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Lake Effect Snow Kicks into High Gear

10 Dec 2009, 1:38 pm

‘Tis the season for lake effect snow!  Around this time of year, arctic air begins to invade the Great Lakes but the lake waters are still maintaining their warmth from summer.  As the colder air rushes over the warmer lake waters, moisture is picked up as instability increases (colder air over warmer air) and clouds/precipitation eventually form.  This process is occurring right now downwind of Lake Michigan, Erie and Ontario.  Enough instability developed to produce thundersnow this morning in southwestern Lower Michigan!


Many factors go into lake effect precipitation.  As a rule of thumb, at least a 13° difference in temperature needs to exist between the air and lake water.  Other factors include lake instability, additional storm energy, deep cold airmass with low humidity, and wind speed/direction.  Atmospheric conditions are just right for significant lake effect snow in those favored regions immediately downwind of the Great Lakes.  Today will be colder in the Northeast with a northwest wind exceeding 30 mph at times.


Dangerously cold wind chills exist over the Midwest today.  Again, wind chill is the human apparent temperature outside so your car engine need not apply.  Frostbite can occur on exposed skin in a matter of 30 minutes with wind chill readings -20°.  Brrr.

wind chill

More rain will move into the southwest over the coming days.  An El Nino has developed in the eastern equatorial Pacific Ocean and the forecast is for it to remain at moderate strength or even strengthen a bit over the coming months.  This has and will have an impact on global weather and climate patterns in the next few months.  During El Nino years, the southern U.S receives higher than normal precipitation.  Therefore, the rain that is predicted this weekend in southern California correlates well with the on going El Nino pattern.


Kristin Clark

WeatherNation Meteorologist

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