Marshall was selected by the National Oceanic and Atmospheric Administration (NOAA) to serve on their Quick Response Team (QRT) where he has surveyed tornado damage in Alabama and Georgia in 1994, Nashville, Tennessee in 1998, La Plata, Maryland in 2002, Parkersburg, Iowa in 2008, the 2011 Super Outbreak, the 2011 Joplin tornado, and the 2015 Dallas-Ft. Worth Metroplex tornadoes. He was on the development team of the Fujita Scale Enhancement Project which produced an Enhanced Fujita Scale to update the original Fujita scale of tornado intensity. He was also a major contributor to the committee to update the Saffir–Simpson scale. He has been a principal trainer in damage surveys for the National Weather Service (NWS) since the 1990s. Between 2006 and 2012, he was elected to serve on the Severe Local Storms committee for the American Meteorological Society. In 2009 and 2010, he was part of the government sponsored VORTEX2 experiment working on the Center of Severe Weather Research (CSWR) team with Joshua Wurman. In 2012 he continued working with CSWR on the ROTATE (Radar Observations of Tornadoes and Thunderstorms Project). His job was to deploy in-situ pods in the paths of tornadoes and perform mobile mesonet transects of storm environments.