Advances in Freezing Rain Accumulation Verification, Reporting Practices, Communication, and Governance

The National Weather Service (NWS) officially forecasts ice accumulation on an “elevated horizontal flat surface.” These forecasts primarily support departments of transportation, who message these amounts to partners and to the public. Due to varying partner needs such as electric companies vested interest in ice accretion on trees and power lines, it has been suggested that the NWS should also forecast and report radial ice accumulations. A team has been assembled to investigate the appropriateness of such policies and exploration of changes.

Challenges for developing policies and guidelines for ice accumulation have centered around a lack of objective data. Without a robust gridded ice accumulation analysis of record (similar to those that exist for rainfall and snowfall) NWS cannot evaluate the proficiency of model data, forecasts, storm reports, impacts to society, nor establish effective governance. Efforts are underway between the NWS and research community to capture ice accretion reports through citizen science, and to develop a robust gridded ice analysis.

As the agency continues to transform from deterministic forecasts to communicating uncertainty through probabilistic data and guidance, the prediction of freezing rain accumulation must also evolve. The lack of probabilistic ice accumulation guidance has hindered forecasters from effectively communicating winter storm scenarios that support key messages and decision support services. Meteorologists across the NWS are working together to develop a reliable probabilistic dataset of freezing rain to better communicate the range of potential outcomes of hazardous winter storms.

This talk will encompass updates regarding the spectrum of advances in freezing rain accumulation verification, reporting, prediction, communication and governance. These efforts will modernize partner messaging, training, and public outreach.