This winter is likely to feature more snow and short durations of significant cold as La Nina is influencing what the season will bring to Minnesota in terms of weather.
The weather phenomena of La Nina and El Nino is based on water temperatures along the equator in the Pacific Ocean. Water temperatures cooler than normal mean La Nina. Water temperatures warmer than normal mean El Nino. The water temperature plays a role in influencing the jet stream’s track, which in turn influences temperature and precipitation patterns.
“This winter strongly favors La Nina,” said Joe Moore, meteorologist with the National Weather Service in Duluth, during a recent winter spotter online training. A recording of the training is available online at www.weather.gov/dlh/winterspotter2020. Moore is part of a staff of about 20 at the Duluth office, which includes 16 meteorologists focused on weather in northeast Minnesota and northwest Wisconsin, including a segment of Lake Superior.
Moore said modeling outlooks with the influence of La Nina generally means more storms and more chances for more snow than normal for this winter, which begins Dec. 21. But La Nina isn’t simple to pin down to a specific result. While La Nina can mean more snow, that is not always the case. La Nina also has greater chances of bouts of significant cold air, perhaps record-breaking cold.
“But it might not mean sustained, long periods of very cold temperatures,” Moore said. “So it might mean that one or two days we see some extremely cold temperatures and then they warm up, they moderate.”
Looking back at past La Nina winters in Duluth for example, Moore said while those winters typically mean more precipitation, it hasn’t always translated to more snow.
Right now there is an equal chance of above or below normal temperatures for the winter outlook. Moore said there is confidence the winter will bring above normal precipitation, which could translate to an above normal snowfall or just more “wet” snow events.
The Upper Midwest is typically covered with a continental polar air mass during the winter with cold, dry air. Moore said because of this air mass, which is not as cold as the arctic air to the north, an infusion of moisture is needed for snowfall. And that typically comes from storms out of the west tapping into moisture from the Pacific Ocean or from the southwest or south tapping into the Gulf of Mexico.
The two main storm tracks affecting Minnesota come from the northwest out of Canada or the southwest portion of the U.S. The “Clipper” storm, also called the Alberta Clipper, comes from the northwest with lighter amounts of snow, typically 3-5 inches, followed by cold, dry air.
The “Panhandle hook” or “Colorado low” is less common and has the potential for greater snowfall or mixed precipitation as it taps into the warm, moist air. The 1991 Halloween blizzard is an example of this type of storm. That storm started in Texas, nearly in the Gulf of Mexico.
A relatively new winter warning from the weather service — in addition to the normal weather warnings of winter storms, blizzards or wind chills — is a snow squall warning, which indicates a rapid reduction in visibility due to snow and sub-freezing road conditions on what may otherwise be a normal, even sunny day. The warning was developed due to the sudden onset of dangerous conditions with the potential to cause multi-vehicle crashes that didn’t fit within the existing warning structure. An example is the 29-vehicle crash near Monticello two weeks ago.
How can it rain or sleet when it’s below freezing?
In weather terms freezing rain is liquid rain that freezes on the ground. Sleet is hard, translucent balls of ice. Snow is frozen ice crystals.
Moore noted if thousands of feet overhead the temperatures are below freezing, the precipitation will be snow.
“However, if there is warm air aloft or if there is warm air at the surface, say if it’s 40 degrees, then there is going to be rain,” Moore said. So it could be 30 degrees outside, but if there is warm air at higher altitudes, perhaps 35-40 degrees, the snow will melt as it falls through the warm air layer. The rain will freeze on contact.
When there is a warm layer of air above with cold air below, the snow melts to rain as it falls and then refreezes and becomes sleet. Sleet is similar to hail, Moore said.
Graupel is like snow covered in snow, Moore said. The snowflakes collect supercooled water droplets on their surface. The Brainerd lakes area experienced graupel last season.
Diamond Dust is the term for suspended ice crystals, which is common in very cold conditions where pillars of light are visible in the sky as the ice crystals are illuminated.
Any shoveler knows not all snow is created equal. Dry, powdery snow that can be easily swept or blown away can have a ratio of 20 or 30 inches of snow to 1 inch of liquid. That back-breaking heavy wet snow may have a ratio of 5 inches of snow to 1 inch of liquid.
“It almost feels like concrete when you try to push it,” Moore said of the heavy wet snow.
Prepare and stay home
In advance of a major winter storm, the weather services advises completing a checklist to make sure there are enough supplies to last three days. While it’s good to have winter survival kits in vehicles, Moore said one of the best responses is to stay off the road, which also means roads can be cleared faster.
“If you do not need to be out there, you should not travel during a winter storm,” Moore said.
