For the first time, the NOAA National Severe Storms Laboratory’s Warn-on-Forecast System (WoFS) has successfully run short-term forecasts for three geographic areas at once—predicting severe weather, winter weather, and fire weather. The historic milestone demonstrates the system’s adaptability and marks a significant step toward transition to operational use by the National Weather Service (NWS). 

As an experimental system, WoFS has typically run in one geographic area, or domain, at a time. Running three domains at once enables forecasters to see the bigger picture while also covering more individual local hazards.

Enhancing Forecasting Across Multiple Hazards

This latest achievement further demonstrates that WoFS is not limited to just severe weather and flash flooding. The system is increasingly in demand for fire weather forecasting, and this initial test showed that forecasters are eager to apply WoFS to winter storms.

“We at CRP (NWS Weather Forecast Office Corpus Christi) were on the far southern edge of the fire domain,” said NWS Science and Operations Officer, Nicholas Carr. “We did find the Red Flag Threat Index trends useful for messaging in emergency managers and Spots [requests for spot forecasts of weather trends at the location of an ongoing fire] regarding when the peak fire danger would be. It also better captured the magnitude of the extreme fire danger in the mid-afternoon period than other guidance sources.”

Feedback gathered from forecasters after the winter weather run has pointed to WoFS products that could be developed to predict areas of heavy snowfall and icy conditions. Designing the system toward specific uses ensures that NWS offices covering these threats will receive tailored guidance, improving coordination and response.

“I found the soundings to be the most useful element in terms of assessing the timing of rain to snow change over,” said NWS Science and Operations Officer, Brian Barjenbruch, of WFO Omaha. 

WoFS represents a paradigm shift for severe weather forecasting. By shifting from warnings based on current observations of ongoing storms to warnings based on future-looking computer model forecasts, WoFS provides forecasters with probabilistic, high-resolution, rapidly-updating guidance. The confidence and insights gained from WoFS guidance can improve warning accuracy and lead time.

Faster, More Accurate Warnings

Traditional numerical weather models update only a few times per day, leaving forecasters with gaps in rapidly evolving situations. WoFS, however, updates every 30 minutes, incorporating the latest observations to provide near-real-time probabilistic forecasts (or the likelihood of severe hazards in a given area). This allows forecasters to detect subtle but crucial changes in the atmosphere that could impact storm evolution, snowfall rates, or fire spread.

For severe weather, WoFS can provide earlier indications of tornado development, sometimes at 1 to 2 hours lead time as illustrated by the 2024 Greenfield, Iowa, tornado. This helps forecasters issue warnings with greater confidence. In winter storms, WoFS may be able to identify local bands where the heaviest snow will fall, allowing better preparation for hazardous road conditions. 

For fire weather, it can predict where exceptionally low humidity will combine with gusty winds to make fire starts more likely. WoFS also predicts the timing and intensity of changes in wind direction. This is a critical issue for fire-fighting crews who could become exposed as a fire changes. WoFS information is monitored by forecasters who work with fire and forestry officials, giving them the critical time they need to reposition personnel. This range of invaluable insights across multiple weather hazards can help achieve the NOAA mission to protect life and property.

WoFS IN THE CLOUD
By covering three regions at once, researchers continued to explore the capabilities of the cloud-based WoFS. During the historic run they ramped up cloud resources on-the-fly and documented ways to make multi-region runs better automated and more efficient in the future. As more real-world applications for WoFS are discovered, it will become important to provide coverage that can support a variety of operational warning operations.

Preparing for Operational Use

This milestone is a major step toward making WoFS an operational tool for the NOAA National Weather Service. The possibility of WoFS guidance supporting forecasters nationally for extreme hazardous weather events such as fire, severe, winter, and flooding is more likely after accomplishing this major milestone. 

This year the NWS will begin a demonstration period in which it will lead WoFS operations; meanwhile NSSL researchers will continue to improve WoFS and iterate on it to create better and more useful tools for users. 

WoFS is proving its potential to transform how the NWS issues warnings, and is increasingly capable of covering multiple weather hazards across the country. By reducing uncertainty and increasing lead time, the system empowers forecasters to make faster, more accurate decisions—ultimately protecting lives and property.