Ask A Scientist© Environmental Science Archive

Author:      patti l rozensky
What is the cause for the record cold in Chicago (January 1994)?

Response #:  1 of 1
Author:      rcwinther
This came from the Weather Underground National Weather Summary for
today (1/20/94).  What caused this record cold outbreak?
   The current cold wave began last week as a deep upper trough of low 
pressure swept across south central and southeastern Canada.  Circulation 
around this low resulted in a cold northwesterly flow of air from western 
Canada deep into the central and eastern U. S.  This allowed bitter cold air 
over the Northwest Territories of Canada to plunge southeastward across the 
northern plains and the upper Mississippi Valley into the south Atlantic and 
Gulf coasts.
   The cold air came basically in two waves.  The first swept across the 
central and eastern U. S.  Late last week and resulted in at least 21 record 
low temperatures over the weekend.  The second wave of cold air was preceded 
by an influx of moisture, which resulted in snow early this week on the order 
of feet in some locations from the Ohio valley into portions of northern New 
England.  Twenty four to thirty inches of snow fell in south central Ohio near 
Lucasville.  Louisville, KY received a record sixteen inches (15.9) of snow 
from the storm.
   The extensive snow cover across the nation, from the northern tier states 
into the Ohio Valley, allowed an even colder surge of air to plunge across the 
central and eastern United States with little modification.