Tuesday, January 10, 2017

Strong Winds Tuesday Evening - Slick Spots Wednesday morning

A Wind Advisory remains in effect for northern Illinois and southern Wisconsin through 10pm Tuesday evening.  Peak wind gusts during the afternoon and early evening reached 50 to 55 mph!  Wind gusts will remain between 40 and 45 mph through 9pm, slowly winding down after midnight.

Highs Tuesday reached 51 degrees in Rockford.  But following the cold front, colder air has quickly moved in with temperatures falling into the 20's and 30's.  With the drop in temperatures below freezing, there could be a few slick spots on untreated roads late Tuesday night and Wednesday morning.

The strong wind gusts may have caught some people off guard this afternoon, especially considering how fast the winds increased.  The image on the left is a '3 hour pressure change' map and indicates where - within the past 3 hours - atmospheric pressure has either increased or decreased and by how much.  The red lines indicate pressure falls and the blue hashed lines indicate pressure rises.  The rapid development of low pressure caused a quick drop in surrounding pressure over the Great Lakes.  As a result, it caused a quick rise in pressure behind the low.  The rapid drop and rise in pressure over a short distance is what caused the increase in wind speeds this afternoon.  As low pressure weakens later tonight the winds will also relax as the difference in pressure won't be as great.

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