Moore noted hypothermia deaths, which outpace heat and flood/storm/lightning-related deaths, affect older people the most, rising steeply in the 75 and older age brackets. In Minnesota and Wisconsin in 2014, there were 70 hypothermia deaths, the largest number recorded between 1999 and 2018. In 2018, there were 60 hypothermia deaths in both states.
Hypothermia isn’t just a risk at very cold temperatures and can happen at temperatures above 40 degrees if a person is wet from rain, water or sweat and becomes chilled. If an individual’s temperature is below 95 degrees, they should get medical attention immediately, the weather service reported.
Average snowfall in the region for the winter season
Brainerd area about — 40-50 inches,
Duluth — about 86 inches,
International Falls — about 71 inches,
Northern Wisconsin, Upper Michigan — about 96 inches and more.
Be ready for three days off the grid in case of a major snowstorm,
Check flashlight batteries and be sure cellphones are charged,
Have winter boots and jackets ready,
Keep an extra blanket in vehicles, along with extra boots, mittens, scarves/hats, snacks, and dry clothing like socks available. Keep a bag of kitty litter for wheel traction, and have a full tank of gas,
Have supplies stocked for enough water, food, medications, and pet food for three days, including food that can be consumed without being heated in case the power supply is interrupted,
Be careful of alternative heating options like candles or wood-fire stoves,
Check smoke and carbon monoxide detectors to make sure they are functioning,
Have ice melt handy,
If warming up a car, make sure the tail pipe is clear of snow. Also be cautious of warming the car in the garage, even with the exhaust by the open door, particularly if there is a wind driving fumes back inside. Deadly carbon monoxide levels can build up,
Know where your important documents are kept,
Be able to recognize hypothermia’s warning signs of confusion, shivering, difficulty speaking, sleepiness and stiff muscles as the body experiences an abnormally low temperature. This can affect older adults and babies sleeping in cold bedrooms as well as people who are outdoors for long periods of time,
In extreme cold, check on neighbors and make sure pets and animals also have shelter,
Signs of frostbite, white or grayish-yellow skin, with skin feeling unusually firm or waxy or numb,
Dress in layers and cover hands and head,
Remember storm forecasts are likely to change.
Measure snowfall and be a weather reporter
To help gather information for the region, recording and reporting weather as it happens is an assist for the weather service.
To measure snow, have a ruler or yardstick or measuring stick and a 2-by-2 snow board painted white so it doesn’t absorb light and thus heat from sunlight. The best area to measure snow is in a flat, open, grassy area, using the snow board in the yard. The National Weather Service recommends putting out a marker so the snow board can be found even after a heavy snowfall event. Be mindful to find a spot that doesn’t drift. Round to the nearest 10th of an inch or round to the nearest whole inch when measuring the snowpack.
“Do your best, make the best estimate and let us know the details of your measurement,” Moore said, regarding wind conditions, continuing snowfall, and time of day.
Place the snow board in a broad open area away from buildings, trees and obstructions. It should ideally be twice as far as the nearest building’s height. A two-story home may be 25 feet tall and in that case the snow board should be 50 feet away from the house. Moore noted it can be difficult to find the perfect spot so they just ask people to do their best in setting up a spot that will work, which may have trees nearby. Spots that don’t typically work are deck patios or deck railings.
Depending on wind, measurements don’t have to always be in the same spot.
Measure snowfall ideally at the end of the snow event or at 7 a.m. each morning. If no snow board, make measurements in a couple of places. After measuring, clear the snow from the snow board as long as that doesn’t happen too often. Once a day is fine. Measuring after the snowfall ends is a good way to give an update to the weather service.
Measuring ice is challenging but helpful for the weather service. Measure ice to a 10th of an inch. Ice can be reported on an elevated flat surface, deck railing or patio furniture. Repeat the measurement on a couple of surfaces and take an average. Photos are welcome.
Branches are also a way to take a radial ice measurement looking at the ice on the branch.
To measure rain, use a 4-inch rain gauge, available at www.cocorahs.org for $40. Having a standard rain gauge makes it easy to compare reports from multiple sources and areas.
To report weather, observers can join CoCoRahs, which stands for the Community Collaborative Rain, Hail and Snow Network, a nonprofit organization sponsored by the National Oceanic and Atmospheric Administration, to submit regular weather reports via the website or a free app. The weather service noted volunteers of all ages are welcome and training is available.
Other reporting mechanisms include an online storm report form at https://inws.ncep.noaa.gov/report/, email email@example.com, or report via Facebook or Twitter or call 218-720-6697 and include the location and photos are welcome.