February 18 Snow Squall Event
On the afternoon and evening of Friday, February 18, 2022 dangerous snow squalls impact portions of Wisconsin, Iowa, and Illinois.
Snow Squalls
Snow squalls bring heavy snow, strong winds, and whiteout conditions. Arctic cold fronts are often the focus for these snow squalls, which also introduce plummeting temperatures and concerns for a flash freeze.
Skies may be clear and the sun may be out ahead of a snow squall, but as it moves through travel conditions rapidly deteriorate and become dangerous. These deteriorating conditions, especially when a flash freeze is occurring and roads quickly become snow covered and icy, have been known to cause large chain-reaction accidents on heavily traveled highways or interstates.
The National Weather Service issues Snow Squall Warnings as a way to warn motorists of the impending whiteout conditions.
These warnings are typically short-fused and affect areas for roughly 30 to 60 minutes, and will trigger Wireless Emergency Alerts on smart phones.
Synoptic Setup
At 500mb
The 500mb height and wind analysis shows the upper-level trough that tracked across the upper Great Lakes region on February 18th. Impressive momentum fields were observed with this system, even in the mid-levels as a 100+ kt jet streak tracked across Minnesota and Wisconsin.
At 850mb
The 850mb height, temperature, and advection analysis shows strong warm air advection out ahead of the arctic front, quickly replaced with strong cold air advection behind the front.
Warm air advection out ahead of the arctic front led to the development of light rain and/or snow across portions of Wisconsin before snow squalls developed.
4pm Friday Temperatures
Warm air advection out ahead of the cold front and clear skies for some allowed temperatures to warm into the mid to upper 30s across southwest Wisconsin ahead of the Arctic front. While, much of central and southeast Wisconsin weren't quite as warm.
Strong Winds
Strong momentum fields were observed with the system as it tracked across the region, both ahead of and behind the arctic front.
Wind advisories were issued for much of Wisconsin for strong southwest winds ahead of the front and west to northwest winds behind the front.
Overall, models did a good job handling the winds both ahead of and behind the front. The High Resolution Ensemble Forecast (HREF) maximum potential wind gust fields picked up on smaller pockets of winds in excess of 60 mph immediately behind the front across east-central Wisconsin.
The Northern American Ensemble Forecast System (NAEFS) shows how anomalously strong the momentum fields were with this system, especially within the zonal (west to east) direction.
Ahead of the Arctic front, momentum fields were already anomalously strong. Based on climatology, the NAEFS showed southwest winds just above the surface were a 1 in 10 year event.
Along and behind the Arctic front, momentum fields ramped up quickly. The NAFES showed the west to east component of the winds were so strong that they fell outside of the climatology ranges!
Peak Wind Gusts (mph) as of 4pm
An enhanced surface pressure gradient and an anomalously strong low-level jet allowed for strong, gusty southwest winds ahead of the Arctic front.
Note the increase in wind speeds across western Wisconsin as the arctic front had begun to move across northwest and western Wisconsin.
The Arctic Front
As analyzed by the Weather Prediction Center, a strengthening surface low tracked across the upper Great Lakes with the trailing arctic cold front moving east-southeast across Minnesota, Wisconsin, Iowa, and Illinois.
The strong arctic high dropping south from Canada into the northern Plains reinforced the arrival of the colder, Arctic air mass behind the front.
Mesoscale Environment
Incoming Cold Air Mass
Across portions of western Wisconsin where temperatures were able to warm into the mid to upper 30s ahead of the snow squalls, falling temperatures behind the Arctic front may have led to a flash freeze in spots.
Across central and southeast Wisconsin, temperatures mostly remained below freezing ahead of the arctic front. This allowed for snow to quickly accumulate on roads as the arctic front and snow squalls arrived.
Strong Frontogenesis
An area of strong frontogenesis developed along the arctic front and intensified as the front moved east-southeast across Minnesota, Iowa, Wisconsin, and Illinois.
This frontogenesis provided a focused area for ascent within the low levels of the atmosphere, coincident with increasing large-scale ascent as the main trough and mid-level jet streak moved into the region.
Heavy Snow
As cold air advection increased along and behind the arctic front, strong low-level ascent along the frontal boundary was focused within the dendritic growth zone (DGZ). This resulted in high levels of saturation within the DGZ, which is a favorable signal for efficient snowfall.
Steeper mid-level lapse rates likely allowed for deeper lift to focus along the arctic front, helping to contribute to increased snowfall production as well.
Thundersnow!
MRMS reflectivity data and Geostationary Lightning Mapper Group Energy Density, courtesy of CSU/CIRA and NOAA/NESDIS , show the snow squall intensifying in time with lightning periodically observed as it moved southeast across Wisconsin.
The Snow Squall Parameter
The snow squall parameter focuses on favorable atmospheric characteristics, such as low-level moisture, low-level instability, and strong winds.
