Monday, January 5, 2015

Biggest snow of the season for some set to move in Monday night

12:30pm Update: Latest discussion regarding heavy snow that looks to set up just to the west of the immediate Stateline later this afternoon and evening.  Current forecast still looks on track with higher snowfall totals southwest of Rockford.  Onset time of snow still looks on track...between 4pm and 6pm from Freeport on west and between 6pm and 8pm east.

Click here to read the latest discussion regarding the heavy snow.



After coming off of the 5th least snowiest December on record in Rockford, Mother Nature has a different plan in mind for the first full week of January.  Snowfall over the weekend ranged anywhere between 1" to 3" and it looks like we'll be doubling that by Tuesday morning.

A Winter Storm Warning remains in effect for Stephenson, Jo Daviess, Carroll and Whiteside counties beginning at 6pm this evening.

A Winter Weather Advisory has been issued for Winnebago, Boone, McHenry, Ogle, Lee, DeKalb, Green, Rock and Walworth counties beginning at 6pm this evening.


A fast moving, but strong, Alberta clipper will dive south out of the northern Rockies this morning and nearly overhead the Stateline this evening and overnight.  The snow will come quick this evening and then be done with by Tuesday morning.  Snow to liquid ratios, the amount of moisture within the snow, will be high, meaning once the snow falls it will accumulate fairly quickly.   An average snow to liquid ratio is 10:1.  Meaning 10" of snow is the equivalent (when melted) to one inch of water.  Ratios closer to 8:1 mean the snow has more weight, it's a heavier and wet snow, and is usually called 'heart-attack' snow because it's tough to shovel.  Once you get into ratios that are close to 15 to 20:1, the snow is drier and has more fluff to it.  That's when you can get those higher snow totals.  Also, if the growth zone within the atmosphere for snow is just right, usually around -15°C, then snowfall rates and totals can be enhanced.  It looks like we'll be very near that going into the afternoon and evening as the clipper moves through.  Because of that, snowfall totals near 6" are not out of question, especially for areas along and south of Highway 20, including cities like Elizabeth, Stockton, Lena, Pearl City, German Valley, Shannon, Byron, Polo, Mt. Morris, Amboy and Paw Paw.

North of the border, snowfall totals will likely be close to 3" to 4".  This includes areas such as Monroe, Brodhead, Janesville and Sharon.  Some locations could locally receive 5". 

Once the snow begins, the roads will quickly become snow covered and tough to travel.  Temperatures will be in the low single digits as the snow falls which means salt will be less effective.  Winds will be light during the duration of the snow through Tuesday morning, but then increase by Tuesday afternoon.  Blowing and drifting snow will be possible through Tuesday night.  Following the snow, temperatures will drop to the coldest we've felt all season!  Wind chills by Wednesday morning could be as cold as -30°.  Temperatures through the day will struggle to break 0°.

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