Light Snowfalls Just as Dangerous For Drivers as Major Winter Storms, Study Finds

Chris Dolce
Published: December 3, 2019
Plotted above are fatal snow-related traffic accidents during the 2015-16 and 2016-17 winter seasons (October-March). Fatal accidents where a National Weather Service advisory or warning was in effect are plotted yellow and red. Fatal accidents in minor winter weather events where no warning or advisory was in effect are plotted green.
(NOAA/CIMMS)

Light snowfalls typically don't receive much attention, but for drivers they can be just as dangerous as major winter storms.

The National Weather Service issues winter storm warnings and winter weather advisories when snow or ice is expected to be significant enough to pose a danger to travel or property. Each region has varying criteria for when the warnings or advisories are issued.

Only 46% of deadly snow-related accidents were in an area where an NWS warning or advisory was in effect during the 2015-16 and 2016-17 winter seasons, according to NTSB statistics compiled by Joe Burzdak, undergraduate researcher for the Cooperative Institute for Mesoscale Meteorological Studies (CIMMS). That means 54% of fatal snow-related traffic accidents occurred where snowfall was too light or too short in duration to warrant the NWS to issue a winter storm warning or winter weather advisory.

Researchers from NOAA’s National Severe Storms Laboratory and National Weather Service are hoping to combat the problems caused by lighter snowfalls that don't meet the criteria for a warning or advisory.

“We have gotten really good at predicting when a big event is going to happen and what regions it will impact,” said CIMMS research Heather Reeves in a NOAA press release. “The real danger now are these events where people don’t have to stay inside. They can still go out and live their lives, but there may be moments where they need to exercise caution."

Further evidence of this was provided in statistics compiled by the NWS in Milwaukee in November 2017. Accidents in snow in Milwaukee and Madison, Wisconsin, were much more frequent when snow totals were less than 2 inches.

One tool aimed at helping forecasters predict hazardous winter weather driving conditions is being developed by CIMMS researcher Shawn Handler.

The tool will help NWS forecasters see where road temperature are below freezing. Road temperatures are critical when forecasting how easily snow or ice will accumulate.

In this forecast model example, the colored contours show the probability of where roadway temperatures are predicted to be below freezing.

The NWS has also taken strides in recent years to provide the public more warning information.

Snow squalls cause a brief, but blinding drop in visibility and are notorious for causing pileups in winter. They are too short in duration to warrant a winter storm warning or winter weather advisory, but are still a major threat to drivers. For this reason, snow squall warnings can now be issued by the NWS to provide short-duration warnings in small areas. They're somewhat similar to tornado warnings.

New research will likely involve how to provide the public with even better messaging during winter weather, the NOAA release said. This could include talking to local DOT officials and emergency managers to determine how their areas might react to new ideas for weather warning levels.


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