They’re rarely the stuff of legend like tornadoes or hurricanes, but snow squalls too can be deadly — particularly when their sudden whiteout conditions trigger massive highway pileups.
Now the National Weather Service is acknowledging that hazard by introducing a new weather-alert product, a Snow Squall Warning, that will be piloted in southeast Michigan and six other areas starting in early January.
“It gives us a vehicle to issue a warning when there are potentially life-threatening conditions out there,” said Richard Pollman, the warning coordination meteorologist at the weather service’s Detroit office in White Lake, Mich.
Snow Squall Warning, a new weather-alert product alerting drivers to hazards, will be piloted in southeast Michigan and six other areas starting in early January.
The weather service describes a snow squall as “an intense, but limited duration, period of moderate to heavy snowfall accompanied by strong, gusty surface winds and possibly lightning.”
Snow accumulation may be significant during a squall, but is not part of the definition.
Mr. Pollman said the key factors are visibility below a quarter mile, radar or camera-based indication of intense precipitation, and pavement temperature that is either below freezing or rapidly dropping toward freezing.
Warnings are intended to be issued for smaller geographic areas for periods of up to 60 minutes, similar to severe thunderstorm warnings. The weather service anticipates being able to provide typical lead times of about 20 to 30 minutes for a given area.
The other weather-service districts involved in the pilot program are based in Buffalo and Binghamton, N.Y., Pittsburgh and State College, Pa., Burlington, Vt., and Cheyenne, Wyo.
Mr. Pollman said staff at those seven districts volunteered for the roll-out “because these were the offices that have looked at this problem the longest.”
Starting with a limited geographic area is intended to identify any problems that might exist with the warning’s use before it goes national, he said.
“I think we’ll learn a lot this year as to how to best issue it,” Mr. Pollman said. “It’s all about giving motorists the best information available so they can act accordingly.”
The warning’s use is scheduled to expand to the rest of the United States during the winter of 2018-19.
Monroe and Lenawee counties are part of the Detroit office’s coverage area.
Toledo and other areas along and east of I-75 in northern Ohio are covered by a weather service office in Cleveland, while an office in North Webster, Ind., covers Ohio’s far northwestern counties and Michigan border counties from Hillsdale west.
Lake-effect snow belts are particularly prone to snow squalls because of the wind, and sometimes such squalls can occur far downwind of the pertinent lake, Mr. Pollman said.
“We’re close enough to get these [snowfall] streamers, but not close enough to issue a Winter Weather Advisory” or a Lake Effect Snow Warning, he said.
One such squall from Lake Michigan struck U.S. 23 between Milan and Ann Arbor in January, 2015, leading to a 50-vehicle pileup that killed one traveler.
Arctic cold fronts are the other most common medium for snow squalls, and that was what occurred March 12, 2014, when dozens of vehicles piled up on the Ohio Turnpike in two separate crashes near Vickery. Three travelers were killed and an Ohio Highway Patrol trooper who became pinned between two vehicles was seriously injured.
“The Ohio Turnpike example is one of the ones we’ve cited in forecaster training,” Mr. Pollman said.
More recently, six people were injured — one seriously — March 17 when 21 vehicles piled up during a snow squall on northbound I-75 between Perrysburg and Bowling Green, shutting the freeway down for nearly four hours.
Cindy Antrican, a regional spokesman for the American Automobile Association, said squall warnings should reduce the risk of crashes. She also recommended that drivers leave as much room as they can between themselves and other vehicles during winter weather.
“Stay out of the pack,” Ms. Antrican said. “Even if you feel you’re a good driver in challenging winter conditions, not everyone is. Oftentimes we see vehicles all bunched up ... [and] if one driver loses control, that driver can cause a multiple-vehicle crash.”
The same recommendation applies, she noted, during smoke or fog conditions. Fog in particular has been blamed for about 20 percent of crashes involving 10 or more vehicles nationwide, according to the auto club.
Particularly counterproductive, AAA said, is motorists’ tendencies to try to stay within sight of the vehicle in front of them during poor visibility when that may put them too close to that vehicle. At the same time, drivers routinely fail to slow down enough when their sight distance is reduced.
With snow squalls typically being of short duration, the National Weather Service’s recommendation is for drivers to pull over into a safe place, if possible, and wait for a whiteout to ease.
Like other warnings, watches, and advisories, snow squall warnings will be broadcast on National Weather Service radio channels, published on agency web sites, and distributed to emergency-services agencies and information providers.
Mr. Pollman said it will be at navigation-system providers’ discretion as to whether such alerts appear on in-vehicle systems.
But the weather service is considering whether to add the Snow Squall Warning to the short list of weather hazards it now publicizes using the Wireless Emergency Alerts system that sends free text messages to all cell phones in a given geographic area.
Warnings now distributed using that system are for tornadoes, tsunamis, flash floods, hurricanes/typhoons, dust storms, and extreme winds.
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