FXUS63 KLOT 101838
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1238 PM CST THU DEC 10 2009

.DISCUSSION...
1122 AM CST

ONLY CHANGE TO GOING FORECAST WAS TO TWEAK DIURNAL TENDENCIES OF 
HOURLY TEMPERATURES TODAY WITH TEMPERATURES A BIT SLOWER TO 
WARM...BUT BASED ON LOW LEVEL TEMPS FROM LATEST ACARS DATA DO NOT 
SEE MANY REASONS TO CHANGE ACTUAL HIGHS...ALTHOUGH MAY NEED TO TWEAK 
DOWNWARD A FEW DEGREES ESPECIALLY IN SNOW COVERED AREAS WHERE 
TEMPERATURES ARE JUST STRUGGLING ABOVE ZERO AT 17Z. A FEW SITES 
ACROSS NORTH CENTRAL ILLINOIS ARE STILL HOVERING AT 20 BELOW WIND 
CHILLS AND SHOULD BE IMPROVING TO BELOW ADVISORY CRITERIA BY 18Z
SO WILL LET WIND CHILL ADVISORY EXPIRE AT 18Z. NO OTHER CHANGES
MADE AT THIS POINT.

MARSILI

&&

.AVIATION...

1200 UTC TAFS...

1800 UTC TAFS...AREA WILL BE DOMINATED BY A LARGE HIGH PRESSURE
SPRAWLED ACROSS THE SOUTHERN PLAINS STATES. THIS HIGH WILL BUILD
EASTWARD ACROSS THE TENNESSEE VALLEY BY EARLY FRIDAY WHILE A
RIDGE AXIS EXTENDING NORTHWESTWARD ACROSS THE MID AND UPPER
MISSISSIPPI VALLEY SHIFTS EWD ACROSS THE WRN GREAT LAKES BY
FRIDAY EVENING.

THIS HIGH...BEING POLAR IN ORIGIN...WILL CONTINUE TO PROVIDE COLD
AND VERY DRY AIR TO THE MIDWEST THROUGH FRIDAY. CONDITIONS WILL BE
GENERALLY VFR CLR THOUGH SOME MID LVL CLOUDINESS IS EXPECTED TO
DEVELOP ACROSS NRN IL AND SRN WI FRIDAY MRNG DUE TO ONSET OF WARM
AIR ADVECTION AS WINDS BEGIN TO BACK TO A MORE SLY DIRECTION ON
BACK SIDE OF HIGH PRESSURE RIDGE.

MERZLOCK

&&

.MARINE...
1227 PM CST

A DEEP LOW PRESSURE OVER WESTERN QUEBEC...IN COMBINATION WITH A
SPRAWLING HIGH PRESSURE AREA OVER THE LOWER MISSISSIPPI VALLEY
WILL CONTINUE TO PRODUCE STRONG WEST WINDS ACROSS THE GREAT LAKES
THROUGH THIS EVENING. AS THE LOW CENTER TRACK OFF TOWARD LABRADOR
TONIGHT AND FRIDAY...WINDS WILL SLOWLY ABATE AND BACK SLIGHTLY
INTO THE SOUTHWEST. THE HIGH PRESSURE CENTER WILL SHIFT EASTWARD
TO THE MID ATLANTIC REGION BY LATE FRIDAY...AS A RIDGE EXTENDS TO
THE NORTHWEST...ACROSS THE WESTERN GREAT LAKES. WITH THE PASSAGE
OF THIS RIDGE AXIS FRIDAY EVENING...WINDS WILL DIMINISH MORE
NOTICEABLY...AND BACK INTO THE SOUTH.

MERZLOCK

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
     LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-LMZ868-
     LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL MIDNIGHT SATURDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 6 
     PM THURSDAY.

&&

$$