Canyoneering & Weather Forecasts
Understanding Chance of Rain/Precipitation Basics
A basic outline
This brief article is a basic outline of the process to assess risk of flash flooding before entering a canyon. It is not an exhaustive analysis, but a good start of items to be aware of and dig deeper into if you want to make informed decisions regarding this serious canyoneering risk.
Rain = Risk in Canyons
One of the most prominent risks, and the source of many tragedies in canyoneering are Flash Floods. Getting caught in narrow passages with no escape to higher ground during a flash flood is something to be avoided.
Avoiding Flash Floods:
During the planning phase of the trip: Interpreting the "Chance of Rain/Precipitation" in the weather forecast. Determine canyon catchment area and ground saturation.
Just before the canyon day: Watching the weather patterns in Doppler Radar sources.
Just before dropping in: Watching the sky and checking cloud coverage and cloud types and barometric pressure trend.
PoP
For canyoneers, it is important to get intimate with the meaning of "Chance of Rain/Precipitation"
Here is a quick brief breakdown of PoP (Percentage of Precipitation) Still, forecasters 'hedge' their predictions to remain reliable:
"Your best interpretation is knowing your forecaster. They tend to use the same interpretation each time and will explain further if there are other discussion points to their predictions."
References:
https://www.weather.gov/ffc/pop
Video:
The Steps
Familiarize with the weather patterns of the area and area’s rainy season
Check PoP
Identify the catchment area for your canyon in a topographic map
Check Doppler Radar to see if the precipitation is hovering over the canyon catchment area
If the Doppler radar is showing rain over this catchment area, then it is not a good idea to enter that canyon.
Here a capture of a Doppler Radar image with a PoP of 10%. Now you do not have to guess the Area or Confidence in the PoP formula. It is clear what area is getting the precipitation, along with the timestamp and animation showing the time frame time lapse.
If a cloud like this (Cumulonimbus cloud) is hovering over your targeted canyon, and the temperature is dropping, the risk of the canyon flashing is not worth the risk.
Online Resources
Websites on Apps line Weather Underground or NOAA are great resources of forecasts. For the day or day before the canyon, a Doppler radar site or App is great to overlay the area that is predicted to get rain, over your targeted canyon.
Want to learn more?
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