Operational forecasters at the National Weather Service (NWS) forecast office in Burlington, Vermont utilized calculations of thawing degree hours (TDH) based on forecast temperatures to assess the potential for river ice breakup. With forecast values more than double the benchmark of 300 TDH required for river ice breakup, forecasters had increased confidence that ice jams would occur and issued a flood watch with 24 hours of lead time prior to the first flood reports. Significant ice jams remained in place after their initial occurrence, causing sustained concerns for several weeks in a few towns and communities.
Severe flooding in Swanton, Vermont and Plattsburgh, New York resulted in home evacuations. In Johnson, Vermont, high water on the Lamoille River backing up from an ice jam along State Route 15 flooded the post office and grocery store. The ice jam in Swanton remained in place and resulted in a prolonged period of time that NWS Burlington provided Decision Support Services (DSS) - in the form of on-site visits, phone calls and email briefings - to the town Emergency Managers. DSS provided the needed lead time for Emergency Managers to order evacuations, preventing any casualties.
This presentation will detail effective messaging strategies unique to ice jams learned and utilized during the January 2018 event.
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