Update - 1/25/2014 - Waves of Arctic Air and Snow to Continue To Barrage the Great Lakes and Southeast Lower Michigan!

Update 1/25/2014 Noon - Temperature Roller Coaster To Gin Up More Snow and Blustery Conditions!

After temperatures "popped" into the mid 20s Saturday morning; cold air advection is on the move and will overspread Southeast Lower Michigan on gusty northwest winds throughout this Saturday afternoon and night. Look for readings to drop around zero and below overnight Saturday into Sunday morn.

Our fast moving clipper over Saskatchewan in Southwest Canada is on course to sail southeast across the snow-laden landscape into Northern Illinois and is projected to be near Chicago by the late morning hours of Sunday. Meanwhile; another plunge of Arctic air will organize over the Dakotas and dive into the Western Lakes system during the day, Sunday.  Ahead of this system; another brief period of moderating air will help Sunday's temperatures climb into the 20 to 25 degree range Sunday. This entire system will bring another 1 - 3" of snow and blustery conditions over Southeast Lower Michigan Sunday and Sunday evening before the colder Arctic air, once again overspreads our region Sunday night into Monday. Wind chills will lower below zero again overnight and then Sunday night into Tuesday.

Looking ahead; several days of high temperatures in the single figures to teens and overnight lows around zero and below are likely at least into mid week. Ground Hog Day is next weekend on Sunday 2/2/14.... Hmmm.

More and more information is unfolding about the onslaught of waves of fresh, bitter cold Arctic air and it's impacts across the eastern US into next week.

As mentioned in yesterday's blog, the first (in a series) of Arctic plunges is on track to engulf the region Saturday. This air mass will basically replace the bone-chilling cold already in place (and also seen this earlier this month) with a freshly stored batch of Arctic chill but the transition will also be accompanied by bitter cold dangerous wind chills.

As the first wave of Arctic air approaches Friday; strong and gusty southwest to west winds of 18 to 28 mph with gusts up to 35 to 40 mph will herald it's delivery by creating wind chills of -10 to -30; even as temperatures slowly moderate by rising through the teens and into the lower to mid 20s by early Saturday morning. Then by Saturday afternoon; look for the Arctic front to sweep through Southeast Lower Michigan and the temperature roller-coaster dives back down to around zero or below by Sunday morning. Widespread blustery snow, snow showers and blowing snow will accompany this interchanging of air masses with the first wave of snow accumulations though Saturday, mainly 1" to 3" of snow with locally higher amounts due to Lake Effect snow.

Latest indications are now a new Alberta Clipper Low pressure system will dive quickly southeast along the perimeter of the freshly laid Arctic air mass hovering across the southern Great Lakes on Sunday. Initially; all models are indicating the dynamics with this system and available moisture available from the south will contribute to bring more accumulating snow on Sunday. Of course this being so far out; the exact track and amounts of snow are questionable, therefore I'll update as this potential snow making system is bettered sampled with upper air soundings. The last two maps are estimates of the low's track and intensity. It's almost a certainty that this January will be the snowiest on record for Detroit and possibly Flint; especially if the Alberta Clipper on Sunday holds true to form.

After the Clipper blows through Sunday, the Arctic air will remain over the region in its wake well into the work week with yet another clipper possible later in the week.  Bundle Up!

 Making weather fun while we all learn,
 Bill Deedler -SEMI_WeatherHistorian


  1. Curious about the isobar maps showing the air pressure for 1/25/2014. I understand that low spots of around 950 can produce strong storm conditions, BUT am more curious about the red and blue lines on the map with numbers in the 400's/500's. What do the red/blue lines represent ?

  2. I assume you mean the pressure HEIGHTS on the 500 MB upper air maps in many of my posts. They are alike pressure at the posted height contours (similar to isobar contours of pressure at the surface). On the 1/25/2014 map the red and blue line section drawn in are stationary fronts whereas the solid blue cold fronts & solid red warm fronts.

    To have an understanding of the average height of each of these important levels. 1000 mb is near the surface (sea level), 850 mb is near 1,500 meters (5,000 ft), 700 mb is near 3,000 meters (10,000 ft), 500 mb is near 5,500 meters (18,000 ft), 300 mb is near 9,300 meters (30,000 ft). All of these values are in geopotential meters; Zero geopotential meters is near sea level. The height of these pressure levels on any given day depends on the average temperature of the air and whether the air is rising or sinking (caused by convergence / divergence). If a cold air mass is present, heights will be lower since cold air is denser than warm air. Denser air takes up a smaller volume, thus heights lower toward the surface. Rising air also decreases heights. This is because rising air cools.