Tuesday, January 3, 2012

Tuesday morning chills followed by end of the week warmth

Temperatures early this morning fell just on either side of 10° with Rockford hitting 9° for the low.  There were even a few spots that had wind chills below zero.  The last time we were that cold was back on the 10th of December.  While this afternoon will be a chilly one, the cold won't last.  The deep trough centered across the U.S. will begin to weaken and push into the Atlantic as mild Pacific air moves back in.  The jet stream pattern by the end of this week will turn a little more zonal pushing the cold air back north and allowing temperatures to modify back above average.  The fact that we don't have any snow cover is also aiding in the warmer temperatures.  Snow has a high albedo, meaning the majority of the sun's rays are reflected back out to space.  When this occurs the surrounding atmosphere doesn't warm.  Since we have no snow on the ground the sun's rays are absorbed into the ground, thus heating it.  Temperatures by the end of the week will reach the low to mid 40s on the heels of a brisk southwest wind.  Unfortunately, with this type of pattern we're in there are no major winter storms expected in our future.  

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