Sharp Temperature Drop Experienced Thursday

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   A classic strong autumn cold front progressed through the entire Midwest by Thursday Night.  Here is a look at a surface weather map from 4 pm Thursday afternoon with temperatures as an image.  The front clearly stands out, highlighted not only by a temperature gradient but an abrupt shift in the wind from south to west northwest!

Temperature Map

   The cold front which plowed across the area during the afternoon and early evening hours of Thursday, October 25th dropped temperatures 20 degrees or more in less than 2 hours! From afternoon temperatures in the low-mid 70s, readings slid into the 40s by mid-evening. Here is a graphic which shows the temperature (red curve) and dew point (green) at O'Hare and Rockford. Note the sharp drop toward the right side of each graph - the passage of the cold front is easy to see!  Below that is a text listing of temperature drops experienced across the area.

Temperature and Dew Point Trace

 

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE CHICAGO IL
917 AM CDT FRI OCT 26 2012 /1017 AM EDT FRI OCT 26 2012/

...DRASTIC TEMPERATURE DROP EXPERIENCED ON THURSDAY...

A POWERFUL AUTUMN COLD FRONT MOVED ACROSS NORTHERN ILLINOIS
BETWEEN 3 AND 630 PM AND THROUGH NORTHWEST INDIANA BETWEEN 630 AND
800 PM ON OCTOBER 25TH. WITH STRONG SOUTHERLY WINDS AHEAD OF THE
FRONT AND SOME SUNSHINE DURING THE DAY...TEMPERATURES HAD WARMED
INTO THE MID TO UPPER 70S. THE COLD FRONT BROUGHT TEMPERATURES
RAPIDLY DOWN INTO THE 40S...INCLUDING A 22 DEGREE DROP IN ONE HOUR
AT GARY. BELOW IS A LISTING OF THE MAXIMUM TEMPERATURE DECREASES
BETWEEN THE TOP OF THE HOUR OBSERVATIONS AT AREA SITES DURING THIS
EVENT. NOTE THAT EVEN MORE SIGNIFICANT DROPS MAY HAVE OCCURRED
BETWEEN THE HOURLY OBSERVATIONS.


LOCATION   TWO-HOUR TEMPERATURE DROP   FOUR-HOUR TEMPERATURE DROP
-----------------------------------------------------------------
AURORA               -21F                         -29F
CHICAGO DUPAGE       -23F                         -29F
CHICAGO MIDWAY       -22F                         -28F
CHICAGO OHARE        -20F                         -28F
DEKALB               -22F                         -28F
GARY                 -23F                         -29F
JOLIET               -23F                         -29F
KANKAKEE             -25F                         -28F
MORRIS               -24F                         -29F
PERU                 -20F                         -29F
PONTIAC              -23F                         -29F
RENSSELAER           -20F                         -26F
ROCHELLE             -21F                         -27F
ROCKFORD             -20F                         -27F
ROMEOVILLE           -23F                         -29F
VALPARAISO           -19F                         -27F
WAUKEGAN             -20F                         -29F

$$

MTF

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