – An overview of recent precipitation and flooding conditions across the state, using MetStorm Live data.

The goal of the FTB products is to provide an early outlook for threat awareness and is not meant to be a real-time warning system. For all real-time flood related warnings, please tune into your local National Weather Service (NWS) office:
Boulder  Grand Junction   Pueblo   Goodland

What do the Flood Threat definitions mean?

On a daily basis, users may see the following flood threats posted on the map. The green threat level will represent NWS Flood Warnings (riverine) that are active at the time of the FTB post.

Threat Levels

What goes into determining a threat level?

On a daily basis, our meteorologists look at six primary factors when deciding upon a flood threat.

  1. Intensity of precipitation.
  2. Duration of precipitation: considered durations range from anywhere between 30 minutes to as long as 48 hours.
  3. Probability of precipitation: a higher probability of heavy rainfall translates into a higher threat of flooding.
  4. Ground type: when rain falls on hard, non-porous surfaces such as roofs and streets in urban areas, it runs off into drainage systems much faster than rural locations. Similarly, forests that have been recently burned experience significant runoff problems compared to pristine areas.
  5. Spatial coverage of precipitation: by their very nature, isolated thunderstorms potentially producing heavy rain are difficult to forecast, while large, slow moving general rain systems can be more accurately forecast.
  6. Antecedent moisture – When the ground is already saturated with moisture from previous rainfall, it is much easier for flooding conditions to be initiated.

What are common scenarios that can result in a flood threat?

Due to the varying topography of the State of Colorado, we are generally concerned with four types of scenarios that can result in a flood threat:

  1. Short-term very heavy (i.e. thunderstorm) rainfall: 1 inch/hour over mountainous terrain, 2 inches/hour over the Plains, 0.75 inches/30 minutes over urban areas
  2. Prolonged moderate/heavy rainfall: 3+ inches/6 hours, 4+ inches/12 hours, 5+ inches/24 hours.
  3. Rain on snow, which can even occur given light, but long duration rainfall.
  4. Snowmelt induced flooding, which can occur even in the absence of any rainfall.
  5. Riverine flooding, which can occur due to spring/early summer snow melt in the high country, or as a combination of snow melt and heavy rainfall.

What is the Fire Burn Forecast?

The Fire Burn Forecast (FBF) is issued daily by 11AM for select, high-risk burn areas in Colorado (May to Sept). This standalone forecast system was created to separate the higher-sensitivity burn area forecasts from the existing FTB product, but complement the overall goals of the program. Similar to the FTB, the purpose of the FBF is to provide an early outlook for threat awareness, and not be used for real-time warning and monitoring. For real-time Flash Flood Warnings over burn areas, be sure to tune into your local NWS office.

For the 2021 season, the FBF will be issuing daily threats for the following burn areas: Calwood, Cameron Peak, East Troublesome, Grizzly Creek, Pine Gulch, and Spring Creek. These six selected burn areas have the potential to cause excessive runoff, flash flooding, and dangerous mud flows and/or debris slides due to their lack of vegetation, hydrophobic soils, steep topography and aerial coverage. For recent burn areas, it can take as little as 0.25 inches of rain per hour to trigger flooding! Be sure to check out FBF burn areas below (purple) along with other vulnerable burn areas across the state. All vulnerable burn areas will continue to be included in our daily FTB threat maps.

Forecast Zones

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