Using Probabilistic Impact Decision Support Services along the Pacific Crest Trail

The Pacific Crest National Scenic Trail (PCT) is a consistently marked route, through varied terrain and weather from the United States-Mexico border to the Canadian-United States border. The PCT is 2,653 miles long and travels to its highest point of 13,153 feet above mean sea level at Forester Pass, which is located in the Sierra Nevada mountains of the County Warning Area (CWA) of the National Weather Service (NWS) in Hanford, CA. All six high mountain passes (11,000 feet and above) of the PCT (Forester, Donohue, Muir, Pinchot, Glen and Mather) reside within NWS Hanford’s CWA. In the past, IDSS would have been tricky without the new National Blend of Model (NBM) probabilistic datasets that are now available. For example, lightning is one of the greatest dangers on a trail which contains long stretches of granite, so the NBM Probability of Lightning/Dry Lightning is used explicitly to compose the 5-tiered (None, Low, Moderate, High, Extreme) color coded Hiker Risk graphic. Other weather hazards such as Snow Depth, Wind, Rain and Visibility combine with Lightning to create an overall Hiker Risk along the path. Many locations receive no cellular service and some cannot receive the specific NOAA Weather Radio forecasts that are tailored for each section of the PCT. Therefore, displaying the Hiker Risk at the last re-supply point before adventurists encounter the high passes mentioned above, allows for folks of all skill levels to be proactive. This fact further emphasizes why Impact Decision Support Services (IDSS) are sorely needed for the National Parks that it traverses. This presentation will discuss how the NBM Probability of Exceedance (POE) for rain, wind, snowfall and visibility is used to calculate the overall Hiker Risk. Outreach conducted with National Parks and other core partners has determined what POE triggers each level of risk along the PCT that is depicted in the final product.