The snow squall parameter on February 18, 2022 clearly showed the development of favorable atmospheric conditions, which intensified at times as the arctic front moved across the region.
SPC Mesoscale Discussions
Two mesoscale discussions were issued by the Storm Prediction Center as snow squalls developed and tracked southeast that evening.
Below is an interactive map with linked graphics showing observations from across the region during the snow squall event. Note, the quick onset of sharply reduced visibilities, strong WNW winds and dropping temperatures as the snow squalls move through. West Bend, Wisconsin and the Timmerman Airport north of the Milwaukee Metro observed the strongest wind gusts as the snow squalls moved through with gusts to 72 and 75 mph, respectively.
La Crosse, Wisconsin
La Crosse, Wisconsin. Click to expand.
Wausau, Wisconsin
Wausau, Wisconsin. Click to expand.
Wisconsin Dells
Wisconsin Dells. Click to expand.
Appleton, Wisconsin
Appleton, Wisconsin. Click to expand.
Fond du Lac, Wisconsin
Fond du Lac, Wisconsin. Click to expand.
West Bend, Wisconsin
West Bend, Wisconsin. Click to expand.
Platteville, Wisconsin
Platteville, Wisconsin. Click to expand.
Janesville, Wisconsin
Janesville, Wisconsin. Click to expand.
Kenosha, Wisconsin
Kenosha, Wisconsin. Click to expand.
Rockford, Illinois
Rockford, Illinois. Click to expand.
Davenport, Iowa
Davenport, Iowa. Click to expand.
Wheeling, Illinois
Wheeling, Illinois. Click to expand.
La Crosse, Wisconsin
Wausau, Wisconsin
Wisconsin Dells
Appleton, Wisconsin
Fond du Lac, Wisconsin
West Bend, Wisconsin
Platteville, Wisconsin
Janesville, Wisconsin
Kenosha, Wisconsin
Rockford, Illinois
Davenport, Iowa
Wheeling, Illinois
Warnings
In 2019, the National Weather Service introduced the Snow Squall Warning, a way to warn motorists of the impending whiteout conditions.
Prior to the February 1 snow squall event, only 2 snow squall warnings had been previously issued for the State of Wisconsin. On the afternoon and evening of February 18, 2022 a total of 24 snow squall warnings were issued.
Warnings were issued along the arctic cold front as snow squalls developed initially back in western and far northern Wisconsin. As the snow squalls continued to move east-southeast in time, the warnings continued.
After moving through Wisconsin, the snow squalls continued to bring dangerous travel conditions to portions of eastern Iowa and northern Illinois.
As the arctic front moved east the following day snow squalls redeveloped causing significant travel concerns as it pushed east across New York, Pennsylvania, New Jersey, Connecticut, Massachusetts, and Rhode Island!
This triggered snow squall warnings along the arctic front as it moved through the Northeast.
Impacts & Photos
Travel conditions deteriorated rapidly as the arctic front and snow squalls moved across western, central and southern Wisconsin, eastern Iowa, and northern Illinois. Within a matter of minutes, roads went from clear to snow covered and icy within minutes and near whiteout conditions developed.
TMJ4 News on Twitter: "SNOW SQUALL! ❄️This is a time-lapse in Milwaukee. A snow squall is an intense, but brief burst of snow. pic.twitter.com/qjpk0MLKTz / Twitter"
Strong winds and whiteout conditions resulted in major impacts on a few inland lakes that evening as well. This event provides a good reminder of how quickly you can become disoriented in whiteout conditions.
Collection of Tweets from NWS Offices service Minnesota, Wisconsin, Iowa, and Illinois highlighting the event as conditions deteriorated.
Safety
This event serves as a critical reminder that snow squalls move in fast and result in rapidly deteriorating travel conditions. Conditions may go from sunny and clear to blizzard, whiteout conditions in a matter of minutes.
TMJ4 News on Twitter: "Here is another snow squall time-lapse! This was taken in Waukesha tonight. pic.twitter.com/mWqTglB0CV / Twitter"
On days when snow squalls are expected, stay weather aware!
- If snow squall warnings are issued, your smart phone should alert you. We highly recommend that your keep those Wireless Emergency Alerts turned on!
- If traveling:
- SLOW DOWN! Traveling at high rates of speed in whiteout conditions and on icy roads can lead to devastating consequences.
- If possible, delay your travel until the snow squalls have passed. Keep in mind, roads may still be icy after the snow squall passes!
- If outside:
- You will quickly become disoriented in whiteout conditions!
- Get out of the elements if you can do so safely, seek shelter in a vehicle or nearby building.
Below is a great Twitter thread with more information from our colleagues out in Pennsylvania where snow squalls have been known to cause dangerous travel conditions.
NWS State College on Twitter: "🧵Ahead of today's snow squall threat, let's review all you need to know to say safe from this potentially-deadly hazard.There is no safe place on a highway during a snow squall. #PAwx (1/9) pic.twitter.com/JSHpQ2Pt68 / Twitter"
